source of original ocr-text:
https://archive.org/details/bub_gb_FZsIAAAAIAAJ/page/n499/mode/2up
pagination of original + 17 = pagination of pdf file.
This is a manually corrected version of the OCR-text provided by google books.
Italics are marked with ... (probably incomplete).
Tables are formated with tab (ASCII 09) for easy export into spreadsheets.
Lines of original printed copy are closed by 0D0A. Paragraphs of printed copy are separated by a blank line.
˚ stands for the little ring denoting temperature.
pages 156 to 157 are missing in the scan used by me and also some words on p. 478f - this has been emendated using the 1810 Philadelphia edition.
THE
ELEMENTS
OF
CHEMISTRY.
BY
THOMAS THOMSON, M.D. F.R.S.E.
EDINBURGH:
PRINTED FOR W. BLACKWOOD, SOUTH BRIDGE-STREET;
AND LONGMAN, HURST, REES, ANH OHME,
PATERNOSTER-ROW, LONDON.
1810.
ADVERTISEMENT.
My intention in the following little
Treatise, was to furnish an accurate Outline
of the present state of Chemistry, to those per-
sons who are commencing the study of the
Science, or who may be unable or unwilling
to peruse my larger and more complete work
on the subject. All historical details, and
all references to authorities were out of the
question. My sole object was to include the
greatest possinle number of facts within the
smallest possinle space, and to arrange them
in a clear and perspicuous manner. And
though a variety of Chemical epitomes have
appeared, both in this country and on the
Continent, possessed, many of them, of
( iv )
much merit, and doing great credit to their
author, yet I flatter myself, that I may say
with confidence, that there is hardly any of
them that contains the same quantity of mat-
ter within so small a space. My view in the
present Treatise, was limited to present a use-
ful little book to Students, and to furnish
them with a great number of important facts
in a small space, and at a small expence.
How far I have succeeded in my endeavours,
I must leave to the determination of my
Readers.
CONTENTS.
BOOK 1. OF SIMPLE SUBSTANCES 1
DIVISION I. Of CONFINABLB BODIES 2
Chap. I. Of Simple Supporters of Combustion 2
Sect. 1. Of Oxygen
Chap. II. Of Simple combustibles 4
Sect. 1. Of Hydrogen 5
2. Of Carbon and Diamond 6
3. Of Phosphorus 9
4. Of Sulphur 11
5. Of Boracium 15
Chap. III. Of Simple Incombustibles 18
Sect. 1. Of Azote 19
2. Of Muriatic Acid 21
CHAP. IV. Of Metals 24
Sect. 1. Of Gold 28
2. Of Platinum 30
3. Of Silver 32
4. Of Mercury 34
5. Of Palladium 37
6. Of Rhodium 38
7. Of Iridium 39
8. Of Osmium 40
9. Of Copper 41
10. Of Iron 44
VI CONTENTS.
11. Of Nickel 49
12. Of Tin 50
13. Of Lead 53
14. Of Zinc 56
15. Of Bismuth 59
16. Of Antimony 60
17. Of Tellurium 62
18. Of Arsenic 62
19. Of Cobalt 64
20. Of Manganese 65
21. Of Chromium 67
22. Of Uranium 67
23. Of Molybdenum 68
24. Of Tungsten 69
25. Of Titanium 70
26. Of Columbium 71
27. Of Cerium 72
28. General Remarks 72
DIVISION II. Of unconfinable bodies
Chap. I. Of Light 77
II. Of Caloric 80
Sect. 1. Of the nature of Caloric 81
2. Of the motion of Caloric 82
3. Of the equal distrinution of temperature 89
4. Of the effects of Caloric 90
5. Of the quantity of Caloric in bodies 9S
6. Of the sources of Caloric 104
BOOK II
OF COMPOUND BODIES 112
DIVISION I. Of salifiable bases 113
Chap. I. Of Volatile Alkalies 113
Sect. 1. Of Ammonia 114
Chap. 11. Of Fixed Alkalies 117
CONTENTS. vii
Sect 1. Of Potash 117
2. Of Soda 120
Chap. III. Of the Alkaline Earths 122
Sect. 1. Of Lime 122
2. Of Magnesia 125
3. Of Barytes 126
4. Of Sirontian 127
Chap. IV. Of the Earths Proper 128
Sect. 1. Of Alumina 128
2. Of Yttria 130
3. Of Glucina 131
4. Of Zirconia 131
5. Of Silica 133
DIVISION II. Of primary compounds 134
Chap. I. Of Oxides 134
Sect. 1. Of the Oxide of Hydrogen 135
2. Of Carbonic Oxide 137
3. Of the Oxides of Azote 138
Chap. II. Of Acids 142
Class 1. Acid Products 144
Sect. 1. Of Sulphuric Acid 145
2. Of Sulphurous Acid 146
3. Of Phosphoric Acid 148
4. Of Phosphurous Acid 148
5. Of Carbonic Acid 149
6. Of Boracic Acid 151
7. Of Fluoric Acid 152
Class 2. Acid Supporters 153
Sect. 1. Of Nitric Acid 154
2. Of Nitrous Acid 156
3. Of Oxymuriatic Acid 157
4. Of Hyperoxymuriatic Acid 159
5. Of Arsenic Acid 160
6. Of Tungstic Acid 161
7. Of Molybdenic Acid 161
8. Of Chromic Acid 162
viii CONTENTS.
9. Of Columhic Acid 162
Class 3. combustible Acids 163
Sect. 1. Of Acetic Acid 164
2. Of Benzoic acid 166
3. Of SebacicAcid 166
4. Of Succinic Acid 167
5. Of Moroxylic Acid 168
6. Of Camphoric Acid 168
7. Of Oxalic Acid 168
8. Of Mellitic Acid 169
9. Of Tartaric Acid 170
10. Of Citric Acid 171
11. Of Kinic Acid 171
12. Of Saclactic Acid 172
13. Of Uric Acid 172
14. Of Malic Acid 173
15. Of Suberic Acid 174
16. Of Formic Acid 174
CHAP. III. Of Colorific Acids 175
Sect. 1. Of Prussic Acid 175
2. Of Gallic Acid 178
3. Of Tannin 179
CHAP. IV. Of Compound combustibles 186
Sect. 1. Of Alcohol 186
2. Of Ethers 190
3. Of Volatile Oils 197
4. Of Fixed Oils 199
5. Of Bitumens 203
DIVISION III. OF SECONDARY COMPOUNDS 206
Chap. I. Of Combinations of Earths 207
Chap. II. Of Glass 208
Chap. III. Of Salts 211
Sect. 1. Of Alkaline and Earthy Salts 213
Genus 1. Muriates 215
2. Fluates 218
3. Borates 220
CONTENTS. ix
4. Phosphates 221
5. Phosphites 224
6. Carbonates 225
7. Sulphates 228
8. Sulphites 233
9. Nitrates 235
10. Nitrites 239
11 Oxymuriates 239
12. Hyperoxymuriates 239
13. Arseniates 241
14. Arsenites 242
15. Molybdates 242
16. Tungstates 243
17. Chromates 243
18. Columhates 244
Order II. combustible Salts 244
Genus 1. Acetates 244
2. Benzoates 245
3. Succinates 246
4. Moroxylales 245
5. Camphorates 247
6. Oxalates 248
7. Mellates 250
8. Tartrates 250
9. Citrates 253
10. Kinatcs 254
11. Saccolatcs 254
12. Sebates 254
13. Urates 254
14. Mutates 255
15. Formiates 255
16. Subcrates 255
17. Gallates 255
18. Prussiares 256
Sect. 2. Of Metalline Salts 256
Genus 1. Salts of Gold 257
2. Salts of Platinum 258
X. Contents.
Genus 3. Salts of Silver 259
4. Salts of Mercury 262
5. Salts of Palladium 266
6. Salts of Rhodium 266
7. Salts of Iridium 266
8. Salts of Osmium 267
9. Salts of Copper 267
10. Salts of Iron 270
11. Salts of Tin 274
12. Salts of Lead 276
13. Salts of Nickel 280
14. Salts of Zinc 281
15. Salts of Bismuth 283
16. Salts of Antimony 285
17. Salts of Tellurium 286
18. Salts of Arsenic 287
19. Salts of Cobalt 288
20. Salts of Manganese 289
21. Salts of Chromium 290
22. Salts of Molifbdenum 290
23. Salts of Uranium 291
24. Salts of Tungsten 292
25. Salts of Titanium 292
26. Salts of Columbium 293
27. Salts of Cerium 293
Chap. IV. Of Hydrosulphurets 295
Chap. V. Of Soaps 299
Sect. 1. Of Alcaline Soaps 299
2. Of Earthy Soaps 301
3. Of Metallic Soaps 301
DIVISION IV. Of VEGETABLE substances 302
CHAP. I. Of Acids 304
II. Of Sugar 306
III. Of Sarcocoll 310
IV. Of Asparagin 311
CONTENTS. xi
Chap. V. Of Gum 312
VI. Of Mucus 316
VII Of Jelly 317
VIII. Of Ulmin 318
IX. Of Inulin 319
X. Of Starch 320
XI. Of Indigo 324
XII. Of Gluten 330
XIII. Of Albumen 334
XIV. Of Finria 335
XV. Of the Bitter Principle 337
XVI. Of Tannin 342
XVII. Of the Extractive Principle 343
XVIII. Of the Narcotic Principle 346
XIX. Of Oils 349
XX. Of Wax 353
XXI. Of Camphor 356
XXII. Of Bird-lime 360
XXIII. Of Resins 363
XXIV. Of Guaiacum 374
XXV. Of Balsams 376
XXVI. Of Caoutchouc 382
XXVII. Of Gum Resins 385
XXVIII. Of Cotton 390
XXIX. Of Suber 391
XXX. Of Wood 392
XXXI. Of Alkalies 393
XXXII. Of Earths 394
XXXIII. Of Metals 395
DIVISION V. Of animal sudstances 396
Chap. I. Of Animal Substances 397
Sect. 1. Of Gelatine 397
2. Of Albumen 400
3. Of Mucus 405
4. Of fibrin 407
5. Of Urea 409
xii. CONTENTS.
6. Of Saccharine Matter 413
7. Of Oils 415
8. Of Resins 417
9. Of Acids 419
10. Of Earths and Metals 422
Chap. II. Parts of Animals 423
Sect. 1. Of Bones, Shells and Crusts 425
2. Of Horns, Nails and Scales 430
3. Of Muscles of Animals 432
4. Of the Skin 434
5. Of Membranes, Tendons, Ligaments
and Glands 437
6. Of the Brain and Nerves 438
7. Of Marrow 440
8. Of Hair and Feathers 442
9. Of Blood 445
10. Of Milk 448
11. Of Saliva 453
11. Of Bile 454
13. Of the Cerumen of the Ear 458
14. Of Tears and Mucus 459
15. Of the Liquor of the Fericardiumm 460
16. Of the Humours of the Eye 461
17. Of Sinovia 462
18. Of Semen 464
19. Of Animal Poisons 466
20. Of Sweat 468
21. Of Urine 471
26. Of Morbid Concretions 475
BOOK III.
OF AFFINITY 478
CHAP. I. Of Cases 480
II Of Liquids 488
III. Of Solids 490
Table of Chemical Decompositions 494
THE
ELEMENTS
OF
CHEMISTRY.
The object of Chemistry is to ascertain the ingredients of
which bodies are composed, to examine the compounds
formed by the combination of these ingredients, and to in-
vestigate the nature of the power which occasions diese com-
binations. It may be divided into three parts: 1. A descrip-
tion of the component parts of bodies, or of simple substan-
ces. 2. A description of compound bodies. 3. An account
of the power which occasions combinations. This power is
called affinity. These three particulars form the subject of
the three following books.
BOOK I
OF SIMPLE SUBSTANCES.
We are probably ignorant at present of bodies, strictly
speaking, elementary or simple. All that is understood in
2 CONFlNABLE BODlES. CHAP. I.
Chemistry by a simple substance, is a substance not yet de-
composed, and which we cannot shew to be a compound.
Those of that kind at present known are about 48. They
may be divided into two classes; those which can be con-
fined in vessels, and of course exhibited in a separate state;
and those which cannot be confined in any vessel that we
possess, and the existence of which is only inferred from
certain phenomena exhibited by the first class of bodies in
certain circumstances. The first class of bodies may be
called confinable, the second unconfinable.
DIVISION I
OF CONFINABLE BODIES.
The confinable bodies may be arranged under the four fol-
lowing heads:
1. Simple supporters of combustion-
2. Simple combustibles.
3. Simple incombustibles.
4. Metals.
These classes shall be treated of an order in the four follow-
ing chapters.
Chap. I.
OF SIMPLE SUPPORTERS OF COMBUSTION.
The term, Supporter of Combustion, is applied to those
substances which must be present before combustible sub-
stances will burn. Thus air is a supporter of combustion,
because a candle will not burn unless it be supplied with air.
SECT. I. OXYGEN.
All supporters, not yet decompounded, are called simple.
We know only one such body, namely oxygen.
SECT. I. of Oxygen.
This substance is an air, or, as chemists use to call aerial
bodiesy a gas.. It was discovered by Dr Priestley. It may
be obtained by heating black oxide of manganese in an iron
bottle fitted with a long iron tube. The extremity of the
tube is plunged into a trough of water having a shelf a little
below the surface, on which stands an inverted glass cylinder
full of water. The open mouth of this cylinder is brought
over the extremity of the iron tube. As soon as the man-
ganese is red hot, air issues from the extremity of the tube,
and gradually fills the glass vessel, displacing the water. In
this way any quantity of oxygen gas may be procured. Red
lead or red precipitate may be substituted for the manganese,
but they do not yield so much oxygen. The salt called hy-
peroxymuriate of potash may also be used, and it yields a
very great proportion of oxygen. Oxygen gas may also be
obtained by putting the manganese in powder into a glass re-
tort and pouring on it as much sulphuric acid as will make it
into a thin paste. The heat of a lamp benng applied to the
retort while its beak is plunged into the water trough, the gas
is disenged in considerable quantity.
Oxygen gas possesses the mechanical properties of com-
mon air. It is colourless, invisinle and capable of indefinite
expansion and compression.
combustibles burn in it better and brighter than in com-
mon air. Animals can breathe it longer than common air
without suffocation.
. The term gas is applied by chemists to all airs except common air.
4 SIMPLE COMBUSTinLBS. CHAP. II.
It has been ascertained, that one-fifth of the air of the at-
mosphere is oxygen gas, and that when this portion is ab-
stracted, the air can neither support combustion nor animal
life.
When substances are burnt in oxygen gas or air, or
when animals breathe them, a portion of the oxygen always
disappears, and, in some cases, even the whole of it.
Its specific gravity, according to Kirwan, is 1.103, ac-
cording to Davy 1.127, according to Fourcroy, Vauquelin
and Seguin 1.087, that of air being 1.000. At the tem-
perature of 60˚ and when the barometer stands at 30 inches,
100 cubic inches of common air weigh very nearly 31 grains
troy. 100 cubic inches of oxygen in the same temperature
and pressure, weigh, according to these results, 34 grains,
34.74 grains and 33.69 grains troy.
It is not sensinly absorbed by water. 100 cubic inches of
water freed from air by boiling, absorb 3.55 inches of this
gas.
Oxygen is capable of combining with a great number of
bodies, or it has an affinity for them, and forms compounds
with them.
Chap. lI.
OF SIMPLE combustibleS.
By combustible is understood a substance capable of burn-
ing; and by simple combustibles, bodies of that name not
yet decomposed. They are five in number, namely hydro-
gen, carbon, phosphorus, sulphur and boracium. It is not
improbable that the bases of all or most of these substances
are metals; but the opinion has not yet been made out in a
satisfactoiy manner.
Sect. I. Of Hydrogen 5
Hydrogen, like oxygen, is a gas. It was first callEd iN-
Flammable air<7i>, and Mr CaveNDISH must be considered as its
real discoverer.
It may be procured by putting some clean iron filings into
A glass retort, and pouring over them sulphuric acid diluted
with thrice its bulk of water. A violent boiling takes place,
or, as chemists term it, an effervescence, gas issues abundantly
from the beak of the retort, and may be received like the
oxygen in glass vessels standing in a trough of water.
It is invisinle and colourless, and possesses the mechanical
properties of common air.
When prepared by the above process, it has a peculiar
smell, ascrined at present to the presence of a little oil, form-
ed by the action of the acid on the iron filings.
It is the lightest gaseous body known. Its specific gra-
vity, according to Kirwan is 0.0843, according to Lavoisier,
0.0756, according to Fourcroy, Vauquelin and Seguni 0.0887.
According to these variouis estimates, 100 cubic inches un-
der the mean pressure and temperature weigh 2.613 grains,
2.372 grains and 2.75 grains Troy. It is about 12 times
lighter than than ommon air.
No combustible substance will burn in it; and no animal
can breathe it for any length of time without death.
It burns when touched with a red hot iron, or when
brought near a flaming taper. The colour of the flame is yel-
lowish, and it gives but little light. If it be previously
mixed with half its bulk of oxygen gas, it burns instantane-
ously, and with a loud explosion like the report of a pistol.
If the mixture be put into a strong glass cylinder, standing
over water, and kindled by an electric spark, the whole of the
two gases disappear, and the cylinder is filled with the wa-
A3
6 SIMPLE combustibleS CHAP. II
ter. If the vessel be standing over mercury, or be hermeti-
cally sealed, its inner surface becomes coated with pure wa-
ter. This water was found by Cavendish equal in weight to
the two gasses. Hence it has been inferred, that water is a
compound of oxygen and hydrogen in the proportions of 85 2/3
by weight of oxygen to 14 1/3 of hydrogen.
Hydrogen is not sensinly altered or absorbed by water.
100 cubic inches of water deprived of air absoin 1.53 inches
of hydrogen.
Sect. n. Of Carbon and Diamond.
If a piece of wood be heated to redness in an iron bottle,
or a crucinle filled with sand, it is converted into a black
brittle substance called charcoal, the properties of which are
nearly the same from what wood soever it has been obtained,
provided it has been exposed to a sufficiently strong heat.
Charcoal is insoluble in water, and not affected (provided
air be excluded) by the most violent heat that can be ap-
plied.
It conducts electricity, is not liable to putrify, deprives
meat of its putrid taste and smell, and is an excellent tooth
powder.
It absorbs moisture with avidity, and likewise common air,
oxygen and hydrogen gas; but less of the last than of the
two former.
When heated to 802˚ it takes fire, and, if pure, burns all
away without leaving any residuum. If the experiment be
made in a glass vessel filled with oxygen gas, and the char-
coal be heated by means of a burning glass, the bulk of the
oxygen gas is not altered, but a portion of it is converted in-
to another gaa possessing quite different properties. It ren-
ders lime water milky, and is quite absorbed by it, and can-
not be breathed without occasioning instant death. This
gas is called carbonic acid. It very nearly equals in weight
the charcoal and the oxygen which have disappeared. Hence
it is considered as a compound of them, and from the pro-
portion of each employed, it is considered as composed of
very nearly 28 parts of charcoal and 72 of oxygen.
When considerable quantities of charcoal are burnt in this
manner, a portion of water also appears. Hence it is con-
ceived, that charcoal contains a small portion of hydrogen.
The constituent which constitutes by far the greatest part of
it is called carbon. This supposition is corroborated by the
late experiments of Mr Davy. Carbon exists in two other
states, namely the diamond and plumbago.
2. The diamond is a precious stone, transparent, and of-
ten crystallized in a six sided prism, terminated by six sided
pyramids. It is the hardest of all bodies. Its specific gra-
vity is about 2.3. It is a non-conductor of electricity.
When heated to the temperature of 14˚ of Wedgewood's
byrmomter, or not so high as the melting point of silver, it
gradually wastes away and burnes. It combines with nearly
the same quantity of oxygen, and forms the same proportion
of carbonic acid as charcoal. Hence it consists chiefly of
carbon. From the experiments of Davy, there is reason to
believe that it contains a minute portion of oxygen as one of
its constituents. The other constituent is carbon.
3. Plumbago, called also black lead and graphite, is well
known as the substance of which pencils are made. It is dug
out of the earth. It is of a dark blue colour, and has some
metallic lustre. It is soft, brittle and infusinle. When
heated to redness, it gradually wastes away, and is converted
into carbonic acid, leaving a little iron behind. It seems a
compound of pure carbon, with about one 2Oth part of its
weight of iron*
Carbon combines with hydrogen, and forms a gas for-
merly called heavy inflammable air, now carbureted hydro-
. From the recent experlments of Thenard and Gay-Lussac, there is reason
to belive that it contains a little hydrogen.
8 SIMPLE COMBUSTBLES. CHAP. II
gen. Various gases were formerly called heavy inflamable
air. The three following are the chief.
l. Carburated hydrogen. It rises spontaneously in hot
weather from stagnant water. It is evolved probably during
the distillation of acetate of potash. It is invisinle and pos- '
seses the mechanical properties of common air. Its specific
gravity is 0.67774. One hundred cubic inches weigh 21
grains. For complete combustion it requires twice its weight
of oxygen, The products are carbonic acid and water,
Hence its constituents are carbon and hydrogen. The fol-
lowing are nearly the the proportions
28 1/2 hydrogen
7l 1/2 oxygen
______
100
The gas obtained from pit coal by distillation consists chiefly
of this gas.
2. When 4 parts of sulphuric acid and one part of alcohol
are heated in a retort a gas comes over called olefiant gas or
super carbureted hydrogen. It is invisinle, has a disagreeable
smell, its specific gravity is 0.905. It burns with a dense
white flame, and great splendor, and requires thrice its bulk
of oxygen for complete combustion. The products are wa-
ter and carbonic acid. Hence it has been concluded that
this gas is composed of
83 carbon
17 hydrogen
___
100
When mixed with oxymuriatic acid gas the bulk diminishes
and an opal coloured oil is produced. Hence the name ole-
fiant gas given it by the Dutch chemists. Five measures of
olefiant gas and 6 of oxymuriatic acid gas when mixed lose
their gaseous form entirely and this oil appears.
SECT. III. PHOSPHORUS. 9
3. Carbonic oxide. When a mixture of equal parts iron
filings and dry chalk is heated to redness in an iron retort a
gas comes over partly carbonic acid and partly carbonic ox-
ide. The former is washed away by means of lime water.
Carbonic oxide gas is invisinle, its specific gravity is 0.956.
It burns with a deep blue flame and gives out but little light.
For complete combustion 100 measures of it require 40 of
oxygen gas. The product is 92 measures of carbonic acid.
As the carbonic acid produced is almost equal to the weight
of the carbonic oxide and oxygen consumed, it is presumed
that there is no other product. Hence carbonic oxidw is
considered as a compound of carbon and oxygen in the fol-
lowing proportions;
39 carbon
61 oxygen
___
100
Sect. III. Of Phosphorus.
Phosphorus may be obtained by pouring acetate of lead
into urine, mixing the white powder which precipitates with
charcoal, and distilling it in an earthen retort by means of a
violent heat. The beak of the retort ought to be plunged
under water. The phosphorus drops into the water like
melted wax. It is usually obtained from burnt bones.
It was discovered in 1669, by Brandt, a Chemist of Ham-
burgh. Afterwards by Kunkel, and last of all by Boyle,
who taught his operator, Godfrey Hankwitz, to make it, and
he for several years was the only person that could make it.
Phosphorus when pure is semitransparent and yellowish,
but when kept in water it becomes white and opake, and has
some resemblance to white wax. It is soft and may be ea-
10 SIMPLE COMBU8T1BLES. CHAP. II
sily cut with a knife. It is insoluble in water. Its specific
gravity is 1.770.
It melts at the temperature of 99˚. It canniot easily be
melted in the open air without taking fire. If air be ex-
cluded it evaporates at 219˚, and boils at 554˚.
When exposed to the air it emits a white smoke with the
smell of garlic and is luminous in the dark. This smoke is
more abundant the higher the temperature, and is occasioned
by the gradual combustion of the phosphorus. In oxygen
gas it is not luminous unless the temperature be as high as
80˚. Hence we learn that it burns at a lower temperature
in common air than in oxygen gas. This slow combustion
in the open air renders it necessary to keep phosphorus in
phials filled with water and well corked.
When heated to 148˚ it takes fire and burns with a vivid
white flame and emitting a vast quantity of smoke. It leaves
(if pure) no residuum, but the white smoke when collected
is an acid, and is called phosphoric acid. If the combustion
be conducted in a jar filled with oxygen gas, the oxygen will
be found to diminish so much, that every 100 parts of pos-
phorus occasion the disappearing of 114 parts of oxygen.
The acid formed weighs as much as the phosphorus and the
oxygen which have disappeared. Hence it is considered as a
compound of these two in the proportion of 100 parts of
phosphorus to 114 of oxygen.
Phosphorus is supposed capable of combining with a
small portion of oxygen and of forming a compound called
oxide of phosphorus. It may be formed by putting a bit of
phosphorus in a long glass tube and exposing it to the heat
of boiling water. It sublimes and lines the tube in fine white
flakes. The substance is very combustible and often takes
fire of its own accord when exposed to the air.
When melted by means of a burning glass in hydrogen gas,
a portion of it is dissolved, and a new gas formed, first disco-
SECT.IV. SULPHUR. 11
vered by Gemgembre, and called phosphurated hydrogen gas.
It has a fetid odour like the smell of putrid fish. It burns
spontaneously when it comes into contact with common air
or oxygen gas. Water dissolves a small portion of this gas
and acquires a bitter taste and unpleasant odour. The phos-
phorus gradually precipitates, and the hydrogen at the same
time separates from the water. When kept in a glass jar it
soon loses its property of burning spontaneously.
Phosphorus combines with charcoal and forms a com-
pound of an orange red colour called phosphuret of carbon.
Common phosphorus contains a portion of this compound
which remains behind when the phosphorus is burnt. It is a
light flocky powder without taste or smell. When heated
sufficiently it burns, and the charcoal remains behind.
Te compounds which phosphorus forms with other bo-
dies are distinguished by the name of phosphurets.
Phosphorus is very poisonous when used internally. It
has been recommended as a medicine, and said to be very
efficacious in restoring the force of young persons exhausted
by sensual indulgence.
From the experiments of Davy, it is very probable that
common phosphorus contains hydrogen. Pure phosphorus
diprived of its hydrogen would probably be metallic.
Sect. IV. Of Sulphur.
Sulphur, distinguished also by the name of brimstone, has
been known since the earliest ages.
It is a hard brittle substance of a greenish yellow colour,
without any smell and with very little taste. It is a noncon-
ductor of electricity and becomes electric negatively by fric-
tion. Its specific gravity is 1.990. It is not altered by ex-
posure to the air, nor is it soluble in water.
12 SIMPLE combustibleS. CHAP. II
When heated to 170˚ it rises up in the form of a fine pow[??]
red which may be easily collected and is called flowers of
sulphur. It is then said to be volatilized or sublimed. It is
obvious from this property that sulphur is a volatile sub-
stance.
When heated to about 218˚ it melts, becomes transparent
and looks like a brown coloured oil. At 560˚ it boils, and
the vapour kindles as it exhales and burns with a blue flame
and an extremely disagreeable smell. If it be set on fire
and plunged into a jar filled with oxygen gas, it burns with a
strong violet flame. In both cases (provided the quantity of
air or oxygen be sufficient, it burns away completely with-
out leaving any residue. But if the fumes be collected, they
are found to be an acid which is known by the name of sul-
phuric acid. A portion of the oxygen disappeares, and from
the experiments of Lavoisier, it follows that the sulphuric
acid formed is exactly equal in weight to the sulphur and
the oxygen which have disappeared during the combustion.
Hence it is concluded, that this acid is composed of these
two substances united together.
Many experiments have been made to ascertain the com-
position of sulphuric acid exactly. The following is the re-
sult which appears to me most accurate. It was obtained
by Klaproth.
100 sulphur.
136.5 oxygen.
_____
236.5
But sulphuf does not always combine with so great a portion
of oxygen. It usually burns with a blue flame, and the suf-
focating vapours which it emits may be collected in glass cy-
linders filled with mercury, and standrng in a trough con-
taining mercury. They constitute a gas called sulphurous
SECT. IV. SULPHUR. 13
acid. They contain less oxygen than sulphuric acid. By
my experiments they are compounded of
100 sulphur.
88.6 oxygen.
____
188.6
When sulphur is kept melted in an open crucinle, it
becomes gradually thick and viscid. If it be now poured
into water, it assumes a purple colour, and remains for
some days soft. But it gradually becomes brittle, and
of a light violet colour. Its texture is finrous, and its speci-
fic gravity 2.325. In this state it is called oxide of sulphur,
from an opinion that it has combined with a little oxygen,
and that this addition has altered its properties. From a set
of experiments made by me on this substance, it follows that
it is composed of 100 sulphur and 7 oxygen.
When sulphur is dissolved in any liquid, as in a solution of
potash, and then precipitated by an acid, it is always in a
state of a white powder, known by the name of lac sulphuris.
This powder consists of sulphur combined with a little wa-
ter. When the water is driven off by heat, the white co-
lour of the sulphur disappears, and its natural yellow colour
returns.
Sulphur combines readyly with hydrogen gas, and forms a
gas known by the name of sulphureted hydrogen, which was
first descrined by Scheele.
It may be formed by mixing together potash and sulphur,
and boiling them together in a glass flask. When sulphuric
acid is poured into the yellowish coloured liquid that is
formed, an effervescence takes place, and the gas may be col-
lected in proper vessels.
Sulphureted hydrogen gas is colourless, and possesses the
mechanical properties of common air. It has a strong fe-
tid smell, like that of rotten eggs. It neither supports com-
14 SIMPLE combustibleS CHAP. II
bustion, nor animal life. Its specific gravity, according
Kirwan, is 1.106, according to Thenard, 1.231. Water ab-
sorbs about its own weight of this gas, and acqiures a fetid
smell, a sweetish nauseous taste, and many of the properties
peculiar to acids.
When this gas is set on fire, it burns with a reddish blue
colour, and deposits a quantity of sulphur. When the elec-
tric spark is passed through it, sulphur is deposited, but the
bulk of the gas is not altered. Sulphur is also deposits
when nitric acid is dropt into water impregnated with [?]
When mixed with oxygen gas, and burnt, the only substances
formed are sulphuric acid and water. Hence it is obvi-
ous that its constituents are sulphur and hydrogen. From
an experiment of Thenard, not indeed susceptible of much
accuracy, it seems to be composed of
100 hydrogen.
118 sulphur.
___
218
Sulphur acts upon charcoal at a red heat. If a quantity of
charcoal be put into a porcelain tube, and heated to redness
by passing it through a furnace, and sulphur be made to pass
through it while in that state without any communication
with the external air, a substance issues from the extremity
of the tube, which may be obtained by means of a crooked
glass tube luted to the porcelain tube, and plunged to the
bottom of a glass vessel filled with water. This substance is
a liquid colourless and transparent when pure, but often tin-
ged greenish yellow. Its taste is cooling and pungent, and
its odour strong and peculiar. It does not dissolve in water.
Its specific gravity is 1.3. In an exhausted receiver, or at
the top of a barometrical tube, it assumes the gaseous form.
It burns very easily, and detonates when mixed with oxygen
gas and kindled. It was first discovered by Lampadius and
SECT. V BORACIUM. 15
Clement and Desormes; and Berthollet junior investigated its
properties. It is composed of sulphur and hydrogen, but
contains more sulphur than sulphureted hydrogen. It may
therefore be called supersulphureted hydrogen.
Sulphur and phosphorus readily combine and in various
proportions, but the compound seems to be most intimate
when the weights of the two ingredients are equal. The
combinations may be made by mixing the two ingredients in
a small phial and melting them together, or by cautiously
heating them in a flask filled with water. But the first me-
thod is less hazardous; for the compound acts upon the wa-
ter and gases are formed which sometimes occasion violent
explosions. The compound has a yellowish green colour;
it may be distilled over in a glass retort without decomposi-
tion. It has a tendency to the liquid form, which is greatest
when equal proportions of the constituents are used. It then
remains liquid in the temperature of 41˚. When the sulphur
predominates in this compound, it may be called phosphuret
of sulphur; when the phosphorus, sulphuret of phosphorus.
It is very combustible and often takes fire spontaneously
when exposed to the air.
From the experiments of Clayfield and Berlhollet junior,
there is reason to conclude that sulphur contains a small
quantity of hydrogen, and Mr Davy has shewn that oxygen
is also present in it. Hence it follows that the simple sub-
stance sulphur, which constitutes the base of sulphuric acid,
has never yet been seen in a pure state.
Sect. V. Of Boracium.
This substance was discovered by Mr Davy, but it was
first descrined by Thenard and Gay-Lussac. Mr Davy has
just published a more detailed account of its properties.
To procure it equal weights of the metal called potassium
3
16 SlMPLE combustibleS. CHAP. II
and dry boracic acid to be put into a copper tube and ex-
posed for some minutes to a slight red heat. When cold, the
mass is to be washed out with water, the potash saturated
with muriatic acid, and the whole thrown upon a filter. An
olive coloured matter remains which must be washed and
dried. It is boracium.-
Boracium is of a dark olive colour, opake, brittle, [?]
powder does not scratch glass, it is a non-oonductor of elec-
tricity, and has some resemblance to charcoal. When heated
to whiteness in a metallic vessel, it remains unaltered, pro-
vided common air or oxygen be excluded. After this proc[?]
it sinks in strong sulphuric acid; but in its ordinary state it
swims upon that liquid.
When heated in common air or oxygen gas to a tempera-
ture not quite so high as 600˚, it takes fire and burns with
considerable brilliancy, somewhat like charcoal, and is con-
verted into boracic acid. By this process a portion of the
oxygen disappears. Hence boracic acid is considered as a
compound of boracium and oxygen. The exact proportion
of the constituents of this acid have not yet been ascertained
According to Mr Davy's expenments, it is composed of one
part boracium and two parts oxygen; while Thenard and
Gay-Lussac consider it as a compound of two parts bora-
cium and one of oxygen.
When placed in contact with oxymuriatic acid gas, it burns
spontaneously with a white light, and is partly converted into
boracic acid, partly into a black matter which is considered
as an oxide of boracium. It burns when slightly heated,
and is converted into boracic acid. It decomposes sulphuric
and nitric acids with the assistance of heat, and is converted
into boracic acid. When melted with sulphur and kept
long in contact with it, a kind of combination takes place as
. The French chemists have called it bors[?].
SECT. V. BORACIUM 17
the sulphur acquires an olive colour. It does not combine
with phosphorus. Whether it combines with hydrogen and
with charcoal has not been tried.
Potash and soda dissolve it both when liquid and when
melted with it in a crucinle, forming pale olive compounds
which give dark-coloured precipitates when treated with mu-
riatic acid. It did not combine with mercury by heat.
Mr Davy has rendered it probable that it contains a little
oxygen, and that, when deprived of this principle, it combines
with metals and forms compounds capable of conducting
electricity. Hence he is inclined to believe, that if it could
be obtained pure, it would be of a metallic nature: a sup-
position by no means improbable, not only with respect to
boracium but almost all the simple combustibles.
SUCH are the properties of the simple combustible bodies;
none of which, unless hydrogen be an exception, are, strictly
speaking, simple substances, though we are not in possessin
of any accurate method of separating their constituents and
exhibiting them in a separate state. It is even possinle,
though not very likely, that the hydrogen and oxygen sepa-
rated from several of them, may be owing to the presence of
water in them, from which it is very difficult to separate them
completely.
Two of them, boracium and carbon, are solids which we
are incapable of melting or altering by heat; two of them,
sulphur and phosphorus, easily melt, and may be exhibited
in a solid, liquid, or even gaseous state; while one of them,
hydrogen, is always, when pure, in the state of a gas.
They all combine with oxygen, but in different propor-
tions, as is obvious from the following table, exhibiting the
quantity of oxygen capable of combining with 100 parts of
each.
18 SIMPLE combustibleS. CHAP. II.
100 Hydrogen unites with 600 oxygen.
100 Carbon _ _ 257
100 Boracium _ _ 200
100 Sulphur _ _ 138.7
100 Phoshorus_ _ 114
It has been supposed by some that the affinity of different
bodies for oxygen, is proportioned to the quantity of it with
which they combine. According to this notion, the affinity
of the simple combustibles for oxygen, is in the order of the
prededing table.
Hydrogen unites to oxygen as far as is known only in one
proportion, boracium and carbon in two, phosphorus and
sulphur in three.
Hydrogen unites with all the simple combustibles, unless
boracium be an exception. It is probable that they are all
capable of combining with each other at least in one propor-
tion, and some are known to combine in several. Chemists
have agreed to give such compounds a name derived from
one of the ingredients and ending in uret, as sulfuret of
phosphorus, phosphuret of carbon. When the compound is
gaseous, the term is converted into an adjective, as sulphu-
reted hydrogen gas, carbureted hydrogen gas.
CHAP. III.
OF SIMPLE INcombustibleS.
By ample incombustibles are meant all substances incapable
of combustion which have not yet been decompoaed. We
are acquainted with only two such bodies at present, namely
azote and muriatic acid. There can be litde doubt that both
SECT. I. AZOTE. 19
are compounds, though hitherto all attempts to analyse them
have failed.
SECT. I. Of Azote.
1. AZOTE, called also nitrogen, which was first particu-
larly pointed out by Dr Rutherford in 1772, constitutes four-
fifths of the atmosphere. The other fifth is oxygen. To
obtain it pure, we have only to deprive any portion of air of
the whole of its oxygen. This is easily done by confining
in it for some time a mixture of sulphur and iron filings made
up into a paste, or a quantity of pnosphorus.
Azotic gas is invisinle, and possesses the mechanical pro-
perties of common air. Its specific gravity, according to
Kirwan, is 0.985; according to Lavoisier 0.978; according
to Biot and Arago 0.969; that of common air being 1.000.
It neither supports flame nor animal life. Water does not
sensinly absorb it. 100 cubic inches of water, freed from
air by boiling, absorb about 1 1/2 inches of this gas.
2. Though incombustible it is capable of combining with
oxygen gas. When electric sparks are passed through a mix-
ture of oxygen and azotic gases for some time, the bulk of
the mixture diminishes, and an acid is formed. If the gases
be mixed in the proper proportions they disappear entirely,
and are of course totally converted into an acid. This acid
is the nitric. Hence it follows that nitric acid is composed
of oxygen and azote. This important discovery was made
by Mr Cavendish. The result of his experiments gives us
nitric acid composed very nearly of
30 azote,
70 oxygen.
___
100
or one part azote united to of 2 1/2 of oxygen.
B 2
20 SIMPLE INcombustibleS. CHAP. III
Nitric acid is a yellow corrosive liquid of great importance
in industry. It acts with great energy on most other bo-
dies, in consequence of the facility with which it parts with
its oygen. If copper or silver, for example, be put into it,
the metals absorb oxygen and dissolve. The portion of
acid which loses a part of its oxygen, assumes the gaseous
form, and makes its escape out of the liquid occasioning an
effervescence. The gas which escapes is a compound of
azote and a smaller proportion of oxygen than exists in nitric
acid. It is usually called nitrous gas. It has the curious
property of combining with oxygen gas whenever it comes
in contact with it, and of thus being again converted into ni-
tric acid. The mixture becomes yellow, and, if standing
over water, its bulk diminishes very much, because the water
absorbs the acid as it forms.
If iron filings be kept for some days in a jar of nitrous
gas its bulk diminishes, and it loses the property of becoming
yellow when mixed with common air. Its properties are
now changed and it is called gazeous oxide of azote. This
new gas is composed of the same constituents as the former,
but it contains a smaller proportion of oxygen. It supports
combustion and bodies burn in it almost with as much splen-
dour as in oxygen gas.
Thus it appears that azote has the property of combining
with three different doses of oxygen.
3. The combinations of azote with the simple substances
are not numerous, but some of them are important.
When putrid urine, wool, and many other animal sub-
stances are distilled, among other products there is obtained
a substance of a pungent odour and taste, known by the
names of hartshorn, volatile alkali, ammonia . It may be
obtained pure by heating a mixture of three parts of
quicklime and one part of the salt called sal ammoniac in a
glass flask and receiving the product over merciuy. It is a
Sect. II MURIATIC ACID. 21
gas. When electric sparks are passed through it, its bulk is
doubled, and it is converted into a mixture of azotic and hy-
drogen gases. Hence it was considered as a compound of
these two substances; but the late experiments of Davy
have rendered it very probable that it likewise contains oxy-
gen.
Azotic gas is said to have the property of dissolving a little
charcoal, which it again deposites when allowed to stand
over water.
It dissolves likewise a little phoshorus and increases about
1-40th part in bulk. When this phosphureted azotic gas is
mixed with oxygen gas it becomes luminons, in consequence
of the combustion of the dissidved phosphorus.
Azotic gas is said likewise to dissolve a little sulphur
when assisted by heat. Sulphureted azotic gas is said to re-
semble sulphureted hydrogen gas in its properties.
There is reason to believe, from the late experiments of
Davy, that oxygen is one of the constituents of azote. But
the nature of the other constituent is unknown. Some have
supposed that it is hydrogen, and that azote differs from wa-
ter merely in containing less oxygen. But this opinion has
not been confirmed by any satisfactory experiment. Dr
Priestley called this gas phlogisticated air, and considered it
as a compound of oxygen and the supposed universal inflam-
mable principle to which the name phlogiston was given.
Sect. II. Of Muriatic Acid.
Muriatic acid, the second of the simple incombustibles, is
a gas, and may be obtained by putting some common salt in
a small glass retort, pouring over it sulphuric acid and re-
ceiving the product over mercury.
1. Muriatic acid gas is invisinle, and possesses the mecha-
nical properties of common air. Its specific gravity, accord-
B 3
22 SIMPLE INcombustibleS. CHAP. III
ing to Kirvan, is 1.929, that of air being 1.000. Its smell
is pungent and peculiar, and when mixed with air it forms a
visinle smoke, owing to its great avidity for moisture.
It does not support combustion, nor can it be breathed by
animals. When a lighted taper is plunged into it, it goes
out with a green coloured flame.
If a little water tinged blue by red cabbage, mallows, or
litmus be let up into it, the blue colour is immediately
changed into red. This change of colour from blue to red,
is considered by chemists as characteristic of acids.
Water when brought into contact with this gas absorbs it
with great rapidity and the whole disappears. Water ab-
sorbs 515 times its bulk of the gas, and six cubic inches of
water by this absorption are converted into nine. The affinity
between this gas and water are very great. It always contains
a great portion of water in the state of vapour, probably
more than one-third of its weight, and all attempts to sepa-
rate this water have failed. Water seems to be essential to
the gaseous state of this acid.
Water saturated with this gas is known by the name of li-
quid muriatic acid. It has been long known and is very
much employed by chemists. When pure it is transparent
and colourless: but it very often has a greenish yellow co-
lour, owing to the presence of iron or of some other impuri-
ty. It has the smell of muriatic acid gas, and smokes when
exposed to the air. Its specific gravity is never greater than
1.203 and seldom exceeds 1.196; and when strongest never
contains more than one-fourth of its weight of acid; the rest
is water.
2. Muriatic acid combines with oxygen and fonns with it
two compounds of considerable importance, called oxymuri-
atic acid and hyper-oxymuriatic acid.
When liquid muriatic acid is poured upon the black oxide
of manganese in effervescence takes place, and by the assist-
Sect. II MURIATIC ACID. 23
ance of heat a gas is extricated of a green colour. It was
discovered by Scheele, and is called oxymuriatie acid gas.
It has an extremely offensive and noxious odour, and cannot
be breathed without the most fatal effects. It supports
combustion; and indeed many substances, as phosphorus, take fire
spontaneosly when plunged into it. It destroys vegetable
colours, and is, on that account, useful in bleaching, from
the analysis of Chevenix it appears to be composed of
77.5 muriatic acid,
22.5 oxygen.
___
100
When a current of oxymuriatic acid is passed through
water, holding potash in solution, a number of small shining
crystals is gradually deposited. They constitute the salt
called hyper-oxymuriate of potash, which possesses many
curious properties. This salt is composed of potash and hy-
per-oxymuriatic acid, an acid which contains much more
oxygen than the oxymuriatic. It has not yet been obtained
sqiarat,y. According to the analysis of Chevenix, it is
composed of
34 muriatic acid,
66 Oxygen
___
100
3. The action of muriatic acid on the simple combustibles
has not, hitherto, been examined with much attention.
Hydrogen is not acted on by it. Charcoal absorbs it ra-
pidly; but the change produced by the absorption has not
been examined. Phosphorus does not sensinly absorb it.
Sulphur imbines it very slowly. When a current of oxy-
muriatic gas is made to pass over flowers of sulphur, the sul-
phur is gradually converted into a very volatile red coloured
liquid, to which I give the name of sulfureted muriatic
n 4
24 METALS. CHAP. IV.
acid. Its specific gravity is 1.625 [?]. It smokes very strongly,
has a strong smell, and is very volatile. It dissolves phos-
phorous readily. When mixed with water, it is decomposed,
and a quantity of sulpur separates. It consists of muriatic
acid, sulphur and oxygen, and I think it not improbable that
the oxygen is combined with the sulphur constituting an oxide.
We are not aquainted with any action which muriatic acid
has on azote. When mixed with nitric acid, it constitutes
the compound acid called aqua regia or nitro-muriatic acid.
Boracium tinges mnriatic acid greem. but does not act vio-
lently on it.
Such are the properties of the simple incombustibles.
Like the combustiles they combine with oxygen. But they
unite without combustion, and the compounds which they
form are supporters. Azote unites with 3 doses of oxygen,
while muriatic acid combines with two.
We know little of the action between the simple combus-
tinles and incombustibles.
Chap. IV.
OF METALS.
Metals, one of the most important classes of bodies, and to
which we are indebted for most of our improvements, are
very numerous. Indeed the present state of Chemical ana-
lysis leads to the opinion that all bodies will ultimately divide
themselves into two sets; namely, metals and oxygen.
1. Metals are distinguished by a peculiar lustre, well
known by the name of the metallic lustre. They are per-
fectly opake or impervious to light, even in the thinnest plates
to which they can be reduced. The only exception is gold
leaf. Its thickness does not exceed 1/210000th part of an
CHAP, IV. METALS. 25
inch, and it allows the light to pass through it. If other
metals could be reduced as thin, it is probable that they also
would be pervious to light. They may all be melted when
heated Sufficiently. Some, as mercury, require very little
heat to melt them while others, as platinum, require a great
deal. Their specific gravity is exceedingly various. All the
old metals are at least 5 times heavier than water, and some,
as platinum, more than 20 times heavier. But some of the
new metals discovered by Davy are much lighter than water.
They are the best conductors of electricity of all known bo-
dies. None of them is very hard. But some of them may
be hardened artificially, so as to exceed most other bodies.
Their elasticity may likewise, in some cases, be artificially
increased. Some of them are malleable, or may be extended
by the blows of a hammer, while others are brittle. Some
of them are ductile, or may be drawn out into wire, while
others cannot. They differ considerably from each other in
their tenacity, or the weight which they are capable of
supporting without breaking.
Several of them take fire when heated, and burn with
considerable splendour, and almost all of them may be burnt
by peculiar contrivances. After combustion their appearance
is totally changed. They have lost the metallic lustre, and
are converted into earthy-like powders, formerly called cal-
ces, and now oxides. These oxides are of various colours,
white, red, yellow, blue, &c. according to the metal, and se-
veral of them are employed as paints. Most metals are con-
verted into oxides, merely by exposing them for a sufficient
length of time to the action of heat and air, and all by the
action of acids.
When these oxides are mixed with charcoal powder, and
heated, they lose their earthy-like appearance, and are restored
again to the metallic state. This process is called reduction.
Some metallic oxides, as those of gold and silver, require
26 METALS. CHAP. IV
only to be heated in order to be reduced; but most of them
require also the presence of charcoal or of some other com-
bustinle substance, These oxides were at first considered as
simple substances, and the metals were supposed to be com-
posed of them and the principle of inflammability, called
phlogiston. But it was shewn by the experiments of Lavoi-
sier, that the oxides are compounds, and that they are com-
posed of the metals from which they were obtained, united to
oxygen. Thus oxide of gold is a compound of gold and oxy-'
gen. It was the discovery of this fact that induced chemists
to substitute the word oxide for calx.
Most metals are capable of combining with various doses
of oxygen, and of forming various oxides, which it is of con-
sequence to be able to distinguish. This may be done by
prefixing to the term oxide, the Greek ordinal numeral, ex-
pressing the peculiar oxide. Thus protoxide of tin is the first
oxide of tin, or tin combined with a minimum of oxygen.
Deutoxide of tin is the second oxide of tin, or tin combined
with two doses of oxygen. The terms tritoxide, tetroxide,
pentoxide, &c. are to be understood in the same way. The
last oxide of a metal is called Peroxide. Peroxide, means a
metal combined with as much oxygen as it can take up, or a
metal saturated with oxygen.
3. Metals combine with the simple combustibles, and form
compounds, many of which are of considerable importance.
These compounds are denoted by a word formed from the
simple combustible present, and terminating in uret. Thus
sulphuret of tin is a compound of sulphur and tin. In like
manner, carburet and phosphuret of iron, means iron com-
bined respectively with carbon and with phosphorus. Hy-
drogen gas dissolves some of the metals. These solutions are
denoted by prefixing the metal converted into an adjective
before the word hydrogen. Thus arsenical hydrogen gas,
means a solution of arsenic in hydrogen gas. When hydrogen
CHAP. IV. METALS. 27
combines with a metal and forms a solid comound, it is de-
noted by the term hydroguret.
4. The metals are not known to combine with simple in-
combustibles. But they combine with each other, and form
a set of important compounds, called alloys. Thus brass si
an alloy of copper and zinc; and bell metal an alloy of copper
and tin. When mercury is one of the metala cobbined, the
compound is not called an alloy, but an amalgam. Thus
the amalgam of gold, is gold dissolved in mercury.
5. The metals at present known (excluding the new ones
discovered by Davy, which will be better descrined after-
wards) amount to 27. They may be divided into the 4 fol-
lowing sets.
I MALLEABLE
1. Gold. 8. Osmiwn.
2. Platinum. 9. Copper.
3. Silver. 10. Iron.
4. Mercury. 11. Nickel.
5. Palladium. 12. Tin.
6. Rhodium. 13. Lead.
7. Iridium. 14. Zinc.
II. BRITTLE, AND EASILY FUSED.
1. Bismuth. 3. Tellurium.
2. Autinomy. 4. Arsenic.
III. BRITTLE, AND DIFFICULTLY FUSED.
1. Cobalt. 4. Molybdenum.
2. Manganese. 5. Uranium.
3. Chrominm. 6. Tungsten.
28 METLALS CHAP. IV
IV. REFRACTORY.
1. Titanium. 3. Cerium.
2. Columbium.
The fourth set consists of metals which have not hitherto
been obtained in quantities, except in the state of oxides.
Formerly the brittle metals were called semimetals, and the
malleable, metals. The first four malleable metals were once
considered as noble, because their oxides may be reduced by
mere heat.
Sect. I Of Gold.
Gold seems to have been the first known of all the metals.
As it occurs always in the metallic state and is very soft and
ductile, less skill would be necessary to work it.
1 Gold has a reddish yellow colour, considerable lustre,
and is destitute of taste or smell. It is very soft. Its specific
gravity is 19.376 that of water being 1.000. It is the most
ductile and malleable of all known bodies. It may be beaten
out into leaves only 1/230000th part of an inch in thickness, and
drawn out into wire extremely fine. Its tenacity is con-
siderable, a gold wire 0.078 inch in diameter being capable
of supporting 150.07 lins Avoirdupois without breaking.
It melts at 32˚ Wedgewood, and when melted has a bluish
green colour. It does not sensinly waste nor alter, though
kept very long in the state of fusion. In very violent heats
however it has been perceived to be partially volatilized.
When carefully cooled after fusion it sometimes crystallizes
in four-sided pyramids. Gold is not altered by exposure to
the air, it does not even lose its lustre.
SECT. I. GOLD. 29
2 It combines with oxygen and forms different oxides,
the number and properties of which are but imperfectly
known. Two have been descrined. The firt purple is form-
ed when violent electrical explosions are passed through
gold leaf, or when gold is subjected to combustion. It is
probably a compound of 100 gold and 8 oxygen.
The second or peroxide is of a yellow colour. It may
be obtained by dissolving gold in nitro-muriatic acid and then
precpitating the metal by means of lime water. It falls in
the state of this yellow oxide. When carefully washed and
dried it is insoluble in water and tasteless. I attempted to
analyse it, but did not succeed. From an experiment of
Proust we may infer that it is composed of 100 gold and 32 oxygen.
3. Hitherto gold has been united with only one of the
simple combustibles, namely phosphorus. Hydrogen and
charcoal are said to precipitate it from its solutions in the
metallic state. With sulphur it does not combine. The action
of boracium has not been tried.
The compound of phosphorus and gold is called phosphu-
ret of gold. It may be formed by dropping small pieces of
phosphorus into gold in fusion. It is brittle, whiter than
gold, and contains 1/24th of phosphorus. The phosphorus may
be dissipated by exposing the compound to a sufficient
heat.
4. As far as is known gold does not combine with either
of the simple incombustibles.
5. It combines readily with most of the metals, and forms
a variety of alloys.
Gold is so soft that is is seldom employed quite pure.
It is almost always alloyed with a little copper or silver.
Goldsmiths usually announce the purity of gold in the follow-
ing manner. Pure gold is divided into 24 parts called ca-
rats. Gold of 24 carats means pure gold. Gold of 23
30 METALS CHAP. IV,
carats means 23 parts of gold alloyed with 1 part of some
other metatl; gold of 22 carats, 22 parts of gold alloyed
with 2 parts of some other metal. The number of carats men-
tioned specifies the pure gold, and what that number wants
of 24 indicatea the quantity of alloy.
Sect. II. 0f Platinum.
Platinum, which approaches gold in many of its properties
was unknown in Europe as a peculiar metal till 1749.
Hitherto it has been found only in South America and in the
Silver mine of Guadal-canal in Spain. For the first accu-
rate investigation of its properties we are indebted to Dr
Lewis, and since his time it has been investigated by a great
number of very eminent Chemists.
It is brought from America in small flat grains having a
silvery lustre. These grains besides platinum contain no
less than 8 other metals. The platinum may be obtained
pure by dissolving the grains in nitro-muriatic acid and pour-
ing a solution of sal ammoniac into the liquid. An orange
yellow precipitate falls. This precipitate is to be washed
and dried and exposed to a red heat. The powder which
remains is pure platinum. It may be amalgamated with
mercury and, by cautious heating and hammering, it may be
reduced into an ingot.
1. Platinum has a white colour like silver, but not so
bright. It is as hard as iron. Its specific gravity, when ham-
mered, is at least 23, so that it is the heaviest of all known
bodies. It is very ductile and malleable. A platinum wire
of the diameter O.078 inch, is capable of supporting 274.31
lbs. avoirdupois without breaking. It is very difficult of fu-
sion, and indeed cannot be melted in any quantity by the
greatest heat which we can produce. But at a white heat
pieces of platinum may be welded together like pieces of
hot iron. It is not altered by the action of heat and air.
SECT. IL. PLATINUM. 31
2. Platinum cannot be converted into an oxide by the ac-
tion of heat and air; we must have recourse to the action of
acids. There are two oxides of platinam known: the prot-
oxide is green, the peroxide brown.
The peroxide may be obtained by pouring lime water into
the solution of platinum in nitro-muriatic acid. The brown
powder which precipitates is to be dissolved in nitric acid,
the solution evaporated to dryness, and the acid driven off by
a cautious application of heat. The brown powder which
remains is the peroxide. It is tasteless, insoluble in water,
and decomposed by a red heat. It is composed, according
to Mr Chenevix's experiments, of
87 platinum,
13 oxygen.
____
100
If the peroxide is gradually heated it assumes a green co-
lour, owing to the separation of a quantity of oxygen. This
green powder is- he protoxide composed of
93 platinum,
7 oxygen.
____
100
3. The simple combustibles have but little action on pla-
tinum. Neither hydrogen nor carbon unites with it. Phos-
phorus combines readily and forms a phosphuret. It may be
obtained by projecting phoshorus on red hot platinum. Its
colour is silver white, it is very brittle and hard, and easily
melts. The phosphorus may be driven off by heat. Plati-
num cannot be made to unite with sulphur. In this respect
it resembles gold.
4. The simple incombustibles do not combine with pla-
tinum.
32 METALS. CHAP. IV.
5. It comhines with most of the other metals, and forms
alioya, first examined by Dr Lewis.
Gold unites to it, but a strong heat is necassary to combine
them uniformly. Platinum alters the colour of gold very
much. An alloy of 4 parts of gold and one of platinum has
the colour of pure platinum. The colour is much affected
unless the platinum be less than 1/17th of the gold. If such
an alloy be digested in nitric acid the platinum is dissolved.
Thus it is easy to detect any attempt to debase gold by the
addition of Platinum.
SECT.III. Of Silver.
Silver seems to have been known almost as early as gold.
1. It has a fine white colour, with a shade of yellow, and
is remarkably brilliant when polished. It is rather harder
than gold. Its specific gravity is about 10.510. In mallea-
bility and ductility, it is inferior to none of the metals except
gold. It may be hammered out into plates not more than
1/100000th of an inch thick, and drawn out into wire finer than
a human hair. A silver wire 0.078 inch thick, is capable of
supporting 187.13 lbs. avoirdupois, without breaking. It
melts when thoroughly red hot, or at the temperature of 22˚
Wedgewood. By a very violent heat it may be boiled, and
partly volatilised. When cooled slowly it crystallizes in 4
sided pyramids.
2. By very long exposure to heat and air silver may be
oxidized, but the process is so tedious and difficult that we
cannot have recourse to it. There are two oxides of silver
known, both of which have an olive green colour.
The peroxide may be formed by dissolving silver in nitric
acid, and precipitating, by means of lime water. The pow-
der which falls, when washed and dried, is the peroxide.
It is tasteless and insoluble in water. When exposed to light
SECT. III. SILVER. 33
or to heat, it is decomposed, and the silver reduced. It is
composed of about
89 silver
11 oxygen.
___
100
The protoxide may be formed by heating the solution of sil-
ver in nitric acid in contact with a quantity of granular silver.
It resembles the peroxide in colour, but its combination with
nitric acid is more soluble.
S. Neither hydrogen nor carbon have been combined with
silver, but it combines readily with sulphur and phosphorus.
When thin plates of silver and sulphur are laid alternately
in a crucinle, they melt by a moderate heat, and form sulphu-
ret of silver. This compound is found in silver mines, or it
exists native, as mineralogists term it. It has a dark grey
color, a metallic lustre, and the softness, flexinility, and mal-
leability of lead. Its specific gravity is 7.2. It is composed
of 85 silver, and 15 sulphur. When silver plate is long ex-
posed, it contracts a thin covering of this substance. Hence
the tarnish of silver is owing to its combining with sulphur.
Phosphuret of silver may be formed by projecting phos-
phorus into melted silver. It is white, composed of grains,
breaks under the hammer, but may be cut with a knife. It
is composed of four parts of silver and one of phosphorus.
Heat decomposes it by dissipating the phosphorus.
4. Silver does not combine with the simple incombustibles.
5. It combines readily with most of the metals.
When gold and silver are melted together, they combine
spontaneously, in the proportion of one part of silver and 6
of gold. They may, however, be melted together and mixed
in any proportion whatever. This alloy is harder and more
sonorous than pure gold. Its hardness is a maximum when
the alloy consists of two parts gold and one of silver. The den-
34 METALS. CHAP. IV.
sity of the alloy is a little diminished, and the colour of the
gold is much altered, even when the proportion of silver is
small. It is not only pale, but has a very sensible greenish
tinge.
Silver and Platinum may be combined by fusion and form
a hard alloy not so ductile as silver. The two metals sepa-
rate when the alloy is kept in fusion. Hence there appears
but little affinity between them.
Sect. IV. Of Mercury.
Mercury, called also qicksilver, was known to the anci-
ents, and applied by them to the same purposes as it is by the
moderns.
1. Its colour is white like that of silver; it has a good deal
of lustre, and is destitute of taste and smell. Its specitic
gravity is 13.568. At the common temperature of the at-
mosphere it is always in a state of fluidity. But if it be
cooled down to 39˚ below zero, it becomes solid like any
other metal. The congelation of Mercury by cold was ac-
cidentally discovered by Professor Braun, at Petersburg,
in 1739. The freezing point was ascertained by Mr but-
chins, at Hudson's bay, in consequence of the directions of
Mr Cavendish. Solid mercury is malleable; but neither
the degree of its malleability nor its ductility have been ascer-
tained by experiment. Mercury boils when heated to 656˚.
Its vapour is invisinle and elastic like air. It may be easily
distilled over in proper vessels, and by this means is obtained
pure.
2. Mercury is not altered by being kept in water. But
when long agitated in air, or when kept heated in the open
air, it gradually loses its metallic appearance and is oxidized.
Only two oxides of mercury have been yet ascertained in a
SECT. IV. MERCURY. 35
satisfactry mamer, the protoxide, which is black, and the
peroxide, which is red.
The protoxide is a black powder, which may be obtained
by agitating mercury for a long time in a stout phial; or by
heating the salt called calumel or muriate of mercury with a
solution of potash. It is black, insoluble in water, and con-
tains about 5 per cent of oxygen.
The red oxide, called also red precipitate, may be obtained
by keeping mercury for several days, nearly at the boiling
point, in a tall glass vessel so contrived as to prevent the eva-
poration of the mercury and admit a communication between
the anterior of the vessel and the atmosphere. The mercury
becomes at first black and gradually changes to red. It may
be formed more speedily and easily by dissolving mercury in
nitric acid, evaporating the solution to dryness, and heating
the dry salt gradually almost to redness in a crucinle or cap-
sule. Nitric acid fumes exhale, and the whole assumes a fine
red colour. The red oxide of mercury has an acrid and dis-
agreeable taste, acts as an escharotic and possesses poisonous
qualities. When heated with zinc or tin filings it sets them
on fire. It contains about 1O per cent of oxygen. When
heated it gives out oxygen gas and the mercury is reduced.
3. Mercury does not combine with hydrogen or carbon;
but it unites readily with sulphur and phosphorus.
When two parts of sulphur and one of mercury are tritu-
rated together in a mortar, they gradually assume the appear-
ance of a black powder formerly called athiops mineral.
The same compound is formed by adding mercury slowly to
its own weight of melted sulphur. When formed by the first
process the powder is black, but a microscope detects in it
small globules of mercury; when formed by the second pro-
cess the powder is black, with a shade of purple. This com-
pound has been ascertained to consist of mercury and sulphur
united together, in what proportion is not well known.
c 2
36 METALLS. CHAP. IV
When this black sulphuret is exposed to a red heat in a
glass vessel it sublimes and forms a cake of a fine scarlet co-
lour. In this state it is usually called cinnabar, and when
reduced to a fine powder, vermilion. It is well known as a
red paint. Its specific gravity is about 10. It is tasteless,
insoluble in water and in muriatic acid. When suddenly
heated it burns with a blue flame. When mixed with iron
filings, and distilled, it is decomposed, and running mercury
obtained in the receiver. It is composed of about 85 parts
mercury and 15 sulphur.
When Phosphorus is mixed with the black oxide of mer-
cury and exposed to heat, the mixture readily combines,
forming a black mass which seems to be phosphureted oxide
of mercury. At least phosphorus and mercury do not unite
when heated together.
4. Mercury does not unite with the simple incombustibles.
5. It combines with most metals, and forms compounds
called amalgams.
The amalgam of gold is formed very readily by throwing
small pieces of red hot gold into hot mercury. The two
metals combine in any proportion. The amalgam is white
and fluid if the mercury exceed. But by squeezing it through
leather, the excess of mercury separates, and a solid amalgam
remains, of the consistence of butter, which gradually crystal-
lizes. It consists of one part of mercury to 2 of gold. This
amalgam is much used in gilding.
The amalgam of platinum may be formed by triturating
the powder of platinum with mercury, adding gradually a
portion of either ingredient till the combination is completed.
When the process of amalgamation is once begun it goes on
easily. This amalgam has the consistence of butter, a white
colour, much lustre, and does not tarnish by keeping. The
mercury may be driven off by heat.
SECT. V. PALLADIUM. 37
The amalgam of silver may be made in the same manner
as that of gold, and with equal ease. It has a white colour,
is always soft, and crystallizes.
All these amalgams are decomposed and the mercury dri-
ven off by heat.
Sect. V. Of Palladium.
This metal was lately discovered by Dr Wollaston in crude
platina. Mr Chenevix announced soon after that he had
succeeded in forming this metal artificially, by combining to-
gether platinum and mercury; but as no body has been able
to repeat his experiment with success, we must suppose him
mistaken.
To obtain palladium dissolve a sufficient quantity of crude
platina in nitro muriatic acid, and pour a solution of the salt
called nitrate of mercury into the liquid. A yellowish white
powder falls. When this powder is washed and dried, and
exposed to a red heat, it leaves a white matter which is pa-
ladium. When strongly heated with sulphur and borax it
may be melted into a butter.
1. Palladium thus obtained is a white metal, very like pla-
imum in its appearance. Its specific gravity, when hammered,
is 11.871. It is as malleable as platinum, breaks with a
finrous fracture, and appears of a crystallized texture. It is
not altered by exposure to the air, and a very violent heat is
necessary to fuse it.
2. When kept strongly heated its surface acquires a blue
colour. This is supposed a commencement of oxydizement.
A more violent heat makes it resume the original metallic ap-
pearauce. Sulphuric, nitric and muriatic acids dissolve a
portion of it when assisted by heat, and assume each a red
colour. Nitro-muriatic acid is the best solvent of it.
c 3
38 METALS. CHAP. IV.
3. Neither hydrogen nor carbon combine with this metal.
But uhen brought into contact with sulphur while red hot it
melts immediately, and the sulpuret formed continues in fu-
sion till only obscurely red. It is rather paler than the pure
metal and very brittle.
4. The simple incombustibles do not combine with palla-
dium; but it unites with the metals, and forms alloys, which
have been examined and descrined by Mr Chenevix.
Sect. VI. Of Rhodium.
This metal exists also in crude platina, and was discovered
by Dr Wollaston still more recently than the last.
The process followed by Dr Wollaston for obtaining it, is
somewhat complicated. Crude platina is dissolved in nitro-
muriatic acid, and the platinum precipitated by sal ammoniac.
A piece of clean zinc is immersed into the residuary solution
which throws down a black powder. This black powder is
digested with dilute nitric acid in a very gentle heat, to dis-
solve some copper and lead with which it is frequently conta-
minated. It is then dissolved in nitro muriatic-acid, common
salt is added to the solution, and the whole is gently evapo-
rated to dryness. The residuum is washed repeatedly with
small quantities of alcohol, which dissolves two salts consisting
of the oxides of platinum and palladium in combination with
common salt. There remains behind a deep red-colored
substance consisting of the oxide of rhodium united to com-
mon salt. By solution in water and gradual evaporation
rhomboidal crystals of a deep red colour are obtained. These
crystals being dissolved in water, and a plate of zinc immer-
sed into the solution, a black powder precipitates, which being
strongly heated with borax becomes white, and assumes a
metallic lustre. In this state it is rhodium.
SECT. VII. IRIDIUM. 39
1. Rhodium thus obtained is white. Its specific gravity
exceeds 11. No degree of heat hitherto applied is sufficient
to melt it. Of course its malleability and other similar pro-
perties are unknown.
2. It is not oxidized by exposure to heat and air. Neither
is it much acted on by acids. The only oxide of rhodium
known is of a yellow colour. It may be obtained by dissolv-
ing the red crystals mentioned above, and precipitating by
means of potash. This oxide when dissolved in nitric or mu-
riatic acid does not crystallize.
3. It unites readily with sulphur and by that means is easily
melted. When the sulphur is driven off by heat the metallic
button obtained is not malleable. The action of the odther
simple combustibles is not known.
4. It does not combine with the simple incombustibles.
It forms alloys with all the metals tried by Dr Woliaston,
except mercury, with which it does not combine. It does
not like platinum and palladium destroy the colour of gold
when alloyed with- it.
Sect. VII. Of Iridium.
This metal was discovered by Mr Smithson Tennant, in
180J. Attempts were made by Descotils, and by Fourcroy
and Vanquelin soon after, to obtain the same metal, but they
succeeded but imperfectly.
When crude platina is dissolved in nitro-muriatic acid a
black powder remains, which preceding chemists Considered
as plumbago, but which Mr Tennant ascertained to be a
compound of two new metals. When kept for some time in
a red heat mixed with its own weight of potash in a platinum
crucinle, water poured on the mixture forms a deep orange-
colored solution. Muriatic acid being digested on the pow-
der which remains, becomes first blue, then green, and at last
c 4
40 METALS CHAP. IV.
deep red. By repeated fusions with potash, and digestions
in muriatic acid, the whole of the black powder is decom-
posed and dissolved. The potash solution contains the me-
tal called osmium, the muriatic acid solution the metal called
iridium.
A piece of zinc being put into this last solution, precipi-
tates a black powder, when heated, it becomes white, and is
iridium.
1. It has the appearance of platinum, and seems as diffi-
cult of fusion as that metal. It resists Lbe action of acids,
even the nitro-muriatic, almost completely.
2. Its affinity for oxygen seems weak; but, like other me-
tallic bodies, it unites with that principle. The change of co-
lour which its solution in muriatic acid assumes, seems to
prove that it is incapable of combining with different dozes
of oxygen. When the colour is blue, the metai seems oxy-
dized to a minimum, when red, it seems oxydized to a maxi-
mum.
3. The simple combustibles do not seem to combine with
iridium. Mr Tennant did to succeed in his attempt to unite
it with sulphur.
4. It formed alloys with all the metals tried except arse-
nic. It does not alter the colour of gold, and cannot be se-
parated from gold and silver by cupellation.
Sect. VIII. 0f Osmium.
This metal was discovered by Mr Tennant at the same
time with the preceding. It exists in the black powder so-
parated during the solution of crude platina, and may be ob-
tained in solution in potash, by the process descrined in the
last section. When sulphuric acid is mixed with this solu-
tion and the whole subjected to distillation, a colourless li-
quid comes over, consisting of water, holding the oxide of
SECT. IX. COPPER. 41
osmium in solution. It has a peculiar smell. Hence the name
osmium applied to the metal. When mercury is agitated in
this solution, the osmium combines with it, acid leaves the
water, and by applying heat, the mercury is driven off, and
the metal obtained in a state of purity.
l. Osmium has a dark grey or blue colour, and the me-
tallic lustre. In the open air it is easily dissipated by heat,
but in close vessels it resists any degree of heaat without alte-
ration. It is not acted on by any acid, not even the nitro-
muriatic, but is easily obtained in solution by the action of
potash.
2. Osmium is easily oxidized by heat in the open air. The
oxide has a peculiar smell and a kind of oily appearance.
It is volatile and soluble in water. The solution is colour-
less, does not alter vegetable blues, and strikes first a purple,
then a blue, with the infusion of nut-galls.
3. The action of the simple combustibles on this metal is
not yet known. Neither do we know much of its com-
bination with other metals. It amaigamates with mercury,
and Mr Tennant united it by fusion with copper and gold.
Sect. IX. Of Copper.
Copper seems to have been known as early as any metal
except gold and silver. It was very much employed by the
ancients before the method of manuftcturing steel became
familiar.
1. Copper has a fine red colour, but it soon tarnishes
when exposed to the air. Its taste is styptic and nauseous,
and when rubbed, it emits a disagreeable odour. It is very
poisonous when taken internally. It is softer than iron, but
harder than gold. Its specific gravity when pure is about
8.9. Its malleability and ductility are very considerable.
A copper wire 0.078 inch in diameter is capable of support-
42 METALS. CHAP. IV.
ing 302.2 lbs. avoirdupois without breaking. It melts at
27˚ Wedgewood, and gradually evaporates in visinle fumes.
When melted it has a bluish green colour, something like
that of melted gold. When allowed to cool slowly, it crys-
tallizes in quadrangular pyramids.
2. It is not altered though kept under water. When
heated in contact with air, it is gradually converted into
a black oxide by the combination of oxygen. Before a blow-
pipe of oxygen and hydrogen gases, it burns with a fine green
flame. There are two oxides of copper. The protoxide is
found naturally of a red colour, but when formed artificially
it is orange. The peroxide is black.
The protoxide was first recognised by Mr Proust. It
may be prepared by heating together a mixture of equal
parts of black oxide and copper in powder in muriatic
acid. Almost the whole is dssolved, and the solution is
colourless. By pouring potash into the solution, the pro-
toxide precipitates in the state of a yellow powder. This
oxide is composed of 88.5 parts copper, and 11.5 oxygen.
It attracts oxygen with such avidity, that it can scarcely be
dried without becoming black.
The peroxide of copper is easily formed by keeping copper
filings a sufficient time red hot. It contains BO parts copper,
and 2O oxygen. It is black. It combines with water, and
forms a blue coloured matter called hydrate of copper.
3. Copper has not been combined with hydrogen or car-
bon; but it unites with sulphur anu phosphorus forming the
sulphuret and phosphuret of copper.
When equal parts of sulphur and copper are stratified in a
crucinle, they combine at a red heat, and form sulphuret of
copper, of a very deep blue colour. It is brittle, and com-
posed of 78 copper and 22 sulphur. If copper filings and
sulphur in powder be mixed, and gradually heated in a fiask,
SECT. IX. COPPER. 43
they combine before they are heated to redness; but at the
instant of combination, a quantity of heat is evolved sufficient
to convert the sulphuret into a glowing red, as if in a state of
vivid combustion.
Sulphuret of copper is capable of combining with an addi-
tional dose of sulphur, and forming a super-sulphuret. It is '
brittle, has a yellow colour, and the metallic lustre. It is
found native, and known under the name of copper piyrites.
Phosphuret of copper may be formed by projecting phos-
phorus on red hot copper. It it white, tough, but not duc-
tile, hard, and contains the 5th of its weight of phosphorus.
When repeatedly melted, it still retains about 1-12th of its
weight of phosphorus, and then has much the appearance of
steel, and admits of an equally fine polish.
4. Copper does not combine with the simple incombusti-
bles. But muriatic acid oxydizes it, and combines with the
oxide.
5. It combines with most of the metals, and some of its
alloys are of considerable importance.
Copper unites readily with gold, and even heightens the
colour, while it incrcases the hardness, and does not injure
the ductility. Gold coin consists of gold alloyed with cop-
per or silver, or with both. Our coin contains l-12th of
alloy, usually both silver and copper. A pound of standard
gold is coined into 44 1/2 guineas.
Platinum combines with copper, but a violent heat is ne~
cessary. The alloy is white, hard, ductile, takes a fine po-
lish, and is not liable to tarnish. Hence it has been proposed
for the mirrors of telescopes.
Copper and silver easily unite by fusion. The alloy is
harder and more sonorous dban silver, and retains its white co-
lour, even when the proportion of copper is considerable.
Our silver coin consists of 12 1-3rd silver, alloyed with one of
copper. A pound Of standard silver is coined into 62 shillings.
44 METALS. CHAP. IV.
Copper may be united to nercury by pouring a small
stream of it melted into mercury, heated nearly to the boiling
point; or by keeping plates of copper in a solutioo of mer-
cury in nitric acid. It is white, and at first softy but gradu-
ally hardens when exposed to the air.
Sect. X. Of Iron.
Iron was not known at so early a period as gold, silver and
copper. The art of working it was discovered in the east,
and first communicated to the Greeks by the Phrygians,
from whom it gradually made its way through the rest of
Europe.
1. Iron has a bluish white colour, a styptic taste, and
emits a smell when rubbed. It is one of the hardest of the
metals. Its specific granty varies from 7.6 to 7.8. It is
attracted by the magnet or loadstone, and is itself the sub-
stance which constitutes the loadstone. When iron is per-
fectly pure, it retains the magnetic virtue but a short time.
It is malleable in every temperature and its malleability
increases with the temperature. It cannot be hammered
into so thin plates as gold or silver. But it may be drawn
out into very fine wire. An iron wire of 0.078 inch in dia-
meter is capable of supporting 549.25 lbs avoirdupois witb-
out breaking. When heated to 158˚ Wedgewood, it melts;
a temperature so high, that it is difficult to go much be-
jond it.
It is much more easily converted into oxide than any of
the metals descrined in the preceding sections. When left
exposed to the air, especially in a moist place, it is soon con-
verted to a red or yellow powder, called rust, which is no-
thing else than an oxide of iron usually combined with car-
bonic acid. When kept under water, especially in warm
weather, it is gradually converted into a black brittle matter,
Sect. X. IRON. 45
which is also an oxide, while some hydrogen gas is disenga-.
ged, owing to the decomposition of the water. If vapour of
water be passed through red hot iron, the iron is rapidly oxi-
dized and much hydrogen gas is obtained. If an iron wire,
having a small bit of lighted cotton at its extremity, be
plunged into a jar of oxygen gas, it burns with great brillian-
cy, and is converted into the same black oxide, which falls
to the bottom of the jar in melted drops.
There are two oxides of iron which have been ascer-
tained in a satisfactory manner, and I think that I have
observed also a third. The black oxide may be obtained
by keeping iron filings a sufficient time in water, by
making steam pass through iron filings at a red heat, by
burning iron wire in oxygen gas, or by dissolving iron in di-
luted sulphuric acid, and dropping potash into the solution.
It is a black powder, insoluble in water, is attracted by the
magnet, and has a good deal of metallic lustre. It is a
compound of 73 parts iron and 27 oxygen.
The red oxide, or peroxide, may be obtained by keeping
iron filings red hot in an open vessel and agitating them con-
stantly till they are converted into a red powder; or by ex-
posing a solution of iron in sulphuric acid for a long time to
the atmosphere, and then precipitating by means of potash.
It is a red powder, insoluble in water, and constitutes the
base of several of the common red paints. Clay and bricks
owe to it their yellow and red colours. It is composed of
52 iron and 48 oxygen.
Among the ores of iron there occurs one by no means un-
common, which seems to contain only one-half of the oxygen
present in black oxide. It is black, has a good deal of me-
tallic lustre, and is magnetic. This seems to be a peculiar
oxide, and is probably the real protoxide of iron. Though,
as my attempts to form it artificially did not succeed, there
are still some doubts remaining about its reality.
46 METALS. CHAP. IV.
3. Iron seems capable of combining with all the simple
combustibles. Hydrogen, indeed, has never been united to
it in a solid state, but hydrogen gas dissolves a little iron
which it gradually deposites when kept over water.
Carburet of iron is found native, and is the substance
mentioned in a preceding section under the name ofplumba-
go or black lead. It is a soft substance, of a dark blue co-
lour, a granular texture, and the metallic lustre. It does not
burn with a flame, but gradually wastes away when kept red
hot. When thrown into melted nitre a very splendid com-
bustion is poduced. Its nature was first developed by Dr
Lewis, and afterwards more fully explained by Scheele and
the French chemists. It seems to consist of about 19 parts
of carbon and one part of iron.
Phosphuret of iron may be formed by dropping bits of
phosphorus upon red hot iron. Its colour is dark steel-grey,
it is very brittle, and does not easily dissolve in acids. It
exists in different ores of iron, and is considered as giving to
the variety of iron called cold short iron, the property of be-
ing brittle while cold, though it be malleable while hot.
Phosphuret of iron was at first considered by Bergman as a
peculiar metal and called siderum.
Sulphuret of iron may be formed by melting together in
a crucinle equal parts of iron filings and flowers of sulphur.
It is of a black or very deep grey colour, brittle and very
hard. When the two consituents of it combine, a great
quantity of heat is evolved which makes the whole strongly
red hot. This sulphuret is composed of 62.5 iron and 37.5
sulphur. It exists native, and is known by the name of
magnetic pyrites. Its colour is that of bronze, it has the me-
tallic lustre, but its powder is blackish grey. Its specific
gravity is 4.518. It strikes fire with steel, and easily melts
when heated. It is not only magnetic, but is itself capable-
SECT. X. IRON. 47
of being converted into a permanent magnet, as Mr Hatchett
discovered.
Iron is capable of combining with a still greater propor-
tion of sulphur, and of forming a compound which may be
caled super-sulphuret of iron. It occurs native in great
abundance, and is kown by the name of pyrites, of iron py-
rites. It is yellow, has the metallic lustre, is brittle, strikes
fire with steel, and is often crystallized in cubes. Its specific
gravity is 4.5. When distilled it loses its excess of sulphur,
and is converted into common sulphuret of iron. By this
process sulphur is sometimes obtained for the purposes of
manufactures. Pyrites is composed of 80 common sulphu-
ret of iron and 20 sulphur, or more exactly of about 47 iron
and 53 sulphur. The super-sulphuret is not magnetic nor
susceptible of becoming a magnet. Mr Hatchett found
that phosphuret of iron is also capable of magnetic impreg-
nation, and it is well known, that iron containing a portion of
carbon or steel, possesses the same property in perfection.
Hence Mr Hatchett concludes, that permanent magnets con-
sist of iron combined with a certain proportion of a simple
combustible. But, when saturated with simple combustibles
it loses its magnetic properties entirely. This is known with
respect to iron saturated with sulpnur and carbon, and is pro-
bable with respect to iron saturated with phosphorus. The
subject requires. and deserves farther investigation.
There are a great many varieties of iron which artists dis-
tinguish by different names; but they may be all reduced un-
der the following classes: Cast iron, wrought or soft iron,
and steel.
Cast-iron, or pig-iron, is the name of the metal when first
extracted from its ores. The ores of iron commonly used
are a mixture of the oxide of the metal and clay. They are
reduced to small pieces and exposed to a violent heat mixed
with charcoal and lime. The charcoal separates the oxygen,
48 METALS. CHAP. IV.
vhile the lime, combining with the clay, forms a liquid
through which the melted iron falls and is collected at the
bottom of the furnace. It is let out and cast in moulds.
The cast iron thus obtained varies considerably aocording to
circumstances. Three varieties have been well distinguished;
namely, white cast iron, which is very hard and brittle; grey
or mottled, which is softer and less brittle; and black, which
is the softest and most fusinle. Cast iron melts at 130˚
Wedgewood. Its specific gravity varies from 7.2 to 7.6. It
contracts considerably when brought into fusion.
Cast iron is converted into wrought or soft iron by keeping
it melted for a considerable time in a bed of charcoal and
ashes and the scoria or black oxide of iron, and then forging
it repeatedly till it becomes compact and malleable. In this
state it is the substance descrined in the beging of this
section under the name of iron. It is considered when pure
as a simple body; but it is difficult to procure it quite pure.
It is almost always contaminated with some foreign body, ei-
ther some of the other metals, or oxygen, carbon, or phos-
phorus.
When soft iron is kept red hot for some time in a bed of
charcoal it is converted into steel. Steel is so hard as to be
unmalleable while cold. It is brittle, resists the file, cuts
glass, strikes fire with flint, and retains the magnetic virtue
when impregnated with it. It is more sonorous and its spe-
cific gravity is greater than that of soft iron. It varies from
7.78 to 7.84.
These different states of iron have been long known, and
many attempts were made to ascertain the cause of the dif-
ferences among them. At last it was recognised by Berg-
man and the French chemists. Soft iron is the simple me-
tal. Steel is iron combined with a portion of carbon, and
has been for that reason called subcarburet of iron. The
carbon, from Vauquelin's analysis, amounts to 1/140th part of
SECT. XI. NICKEL. 49
the whole. Cast iron is iron combined with a still greater
proportion of carbon. It usually contains likewise a little
oxygen.
4. Iron does not combine with azote, nor with muriatic
acid. But that acid oxidizes iron and unites with its oxide.
5. Iron unites with most of the metals. Gold combines
readily with iron, and forms a ductile alloy of a pale yellow
or white colour accoiding to the proportions. Platinum is
found usually alloyed with iron, but it is difficult to combine
the two metals artificially on account of the high temperature
necessary to fuse them. Silver and iron combine and form
a very hard alloy of a white colour. Mercury does not rea-
dily unite to iron, but an amalgam may be formed artificially.
Iron may be united to copper by fusion, but not without
considerable difficulty. The alloy is grey, imperfectly duc-
tile, and very infusinle. It is probable that the variety of
iron called hotshort, because it is brittle when red hot, owes
that property to the presence of a little copper with which it
is alloyed.
Sect. XI. Of Nickel.
Nickel was first recognised as a peculiar metal in conse-
quence of the experiments of Cronstedt in 1751. It is ob-
tained from an ore which occurs in different German mines,
and called Kupfer nickel, or false copper, because it re-
sembles copper, though no copper can be extracted from it.
It has been examined by many eminent chemists, especially
by Richter, to whom we are indebted for the most exact ac-
count of its properties.
1. Nickel has a white colour like silver, it is softer than
iron; its specific gravity, when hammered, is 8.666. It is
malleable both cold and hot, and may be easily hammered
out into thin plates. It is powerfully attracted by the mag-
50. METALS. CHAP. IV.
net, and may be converted into a magnet precisely like bars
of steel. It requires for fuusion a temperature at least equal
to 160˚ of Wedgewood. It is not altered by air nor water.
2. When moderately heated it tarnishes, and, if in powder,
may be even converted into an oxide, but a strong heat re-
duces it again to the metallic state. We are at present ac-
quainted with two oxides of nickel, the green and the black.
The protoxide may be obtained by dissolving nickel in ni-
tric acid, precipitating the oxide by carbonate of potash,
washing It and exposing it to a slight red heat. It is of a
dark olive green, and is composed of 78 nickel and 22 oxy-
gen. It is tasteless, soluble in acids, and the solution is grass-
green. It dissolves likewise in ammonia.
The peroxide may be formed by mixing the protoxide
with water, and passing a current of oxymuriatic acid gas
through the liquid. A portion of the oxide dissolves and a
portion acquires a black colour. When this black oxide is
dissolved in acids, an effervescence takes place, owing to the
escape of a portion of its oxygen.
3. Nickel has not been combined with hydrogen or car-
bon, but it unites readily with phosphorus and sulphur.
Cronstedt formed sulphuret of Nickel by fusion. The phos-
phuret may be obtained by dropping bits of phosphorus on
red hot nickel.
4. Nickel does not unite with the simple incombustibles.
5. The alloys which it forms are but imperfectly known.
They are mostly brittle and hard, and have been applied to
no useful purpose.
Sect. XII. Of Tin.
Tin was known to the ancients, and was imported from
Britain at a very early period by the Phenicians.
SECT. XII. TIN. 51
1. Tin has a fine white color with a shade of blue. It
has a slightly disagreeable taste, and emits a peculiar smell
when rubbed. It is scarcely so hard as silver. Its specific
gravity, when hammered, is 7.299. It is very malleable and
may be hammered out into very tbin plates. But its ducti-
lity and tenacity are much inferior. A tin wire 1/12.6 incb in
diameter is capable of supporting only 31 pounds without
breaking. When tin is bent it produces a remarkablie crack-
ling noise. It melts at 442˚, and when slowly cooled crys-
tallizes in rhomboidal prisms.
2. Tin soon tanishes when exposed to the air, but the
tarnished coat is always extremely thin. It is not altered
though kept under water. But, at a red heat it decomposes
water, combines with its oxygen, and disengages the hydro-
gen. When kept melted it is soon covered with a greyish
matter which becomes speedily yellow. But it is very dif-
ficult to oxydize tin completely by heat and air. Tin is ca-
pable of forming three different oxides.
The protoxide has not been obtained in a separate state;
but Proust has shown that it exists in the compound called
Mosaic gold, to be descrined immediately.
The deutoxide, or grey oxide, may be formed by dissolving
tin in muriatic acid by means of heat, and adding potash in '
excess to the solution. A white powder falls, which is gra-
dually converted into a grey matter, having a good deal of
the metallic lustre. This is the grey oxide. It is tasteless
readily soluble in acids, and greedily absorbs more oxygen.
It is composed of four parts tin and one oxygen.
The peroxide may be obtained by heating tin in concen-
trated nitric acid. A violent effervescence ensues, and the
tin is converted into a white powder, which is the peroxide.
It dissolves readily in potash and in muriatic acid. It is
composed of 72 parts tin and 28 oxygen.
D2
52. METALS. CHAP. IV.
3. Tin bas not been combined with hydrogen or eainoot
but it unites to phosphorus and sulphur.
Phosphuret of tin may be formed by throwing bits of
phosphorus on melted tin. It has the colour of silver, is
soft, may be cut with a knife, and extends under the ham-
mer, but separates into laminas. It is composed of 85 tin,
and 15 phosphorus.
Sulphuret of tin may be formed by fusing the two ingredi-
ents together in a crucinle. It is brittle, heavier than tin, and
not so fusinle. It is of a bluish colour, laminated texture, and
capable of crystallizing. It contains l-6th of sulphur, and
5-6ths tin.
When equal weights of peroxide of tin and sulphur are gra-
dually heated in a retort, some sulphur and sulphurous acid are
disengaged, and there is formed a substance called Mosaic
gold, or sulphureted oxide of tin. It consists of gold colour-
ed flakes, light, and adhering readily to the skin. Proust has
shewn that this substance is a compound of sulphur and pro-
toxide of gold. Neither nitric nor muriatic acid acts upon
it, but it dissolves in hot nitro-muriatic acid, and is gradually
changed into sulphate of tin. It dissolves in liquid potash
when assisted by heat, and deflagrates when heated with
twice its weitht okf nitre.
4. Tin does not unite with the simple combustibles, but
it combines with the metals, and forms alloys, some of which
are of considerable importance.
With gold it unites easily by fusion, and was tbought for-
merly to render the metal very brittle; but the experiments of
Altchorne, Hatchett, and Bingley, have shown that this opi-
nion is to a considerable degree erroneous. Tin readily
melts with platinum, and forms a brittle alloy, unless the
proportion of platinum does not exceed 1-9th of the alloy.
The alloy of tin and silver is very brittle and hard. Mer-
cury dissolves tin with facility, and forms an amalgam capa-
4
SECT. XII. TIN. 53
ble of crystallizing. It is used for silvering the backs of
looking-glasses.
Tin unites readily with copper, and forms an alloy known
by the names of gun-metal, hell-mtal, bronze, and mirrors
of telescopes, according to the proportion of the ingredients.
Tin diminishes the ductility of copper, and increases its hard-
ness, tenacity, fusinility, and sonorousness. The specific
gravity is greater than the mean, and is a maximum when
the alloy is composed of 100 copper and 16 tin.
Bronze and gun metal are composed of 100 parts of cop-
per, and from 8 to 12 of tin. Brass guns are made of it.
The ancients used it for making cutting instruments. The
chalkos, of the Greeks and the aer of the Romans was nothing
else.
Bell-metal is usually composed of 3 parts of copper, and
1 of tin. It is greyish white, very hard, sonorous and elastic.
The mirrors for telescopes consist of about 2 parts copper,
and one tin. This alloy is very hard, the colour of steel,
and admits of a fine polish.
When copper if used for culinary vessels, it is covered
with a thin coating of tin, and is then known by the name of
tinned copper. The coating of tin is extremely thin, but it
completely prevents the copper from injuring the articles
dressed in such vessels.
Tin does not unite readily with iron, but the two metals
may be combined by fusing them together in a well closed
crucinle. The formation of tin plate shows the affinity be-
tween the two metals. This very useful compound is made
by dipping clean plates of iron into melted tin.
SECT. XIII. Of Lead.
Lead was very well known to the ancients, but they do not
always seem to distinguish it accurately from tin; though the
properties of the two metals be exceedingly different.
D3
54 METALS. CHAP. IV
1. Lead has a bluish white colour, and when newly melted,
is very bright; but it soon tarnishes when exposed to the air.
It is tasteless, but, when rubbed, emits a peculiar smell. It
stains the fingers or paper dark blue. When taken inter-
nally, it is poisonous. It is very soft. Its specific gravity
is 11.407. It is not encreased by hammering. It is very
malleable; but its ductility and tenacity are not great. A
lead wire 1/126 inch in diameter, is capable of supporting only
18 1/2 lbs. without breaking. It melts at 612˚. When slowly
cooled, it crystallizes in 4 sided pyramids.
2. Lead soon tarnishes in the open air, but the oxydize-
ment never proceeds far. Water does not act upon it,
though it greatly facilitates the action of the external air.
Lead is believed at present to be capable of forming 4 diffe-
rent oxides.
The yellow oxide is the most important, as it constitutes
the basis of almost all the known salts of lead, it may be
obtained by dissolving lead in nitric acid, precipitating by
carbonate of potash, and heating the white powder which
falls almost to redness. It is yellow, tasteless, insoluble in
water, but soluble in potash and in acids. It readily melts
and forms a brittle semitransparent hard glass. It is com-
posed of 100 lead, and 8 oxygen. It may be formed by ex-
posing lead for a sufficient time to the action of heat and air,
and is then known by the name of massicot.
If yellow oxide be dissolved in nitric acid, and the solution
boiled over a quantity of lead filings in a phial, the liquid as-
sumes a yellow colour, and yields yellow, brilliant crystals in
scales. These crystals, according to Proust, consist of ni-
tric acid, united an oxide of lead, containing less oxygen
than yellow oxide. It must of course be considered as a
protoxide. Upon examining this oxide, I found that it pos-
sessed the colour and properties of yellow oxide, and formed
the same quantity of salt with nitric acid.
SECT. XIII. LEAD. 55
If massicot ground to a fine powder be exposed in a fur-
ace to the flame of burning coals, playing upon its surface
for about 48 hours, it is converted into a beautiful red pow-
der called minium, or red lead. This is the tritoxide or
red oxide of lead. It is of an orange red colour of the spe-
cific gravity of 8.940. Insoluble in water, but soluble in
potash. When heated to redness, it gives out oxygen gas,
and is partly reduced and partly melted, to a dark brown
glass. It does not combine with acids. when acids, dis-
solve it, they first reduce it to the state of yellow oxide. It
is composed of 88 lead, and 12 oxygen.
If weak nitric acid be poured upon red lead, a portion is
diussolved, but a portion remains in the state of a dark brown
powder. This brown powder is the peroxide of lead. It is
tasteless, light, and is not acted on by sulphuric or nitric acid.
To muriatic acid it gives out oxygen, and converts it into
oxymuriatic acid. It is composed of 80 lead and 2O oxy-
gen.
When lead is first extracted from its ore, it almost always
contains a portion of silver, which is always extracted when
its quantity is sufficient to repay the expence. The process
is known by the name of refining the lead. The lead is
placed in a large flat dish called a test, composed of burnt
bones and fern ashes, and exposed to the flame of a furnace.
The lead gradually assumes a kind of vitriform state, and is
either blown off or sinks into the test, while the silver re-
mains unaltered. The lead by this process is converted into
litharge. It consists of fine scales, partly red and partly yel-
low. It is yellow oxide combined with a small portion of
carbonic acid.
3. Lead has not been combined with hydrogen or carbon,
but it unites to phosphorus and sulphur.
Phosphuret of lead may be formed by dropping phospho-
rus into melted lead. It has a silver white color with a
shade of blue, and soon tarnishes.
D4
56 METALS. CHAP. IV.
Sulphuret of lead may be formed by mixing the two in-
gredients and melting them in a crucinle. It occurs abun-
dantly native, and is known by the name of galena. It is
brittle, brilliant, of the colour of lead, less fusinle, and usu-
ally crystallizes in cubes. Its specific gravity is about 7. It
is composed of 86 lead, and 14 sulphur.
There is another sulphuret of lead, which I have occasi-
onally found native also. The colour is lighter, and it burns
with a blue flame when placed upon burning coals. It con-
tains at least 25 per cen of sulphur.
4. Lead does not combine with the simple incombustibles.
It forms alloys with the other metals, but few of them are
of much importance.
It renders gold as brittle as glass, when the proportion
of it does not exceed 1/1920th of the gold. It likewise ren-
ders platinum brittle. The alloy of silver and lead is very
brittle, its specific gravity is greater than the mean. Mer-
cury readily dissolves lead, and forms an amulgame capable of
crystallizing. Copper dissolves in lead at a strong red heat.
The alloy is grey and brittle, and when heated gradually, the
lead melts and runs off, leaving the copper nearly pure. Iron
unites with lead with difficulty, and the alloy is eaily de-
composed. Lead and tin may be combined in any propor-
tion. The alloy is harder, and possesses more tenacity than
tin.
Sect. XIV. Of Zinc.
The ancients do not appear to have been acquainted with
this metal. It has been long known in China, and is men-
tioned by European wtiters in the 13th century. The me-
thod of extracting it from its ores was unknown in Europe
till near the middle of the 18th century.
1. Zinc has a brilliant white colour, with a shade of blue,
and is composed of thin plates cohering together. It has a
SECT XIV. ZINC. 57
sensible taste, and acquires, when rubbed a slight smell. It
is rather harder than silver. When hammered, its specific
gravity is 7.1908. In its usual state it can scarcely be said
to be malleable, but when heated a little above 212˚ it be-
comes very malleable, and may be rolled out into thin plates
or drawn into wire. A zinc wire of 1-l0th inch in diameter
is capable of supporting about 26lbs. When heated to about
680˚, it melts, and, if cooled slowly, crystallizes in quadran-
gular prisms.
2. When exposed to the air, its Surface is soon tarnish-
ed, but it hardly undergoes any other change. It is said to
decompose water slowly, and to separate the hydrogen. At
a red heat the decomposition goes on rapidly. When zinc
is heated to redness, it takes fire, and burns with great bril-
liancy, being converted into a white oxide, which flies off in
fine flakes like cotton. It was called pompholyx, nihil al-
bum, lana philosophica, flowers of zinc.
Two oxides of zinc are known. The peroxide is the
white oxide obtained by the combustion of the metal. It is
composed of 80 parts zinc, and 20 oxygen. It may be ob-
tained likewise by dissolving zinc in sulphuric acid, and pre-
cipitating by means of potash. It is very white, ligh, and
has some resemblance to chalk. It is tasteless and insoluble
in water, and is not altered by exposure to the air.
The protoxide of zinc may be obtained by exposing the
white oxide to a violent heat, or by digesting the solution of
zinc in sulphuric acid with metallic zinc for some days. A
flesh coloured substance precipitates, which is the oxide
wanted. It is composed of 88 zinc, and 12 oxygen.
3. Most of the simple combustibles combine with zinc.
Hydrogen gas procured by the acLion of diluted sulphuric
acid on zinc, holds a little of the metal in solution, which it
gradually deposites.
Carbon was considered as an occasional constituent of zinc,
and to occasion the appearance of the black powder which
58 METALS. CHAP. IV.
separates when zinc is dissolved in sulphuric acid. But on
examinig this powder, I found it a mixture of copper and
lead.
Phosphuret of zinc may be formed by dropping bits of phos-
phorus upon melted zinc. It has a considerable resemblance
to lead. It somewhat malleable. -Phosphorus combines
likewise with the oxide of zinc.
Sulphuret of zinc exists native in considerable quantity,
and is known by the name of blende. It may be formed by
fusing a mixture of Sulphur and oxide of zinc.
4. Zinc does not unite with the simple incombustibles,
but it combines with the metals, and forms alloys, some of
which are of great importance.
It renders gold brittle, even when added in a very minute
proportion. It melts readily with platinum, and renders it
brittle. Silver readily combines with it, and forms a bitttle
alloy. Mercury easily amalgamates in any proportion when
poured upon hot zinc. The amalgam is used to encrease the
energy of electric machines.
Zinc combines with copper, and forms one of the most
useful of all the alloys, namely brass. It is prepared by
mixing oxide of zinc, charcoal powder, and granular copper,
and heating them sufficiently in a crucinle. Brass is yellow.
The proportion of zinc which it contains varies somewhat.
In some British manufactures it amounts to l-3d.; while in
Germany and Sweden it is said not to exceed l-4th or l-5th.
Brass is much more fusinle than copper. It is malleable
while cold, but becomes brittle when heated. Tt is ductile,
may be drawn into thin wire, and is much tougher than cop-
per. When zinc in the metallic state is melted with copper,
the alloy is known by the name of pinchbeck, Prinmce\B4s metal,
Prince Rupert\B4s metal. The colour of pinchbeck ap-
proaches more nearly to that of gold, but it is more brittle
than brass.
SECT. XV. BISMUTH. 59
Zinc cannot easily be alloyed with iron. The alloy is hard
and white and somewhat ductile. Tin and zinc easily unite.
The alloy is hard and ductile. Lead and zinc may be united
by fusion.
Sect. XV. Of Bismuth.
This metal was unknown to the ancients. It was well
known in Germany at the begining of the l6th century.
But chemists were long in reckoning it a peculiar metal.
1. Bismuth is of a reddish white colour, and almost desti-
tute of taste and smell. It is composed of broad brilliant
plates adhering to one another. It is harder than silver. Its
specific gravity is 9.822. When hammered cautiously its
density is increased, but it breaks when struck smartly. It
cannot be drawn out into wire. A rod of 1-lOth inch dia-
meter is capable of supporting about 29lbs. It melts at
476˚, and may be distilled over in close vessels. When
cooled slowly it crystallizes in parallelopipeds.
2. It tarnishes in the air, but is not altered when kept un-
der water. When kept melted in an open vessel it is gra-
dually converted into a yellow powder. In a strong red
heat it takes fire and burns with a faint blue flame and emits
a yellow smoke. This, when collected, is a yellow oxide.
It is composed of about 89.3 bismuth and 10.7 oxygen.
This is the only oxide of bismuth at present known. It is
tasteless and insoluble in water. When heated it melts into
a brown glass.
3. Bismuth has not been combined with hydrogen or car-
bon. It does not seem capable of combining in any notable
proportion with phosphorus. But it unites very readily with
sulphur by fusion. The sulphuret is bluish grey, very brittle
and fusinle, and crystallizes in four sided needles. It is com-
posed of about 85 bismuth and 15 sulfur.
2
60 METALS. CHAP. IV.
4. Bismuth does not unite with the simple iucombuatinles,
but it combines with the metals, and forms alloys not hither-
to applied to any useful purpose. It renders gold, platinum
and silver brittle. It amalgamates readily with mercury.
When the mercury exceeds, the amalgam is fluid, and has the
property of dissolving lead, and rendering it also fluid. Bis-
muth renders copper and iron brittle. It facilitates the fu-
sion of tin and lead: a mixture of eight parts bismuth, five
lead, and three tin is called fusinle metal, because it melts at
212˚. Bismuth does not combine with zinc.
Sect. XVI. Of Antimony.
The ancients were acquainted with some of the ores of an-
timony, but it does not appear that they knew the metal it-
self. Who first extracted it from its ores is unknown. But
the process is first descrined by Basil Valentine.
1. Antinomy is of a greyish-white colour, and has consi-
derable brilliancy. Its texture is laminated, and exhibits
plates crossing each other in every direction. It is as hard
as silver. Its specific gravity is 6.712. It is very brittle,
and may be easily reduced to powder in a mortar. It melts
at 810˚ or when just red hot; and, when cooled slowly,
forms oblong crystals perpendicular to the internal surface of
the vessel in which it cools.
2. When exposed to the air it loses its lustre, but under-
goes no other change. Neither is it altered by cold water,
but at a red heat it decomposes water and combines with its
oxygen, while hydrogen gas is emitted. When heated in an
open vessel it gradually combines with oxygen, and evaporates
in a white smoke, which, when collected, was formerly called
argentine flowers of antimony. When suddenly heated anti-
mony burns and is converted into the same white oxide.
Two oxides of antimony are known.
SECT. XVI. ANTIMONY. 61
The protoxide may be obtained thus. Dissolve antimony
in muriatic acid, dilute the solution with water; a white
powder falls, wash it and boil it in a solution of carbonate of
potash. Then wash and dry it. The protoxide thus ob-
tained is a dirty white powder. At a moderate red heat it
melts and becomes opake, and crystallizes in needles on
cooling. It is composed of 81.5 antimony, 18.5 oxygen.
The peroxide may be obtained by keeping the antimony
in a red heat; for the argentine flowers are peroxide of anti-
mony. It may be obtained also by dissolving antimony in
nitric acid, or by throwing it into red hot nitre. It is white,
insoluble in water, and less soluble in acids than protoxide.
It is easily volatilized by heat, but requires a pretty high tem-
perature for fusion. It is composed of 77 antimony and 23
oxygen.
3. Antimony has never been combined with hydrogen or
carbon; but it unites readily to phosphorus and sulphur.
Phosphuret of antimony may be formed by dropping bits
of phosphorus into melted antimony. It is white, brittle,
and appears of a laminated structure.
Sulphuret of antimony exbts native, and was formerly dis-
tinguished by the name of antimony the pure metal being
called regulus of antimony. It has a dark bluish grey co-
lour and the metallic lustre. It is brittle and often crystal-
lized. It is composed of 75 antimony and 25 sulphur.
The protoxide of antimony has the property of dissolving
different portions of the sulphuret by means of heat, and
forming with it a vitreous substance of a reddish brown co-
lour, and differing in transparency according to the proper-
tion of sulphuret. It is called glass of antimony, crocus me-
tallorum, liver of antimony, according to its appearance.
4. Antimony does not comine with the simple incom-
bustinles. But it forms alloys with almost all the metals.
It renders other metals brittle, and none its alloys is of
62. METALS. CHAP. IV.
much consequence, except the alloy of tin and antimony
which constitutes pewter, and of lead and antinomy, which
constitutes the metal of printers types.
SECT. XVII. Of Tellurium.
This metal has been hitherto found only in the mine of
Mariahilf in Transylvania. Its peculiar nature was first sus-
pected by Muller of Reichenstein in 1782, and fully proved
by the experiments of Klaproth in 1798.
1. Its colour is bluish white\82 its texture laminated, and
its brilliancy considerable. It is very brittle. Its specific
gravity is 6.115. It melts a little above the melting point
of lead, and may be easily distilled over in close vessels.
When cooled slowly it crystallizes.
2. When exposed to the blowpipe on charcoal it burns
with a blue flame, and is converted into a white oxide which
disperses in smoke. The same oxide may be obtained by
dissolving the tellurium in muriatic acid and diluting with
water. When heated it melts into a straw-coloured mass.
3. Tellurium may be combined with sulphur by fusion.
The sulphuret has a leaden grey colour and radiated texture.
The action of the other simple combustibles has not been
tried.
4. It may be amalgamated with mercury, but we are ig-
norant of the metallic alloys which it is capable of forming.
Sect. XVIII. Of Arsenic.
The ancients gave the name of arsenic to a compound of
arsenic and sulphur. The white oxide of arsenic, known in
commerce by the name of arsenic, must also havn been
known to them. But they do not seem to have been ac-
quainted with the substance which we call arsenic in its
SECT. XVIII. ARSENIC. 63
metallic state. The discoverer of this substance is unknwn.
But Brandt first ascertained its properties in 1733.
1. Arsenic has a bluish white colour, and a good deal of
brilliancy. When heated in the open air, it blackens, smokes,
and emits the odour of garlic. It is the softest metal known.
Its specific gravity is 8.31. It is remarkably brittle. It is
very volatile, subliming without melting when heated to 356˚.
When slowly sublimed it crystallizes in tretahedrons.
2. It may be kept under water without alteration, but in
the open air, it soon falls into a black powder. We know
two oxides which it is capable of forming.
The white oxide is obtained by exposing arsenic to a mo-
derate heat. The metal takes fire, emits the smell of garlic,
and is volatilized in a white smoke, which is the oxide in
question. It is obtained in the large way during the smelt-
ing of various ores which contain arsenic. It is white, com-
pact, and like glass. Its taste is acrid and sweet, and it is
one of the most virulent poisons known. It dissolves in wa-
ter and exhibits different properties of an acid. It dissolves
also in alcohol, and in oils. It crystallizes in tetrahedrons.
It sublimes at the heat of 385˚. Its specific gravity varies
from 3.7 to 5.0000 according to its state. It is composed of
75.2 arsenic and 24.88 oxygen.
The peroxide of arsenic was discovered by Scheele. It is
usually called arsenic acid. It may be obtained by dissolv-
ving white oxide of arsenic in nitro-muriatic acid, evaporating
to dryness, and applying sufficient heat to drive off these acids.
In this state it is a white mass which readily dissolves in wa-
ter. Its taste is excessively sour, and it possesses all the other
properties of an acid. It is composed of 63.4 parts of arse-
nic, and 34.6 of oxygen.
2. Arsenic combines readily with the simple combusti-
bles, carbon excepted, with which it has not hitherto been
united.
6 METALS. CHAP. IV.
When a mixture of tin and arsenic, or of zinc and arsenic
is dissolved in muriatic acid, the hydrogen which exhales
holds a considerable portion of arsenic in solution, and is
known by the name of arsenical hydrogen. This gas posses-
ses some curious properties, which have been investigated by
Trommsdorf and Stromeyer.
Phosphuret of arsenic may be formed by mixing the two
constituents, and distilling them together over a moderate fire.
It is black and brilliant, and ought to be kept under water.
Sulphur combines readily with arsenic by heat. Two
distinct compounds of these two bodies are found native.
The first called realgar is of a scarlet colour, and often
crystallizes in transparent prisms. It is tasteless, and not
nearly so poisonous as arsenic. It is composed of 60 arse-
nic, and 30 sulphur. The second compound is called orpi-
ment. It is of a fine yellow colour, and may be formed by
pouring a solution of sulphureted hydrogen into arsenic dis-
solved in water. It is foliated, and much heavier than real-
gar. According to Thenard, it is composed of 3 sulphur
and 4 arsenic.
3. Arsenic does not combine with the simple incombus-
tinles, but it unites with the metals, and renders them brit-
tle. None of its alloys have been applied to any useful pur-
pose.
Sect. XIX. Of Cobalt.
Cobalt occurs in different mines in Germany and England,
and has been long employed to give a blue colour to glass.
Its peculiar properties were first ascertained by Brandt in
1733.
1. Cobalt has a grey colour with a shade of red, and is
not very brilliant. It is of the hardness of silver, or a little
harder. Its specific gravity is 7.7. It is brittle, and easily
SECT. XX. COBALT. 65
reduced to powder. It melts at 130˚ Wedgewood, and
crystallizes as it congeals. It is attracted by the magnet,
and may itself be converted into a magnet.
2. It is not altered by air nor water at the ordinary tem-
perature of the atmosphere, but in a red heat it is gradually
converted into an oxide. We are acquainted with 3 oxides
of cobalt.
The protoxide is blue. It may be obtained by dissolving
cobalt in nitric acid, precipitating by potash, washing and
drying the powder, and exposing it to a red heat for some
time. It dissolves in acids without effervescence. It is com-
posed of 83 1/2 cobalt, and 16 1/2 oxygen.
Moist protoxide, when exposed to the air gradually absorbs
oxygen, and assumes an olive colour This is the deutoxide
of cobalt. When digested in mriatic acid, oxymuriatic
acid flies off, and a solution of protoxide is obtained.
By gradual exposure to the air, more oxygen is absorbed,
and the oxide becomes black. This is the peroxide. It
forms abundance of oxymuriatic acid gas when digested in
muriatic acid. It is composed of 80 cobalt and 20 oxygen.
3. Cobalt does not combine with carbon or hydrogen.
Sulphuret of cobalt may be formed by melting the metal
with sulphuret of potash. It is yellowish white, and is com-
posed of 71 1/2 cobalt and 281/2 sulphur.
Phosphuret of cobalt may be formed by throwing bits of
phosphorus upon red hot cobalt. It is white and brittle,
and soon loses its metallic lustre.
4. Cobalt does not combine with the simple incombusti-
bles. It unites with the different metals, and forms alloys
which have been but imperfectly examined.
SECT. XX. Of Manganese.
Ores of the metal called manganese are conmon, in which it
occurs always in the state of an oxide. Scheele, Bergman and
E
66 METALS. CHAP. IV.
Gahn are the chemists to whom we are indebted for the first
investigation of its properties.
1. Manganese has a greyish white colour, and considera-
ble brilliancy. Its texture is granular. It is of the hardness
of iron. It is brittle. Its specific gravity is 6.850, It re-
quires a heat of l60˚ Wedgewood to melt it, and is there-
fore rather more infusinle than iron.
2. It absorbs oxygen when exposed to the air. We are
acquainted with 3 oxides of this metal.
The protoxide is white. It may be obtained by dissolv-
ing black oxide of manganese in nitric acid by the assistance
of sugar, and precipitating by potash. It is a white powder
composed of 80 manganese and 20 oxygen.
The deutoxide may be obtained by exposing the black
oxide to a violent heat, or by dissolving black oxide in sul-
phuric acid, by means of heat, and precipitating with pot-
ash. It is a red powder composed of 74 manganese and
26 oxygen.
The peroxide or black oxide exista native in abundance.
It has the metallic lustre, and is often crystallized. When
heated, it gives out abundance of oxygen gas. It is com-
posed of 60 manganese and 40 oxygen.
3. Manganese does not combine with hydrogen or carbon,
but it unites with hydrogen and sulphur.
Phosphuret of manganese may be formed by dropping
phosphorus on red hot manganese. It is white, brittle, gra-
nular, and disposed to crystallize.
Bergman did not succeed in his attempts to combine sul-
phur with manganese. But he formed a sulphurated oxide
by heating 8 parts of black oxide, and 3 parts of sulphur.
4. Manganese does not combine with the simple incom-
bustinles; but it unites with the metals, and forms alloys
which have been but imperfecdy examined.
SECT. XXI. CHROMIUM. 67
SECT. XXI. Of Chromium
This metal was discovered by Vauquelin, who extracted it
from the red lead ore of Sineria. Owing to the violent heat
necessary to fuse it, its properties are but imperfectly known.
1. Its colour is white, intermediate between that of tin
and steel. Its specific gravity is 5.90. It is very brittle,
assumes a good polish, and is magnetic, though inferior in
this respect to iron, nickel and cobalt. Acids act upon it
with great difficulty. It requires a very high temperature to
melt it, so that hitherto it has only been obtained in small
grains.
2. Chromium is not altered by exposure, but when heat-
ed in the open air, it is gradually oxidized. Three oxides of
this metal are known.
The protoxite or green oxide may be obtained by expos-
ing chromic acid to heat in close vessels. Oxygen is disen-
gaged, and the green oxide remains behind.
The deutoxide is intermediate between the green oxide and
chromic acid. Its colour is brown.
The peroxide or chromic acid is found native in red lead
ore. It is of a red or orange colour, soluble in water, and
composed of 1 part chromium, and 2 parts oxygen.
The remaining properties of chromium have not been ex-
amined.
Sect. XXII. Of Uranium.
This metal was discovered by Klaproth and extracted by
him from an ore which occurs in Saxony, and is known by
the name of pechblende.
l. It requires so violent a heat to melt it that hitherto the
fusion has only been imperfectly accomplished. Its colour
E 2
68. METALS. CHAP. IV.
is iron grey, it has considerable lustre, and is soft enough to
yeald to the file. Its specific gravity is 9.000.
2. It forms various oxides which have been hitherto only
examined by Bucholz.
When heated to redness it undergoes a species of combus-
tion, and is converted into a greyish black powder, which is
the protoxide. It is composed of 95 uranium and five oxy-
gen.
When uranium is dissolved in nitric acid and precipitated
by potash, it is obtained in the state of a peroxide. It is a
yellow, tasteless powder, insoluble in water. It dissolves with
effervescence in muriatic acid, oxymuriatic acid gas being
exhaled. It is composed of 80 metal, 20 oxygen.
Besides these two oxides, Bucholz is of opinion that there
are several others intermediate between them, distinguishable
by their colour. He recognised four, namely, the violet,
the greenish brown, the greyish green, and the orange.
3. Uranium is capable of uniting with sulphur. No ex-
perments have been made of the action of the other simple
combustibles on it. Neither do we know the action of the
simple incombustibles, or the alloys which it forms with
other metals.
Sect. XXIII. Of Molybdenum.
This metal is extracted from a scarce mineral called mo-
lybdena, first examined by Scheele. Molybdenum was first
obtained in the metallic state by Hjelm.
1. Hitherto it has only been obtained in small grains
simply agglutinated. Its colour is silvery white. Its specific
gravity is 8.611. It is brittle, not altered though kept under
water, but the effect of air is unknown.
2. When heated in the open air it gradually combines
with oxygen, and is volatilized in the form of small white
needles. It seems capable of forming four different oxides.
SECT. XXIII. MOLYBDENUM. 69
The protoxide is brown. It is obtained by exposing mo-
lybdenum in powder to a red heat.
By exposing it to a longer and more violent heat it becomes
violet brown. This Bucholz considers as a second oxide.
The blue oxide may be obtained by carrying the heat a
little farther, or by triturating together one part of molybde-
num and two parts of molybdic acid, boiling the mass in
water and evaporating the liquid to dryness. This oxide
possesses several properties of an acid. It converts vegetable
blues to red, and combines with saline bases and forms salts.
It may be called molybdenopus acid. It is composed of 100
metal and 34 oxygen.
The white oxide, or molybdic acid, is obtained by roast-
ing molybdena for some time, dissolving the grey powder in
ammonia, and pouring nitric acid into the solution. The
oxide precipitates in fine white scales, which, when melted
and sublimed, become yellow. It converts vegetable blues
to red, but does not act so powerfully as the blue oxide. It
is composed of two parts metal and one part oxygen.
3. Molybdenum combines with phosphorus and sulphur,
but not with carbon and hydrogen.
Sulphuret of molybdenum occurs native, and is usually
called molybdena. It is of a bluish grey colour, has the
metallic lustre, and is composed of plates. It coustists of 60
parts metal and 40 sulphur.
4. The simple incombustibles do not combine with mo-
lybdenum; but it unites with the metals and forms alloys
which hitherto have been examined only by Hielm. None
of them are of much importance.
Sect.XXIV. Of Tungsten.
Tungsten was discovered by Scheele, and reduced to the
metallic state by the D'Elhuyars. It is so difficult of fusion
E3
70 METALS. CHAP. IV.
that, hitherto, it has been very seldom procured in a tolera-
bly compact state. It is sometimes called scheelium after
the discoverer.
1. It is of a greyish white colour, and has a good deal of
brilliancy. It is very hard and seems to be brittle. Its spe-
cific gravity is 17.6. It requires a temperature at least equal
to 170˚ Wedgewood to melt it. It is not magnetic.
2. When heated in an open vessel it is gradually oxidized.
We are aquainted with two dndifferent oxides of this metal,
blue and the yellow.
The protoxide or blue oxide may be obtained by heating
the yellow oxide for some hours in a covered crucinle.
The peroxide or yellow oxide may be obtained by boiling
tungsten or its ore in muriatic acid, decanting off the acid,
and allowing it to settle. A yellow powder gradually preci-
pitates. This yellow powder is to be dissolved in ammonia,
the solution evapotated to dryness, and the residue kept for
some time in a red heat. This yellow oxide is composed of
80 parts metal and 20 oxygen. It combines with bases,
forms salts, and therefore has been considered as an acid.
Its specific gravity is 6.12.
3. Tungsten combines with sulphur and phosphorus, but
not with hydrogen or carbon.
4. The simple incombustibles do not unite with it, but it
combines with the metals and forms alloys, hitherto exami-
ned only by the Elhuyarts.
Sect. XXV. Of Titanium.
This metal was discovered by Mr Gregor; but it received
its name from Klaproth, who discovered it without any
knowledge of the labours of Gregor.
1. It is so refractory that most persons have failed in their
attempts to reduce it. Lampadius is said to have succeeded.
4
SECT. XXVI. TITANIUM. 71
Its colour is that of copper, and it has considerable lustre.
It is brittle but elastic.
2. It is easily oxidized by exposure to beat and air. We
know three oxides of titanium, the blue, the red, and the
white.
The protoxide, which is blue or purple, is formed by ex-
posing titaium hot to the open air.
The red oxide is found native. It is often crystallized in
four-sided prisms. Its specfic gravity is 4.2, and it is hard
enough to scratch glass. By a very violent heat it seems to
be partially oxdidized. It seems to be comosed of 100 me-
tal and 33 oxygen.
The peroxide, or white oxide, may be obtained by fusing
the red oxide in a crucinle with four times its weight of pot-
ash and dissolving the whole in water. A white powder
gradually precipitates, which is the oxide in question. It is
composed of about two parts metal and one oxygen.
S. Titanium has been combined with none of the simple
combustibles except phosphorus. The phosphuret is of a
white colour, brittle and granular, and does not melt before
the blowpipe.
4. Hitherto titanium has been alloyed with none of the
metals except iron.
Sect. XXVI. Of Columbium.
This metal was discovered by Mr Hatchett during the ana-
lysis of an ore from America, deposited in the British mu-
seum. He obtained from the mineral a white powder which
possessed acid properties peculiar to itself. He shewed that
this powder was a metallic oxide; but all attempts to reduce
it to the metallic state were unsuccessful. We are at pre-
sent ignorant of the properties of this metal.
E 4
72 METALS. CHAP. IV.
Ekeberg, a Swedish chemist, announced, some years ago,
that he had discovered a peculiar metal, to which he gave
the name of tantalum. Dr Wollaston has lately proved that
this new metal is the same with Mr Hatchett's columbium.
Sect. XXVII. Of Cerium.
This metal was discovered by Hisinger and Berzelius in a
mineral found in a Swedish copper minee, and at first con-
founded with tungsten. To procure the oxide of cerium is
easy, but all attempts to reduce that oxide to the metallic
state have failed. The metal appears to be volatile, and is
dissipated by a violent heat, while a moderate heat is not suf-
ficient to reduce it.
1. Cerium appears to be white and brittle, but its other
properties are unknown.
2. It forms, at least, two oxides, the white and the brown;
and, according to the Swedish chemists, there are two oxides
intermediate between these, the yellow and the red.
3. We are unacquainted with the effect of the simple com-
bustinles and incombustibles on cerium. It has been alloyed
with iron, but with no other metal.
Sect. XXVIII. General Remarks.
The following table exhibits a synoptical view of some of
the principal properties of the metals.
SECT. XXVIII. GENERAL REMARKS. 73
Metals. Colour. Hard- Specific Melting point Tenacity
ness gravity Fahrenheit Wedgew.
Gold Yellow 6.5 19.361 32 150.07
Platinum Whit 8 23.000 170 274.31
Silver 7 10.510 22 187.13
Mercury White 0 13.568 39
Palladium White 9 11.871 160+
Rhodium White 11+ 160+
Iridium White 160+
Osmium Blue 160+
Copper Red 7.5 8.805 27 302.26
Iron Grey 9 7.8 158 549.25
Nickel White 8.8 8.666 160+
Tin White 5 7.299 442 31.00
Lead Blue 5.5 11.352 612 18.40
Zinc White 6.5 6.861 680 18.20
_______________________________________________________
Bismuth Reddish 7 9.822 176 20.10
white
Antinomy White 6.5 6.712 810 7
Tellurium White 6.115 612+
Arsenic White 5 8.31O 400+
74 METALS. CHAP. IV.
Table continued.
Metals. Colour. Hard- Specific Melting point Tenacity
ness gravity Fahrenheit Wedgew.
Cobalt Grey 6 7.7 130
Manganese Grey 9 6.850 160
Chromium White 5.90 170+
Uranium Iron-grey 9.000 170+
Molybdenum White 8.611 170+
Tungsten White 9+ 17.600 170+
________________________________________________________
Titanium Red 170+
Columbium 70+
Cerium White 170+
2. All the metals are capable of combining with oxygen.
The knowledge of the number of oxides, and of the proportion
of oxygen which they contain, is of great importance. The
following table exhibits a list of these oxides, as far as known,
of their colours, and of the quantity of oxygen in each, com-
bined with 100 parts of metal.
SECT XXVIII. GENERAL REMARKS. 75
Metals. Oxides. Colours. Oxygen.
Gold 1 Purple
2 Yellow 32
Platinum 1 Green 7.5
2 Brown 15
Silver 1 -
2 Olive 12.8
Mercury 1 Black 5
2 Red 10
Palladium 1 Blue
2 Yellow
Rhodium P Yellow
Iridium 1 Blue?
2 Red?
Osmium P Transpar.
Copper 1 Red 13
2 Black 25
Iron 1 Grey 18
2 Black 37
3 Red 92.3
Nickel 1 Green 28
2 Black
Tin 1 - -
2 Grey 25
3 White 38.8
Lead 1 - -
2 Yellow 8
3 Red 13.6
4 Brown 25
Zinc 1 Yellow 13.6
2 White 25.0
Bismuth P Yellow 12
Antinomy 1 White 22.7
2 White 30
Tellurium P White
Arsenic 1 White 33
Cobalt 1 Blue 19.7
2 Green
3 Black 25
Manganese 1 White 25
2 Red 35
3 Black 66.6
Chromium 1 Green
2 Brown
3 Red 200
Uranium 1 Black 5.17
2 Yellow 28
Molybdemum 1 Brown
2 Violet
3 Blue 34
4 White 50
76 METALS. CHAP. IV
Table continued.
Metals. Oxides. Colours. Oxygen.
Tungsten 1 Black 15
2 Yellow 25
Titanium 1 Blue 16
2 Red 33
3 White 49
Columbium P White
Cerium 1 White
2 Red
The Letter P in the second column signifies Peroxide.
3. Of the simple combustibles carbon has been only
united hitherto to one metal, namely iron: hydrogen gas
dissolves arsenic, zinc and iron, seemingly in the metallic
state: phosphorus combines with most of the metals hither-
to tried, but these compounds have been applied to no use-
ful purpose: sulphur likewise combines with most metals;
the sulphurets are often found native; some of them are pre-
pared artificially as paints: we do not know the action of
boracium on the metals.
4. The action of the simple incombustibles on metals is
not striking. Azote has no effect. Muriatic acid oxydizes
some of them, and it readily combines with the metallic
oxides.
5. The combinations of the metals with each other called
alloys, are some of them, as those of zinc and tin, of great
importance. The greater number of them have only been
very superficially examined.
CHAP. I. LIGHT. 77
DIVISION 1.
OF UNCONFINEABLE BODIES.
The unconfineable bodies cannot be examined directly; be-
cause we have no method of retaining them till we ascertain
their properties. We can only draw inferences respecting
them by seeing the changes produced upon those bodies into
which they enter, or from which they separate. They are
four in number, namely, light, heat, electricity and magnet-
ism. But the examination of the two last is not considered
as the province of chemistry. The two first will occupy our
attention in the following chapters.
Chap. I.
Of Light.
Every person is acquainted with the light of the sun, and
of burning bodies, and that it is by means of light that bo-
dies are rendered visinle.
Huygens considered light as a subtile fluid filling space,
and rendering bodies visinle by the undulations into which it
is thrown. While Newton and almost all other philosophers
consider it as a subtile substance, constantly separating from
luminous bodies, moving in straight lines, and rendering bo-
dies visinle by entering the eye.
Light takes about 8 minutes in moving across half the
earth's orbit, which is a space exceeding 90 millions of miles;
of course its velocity is not much less than 200,000 miles in
a second. From this velocity, joined to the imperceptinle
effect produced by the impulse of the particles of light on
78 LIGHT. CHAP. I.
other bodies, it is obvious that its particles are inconceivably
minute. Hence the reason that they produce no perceptinle
effect upon the most delicate balance.
While a ray of light moves in the same medium, or when
it passes perpendicularly from one medium to another, it
does not change its direction. But when it passes obliquely
from one medium to another it changes its direction and is
then said to be refracted. When it passes from a rarer to a
denser medium, it is refracted towards the perpendicular;
when from a denser to a rarer, it is refracted from the per-
pendicular. In the same medium, the sines of the angles of
incidence and refraction have a constant ratio.
When a ray of light strikes obliquely against a plain sur-
face, even though transparent, instead of passing through, it
is bent back in a contrary direction. Just as would happen
if an elastic ball were made to strike obliquely against the
ground. The ray is then said to be reflected. The angle of
reflection is always equal to the angle of incidence.
When a ray of light passes within a certain distance of
another body, it is bent towards it; at a different distance
it is bent from it. In the first case, the ray is said to be in-
flected, in the second to be deflected.
When a ray of light is made to pass through a triaagular
glass prism, and received upon a sheet of paper, the image
or spectrum, as it is called, instead of being round, is oblong.
This spectrum exhibits seven different colours, in the fol-
lowing order, beginning with the lowest; red, orange, yel-
low, green, blue, indigo, violet. In this case the refiraction
of the ray is increased by the figure of the prism, and if it be
heterogeneous, and consist of rays differing in refranginility,
they will separate from each other, the most refranginle go-
ing to the top of the spectrum, the least refiranginle to the
bottom, and the others in their order. This is the case.
Light consists of seven different rays distinguished by seven
different colours. The red is the least refranginle, and the
CHAP. I. LIGHT 79
violet the most. The refranginility of the rest is in the order
of their names.
The rays of light differ in their power of illuminating ob-
jects. The lightest green or deepest yellow gives the most
light, and the light diminishes as we approach either extre-
mity of the spectrum. The violet has the least illuminating
power.
Light is capable of entering into bodies and remaining in
them, and of afterwards being extricated by various means.
Such bodies are said to phophuresce. Almost all bodies
possess this property to a certain extent. If they be exposed
to the sun, and suddenly carried to the dark, they are luminous
for some time, but in general, for a very short period.
Some bodies seem to contain light as a constituent, from
which it may be extricated by various means. Thus fluor
spar, and various other minerals become luminous when
heated. Herring, other fish, meat and wood, often become
luminous just before they begin to putrefy, and often conti-
nue luminous for a considerable time.
Light produces considerable changes upon certain bodies.
The green colour of plants is owing to it, for when they ve-
getate in the dark, they are white. Nitric acid and oxymu-
riatic acid are decomposed by exposure to the light, and
oxygen gas emitted. The oxide of silver, and perhaps also
of gold, is reduced by exposure to light. Till lately it was
supposed that these changes were produced by the co-
lorific rays of light. But it has been recently ascertained,
that muriate of silver is blackened most rapidly when placed
beyond the violet ray, and entirely out of the prismatic spec-
trum. Hence it follows, that the change is produced not
merely by the colorific rays, but by rays which are incapable
of rendering objects visinle, or of producing any sensible
heat. Thus we learn that the solar light contains at least
2 distinct sets of rays, one set which renders bodies visinle,
80 CALORIC. CHAP. II.
and another which blackens muriate of silver, and reduces
metallic oxides. This second set may be called deoxidizing
rays, till some better name is thought of. They are obvious-
ly more refranginle than the coloric rays.
Such are the properties of light. They are sufficient to
induce us to believe that it is a body; but it possesses three
peculiarities, by which it is distinguished from all the sub-
stances hitherto descrined. It has the power of exciting in
us the sensation of vision; it always moves with a prodigious
velocity, and the particles of it are never found cohering
together in masses. This last property cannot well be ac-
counted for, unless we suppose that its particles repell each
other.
The sources of light are, the sun and stars, combustion,
heat and percussion.
The light emitted by the sun is familiarly known by the
name of the light of day. In all cases of rapid combustion
lignt is emitted: but different substances vary very much in
the quantity of light which they give out while burning. All
substances, except gases, become luminous when heated to a
certain temperature (about 700˚). They are then said to be
red hot. When hard substances, as two quartz stones, flint
and steel, are struck against each other, luminous sparks are
emitted. This is sometimes, (as in the case of flint and steel)
owing to the particles given off catching fire; but in other
cases, the appearance of the spark has not been accounted
for.
Chap. II.
Of Caloric.
The meaning of the word heat is so well understood, that
any attempt to define it is unnecessary. When we say that
SECT. I. NATURE OF CALORIC. 81
person thels heat, that a stone is hot, the expressions are un-
derstood readily. Yet in each of these propositions, the
word heat has a distict meaning. In the first it signifiest
the sensation of heat, in the second, the cause of that sensa-
tion. To avoid the supposed ambiguity of these two mean-
ings to one word, the term caloric was invented to signify the
cause of heat. When I put my hand on a hot stone, I ex-
perience a certain sensation, which I call the sensation of
heat, the cause of this sensation is caloric. The phenomena
of heat, which are of the utmost importance in chemistry,
will be treated of in the following sections.
Sect. I. Of the Nature of Caloric.
Two opinions respecting the nature of caloric have divided
philosophers. According to some, like gravity it is merely
a property of matter, while others consider it as a peculiar
substance. The latter opinion was first broached by the
chemists, and is at present acceded to by almost the whole
body of philosophers. A recent discovery of Dr Herschel
has rendered this opinion, if possinle still more plausinle than
before.
Dr Herschel, while employed in examining the sun by
means of telescopes, thought of examining the heating power
of the different rays separated by the prism. He found that
the most refranginle rays have the least heating power, and
that the heating power gradually encreases as the refrangi-
bility diminishes. The violet ray of course has the least,
and the red ray the greatest heating power. It struck Dr
Herschel as remarkable, that the illuminating power and
heating power follow different laws. The illuminating
power is greatest in the middle of the spectrum, but the heat-
ing power is greatest at the red end. This led him to sus-
pect, that the heating power does not stop at the end of the
F
82 CALORIC. CHAP. II
visinle spectrum. On trying the experiment, he found that
a thermometer placed a little beyond the spectrum rose still
higher than when in the red ray. This important experi-
ment was successfully repeated by Sir Henry Englefield.
Hence it follows, that there are rays emitted from the sun
which produce heat, but have not the power of illuminating:
consequently caloric is emitted from the sun in rays, and the
rays of caloric are not the same with the rays of light.
All the illuminating rays have the power of excitifig heat.
It is probable that they derive this power from rays of calo-
ric mixed with them, for the rays from the moon; though
they consist of the seven prismatic rays, do not, even when
concentrated, affect the most delicate thermometer.
Thus it appears that solar light is composed of three sets
of rays, the colorific, the calorific and the deoxidizing.
The rays of caloric are refracted and reflected precisely as
the rays of light. They obviously move with a very consi-
derable velocity, though what that velocity is we do not at
present know. It has been ascertained that caloric produces
no sensible effect upon the weight of bodies; the weight re-
maining sensinly the same, whether a substance be hot or
cold. In this respect it agrees with light. It agrees with
light also in another property, its particles are never found
cohering together in masses.
Sect. II. Of the Motion of Caloric.
When heat radiates from the surfaces of bodies, it moves
with great velocity; but, when it makes its way through bo-
dies, it moves comparatively slowly. Let us consider these
two kinds of motions.
SECT II. MOTION OF CALORIC. 83
1. Escape of Heat from Surfaces.
When bodies artificially heated are exposed to the open
air, they emit heat, and continue to do so till they sink to the
temperature of the surrounding atmosphere. The rapidity
of their cooling depends upon the nature of their surface.
For the investigation of this branch of the subject, we are
indebted chiefly to the sagacity of Professor Leslie. A
globe of bright tin, filled with hot water, lost a certain num-
ber of degrees of heat in 156 minutes. But, when covered
with a thin coat of lamp-black it lost the same number of
degrees in 81 minutes. The rate of cooling was likewise in-
creased by covering it over with a coat of linen, and by paint-
ing it with black or white paint. This difference is only
conspicuos in still air. In a strong wind it diminishes or
nearly disappears.
When a canister of tin, filled with hot water, is placed be-
fore a ooncave mirror of bright polished tin, having a deli-
cate thermometer in the focus, the thermometer experiences
a certain elevation. The differential thermometer invented
by Mr Leslie answers best for these experiments. It con-
sists of a amall glass tube bent into the shape of the letter U
and terminating at each extremity in a small hollow ball.
The tube is filled with sulphuric acid, tinged red with car-
mine. An ivory scale is affixed to one of the legs, and the
top of the liquid stands at the division of the scale marked
o. This thermometer is not affected by any change in the
temperature of the rcom. But if one of its balls be heated,
while the other is not affected, the air within it expands and
pushes away the sulphuric acid which rises in the other leg.
Hence it indicates changes of heat in a particular point, as
the focus of a mirror. The ball of it which is applied to
the point and undergoes the change, is calledfocal ball.
F2
84 CALORIC. CHAP. II.
When the experiment is made in the way above specified,
the rise of the thermometer depends upon the distance of the
canistter from the miror, being always the greater the nearer
the canister is to the mirror. From Mr Leslie's experiments
it follows, that the effect on the thermometer is very nearly
inversely proportional to the distance of the canister from the
reflector.
When the nature and position of the canister is the same,
the rise of the thermometer is always proportional to the dif-
ference between the temperature of the hot canister and that
of the surrounding air.
Heat radiates from the surfaces of hot bodies in all direc-
tions, but the radiation is most copious in the direction per-
pendicular to the surface of the hot body.
When different bodies are applied in succession to the
surface of the canister, their power of radiation becomes evi-
dent by the effect they produce upon the thermometer. The
following table exhibits this effect, as ascertained by the ex-
periments of Mr Leslie.
Lamp-black, 100˚
Water, by estimate, 100+
Writing paper, 98
Rosin, 96
Sealing wax, 95
Crown glass, 90
China ink, 88
Ice, 85
Minium, 80
Isinglass, 80
Plumbago, 75
Tarnished lead, 45
Mercury, 20+
Clean lead, 19
SECT. II. MOTION OF CALORIC. 85
Polished iron, 15
Tin-plate, 12
Gold, silver, copper, 12
Thus it appears that metals radiate heat worst, and that
lamp-black, paper and glass are among the best radiators of
it tried. The radiating power of the metals is increased by
tarnishing and by scratching their surface.
The radiating powers of these bodies were ascertained by
applying thin coats of them to the surface of the canisters.
Now it appears that the radiating power increases somewhat
with the thickness of the coat, till that coat amoonts to the
1/1000th of an inch, when it remains stationary. But this does
not hold with respect to metallic bodies, the thinnest coat of
which produces as great an effect as the thickest.
When the focal ball of the thermometer is glass, let us
suppose that it rises 100˚ If we coat it with tin-foil, the
rise will be reduced to 20˚. Hence it follows that these
bodies that radiate beat best imbthe it best, and that those
which radiate worst imbthe worst.
The contrary holds with respect to reflectors, those sub-
stances refect best which radiate worst, and vice versa. The
following table exhibits the comparative goodness of different
substances as reflectors, according to Mr Leslie's experi-
ments.
Brass, 100
Silver, 90
Tin foil, 85
Block tin, 80
Steel, 70
Lead, 60
Tin-foil, softened by mercury,110
F3
86 CALORIC. CHAP. II
Glass 10
Ditto, coated with wax or oil, 5
when the polish of the reflector is destroyed by rubing it
with sand paper, the effect is very much diminished.
Radiation takes place only in elastic mediums. It is de-
stroyed altogether by plunging the apparatus under water.
It is nearly the same in air and in hydrogen gas, and does not
seem to be affected by the nature of the elastic medium. It
is diminished by rarifying the surrounding air.
When a substance is interposed between the hot canister
and the reflector by way of screen, the effect is varied by its
distance from the canister, by its thickness, and by the nature
of its surface. The nearer it is to the canister the less is the
radiation affected; at a certain distance all radiation is de-
stroyed. The thinner the screen the less of the heat is inter-
rupted; the radiation slowly diminishes as the thickness of
the screen increases. When the surface of the screen radiates
heat well, the radiation is much less interrupted than if it ra-
diate heat ill. Thus, if the screen be glass, the thermometer
still rises a certain number of degrees, but if it be tinfoil the
thermometer does not rise at all. From these phenomana it
cannot be doubted that the screen, in all cases, intercepts the
whole of the heat, that it becomes hotter itself, and then ra-
diates heat from its surface.
Such are the phenomena of the radiation of heat as far as
they have been investigated. It follows very different laws
from light in its radiation. Mr Leslie has endeavoured to
show, that heat is not in reality radiated, but that it is propa-
gated with the velocity of sound by means of undulations or
pulses of air. This opinion he has supported with much in-
genuity. But as he has brought no other evidence for its
truth, but its convenience in explaining the phenomena, and
as it is at variance with the direct experiments of other phi-
SECT. II MOTION OF CALORIC. 87
losophers, it cannot be admitted till direct evidence be
brougnt forward in support of it.
2. Passage of Caloric through Bodies.
Caloric we have seen is incapable of radiating through
solid bodies, yet it is well known that all bodies are pervious
to it. Through them, then, it must make its way in a diffe-
rent manner. In general it passes very slowly through them,
and when it passes in this way, it is said to be conducted
through them.
Bodies seem to conduct heat in consequence of their affi-
nity for it, and of the property which they have of combining
with an indefinite number of doses of it. Hence the reason
of the slowness of the process. Hence also the reason why
the temperature of the body through which it passes dimi-
nishes equally as we advance from the source of heat to the
other extremity.
Bodies vary in their power of conducting heat. The me-
tals are the best conductors of heat of all known bodies.
From the experiments of Ingenhousz, it follows that silver
and gold are the best conductors among the metals. Cop-
per and tin follow next in order, and platinum, iron, steel
and lead are nearly equal among themselves, but much in-
ferior to the others. Stones came next after the metals,
but they are greatly inferior to them. Bricks are still infe-
rior to stones. Glass also is a bad conductor. Hence the
facility with which it cracks when suddenly heated or cooled.
Dried woods are considerably inferior to glass. From the
experiments of Meyer, it appears that they differ considera-
bly among themselves. Charcoal is also a bad conductor.
According to the experiments of Morveau its conducting
power is to that of fine sand, as 2 to 3. Feathers, silk,
wool and hair are still worse conductors than any of the pre-
F 4
ceding substances. Hence the reason that they answer so
well as articles of clothing.
It is admitted on all hands, that all solid bodies are con-
ductors, for they allow heat to pass through them. Liquids
also allow heat to pass through them. But they differ from
solids in the mobility of their particles. When a particle of a
liquid is heated, it becomes specifically lighter, and therefore
rises. Count Rumford has endearoured to prove that heat
passes through liquids only in consequence of the motion of
their particles, and that if the particles of liquids were immov-
able, heat could not pass through them at all. Hence he in-
feres, that liquids are in reality non-coductors of caloric.
But his experiments are not such as to warrant the conclu-
sions he has drawn. The subject has been investigated by
different chemists, with all the requisite care. It has been
shown that heat can make its way downwards through liquids,
in which case their particles cannot be supposed to move.
Hence it follows that they are all conduictors. They are
however very bad conductors. Water, for example, con-
ducts heat much worse than any of the dry woods.
The gases are still worse conductors than liquids. They
differ a good deal among themselves in their oonducting
power. Hydrogen gas appears to be the best, and carbonic
acid the worst conductor. From the experiments of Leslie,
it appears that hydrogen conducts 4 times as well as com-
mon air. The conducting power of gases is diminished by
rarefaction, by vapours of all kinds, and every thing which
has a tendency to dilate air. The following table by Mr
Dalton exhibiting the time taken by a thermometer to cool
a given number of degrees in the different gases will give the
reader some idea of their relative conductive powers.
SECT. III. DISTRinUTION OF TEMPERATURE. 89
Carbonic acid 112''
Sulphureted hydrogen 100+
Nitrous oxide 100+
Olefiant gas 100+
Common air 100
Oxygen 100
Azotic gas 100
Nitrous gas 90
Gras from pitcoal 70
Hydrobgen gas 40
Sect. III. Of the equal Distribution of Temperature.
When substances of different temperatures in placed in
each others neighbourhood, the hotter bodies become colder,
and the colder acquire heat, and the changes continue till
all the bodies acquire the same temperature. This property
of caloric of distrinuting itself equally, has been called the
equilinrium of caloric. It might with more propriety be
called the equal distrinution of temperature.
It had been taken for granted by Sir Isaak Newton, and
was proved by the experiments of Kraft and Richmann, that
when a body is suspended in a medium of a temperature
different from its own, the difference between the tempera-
ture of the bodv and the medium diminishes in a geometrical
ratio, while the time increases in an arithmetical ratio; or,
which comes to the some thing, that in given small times, the
heat lost is always proportional to the heat remaining in the
body.
90 OF CALORIC. CHAP. II
Sect. IV. Of the Effects of Caloric.
The changes which caloric produces on bodies may be ar-,
ranged under 3 different heads; namely, 1 . Changes in bulk;
2. Changes in state; and 3. Changes in combination.
1. Changes in Bulk.
Eyery addition or abstraction of heat produces a corre-
sponding change in the bulk of the body affected. In gene-
ral the addition of heat produces expansion, and the adstrac-
ion of it produces a dminution of bulk. To this general
law there are perhaps one or two exceptions.
The expansion of gases by heat is greatest, that of liquids
much smaller, and that of solids smallest of all. Thus 100
cubic inches of air being heated from 32˚ to 212˚, ex-
pand to 137.5 inches. The same augmentation of tempera-
ture makes 100 cubic inches of iron by the same increase of
temperature expand only to 100.1 inches.
All gases undergo the same expansion by the same aug-
mentation of temperature, and the same contraction by the
same diminution of temperature. This change is nearly
equable, though it is a little less at high temperatures than at
low. From the most exact experiments hitherto made, we
may conclude that air and all gases expand about 1/451 part of
their bulk for every degree of heat thrown into them.
From the experiments of Gay-Lussac, it appears that the
steam of water and the vapour of ether undergo the same
dilation as air when the same addition is made to their tem-
perature. Hence it is reasonable to conclude, that all elas-
tic fluids expand equally and uniformly by heat.
The expansion of liquids differs from that of elastic fluids,
not only in quantity, but in the want of uniformity. Every
SECT. IV EFFECTS OF CALORIC. 91
liquid has a peculiar expansion of its own, different from that
of every other liquid. The expansinility is greater when the
temperature is high, than when it is low. Alcohol expands
most of all the liquids hitherto tried. 100,000 parts of it at
32˚ become 104,162 at l00˚. Nitric acid is the next in or-
der, then lintseed oil, then oil of turpentine, then sulphuric
acid, then water, and mercury is the least expansinle of all
the liquids hitherto tried.
The solids expand much less than the liquids. As far as
observation has gone, their expansion is equable, or at least
their deviation from it is insensible. 100,000 parts of glass
at 32˚ become at 100,083 at 212˚. The order of the ex-
pansinility of the principal metals is as follows, beginning
with the least expansinle. Platiuum, gold, antimony, cast-
iron, steel, iron, bismuth, copper, brass, silver, brass-wire,
tin, lead. zinc.
The property which bodies have of expanding when heat
is applied to them, has suggested an instrument for measur-
ing the relative temperatures of bodies. This instrument is
the thermometer. A thermometer is a hollow tube of glass
hermetically sealed and blown at one end into a hollow globe
or bulb. The bulb and part of the tube are filled with mer-
cury. When the bulb is plunged into a hot body, the mer-
cury expands, and of course rises in the tube; when it is
plunged into a cold body, the mercury contracts, and of con-
sequence sinks in the tube. Thermometers are made in this
way. The requisite quantity of mercury being introduced,
the thermometer is plunged into melting snow, and the
place where the mercury stands is marked. This is called
the freezing point. The thermometer is then plunged into
boiling water, and the point at which the mercury stands
marked. This is called the boiling water point. The dis-
tance between these two points is divided into a number of
92 CALORIC. CHAP. IV.
equal parts called degrees, and these degrees are continued
indefintlely above and below these two points.
The Thermometer gets its name according to the number
of degrees into which the space between the freezing and
the boiling point is divided. There are four thermometers still
used in Europe. In that of Reaumur the space between the
two points is divided into 80˚. The freezing point is marked
0, the boiling point 80˚. In the thermometer of Celsius the
same space is divided into 100 degrees. The freezing point
is marked 0, the boiling point 100˚. This is the thermome-
ter used in Sweden and in France since the revolution. In
the thermometer of Fahrenheit, the space between the two
points is divided into 180 degrees. But the scale begins at
the cold produced by a mixture of snoW and salt, which is
32˚ below the freezing point. The freezing point is marked
in consequence 32˚, and the boiling point 212˚. This is the
thermometer used in Britain. It is the one always used in
this work, except when some other is expressly mentioned.
In the thermometer of Delisle, the space between the two
points is divided into 150 degrees, but the graduation begins
at the boiling point, which is marked 0. The freezing point
is marked -150.
As mercury does not expand equably, the thermometer
does not give us an exact measure of the increase of heat.
Mr DaJton has endeavoured to prove that mercury expainds
as the square of the temperature, reckoning from its freezing
point. This opinion has induced him to construct a new
thermometer, graduated according to that principle. If this
opinion be correct, the common degrees are too large near
the bottom of the scale, and too small towards the upper
part of it. 122˚, or half way between freezing and boiling,
corresponds according the new graduation with 110˚ of the
old.
SECT. IV. EFFECTS OF CALORIC. 93
The exceptions to expansion by heat are of two kinds.
1. Those liquids which have a maximum of density corre-
sponding with a certain temperature, and which of conse-
quence expand whether they be heated or cooled beyond that
temperature.
2. Certain liquids which become solid by cooling, and ex-
pand during the solidification.
Water is the only liquid at present known belonging to the
first class. Its greatest density is at the tempeiature of 40˚,
or a little below it. If it be heated above that temperature,
it expands, and it expands equally if it be cooled below it.
A vast number of experiments have been made upon this
point, and there appears no doubt of the matter of fact.
Dalton has lately endeavoured to show, that 36˚ is the de-
gree at which the density of water is a maximum, and his ob-
servations appear satisfactory. No satisfoctory explanation
of the cause of this singular anomaly has yet been offered.
The second class of bodies is numerous. Water expands
with great force when it freezes, and is converted into ice.
The specific gravity of ice is at 0.92, that of water at 60˚ be-
ing 1.00. Hence ice is lighter than even boiling hot water.
It always, therefore, swims on the surface of the water. A
similar expansion is observable during the crystallization of
most of the salts. Among the metals there are three which
expand in the act of congealing; these are cast-iron,
and antimony. All the rest seem to contract instead of ex-
panding. Sulphur appears also to expand when it congea!s.
This expansion in these bodies must be ascrined to a new ar-
rangement which their integrant particles assume. It would
lead one to suppose a kind of polarity in these integrant par-
ticles, otherwise it is difficult to conceive why they tend to
expansion with so much force. Honey, oils, and most me-
tals contract when they become solid. Sulphuric acid also
appears to contract.
94 CALORIC. OHAP. II.
Changes in the State of Bodies
All substances in nature, as far as we know them, occur in
one or other of the three states, that of solids, of liquids, and
of elastic fluids. In a vast number of cases, the same sub-
stance is capable of assuming each of these states in success
sion. Thus sulphur is usunlly solid, but at 218˚ it becomes a
a liquid, and at 570˚ it boils, and is converted into an elastic
fluid. Water is a liquid, but at 32˚ it freezes into a solid,
and at 212˚ it boils into an elastic fluid.
Ail solids (a very few excepted) may be converted into li-
quids by heating them sufficiently, and almost all liquids by
cooling them sufficiently,may be converted into solids. Li-
quids by heat may be converted into elastic fluids, and many
elastic fluids may by cold be changed into liquids. The law
then is, that solids by heat are converted into liquids and elas-
tic fluids; while elastic fluids and liquids by cold are brought
into the state of solids.
1. When solids are converted into liquids the change in
some cases takes place at once, without any perceptinle in-
terval between solidity and liquidity. In other cases, the so-
lid passes slowly through all the intermediate degrees of soft-
ness, till at last it becomes a complete liquid. The melt-
ing of ice is an example of the first kind, that of wax and tai-
lor of the second. This change takes place at a particular
temperature, which is easily ascertained in the first class, but
not so easily in the second. If the substance at the usual
temperature of the athmosphere be liquid, this point is called
the freezing point; but if it be usually solid, it is called the
melting point. Thus 32˚ is the freezing point of water, and
476˚ the melting point of bismuth.
Though 32˚ be the freezing point of water, it may be cool-
ed down considerably below that point, without freenng. In
SECT. IV. EFFECTS OF CALORIC 95
thermometer tubes, I have cooled it dowAi to 7˚, and in a
wine glass to 20˚. When agitated or touched with a bit of
ice, it freezes very suddenly.
The freezing point of water is lowered by dissolving different
salts in it. Thus water saturated with common salt freezes
at 4˚ with sal ammoniac at 8˚, with Ruchelle salt at 21˚
and with nitre at 26˚. When the proportion of the same salt
dissolved in water is varied, it follows from the experiments
of Sir Charley Blagden, that the freezing point is always
proportional to the quantity of the salt.
The nitric and sulphuric acids vary remarkably in their
freezing points, according to circumstances. When much
diluted with water, the weakest part freezes, while a strong
portion remains liquid. When very much diluted, the whole
freezes, and the freezing point is lower according to the pro-
portion of acid present. The strong acids themselves uuder-
go congelation, and each has a particular strength at which
its congelation is the easiest. If it be stronger or weaker,
more cold is necessary to congeal it. Sulphuric acid of the
spedfic gravity 1.780 freezes at 46˚. But if it be diluted
with a little water, it requires a cold of -45˚, the strongest
sulphuric acid freezes at 1˚. The strongest nitric acid freezes
at -45.5˚. When considerably weaker it freezes at -2˚,
and when still weaker at -27.7˚.
We are indebted to Dr Black tor the first satisfactory ex-
planation of the change of solids into liquids by heat. Ac-
cording to him, solids, in order to liquify, combine with a
quantity of heat which enters into them, and remains in them
without increasing their temperature. Hence he called it
latent heat. Liquids congeal by giving out this latent heat.
This opinion is established by simple but satisfactory experi-
ments, and he ascertained that the latent heat of water is 140˚.
The following table exhibits the latent heat of some other
liquids as ascertained by the experiments of Dr Irvine.
96 CALORIC. CHAP. II
Latent heat Ditto redu-
ced to the
specific heat
of water
Sulphur 143 68 27.14
Spermaceti 145
Lead 162 5.6
Beewax 175
Zinc 493 48.3
Tm 500 33
Bismuth 550 23.25
Dr Black has shewn also, that the softness of such bodies
as are rendered plastic by heat, depends upon their combin-
ing with a quantify of caloric.
2. Thus the ccmversion of solids into liqnids is owing to
their combining with heat. There is another change no less
remarkable to which bodies are liable when exposed to the
action of heat. Almost all liquids, when exposed to a cer-
tain temperature, gradually assume the form of an elastic
liquid, possessing the properties of air. These fluids retain
their elastic form as long as the temperature continues, but
when cooled down they lose that fomn and are converted
into liquids.
Some liquids are gradually converted into elastic fluids at
all temperatures, while others do not begin to undergo the
change till heated to a certain temperature. Water and al-
cohol are well known examples of the first class of liquids;
sulphuric acid, and the fixed oils of the second. Water
gradually evaporates even when in the state of ice, but sul-
phuric acid not till heated above 212˚. The first class of
liquids are said to evaporate spontaneously.
When other circumstances are the same, the evaporation
increases with the temperature, and the elasticity of the va-
l
SECT. IV. EFFECTS OF CALORIC. 97
pour, of course, increases in the same proportion. At a cer-
tain temperature this elasticity balances the pressure of the
atmosphere. When that happens, if the heat be applied be-
low, the liquid assumes the aerial form with great rapidity.
The vapour forces its way through the liquid, and a violent
agitation is the consequence. The liquid is then said to boil.
Every particular liquid has a certain temperature at which it
begins to boil. Thus ether bolls at 98˚, alcohol at 174˚,
and water at 212˚.
The boiling point varies with the pressure of the atmo-
sphere. It is highest when the barometer is high, and lowest
when it is low. All liquids boil in a vacuum about 145˚
lower than under the pressure of the atmosphere. The elas-
ticity of vapour increases with the temperature. At 32˚ the
vapour of water is capable of supporting a column of mer-
cury 0.2 inches high, at 212˚ it supports a column of 30
inches.
Dr Black applied his theory of latent heat to the conver-
sion of liquids into elastic fluids, and showed that it is owing
to the very same cause as the conversion of solids into li-
quids, namely to the combination of a certain dose of caloric
with the liquid without any increase of temperature. From
his experiments, compared with those of Mr Watt and Mr
Lavoisier, it appears that the latent heat of steam is about
1000˚.
Thus, it appears that Dr Black's law is very general, and
comprehends every change in the state of a body. It may
be stated in its most general form as follows. Whenever a
body changes its state, it either combines with caloric or sepa-
rates from cahric.
3. It is probable that all elastic fluids, or gases, owe their
elastic form, like steam, to the combined caloric which they
contain; and that, if they could be subjected to a sufficient
degree of cold, they would lose their elasticity and be con-
98 CALORIC. CHAP. II.
verted into liquids or solids. This bas been done success-
fidiy to some gases; oxymuriatic acid and ammonia, for ex-
ample, become liquid when cooled down low enough. The
experiment has not succeeded with other gases, even though
subjected at once to cold and pressure.
5. Change in Composition.
Caloric not only increases the bulk of bodies and changes
their state, but its action decomposes many compounds alto-
gether, either into their elements, or it causes these elements
to combine in a different manner. Thus ammonia, in a red
heat, is resolved into hydrogen and azotic gases, and alcohol,
by the same heat, is converted into inflammable air and
water.
In general, those compounds, which have been formed by
combustion, resist the action of heat with considerable ob-
stinacy. Those that contain oxygen, and which have been
formed without combostion are easily decomposed, and so
are most of those that contain combustibles.
SECT. V. Of the Quantity of Caloric in Bodies.
This investigation naturally divides itself into two parts:
1. The relative quantities of heat in bodies, or the quantities
in each neccesary to produce a given change of temperature.
This is usually termed specific caloric. 2. The absolute
quantity of heat which exists in bodies.
1. Of the Specific Cabric of Bodies.
If equal weights of water and spermaceti oil be mixed
at different temperatures, it is natural to expect that the
mixture will aquire the mean temperature. Suppose the
SECT. V. QUANTITY OF CALORIC IN BODIES. 99
temperature of the water 100˚, and that of the oil 50˚, it is
reasonable to expect that the water would be cooled down
25˚, and that the oil would be heated 25˚, and that the tem-'
perature after mixture would be 75˚. But, if we make the
experiment, we find the result very different. The tempe-
rature, after mixture, instead of 75˚, is 83˚ 1/3, consequently
the water has lost only 16 2/3, while the oil has gained 33 1/3.
If we mix together equal weights of water at 50˚ and sper-
maceti oil at l00˚, the temperature, after agitation, unll be
only GG 1/3 no that the oil has lost 33 1/3, while the water has
only gained 16 2/3. This experiment demonstrates that the
same quantity of heat does not produce the same effect on
water and spermaceti oil. The quantity which raises water
165 2/3, raises the oil 33 1/3, or it produces double the effect up-
on the oil that it does on the water. If other substances be
tried in the same manner, we shall find that they all differ
from each other in the quantity of caloric necessary to heat
each of them a given number of degrees, some requiring
more than the same weight of water would do, and others
less. Now, the quantity necessary to produce this effect is
called the specific caloric of each. The specific caloric of
water is taken as the standard and called 1, and all the others
referred to it. It is obvious, from the preceding example,
that the specific caloric of water is double that of spermaceti
oil. If we represent the first by 1, we must, of course, re-
present the second by O.5.
This investigation was begun by Dr Black and prosecuted
by Dr Irvine and Dr Crawford, who published a table of
the specific heat of various bodies, and made it the founda-
tion of his enplanation of animal heat. Mr Wilke of Swe-
den likewise investigated the specific heat of various bodies;
Lavoisier and Laplace attempted the investigation, by ascer-
taining how much ice given weights of bodies, heated a cer-
tain number of degrees, was capable of melting during the
G2
100 CALORIC. CHAP. II.
cooling. The subject was afterwards prosecuted by Kir-
wan, Meyer, Leslie and Dalton. The following table exhi-
bits the result of all the experiments hitherto published on
this important subject.
I. Gases.
Sp. Caloric
Hydrogen 21.4000*
Oxygen 4.7490*
Common air 1.7900*
Carbonic acid 1.0454*
Azote 2.7936*
II. Water.
Ice 0:9000+
0.8000(a)
Water 1.0000
Steam 1.5500*
III. Saline solutions.
Carbonate of ammonia 1.851+
0.95(D)
Sulphuret of ammonia (0.818)0.994+
Sulphate of magnesia 1
Water 2 0.844+
Common salt 1
Water 8 0.835+
Ditto (1.197) 0.78(D)
Nitre 1
Water 8 0.8167#
Nitre 1
Water 3 0.646+
Carbonate of potash (1.30) 0,75(D)
Muriate of ammonia 1
Water 1.5 0.798+
Tartar 1
Water 237.5 0.765+
Sulphate of iron 1
Water 2.5 0.734+
Sulphate of soda 1
Water 2.9 0.728+
Alum 1
Water 2.9 0.649+
Nitric acid 9 1/3
Lime 1 0.6189#
Ditto (1.40) 0.62 (D)
Solution of brown sugar 0.086+
Ditto (1.17) 0.77(D)
IV. Acids AMD Alkalies.
Vinegar 0.92(D)
Nitric Acid pale 0.844+
(1.20) 0.76(D)
(1.2989) 0.6613#
0.62(L)
(1.30) 0.66(D)
(1.355) 0.576+
(1.36) 0.63 1/3(D)
Muriatic acid (1.122) 0.680+
(1.153) 0.60(D)
Sulphuric acid (1.885) 0.758+
(1.872) 0.429+
0.34(L)
(1.844) 0.35(D)
(1.87) 0.3345#
0.333(a)
Do. 4, Water 5 0.6631#
Do. 4, do. 3 0.6031#
Do. equal bulks 0.52(D)
Acetic acid (1.056) 0.66(D)
Potash (1.346) 0-759+
Ammonia (0.997) 0.708+
(0.948) 1.03(D)
V. Inflammable Liquids.
Alcohol 0.930(a)
0.6666*
0.64(L)
0.602*
(0.817) 0.70(D)
1.086+
(0.848) 0.76(D)
Sulphuric ether (0.76) 0.66(D)
Oil of olives 0.718+
0.50(L)
SECT. V. QUANTITY OF CALORIC IN BODIES. 101
Linseed oil 0.528+
spermaceti oil 0.5000*
Oil of turpentine 0.472+
0.400(a)
Spermaceti 0.399+
Ditto fluid 0.320(a)
VI. Animal Fluids.
Arterial blood 1.03000*
Venous blood 0.8928*
Cow's milk 0.9999*
0.98(D)
VIL Animal Solids
Ox hide, with hair 0.7870*
Lungs of a sheep 0.7690*
Lean of ox-beef 0.7400*
VIII. Vegetable Substances.
Pinus sylvestris 0.65\B6
Pinus abies 0.60\B6
Tilea Europaea 0.62\B6
Pinus picea 0.58\B6
Pyrus malus 0.57\B6
Betula alnus 0.53\B6
Quercus robur sessills 0.51\B6
Fraxinus excelsior 0.51\B6
Pyrus communis 0.50\B6
Rice 0.5060*
Horse beans 0.5020*
Dust of the pine-tree 0.5000*
Peas 0.4920*
Fagus sylvatica 0.49\B6
Carpinus betulus 0.48\B6
Betula alba 0.48\B6
Wheat 0.4770*
Elm 0.47\B6
Quercus robur pedunculata 0.45\B6
Prunus domestica 0.44\B6
Diospyrus ebenum 0.43\B6
Barley 0.4210*
Oats 0.4160*
Pit-coal 0.28(D)
0.2777*
Charcoal 0.2631*
Cinder 0.1923*
IX. Earthy Bodies, Stone-ware and Glass
Hydrate of lime 0.40(D)
Chalk 0.27(D)
0.256*
Quick-lime 0.30(D)
0.2229*
0.2168#
Ashes of pit-coal 0.1855*
Ashes of elm 0.1402*
Agate 0.195\A7
Stone-ware 0.195#
Crown-glass 0.200(a)
Crystal 0.1929#
Swedish glass 0.187\A7
Flint-glass 0.19(D)
0.174+
X. Sulphur 0.19(D)
0.183+
Muriate of soda 0.23(D)
XI. METALS
Platinum 0.13(a)
Iron 0.143(a)
0.13(D)
0.125+
0.1269*
0.1216\A7
Brass 0.1123*
0.116\A7
0.11(D)(
Copper 0.1111*
0.114\A7
0.11(D)
Sheet-iron 0.1099#
Gun-metal 0.1100 \A6
Nickel 0.10(D)
Zinc 0.0943*
0.102\A7
0.10(D)
Silver 0.082\A7
0.08(D)
102 CALORIC. CHAP. II
Sp. Caloric.
Tin 0.068+
0.0704*
0.07(D)
0.060\A7
Antinomy 0.086+
0.0645*
0.063\A7
0.6(D)
Gold 0.050\A7
0.05(D)
Lead 0.050+
0.0352*
0.042\A7
0.04(D)
Bismuth 0.043\A7
0.04(D)
Mercury 0.033+
0.0357*
0.0290#
0.0496(D)
XII. Oxides.
Oxide of iron 0.320+
Rust of iron 0.2500*
Ditto, nearly free from air 0.1666*
White oxide of antinomy washed 0.220+
0.2272*
Do. nearly freed from air 0.1666*
Oxide of copper ditto 0.2272*
Oxide of lead and tin 0.102+
Oxide of zinc ditto 0.1369*
Oxide of tin nearly free from air 0.0990*
0.96+
Yellow cnide of lead do. 0.0680*
0.68+
. Crawford; + Kirwan; # Lavoisier and Laplace; \A7 Wilcke; \B6 Meyer;
(L) Leslie; \A6 Count Rmnford; (D) Dalton; (a) Irvine.
The specific heats of the gaseous bodies in the preceding
table were ascertained by Dr Crawford by means of very de-
licate experiments, made with every possinle precaution to
insure accuracy. Yet there is little probability that they are
accurate. Nor are we in possession of any means of making
them more so by experiment. Mr Dalton has calculated the
specific heat of the different gases from theory. The fol-
lowing are the numbers he obtained. The specific heat of
water, as usual, being 1.
Hydrogen gas 9.382
Azotic 1.866
Oxygen 1.333
Air 1.759
Mitrous gas 0.777
Nitrous oxide 0.594
Carbonic acid 0.491
Ammonia 1.555
Carbureted hydrogen 1.333
Olefiant gas 1.555
Nitric acid 0.491
Carbonic oxide 0.777
Sulphureted hydrogen 0.583
Muriatic acid 0.424
Aqueous vapour 1.166
Ether vapour 0.848
Alcohol vapour 0.586
SECT. V. QUANTITY OF CALORIC IN BODIES. 103
Dr Crawford supposed, that the specific heat of bodies is
permanent while they retain their state. But Mr Dalton
has lately endeavoured to prove, that it increases with the
temperature of all bodies.
Dr Irvine ascertained that the specific caloric always
changes with the state of a body. When a solid becomes a
liquid, or a liquid an elastic fluid, the specific caloric increa-
ses. When an elastic fluid becomes a liquid, or a liquid a
solid, the specific heat diminishes.
The specific heat of bodies is increased by combining them
with oxygen. Thus, the specific heat of metallic bodies is
greater than that of metals and of acids than of their bases.
2. Of the Absolult Quaillity of Caloric in Bodies,
As the same quantity of heat produces different degrees
of temperature in different bodies, it is obvious that the
thermometer cannot indicate the absolute quantity of heat in
bodies. Now, it becomes a question of considerable im-
portance to enquire, if there be any method of ascertaining
the absolute quantity of heat in bodies. Supposing a body
deprived of all heat, and a thermometer applied to it, at what
point would the thermometer stand?
Dr Irvine is the philosopher who first attempted to solve
this problem. His reasoning was founded upon two suppo-
sitions. 1. That the specific heat was proportional to the
absolute heat of bodies. 2. That the heat emitted or ab-
sorbed by a body, when it changes its state, is merely the
consequence of the change which has taken place in its spe-
cific heat. Thus, when ice is converted into water, 140˚ of
heat are absorbed; because the specific heat of water is so
much greater than that of ice, that 140˚ are necessary to
maintain the temperature. The first of these two supposi-
tions gave him the ratio of the absolute quantity of heat in
4
104 CALORIC. CHAP. II.
bodies, and the second the difference between two absolute
calorics. Thus, if the specific heat of water be 10, and that
of ice 9, then the absolute quantity of heat in water is, to
that in ice, as 10 to 9. Call the absolute heat of ice x, then
that of water is x + 140, and we have x: x + 140:: 9: 10.
Hence we get this equation 10 x = 9 x + 1260, which gives
us x=1260. Water at 32˚ of course contains 1400˚ of ca-
loric. Dr Crawford, from his experiments, stated the real
zero at 1500 below 0; and Mr Dalton places it at 6000 be-
low 0.
Unfortunately, the truth of the two suppositions upon
which this ingenious reasoning is founded, cannot be admit-
ted. We have no proof that the specific beat of bodies is
proportional to their absolute heat. The second supposition
is at variance with the mechanical phenomena which present
themselves when substances change their state, and would
leave that change itself unaccounted for. It cannot therefore
be admitted. Various other methods of ascertaining the ab-
solute heat of bodies have been proposed. But, as they are
all unsatisfactory, it is not necessary to detail them here.
Sect. VI. Of the Sources of Caloric.
The most important sources of heat are the five following,
the sun, combustion, percussion, friction, and mixture.
1. The Sun.
The sun is an immense globe, the diameter of which is
888,246 miles. It was long supposed to be in a state of
violent combustion. But the curious observations of Dr
Herschel render it probable that this notion is erroneous.
From them it appears, that the sun is an opaque globe, sur- '
rounded by an athmosphere of great density and extent. In
SECT. VI. SOURCES OF CALORIC. 105
this atmosphere there float two regions of clouds The lower-
most of the two is opake, and similar to the clouds which
form in our own atmosphere; but the higher region of clouds
is luminous, and emits the immense quantity of light to
which the splendor of the sun is owing,
The sun emits three kinds of rays; the calorific, colorifiCy,
and deoxidizing. The first occasions /heat, the second colour,
and the third separates oxygen from various bodies.
When the solar rays strike transparent bodies, they pro-
duce very little effect; but opake bodies are heated by them.
They pass through transparent bodies; but are retained, at
least in part, by opake bodies. The deeper the colour of
the opake body, the greater is the heat produced. Black
bodies are most heated and white least, and the others in
proportion to the intensity of the colour. The temperature
produced in bodies by the direct action of the sun's rays sel-
dom exceeds 120˚. But when the heat is prevented from
escaping, as, by enclosing a thermometer within a glass ves-
sel whose bottom is cork, the temperature sometimes rises
nearly to 240˚. When the sun's rays are accumulated by
means of burning glasses, the most intense heat is produced
that it is possinle to raise by any known method.
2. Combustion.
Few phenomena are more wonderful or interesting than
cobustion. When a stone or a brick is heated it undergoes
no change; and, when left to itself, it soon cools again, and
becomes as at first. But, when combustible bodies are heat-
ed to a certain degree in the open air, they suddenly become
much hotter of themselves, continue for a certain time in-
tensely hot, and send out a copious stream of light and heat.
When this ceases, the combustible has undergone a most
complete change, being converted into a substance possessed
106. CALORIC. CHAP. II.
of very different properties, and no longer capable of com-
bustion.
The first ingenious attempt to explain conbustion was by
Dr Hooke. According to him, there is an ingrefient in air
capable of dissolving combustibles when their temperature is
sufficiently raised. The solution takes place with such rapi-
dity that it occasions light and heat, which, in his opinion,
were mere motions. The quantity of this solvent in air is
not great. Hence the reason why so great a proportion of
air is necessary to support combustion. This hypothesis was
embraced by Mayow, but without making any great addition
either to its evidence or probability.
Becher and Stahl soon after advanced another, which was
much more universally embraced. According to them, all
combustible substances contain in them a certain hobody called
phlogiston, to which they owe their combustinility. This
substance is the same in all combustible bodies. They owe
their diversity to other ingredients combined with the phlo-
giston. During the combustion, the phlogiston separates,
and the incombustible ingredients remain behind. The light
and the heat are occasioned by the violent motion into which
the phlogiston is thrown during its emission.
Light being considered as a body, occasioned a chan;eg in
the Stahlian theory. Phlogiston was considered as nothing
else than light fixed in bodies. When heat, in consequence
chiefly of the discoveries of Dr Black, came to be consider-
ed as a body, the opinion respecting phlogiston got a new
modification. It was considered as a subtile fluid, the same
with the ether of Hooke and Newton, which occasioned
gravity, and gave the bodies, called heat and light, the pecu-
liar motions which produce in us the sensations of heat and
light.
Dr Priestley first attempted to account for the necessity of
air for combustion. Air, according to him, has an affinity
SECT. VI. SOURCES OF CALORIC. 107
for phlogiston, it draws it out of the combustible body and
combines with it. But if so, whence come the heat and the
light which make their appearance in all cases of combus-
tion? According to Dr Crawford, they existed in the air,
and were displaced by the phlogiston when it united with
that fluid.
These modificatious of the Stahlian theory were evidently
improvements. But they left the nature of phlogiston alto-
gether out of view. Kirwan first attempted to ascertain what
this substance was, and to prove it the same with what is now
called hydrogen gas. This opinion he supported in an inge-
nious Essay on Phlogiston; and it was embraced by many
of the most respectable chemists in Europe.
Meanwhile, Mr Lavoisier had been investigating the sub-
ject with the minutest attention; and, after a very long, ela-
borate and ingenious examination, had satisfied himself that
in every case of combustion, oxygen unites with the burning
body. For a long time, nobody would accede to his opinion.
But at last, in 1783, Berthollet and Fourcroy joined him,
and soon after Guyton-Morveau came over to his sentiments.
They wrote a refutation of Mr Kirwan's essays which was
so satisfactory, that Mr Kirwan himself came over to their
opinion. And after a short, but pretty violent controversy,
the Lavoiserian theory of combustion was universally adopt-
ed. According to this theory, combustion consists of two
processes, a combination and a decomposition. The oxygen
of the air combines with the combustible, and gives out the
heat and light with which it was previously united.
The following observatios may, perhaps, contrinute
somewhat to elucidate what is still obscure in this curious
process.
All bodies, as far as combustion is concerned, may be di-
vided into supporters, combustibles and incombustibles. By
supporters are meant certain bodies, not indeed capable of
108 CALORIC. CHAP. II.
burning, but combustion cannot go on without their pre-
sence. Air, for example, is a supporter. combustibles
and incombustibles require no explnation.
Oxygen is the only simple supporter known. When it
combines with an incombustible, it forms a compound sup-
porter. The following are all the supporters at present
known.
1. Oxygen.
2. Air.
3. Nitrous oxide.
4. Nitrous gas.
5. Nitric acid.
6. Oxymuriatic acid.
7. Hyperoxymuriatic acid.
The combustibles are either the simple substances which
have been already descrined, or combinations of these with
each other, or with oxygen without combustion: in which
last case, they may be called combustible oxides.
During combustion the oxygen of the supporter always
combines with the combustible, and forms with it a new sub-
stance, which mi, be called a jiroiбёti(, of combustion. Now
every product is either, 1. Water; An acid; or, 3. A me-
tallic oxide.
Some products are capable of combining with an addi-
tional dose of oxygen. But this combination is never at-
tended with combustion, and the product, in consequence,
is converted into a supporter. Such compounds may.be
called partial supporters, as a part only of the oxygen which
they contain is capable of supporting combustion.
Since oxygen is capable of supporting combustion only in
the supporters and partial supporters, it is dear that it is in
a different state in ilicse bodies from what it is in products.
It is probable that, in supporters it contains, combined with
SECT. VI. SOURCES OF CALORIC. 109
it, a considerable quantity of heat, which is wanting in pro-
ducts.
It is probable that combustible bodies contain light as a
constituent. For the quantity of light emitted during com-
bustion depends upon the combustible; while the heat seems,
in some measure at least, to depend upon the oxygen. If
these two suppositions be admitted, the phenomena of com-
bustion admit of an easy explanation. The base of the oxy-
gen and of the combustible combine together and form the
product, while the heat of the one and the light of the other
in like manner unite and fly off in the form of fire.
3. Percussion.
It is well known that heat is produced by the percussion
of hard bodies against each other. Iron may be heated red
hot by striking it with a hammer, and the sparks emitted by
flint and steel are well known.
This evolution of heat appears to be the consequence of
the permanent or temporary condensation of the bodies
struck. Iron and most metals become specifically heavier
when hammered. Now condensation always evolves heat.
When air is condensed it gives out a considerable quantity of
heat sufficient to set fire to tinder. When muriatic acid gas
is passed through water, it is condensed, and the water be-
comes hot. On the other hand, when air is rarified, it be-
comes suddenly much colder.
It is not difficult to see why condensation evolves heat.
The particles being forced nearer each other, the repulsive
force of the heat is increased, and a portion in consequence
is driven off. The specific caloric of bodies is diminished
by condensation. Now the specific caloric can scarcely be
conceived to diminish witbout the body giving out heat.
110 CALORIC. CHAP. II.
A part of the heat which follows percussion, is often ow-
ing to another cause. By the percussion, the heat of the
body is raised so high that combustion commences, and this
occasions a still farther increase of the heat. It is in this
way that sparks are produced when flint and steel are struck.
The sparks are small pieces of the steel which have taken
fire and melted during their passage through the air.
4. Friction.
Heat is not only evolved by percussion, but also by fric-
tion. And not only by the friction of hard bodies but even
of soft bodies, as when the hand is rubbed against the slieve
of the coat. No heat has ever been observed from the fric-
tion of liquuids.
The heat evolved by friction seems to be owing to the
same cause as that by percussion; namely, a condensation of
the substances rubbed. This condensation is, in some cases,
permanent; but, when the bodies rubbed are soft, it can on-
ly be momentary.
The heat evolved by friction is sometimes very consider-
able. Thus Count Rumford boiled water by the heat evol-
ved by rubbing a steel borer against a cylinder of gun-metal.
Probably in this case the density of the metal was a little in-
creased. A very small increase would account for the whole
heat evolved.
5. Mixture.
In a great number of cases a change of temperature takes
place when bodies combine chemically with each other.
Sometimes the compound becomes colder than before, and
sometimes hotter.
SECT. VI. SOURCES OF CALORIC. 111
When glauber's salt in crystals pounded is dissolved in wa-
ter, a considerable degree of cold is produced, and the cold
is still more intense if the salt be dissolved in muriutic acid.
If muriate of lime in powder and dry sn ow be mixed toge-
ther, so great a degree of cold is produced that mercury may
be frozen if it be surrounded by such a mixture. Potash
and snow produce an equally great cold. When nitric acid
or sulphuric acid is poured upon snow, the snow dissolves
and an intense cold is produced.
On the other hand, when sulphuric acid and water are
mixed, so great a heat is evolved, that the liquid is consider-
bly hotter than boiling water. Heat also is produced when
nitric acid and water, or water and alcohol are mixed toge-
ther. Heat also is produced if glauber salt, in a state of ef-
florescence, is dissolved in water. An intense heat is produ-
ced by dissolving quick-lime in sulphuric acid.
In most of these cases of change of temperature, water is
either one of the substances combined, or it forms an essen-
tial constituent of one of them. The heat or the cold pro-
duced depends often on this constituent. Thus Glauber's
salt, containing its water of crystallization, produces cold
when dissolved; while the same salt, deprived of its water of
crystallization, produces heat.
If the new compound be more fluid than the two consti-
tuents of it, the temperature sinks; if it be less fluid, the
temperature rises. Thus, when snow and common salt are
mixed, they gradually melt and assume the form of a liquid,
and the temperature sinks to zero. Solid water cannot be-
come liquid without combming with a quantity of heat, and
the same rule applies to all solid bodies which become liquid.
Hence the cold evolved in these cases. The water of crys-
tallization in Glauber's salt is solid: it becomes liquid when
the salt is dissolved. Hence the cold produced. When the
same salt, free from its water of crystallization, is thrown in-
112 CALORIC. CHAP. II.
to water, it first combines with a portion of the water and
renders it solid. Hence the heat evolved. Dr Black's doc-
trine of latent heat affords a satisfnctory expIanation of these
phenomena.
When the density of two liquids united is greater than the
mean, heat is evolved, because specific caloric of the new
compound is less than that of the conntituents. This was
first observed by Dr Irvine, and it accounts for the heat
evolved when water is mixed with sulphuric acid, nitric acid
or alcohol.
Thus it appears that the changes of temperature produced
by mixture, are either occasioned by the change of state
which the water undergoes, or by a diminution of specific
caloric, in consequence of the new combination.
BOOK II.
OF COMPOUND BODIES.
Compound bodies are substances composed of two or
more simple substances united together. They amount to
several thousands; but the present state of the science does
not permit us to give an account of them all under their pro-
per heads.
Compound bodies are of two kinds. Some are formed by
the combination of two or more simple substances with each
other, while others are formed by the union of two or more
compound bodies with each other. To the first class belong
phosphoric acid composed of phosphorus and oxygen; and
ammonia, composed of azote and hydrogen. To the second
CHAP. I. VOLATILE ALKALIES. 113
class belong phosphate of ammonia, composed of phosphoric
acid and ammonia.
Besides the 35 simple substances descrined in the prece-
ding pages, there are a number of others brought into view
by the sagacity of Mr Davy. They constitute the bases of
the substances called alkalies and earths, which form a dis-
tinct order by themselves, and may be called salifiable bases,
This book shall be divided into three parts. I. Salifiable
Bases. II. Primary Compounds. III Secondary Com-
pounds. And we shall terminate it by an account of those
animal and vegetable substances not yet sufficiently known to
admit of their being arranged under either of the preceding
heads.
DIVISION I.
OF SALIFIABLE BASES.
The salifiable bases may be arranged under the four fol-
lowing heads:
1. Volatile alkaies.
2. Fixed alkalies.
3. Alkaline earths.
4. Earths proper.
Chap. I
of volatile alkalies.
The term alkali was introduced into chemistry after having
been applied to a plant that still retains the name of kali.
When this plant is burnt, the ashes washed in water, and the
H
114 VOLATILE ALKALIES. CHAP. I.
water evaporated to dryness, a white substance remains, called
alkali. Alkali may be obtained from many other bodies be-
sides this plant. Chemists gradually discovered that different
substances had been confounded together under the name of
alkali. The word, in consequence, became general, and is
now applied to all substances having the following pro-
perties.
1. A caustic taste.
2. Volatilized by heat.
3. Capable of combining with acids and of destroying
their acidity.
4. Soluble in water, even when combined with carbonic
acid.
6. Capable of converting vegetable blues to green.
The alkalies at present known are three in number: 1. Am-
monia; 2. Potash; 3. Soda. The first is called volatile al-
kali; the two last two fixed Alkalies.
Sect. I. Of Ammonia.
Put into a retort a mixture of three parts quick-lime and
one part sal ammoniac, plunge the beak of the retort into a
trough filled with mercury. Apply heat. A gas comes over
which may be received in glass jars filled with mercury.
This gas is ammonia.
This gas possesses the mechanical properties of common
air. Its taste is acrid and pungent, and it has a strong smell,
not unpleasant when diluted. Animals cannot breathe it, and
combustibles do not burn in it. Its specific gravity is 0.600,
that of air being 1.000. At the temperature of 60˚, 100
cubic inches of it weigh 18.16 grains. When exposed to a
cold of -45˚, it is condensed into a liquid. When passed
through a red hot tube, it is decomposed and converted into
hydrogen and azotic gases.
SECT. I. AMMONIA. ll5
Water absorbs it with great rapidity. This liquid absorbs
780 times its bulk of this gas, and six parts of water, by this
absorption, increase in bulk to 10 parts. The specitic gra-
vity of this solution is 0.900. It is in this state that ammmo-
nia is commonly used. It was known to the alohymists, and
called hartshorn, spirit of urine, and spirit of sal ammoniac.
Ammoniacal gas is not altered by light, but when electric
sparks are made to pass through it, its bulk is nearly doubled,
and it is converted into hydrogen and azotic gases. Hence
it follows that it is composed of hydrogen and azote. The
most exact experiments make the proportion of the consti-
tuents three parts in bulk of hydrogen gas and one part of
azote, or in weight
81.5 azote.
18.5 hydrogen.
_____
lOO.O
When mixed with oxygen gas, it detonates by electricity,
and is decomposed as Dr Henry has ascertained. To ana-
lyse ammonia by means of oxygen, it ought to be first mixed
with half its bulk of oxygen gas. An electric spark occa-
sions a combustion, but the whole of the hydrogen is not
consumed. By adding another quantity of oxygen gas a new
combustion may be produced. Double the oxygen gas con-
sumed indicates the bulk of hydrogen, and the azote remain-
ing in the residuary gas its bulk may be estimated.
Sulphur is the only one of the simple combustibles that
combines with ammonia. The combination may be produ-
ced by mixing it with sulphur in the state of vapour, or bet-
ter by distilling a mixture of equal w ights of sal ammoniac,
sulphur and quick-lime diluted with a little water. A yellow
liquid comes over which consists of water, holding in solu-
tion ammonia and sulphur. It contains an excess of ammo-
nia.
H2
116. Volatile ALKALIES. CHAP. I.
When ammonia comes in contact with phosphorus at a red
heat it is decomposed, and phosphureted hydrogen gas
formed. When anmioniacal gas is made to pass throug red
hot charcoal, a substance is formed called prussic acid.
Ammonia is not acted on by azote, but it combines with
muriatic acid and forms the well known salt called sal ammo-
niac, or muriate of ammonia.
Ammonia is capable of oxidizing some of the metals, and
of dissolving the oxides formed. Liquid ammonia dissolves the
oxides of silver, copper, iron, tin, nickel, zinc, bismuth and co-
balt. When digested upon the oxides of mercury, lead or man-
ganese, it is decomposed, water formed and azotic gas emit-
ted. It combines readily with the peroxides of gold and silver,
and forms two remarkable compounds known by the names
of fulminating gold and silver.
Fulminating gold may be obtained by dissolving gold in
aqua regia, and precipitating it by ammonia. A yellow pre-
cipitate falls which is to be washed and dried. It is fulmi-
nating gold. It is composed of five parts yellow oxide of
gold, and one part of ammonia. It fulminates violently
when heated to the temperature of about 300˚ or 400˚, also
when struck violendy with a hammer, or when triturated in a
mortar. Water is formed and azotic gas emitted.
Fulminating silver was discovered by Berthollet. It may
be prepared by dissolving silver in nitric acid, precipitating
by lime-water, drying the precipitate in a filter, and then
keeping it for twelve hours in liquid ammonia. Its tendency
to explode is so strong, that it is dangerous to prepare it ex-
cept tn small quantities.
If a globule of mercury be put into a hollow in a moisten-
ed piece of sal ammoniac, and exposed to the energy of a
powerful galvanic battery, it increases in bulk and acquires
the consistency of butter. Its specific gravity is reduced to
3. The mercury has obviously amalgamated with somie me-
SECT. I. AMMONIA. 1l7
tallic body. If this amalgam be thrown into water, the mer-
cury resumes its originai state, a little hydrogen gas is exha-
led, and the water is impregnated with a weak solution of
ammonia. Hence it would appear that the amalgamating
metal is the basis of ammonia; that it decomposes water,
emits the hydrogen, and retains the oxygen; and that, by this
combination, it is converted into ammonia. This unknown
metallic basis of ammonia has been called ammonium. It
follows, from the preceding experiment, that ammonia con-
tains oxygen. Yet its presence cannot be detected by expe-
riment. It is said that Mr Davy has lately got over this ap-
parent inconsistency, by ascertaining that azote is a compound
of oxygen and hydrogen. If so, hydrogen in its pure state
is a metal.
CHAP. II.
OF FIXED ALKALIES.
The fixed alkalies are not gaseous. They may be exhibit-
ed pure in a solid state. Two fixed alkalies only are at pre-
sent known; namely, potash and soda.
Sect. I. Of Potash.
Potash, called also vegetable alkali, is obtained from the
ashes of trees and of vegetables that grow at a distance from
the sea-shore. These ashes are lixiviated with water, the
water evaporated to dryness; the residual salt mixed with
twice its weight of quick-lime, and a sufficient quantity of wa-
ter to make the whole into a thin paste. The water is drawn
off in 24 hours, boiled to dryness in a clean iron pot, and
then mixed with a quantity of alcohol equal in weight to half
H3
118 FIXED ALKALIES. CHAP. II.
The original salt. The alcoholic solution, after standing some
days in well closed phials, is decanted off, and the alcohol
distilled away in a silver still. The substance which remains
behind is potash.
Potash is a brittle substance of a white colour, and a
smell like that which is perceived during the slacking of
quick-lime. Its taste is extremely acrid and it is very corro-
sive, destroying the texture of most animal and vegetable
bodies to which it is applied. Its specific gravity is 1.7085.
When heated it melts. At a red heat it evaporates in a
white acrid smoke.
It contains about one-fourth of its weight of water, even
after being exposed to a red heat. When exposed to the air
it apeedily absorbs moisture and runs into a liquid. At the
same time it combines with carbonic acid, for which it has a
strong affinity.
Water dissolves twice its weight of potash. The solution
is limpid and colourless, and almost of the consistency of an
oil. It is in this state that potash is commonly used by che-
mists. When evaporated to the proper consistency, the pot-
ash crystallizes.
2. Potash does not combine with oxygen, nor with any of
the simple combustibles except sulphur. The combination
takes place by simple trituration of the two substances in a
mortar, or by fusing them in a crucinle. This compound is
called sulphuret of potash. It was formerly distinguished by
the name of hepar sulphuris, or liver of sulphur. Its colour
is brown; it is hard, brittle, and has a glassy fracture. Its
taste is acrid and bitter, and it leaves a brown stain on the
skin. It converts vegetable blues to green and soon destroys
them. When exposed to the air it acquires a green colour
and emits the smell of sulphureted hydrogen. In this state
it is a triple compound, being comsposed of sulphur, potash
andl sulphureted hydrogen. The last ingredient is formed by
SECT. I. POTASH. 119
the decomposition of the water absorbed from the atmo-
sphere. It dissolves in water and forms a greenish yellow
solution. In this state it is called hydrogureted sulphuret of
potash.
When liquid potash and phosphorus are heated in a retort,
water is decomposed and phosphureted hydrogen gas is form-
ed and comes over. This gas possesses the curious proper-
ty of taking fire when it comes in contact with the air.
3. Potash does not unite with azote; but it combines with
muriatic acid, and forms the salt called muriate of potash.
4. Several of the metals, when kept in liquid potash, are
oxidized, water being decomposed. This is the case with
iron, zinc and molybdenum, and probably also with tin and
manganese.
Potash dissolves the oxides of lead, tin, nickel, arsenic, co-
balt, manganese, zinc, antimony, tellurium, tungsten, molyb-
denum.
Mr Davy has lately succeeded in decomposing potash, and
in showing that it is a compound of oxygen and a peculiar
metal, to which be has given the name of potassium. The
decomposition was accomplished by exposing potash to the
action of the galvanic battery. The metallic base separated
at the negative extremity while oxygen was evolved at the
other. More lately, Thenard and Gay-Lussac have ascer-
tained that potash is decomposed and potassium obtained
when it is made to come in contact with iron turnings heated
to whiteness in a gun-barrel.
Potnssium, the base of potash, possesses the followning pro-
perties. It is white like mercury. At 50˚, it is a soft mal-
leable solid, which becomes imperfectly liquid at 60˚, and
perfectly so at 100˚. While at 32˚, it is hard, brittle and
crystallized in facets. It is not only lighter than water, but
lighter than any known liquid. Its specific gravity does not
exceed 0.6. Its affinity for oxygen is very great. In the
H4
120 FIXED ALKALIES. CHAP. II.
open air it is covered with a crust of potash in a few minutes.
When thrown upon water it decomposes that liquid with ra-
pidity, hydrogen gas holding potassium in solution is disen-
gaged and takes fire, which occasions the combustion of the
whole potassium.
When heated in a small quantity of oxygen gas it loses its
metallic appearance and assumes a reddish brown colour. In
this state it may be considered as a protoxide of potassium.
Oxymuriatic acid sets potassium on fire and converts it in-
to muriate of potash.
It combines with phosphorus and forms a phosphuret
which has the colour of lead, and remains solid at a heat
little short of that of boiling water. In the open air it burns
and is converted into phosphate of potash.
It combines rapidly with sulphur by heat, and heat and
light are emitted at the moment of combination. The sul-
phuret has a grey colour, and, in the open air, is soon con-
verted into sulphate of potash.
It combines and forms alloys with all the metals tried, but
these alloys are soon destroyed in the open air or in water
and the potassium converted in potash.
Potash, according to the experiments of Mr Davy, is
composed of about 86 potassium.
14 oxygen.
___
100
Sect. II. Of Soda.
Soda, called also fossil or mineral alkali, is found in large
quantities ready formed in the earth. It may be obtained al-
so from the ashes of the different species of salsola and other
marine plants. The process is the same as that for procuring
potash.
8ECT. II. SODA. 121
When pure it has a very strong resemblance to potash in
most of its properties.
Its colour is greyish white; and it agrees with potash in its
taste, smell and action on animal bodies. Its specific gravity
is 1.336.
Heat produces the same effects on it as on potash. In the
open air it absorbs water and carbonic acid, but it does not
become liquid as potash does. Afnter assuming the state of a
paste it soon dries again and crumbles to powder.
It dissolves in water like potash, and may be obtained
crystallized. The action of oxygen, of the simple combus-
tinles and incombustibles, is similar to their action on pot-
ash. The same remark applies to the metals and their
oxides.
Like potash, it is a compound of 0xygen and a peculiar
metal, to which Mr Davy, the discoverer, has given the name
of sodium. It may be decomposed precisely in the same
way as potash.
Sodium is a white metal like silver, solid, but very malle-
able, and so soft that pieces may be welded together by strong
pressure. At 120˚ it begins to melt, and is completely fluid
at l80˚. It is not volatilized in a red heat strong enough to
melt plate-glass. It conducts electricity and heat in the same
manner as potassium. Its specific gravity is 0.9348.
Its affinity for oxygen is similar to that of potassium.
When exposed to the air it is seen covered with a crust of
soda, but as that alkali does not deliquesce, the nucleus is not so
soon destroyed as happens to potassium. Hydrogen gas does
not dissolve it. Hence no combustion takes place when so-
dium is thrown upon water, though it rapidly decomposes
that liquid.
When fused with dry soda in certain quantities, there is a
division of oxgen between the soda and the base, and a
protoxide of sodium is formed of a deep brown colour.
122 FIXED ALKALIES. CHAP. III.
It burns like potassium in oxymuriatic acid. It combines
with phosphorus, sulphur and the metals like potasstium.
From the experiments of Mr Davy, it appears that soda is
composed of
Sodium 78
Oxygen 22
____
100
Chap. III.
OF THE ALKALINE EARTHS.
The term earth in chemistry is applied to all substances
possessing the following properties.
1. Insoluble in water, or at least becoming insoluble
when combined with carbonic acid.
2. Little or no taste or smell; at least when combined
with carbonic acid.
3. Fixed, incombustible, and incapable, when pure, of
being altered by the fire.
4. A specific gravity not exceeding 4.9.
5. When pure, capable of assuming the form of a white
powder.
6. Not altered when heated with combustibles.
The earths have been divided into two classes, namely, al-
kaline earths and earths proper. The alkuline are four in
number; namely, lime, magnesia, barytes and strontian.
Sect. I. Of Lime.
Lime has been known from the remotest ages. It abounds
in every part of the earth, constituting immense ranges of
SECT. I. LIME. 125
rocks and mountains. It may be obtained by burning those
crysstalized limestones called calcareous spars, or certain
white marbles. Oyister shells, also, when burnt, yield it
nearly pure.
Pure lime is white, moderately hard, but easily reduced to
powder. Its taste is acrid like that of the fixed alkalies, and
it in some measure corrodes those animal bodies to which it
is applied. Its specific gavity is 2.3. It tinges vegetable
blues green, and at last renders then yellow. It does not
melt in the most violent heat that can be applied.
When water is poured upon it the lime swells and falls to
pieces, and so much heat is evolved as to evaporate a portion
of the water, and even to set fire to combustible substances,
with which it happens to be in contact. This process is
called slacking the lime. A portion of the water combines
with the lime and becomes solid. Hence the cause of the
heat evolved. Slacked lime is composed of 3 parts lime and
1 water. It has been called hydrate of lime.
The difference between limestone and lime was first ascer-
tained by Dr Black. Limestone is lime combined with car-
bonic acid. By burning it the carbonic acid is driven off
and the pure lime remains.
When lime is exposed to the open uir it gradually attracts
moisture, falls to powder, and, becoming saturated with car-
bonic acid, soon resumes its original state of limestone.
Water dissolves less than O.OO2 parts of its weight of lime.
The solution is called lime-water. It is limpid, has an acrid
tasle, and changes vegetable blues to green. When exposed
to the air, the lime soon combines with carbonic acid and
precipitates, leaving the water pure.
Lime is not acted on by oxygen. Sulphur and phospho-
rus are the only two simple combustibles that unite with it.
Sulphuret of lime may be formed by mixing its two con-
stituents together and heating them in a crucinle. The mass
124 ALKALINE EARTHS. CHAP. III.
has a reddish colour. In the air it hecomes greenish yellow,
sulphureted hydrogen is formed, and the mass is converted in-
to hydrogureted sulpuret of lime. This last componud may
be formed by boiling a mixture of sulphur and lime in about
ten times its weight of water. The solotion has a yellow co-
lour, and is used for absorbing oxygen from air.
Phosphuret of lime may be formed by passing phospho-
rus through red-hot lime in a glass tube. It has a deep brown
cloour, and falls to powder in the air. When thrown into
water, bubbles of phosphureted hydrogen gas are emitted,
which take fire as they separate from the liquid.
Lime does not unite with azote, but it combines with mu-
riatic acid, and forms a salt called muriate of lime.
Lime facilitates the oxidizement of several of the metals.
It dissolves some metallic oxides, as those of mercury and
lead.
It does not unite with the alkalies.
Mr Davy has lately ascertained that lime, like the fixed
alkalies, is a componnd of oxygen and a peculiar metal, to
which he has given the name of calcium. He decomposed
lime by exposing a mixture of moistened lime and red oxide
of mercury to the action of a galvanic battery. A globule
of mercury was placed in the middle of the mixture. The
lime was decomposed, and its base united with the mercury
and formed an amalgam. The mercury was distilled off in
glass tubes filled with the vapour of naphta, and the calcium
remained behmd.
Calcium is white like silver, solid, and four or five times
heavier than water. When heated it burus brilliantly, and
quick-lime is produced
SECT, II. MAGNESIA. 125
Sect. II. Of Magnesia.
Magnesia was discovered about the beginning of the 18th
century by a Roman canon. But little was known about its
nature till Dr Black made his celebrated experiments on it
in 1755.
It may be procured from the salt called sulphate of mag-
nesia, or epsom salt, by dissolving the salt in water and pour-
ing potash into the solution. A white matter falls; when
washed and dried it is pure magnesia.
Magnesia is a very soft light powder, with very little taste
and destitute of smell. Its specific gravity is 2.3. It tinges
vegetable blues green. It does not melt in the strongest heat
that can be raised.
It is not sensinly soluble in water, and has never been ex-
hinited in a crystallized form. When exposed to the air it
attracts carbonic acid very slowly.
It does not combine with oxygen nor with any of the simple
combustibles except sulphur. The sulphuret of magnesia
may be formed by mixing the two constituents and exposing
it to a moderate heat. The result is a yellow powder slightly
agglutinated.
It does not combine with azote, but unites with muriatic
acid, and forms the salt called muriate of magnesia.
It has no action on the metals, nor is it known to combine
with any of their oxides. Neither does it unite with the fix-
ed alkalies or with lime.
Mr Davy succeeded in decomposing magnesia by the same
process that furnished him with the base of lime. Like lime
it is composed of oxygen and a metal, to which the name of
magnium has been given. This metal is white, sinks rapidly
in water, absorbs oxygen when exposed to the air, and is
converted into magnesia. It decomposes water, but not near-
126 ALKALINE EARTHS. CHAP. III.
ly so rapidly as the other alkaline metals, owing doubtless to
the insolubility of magnesia.
Sect. III. Of Barytes.
Barytes was discovered by Scheele in 1774. It is usually
obtained from a heavy foliated brittle mineral, pretty com-
mon, and called ponderous spar or sulphate of barytes. This
Mineral is mixed with charcoal powder and exposed to a
strong heat in a crucinle. It is then dissolved in water and
saturated with nitric acid. The liquid, filtered and evapora-
ted, yields crystals, which being exposed to a strong heat in
a crucinle, leave behind them an earthy matter, which is
barytes.
Barytes thus obtained is a greyish white porous body, and
may be easily reduced to powder. Its taste is more caustic
than that of lime, and when swallowed it acts as a violent
poison. Its specific gravity is 2.374. When water is pour-
on it heat is evolved, and the barytes is slacked precisely
as happens to lime. By this means it combines with water,
and is converted into hydrate of barytes.
Water dissolves about 0,05 of its weight of barytes. The
solution has an acrid taste and tinges vegetable blues green.
Boiling water dissolves more than half its weight of barytes.
As the solution cools, the barytes precipitates in crystals.
Barytes does not combine with oxygen, nor with any of the
simple combustibles except sulphur and phosphorus. The
sulphuret and phosphuret of barytes may be formed precise-
ly in the same way as those tf lime, which they resmble in
most of their properties.
Barytes is not acted on by azote, but it combines with mu-
riatic acid and forms the salt called muriate of barytes.
Barytes has no action on the metals, but it combines with
some of the metallic oxides, and forms compounds hitherto
scarcely examined.
SECT. IV. STRONTIAN. 127
It does not combine with the aklalies, nor has it much ac-
tion upon lime or magnesia.
Mr Davy has shewn that barytes, like the preceding earths,
ia a metallic oxide, being composed of oxygen and a metal to
which the name of barium has been given. The barium was
obtained by the same process as that which furnished him the
bases of lime and magnesia. It is a white solid metal, melts
at a heat below redness, and is not volatilized at the tempe-
tature capable of meltng plate glass. It is at least four or
five times heavier than water. It decomposes that liquid
with great rapidity, and is converted into barytes. It under-
goes the same change when exposed to the open air.
SECT. IV. Of Stronian.
Strontian was first discovered in the lead mine at Strontian
in Argyleshire. It was suspected to be a peculiar earth by
Dr Crawford in 1790, and its properties were soon after in-
vestigated by Dr Hope. Klaproth and Kirwan also ascer-
tained its peculiarity. It is found sometimes combined with
carbonic acid, sometimes with sulphuric acid. From the first
compound it may be obtained by making the mneral into a
ball with charcoal powder and exposing it to a violent heat,
and from the second by treating it precisely in the way de-
scrined in the last Sectton for obtaining barites.
Strontian thus obtained is a porous mass of a greyish white
colour. Its taste is acrid and alkaline, and it changes vege-
table blues to green. Its specific gravity is 1.647. It is not
poisonous.
When water is thrown upon it, the stromtian becomes hot,
combines with water, and is slacked like quick-lime. It is
soluble in water, 168 parts of that liquid taking up one part
of strontian. Hot water dissolves a much larger quantity,
and the strontian crystalizes as the solution cools.
128 EARTHS PROPER. CHAP. IV.
Strontian does not combine with oxygen. The only simple
combustibles that unite with it are sulphur and phosphorus.
The sulphuret and phosphuret of strontin may be formed
precisely as the same compounds of lime, and possess nearly
similar properties.
Strontian does not combine with azote, but it unites with
muriatic acid, and forms the salt called muriate of strontian.
It has no action on the metals, but it combines with somte
of the metallic oxides. It does not unte with the alkalies,
nor with the other alkaline earths.
It tinges flame of a beautiful red colour. The experiment
may be made by aetting fire to paper dipt in an alcoholic so-
lution of muriate of strontian.
Mr Davy has ascertained that stroptian, like the other al-
kaline earths, is composed of oxygen and a peculiar metal,
to which he has given the name of strontium. This metal
bears a close resemblance to barium in its properties.
Chap. IV.
Of the earths proper.
The earths proper neither neutralize acids nor produce
any change on vegetable blues. They are five in number;
namely, alumina, yttria, glucina, zirconia, silica.
Sect. 1. Of Alumina.
Alumina may be obtained from the salt called alum by
the following process. Dissolve alum in water, pour ammo-
nia into the solution. A precipitate appears, separate this
precipitate and wash it. Then boil it in liquid potash till the
whole is dissolved. Pour a solution of sal ammoniac into
SECT. I ALUMINA. 129
this liquid, a white matter precipitates, which, when washed
and dried, is pure alumina.
Alumina is a white matter in powder. It has no taste,
and when pure no smell. Its specific gravity is 2.000.
When heat in applied to alumina, it gradually loses weight
in consequence of the evaporation of moisture. At the same
time its bulk is diminished. Alnmina undergoes a diminu-
tion of bulk proportional to the heat to which it is exposed.
Mr Wedgewood took advantage of this property to contrive
an instrument for measuring high temperatures. It consists
of pieces of clay of a determinate size, and an apparatus for
measuring their bulk with accuracy. One of these pieces is
exposed to the heat, and the temperature is judged of by the
contraction. This contraction is measured by means of two
brass rules fixed to a plate. The distance between them at
one extremity is 0.5 inch, and at the other extremity 0.3
inch. These rules are 24 inches long, and divided into 240
equal parts, called degrees. These degrees commence at the
wide end of the scale. The first corresponds with 947˚ of
Fahrenheit, or a red heat.
Alumina is not soluble in water, though it has a strong af-
finity for that liquid. It may be knedded with it into a very
ductile paste possessed of a good deal of tenacity. Clay
owes its ductility to the alumina which it contains. It retains
water with more obstinacy than any of the other earths.
Alumina has no effect upon vegetable blues It cannot be
crystallized artificially, but it is found native in beautiful
crystals, constituting the precious stone called sapphyr.
It neither combines with oxygen, nor with any of the simple
combustibles.
Azote has no action on it; but muriatic acid unites with
it, and forms the salt called muriate of alumina.
It does not unite with the metals, but it has an affinity for
several metallic peroxides.
I
130 EARTHS PROPER. CHAP. IV.
The fixed alkalies dissolve it readily when they are in a
state of solution in water; but they do not melt with it when
heated in a crucinle. Barytes and strontian combine whith alu-
mina, both when heated with it in a crucinle and when boiled
with it in water. It has a strong affinity for lime, and easily
melts with it when it exceeds the lime in quantity. But
when the lime exceeds, fuion does not take plaoe. Mag-
nesia and alumina have no action on each other.
It is probable that alumina, like the alkaline salts, is a me-
tallic oxide. This notion was entertained long ago by che-
mists. Davy endeavoured to obtain the metallic basis by
means of galvanism, but did not succeed. Though he has
rendered it probabable that a metal exists in it. To this metal
he propses to give the name of alumium.
Sect. II. Of Yttria.
This earth was disovered by Gadoline in a Swedish mi-
neral of a black colour, to which the name Gadolinite has
been given. To obtain it, the mineral is reduced to powder,
dissolved in nitro-muriatic acid, filtered, evaporated to dryness,
re-dissolved, filtered, evaporated to dryness, the residual salt
is heated to redness, re.dissolved in water and ammonia
poured into the solution. A white powder falls, which is
yttria.
Yttria, thus procured, is a fine-white powder without taste
or smell. It has no action on vegetable blues. Heat does
not melt it. Its specific gravity is 4.843.
It is insoluble in water, but, like alumina, it retains a
portion of that liquid, though not with so much obstinacy.
It is insoluble in the liquid fixed alkalies; but it dissolves
in carbonate of ammonia, and in all the other alkaline car-
bonates.
SECT. III. GLUCINA. 131
it does not combine with oxygen, the simple combustibles
or azote, but with muriatic acid it forms the salt called mu-
riate of yttria.
According to kberg, when yttria is treated with muriatic
acid, a quantity of oxymuriatic acid is formed. If so, it
must contain oxygen, and of course be a metallic oxide. The
opinion is probable, though no attempts have been made to
decompose yttria by means galvanism.
SECT. III. Of Glucina.
Glucina was discovertd by Vauquelin In the two minerals
called beryl and emerald. They are pounded and fused with
thrice their weight of potash. The mass is dissolved in mu-
riatic acid and the solution evaporated to dryness. The resi-
duum is digested in water and thrown upon the filter. The
liquid which passes throngh is mixed with carbonate of pot-
ash, and the precipitate dissolved in sulphuric acid. Sul-
phate of potash being added to the solution, it is laid aside
for some time. Alum crystals gradually form. When no
more appear, filter the liquid, add carbonate of ammonia in
excess, filter again and boil the liquid for some time. A
white powder precipitates, which is glucina.
Glucina is a soft white powder, without either taste or
smell. It adheres strongly to the tongue, produces no change
on vegetable blues, does not melt when heated, and does not
harden and contract like alumina. Its specific gravity is
2.976. It is insoluble in water, but forms with it a paste
having some ductility.
It does not combine with oxygen, nor with the simple
combustibles or azote; but with muriatic acid it forms the
salt called muriate of glucina.
It is soluble in the liquid fixed alkalies, like alumina; is
12
132 EART`HS PROPER. CBAP. IV.
insoluble in ammonia, but, like yttria, soluble in carbonate of
ammonia.
Mr Davy has rendered it probable that it is a metallic
peroxide. To the metallic basis he proposes to give the
name of glucium.
SECT. IV. Of Zirconia.
Zirconia was discovered by Klaproih in the two minerab
called jargon or ziron, and hyacinth. Fuse the pounded
mineral with thrice its weight of potash. Wash the mass in
pure water till the whole of the potash is extracted; then dis-
solve the residuum as far as possinle in muriatic acid. Boil
the solution, filter and add a quantity of potash. The zirco-
nia precipitates in the state of a fine powder.
Zirconia is a white powder with a harsh feel. It has nei-
ther taste nor odour, infusinle before the blowpipe, but when
violendy heated, acquires the appearance of porcelain. In
this state it is hard, and its specific gravity is 4.3. It is inso-
luble in water, but, when precipitated from a solution and
dried slowly, it retains water and asumes the appearance of
gum arabic.
It does not combine with oxygen, simple combustibles,
azote, nor metals. But it has an affinity for several metallic
oxides.
It is insoluble in liquid alkalies and infusinle with them;
but it is soluble in alkaline carbonates.
Mr Davy has made it probable that it is a metallic per-
oxide. To the metallic bases he proposes to give the name
of zirconium.
Sect. V. Of Silica. 133
The minerals called quartz, rock-crystal flint, &c. consist
almost entirely of this earth. It may be obtained in the
following manner. Melt in a crucinle a mixture of one part
quartz powder and three parts potash. Dissolve the mass in
muriatic acid, and evaporate to dryness. Towards the end
of the evaporation, the liquid assumes the form of a jelly.
Wash the residue tn water and dry it.
Silica thus obtained is a fine white powder with a harsh
feel, and without either taste or smell. Its specific gravity
is 2.66. It has no effect on vegetable colours, is insoluble in
water, and infusinle by the heat of our furnaces. It does
not form a ductile paste with water like alumina. It is found
native crxstallized, most commonly in hexagonal prisms, ter-
minated by six-sided pyramids.
It does not combine with oxygen, the simple combustibles,
simple incombustibles, or the metals. It may be fused with
several of the metallic oxides.
The fixed alkalies may be fused with it into glass. Am-
monia has no action on it. It may be combined with bary-
tes, strontian, lime and magnesia by heat. There a strong
affinity between it and alumina.
Mr Davy has rendered it probable that silica, like the
other earths, is a metallic peroxide. The metallic basis
of it he proposes to give the name of silicium.
134 OXIDES. CHAP. I.
DIVISION II.
OF PRIMARY COMPOUNDS.
The only primary compounds that can be at present placed
under this division, may be arranged under the following
heads. 1 Oxides; 2. Acids; 3. Compound combustibles.
Chap. I.
OF OXIDES.
Many bodies, as we have seen already, are capable of
combining with oxygen. Now the compounds into which
oxygen enters are of two kinds. They either posses the
properties of acids, or they are destitute of these properties.
To the first class the term acid has been applied; to the se-
cond that of oxide. By oxide, then, is meant a combination
of oxygen and some other substance destitute of the proper-
ties belonging to acids. It is very common to find the same
base combine with different doses of oxygen, and form both
acids and oxides. In all these cases, the smaller proportion
of oxygen constitutes the oxide, and the larger the acid.
Hence it follows, that oxides always contain less oxygen than
acids with the same base.
The oxides which we have to examine are combinations of
oxygen with the simple combustibles and incombustibles.
For the metallic oxides have been ahready descrined in the
first book, while treating of the metals. All that is known
of the oxides of phosphorus and sulphur has also been stated.
To all the combinations of muriatic acid and oxygen, the
2
SECT. I. OXIDE OF HYDROGEN OF WATER. 135
name of acid has been given. We have only to examine in
this place, therefore, the oxides of hydrogen, carbon and
azote.
Sect. I. Of the Oxide of Hydrogen or Water.
This well known liquid is found in abundance in every
part of the world. When pure, in which state it may be
obrained by distillation, it is destitute of colour, taste and
smell.
At the temperaure of 40˚, a cubic foot of pure water
weighs 437102.4946 grains troy or 999.0914161 ounces
avoirdupois. Hence a cubic inch of water at 40˚, weighs
252.933 grains; and at 60˚ 252.72 grains. The specific
gravity of water is always supposed 1.OO0, and it is made the
measure of the specific gravity of every other body.
When cooled down to 32˚ it crystallizes and becomes ice.
At 212˚, it boils and is converted into steam, an elastie fluid,
invisinle like air, and about 1800 times more bulky than water.
The boiling point of water is somewhat altered by dissolving
salt in it. Some salts raise the boiling point, others lower it
a little, while some produce both effects according to the
proportion employed.
Water is not altered by heat. It absorbs a little air and a
certain proportion of all gases exposed to it. By long boil-
ing, or by being placed in an exhausted receiver, it is freed
from the greatest part of this air.
Water has no action on the simple combustibles while cold.
But, at a red heat, charcoal decomposes it. The action of
phosphorus is not known. Sulphur, as far as is known, does
not decompose it.
Of the metals iron, zinc, antinomy and tin decompose
it when assisted by heat; silver, gold, copper and platinum
have no effect on it. The action of the other metals has not
14
136. OXIDES. CHAP. I.
been ascertained. The metallic bases of the alkalies and
earths decompose it with great rapidity at the usual tempera-
ture of the atmosphere.
Water dissolves the alkalies and alkaline earths. The earths
proper are insoluble in it. It dissolves also acids and salts,
and is capable of combinig with a great variety of bodies.
Water unites to bodies two different ways. Some it dissolves
and the compound becomes liquid like water. In this way
it dissolves sugar, common salt, and many other bodies.
Other bodies combine with it without losing their solidity.
The water loses its liquid form and assumes that of the body
with which it unites. In this way it combines with lime,
with alumina, with many salts, and with various metallic
oxides. When the compound of water with another sub-
stance remains liquid, the proportion of water is unlimited;
but when the compound formed is solid, the water combines
alwyy in a certain determinate proportion. To the first
kind of compound, the name of solution has been given; to
the secound, the term hydrate has been applied. Thus, slack-
ed lime is called hydrate of lime; the crystals of barytes and
strontian are called hydrates of barytes and strontian. Most
of the metallic hydrates have lively colours, a strong taste and
are easily soluble in acids, while the oxide which constitutes
the base of the hydrate is usually duller in its colour, often
tasteless and always more difficultly soluble in acids. The
hydrate of copper is blue, that of nickel and iron green, that
of cobalt red, and that of tin white.
All the gases, in their usual state, contain a quantity of
water, from which they are best freed by exposure to a very
low temperature. But this method does not succeed in
freeing muriatic acid gas from water. That gas, even at the
lowest temperature, contains about one-forth its weight of
water.
SECT. II. OXIDE OF HYDROGEN OR WATER. 137
The ancients considered water as an elementary substance.
Van Helmont endeavored to prove that plants could be
nourished by pure water alone, and of course that it could
be converted into all the substances foundl' in vegetables.
Boyle thought that, by long digestion in glass vessels, it could
be converted into silica. His experiment was confirmed by
Margraff. But Scheele and Lavoisier proved that the silica
was obtained by the decomposition of the glass vessel in
which the experiment was made. Mr Cavendish, in 1731,
ascertained that water is a compound of oxygen and hydro-
gen, nearly in the proportion of six parts of the former and
one of the latter, and this discovery was confirmed by a
number of very laborious and rigid experiments.
Sect. II. Of Carbonic Oxide.
The substance at present known by the name of carbonic
oxide is a gas which was confounded with carbureted hydro-
gen, till Dr Priestley drew the attention of chemists to it in
a dissertation which he published in defence of the doctrine
of phlogiston. It was examined, in cosequece, by Mr
Cruikshanks, who showed it to be a compound of oxygen<(i>
and carbon, and not of hydrogen and carbon, as Priestley
had supposed. Clement and Desormes also analysed it with
the same result.
It may be obtained most readily by mixing together equal
weights of iron-filings and chalk, each as dry as possinle, and
exposing them to a red heat in an iron retort. A gas comes
over in abundance. It consists partly of carbonic acid, part-
ly of carbonic oxide. The first gas is removed by washing in
line-water. The carbonic oxide remains behind.
Carbonic oxide is invisinle; and posesses the mechanical
properties of common air. Its specific gravity is O.956, that
138 OXIDES. CHAP. I.
of air being 1.000. No animal can breathe it without death.
Nb combustible substance will burn in it.
It burns with a blue flame, giving out but little light, and
is wholly converted into carbonic acid gas. When mixed
with oxygen gas and kindled by means of an electric spark,
100 parts of it reqire 45 parts by bulk of oxygen gas for
complete combustion. The result is about 90 parts of car-
bonic acid gas. From this experiment it has been deduced
that carbonic oxide is composed of
41 carbon.
59 oxygen.
___
100
The simple combustibles have but little action on this gas.
Hydrogen has none even at a red heat; nor charcoal nor
sulphur. But it dissolves a little phosphorus, and acquires
the property of burning with a yellow flame.
The simple incombustibles have no effect on it at any
temperature tried. But oxymuriatic acid gas gradually de-
stroys it, converting it into carbonic acid gas. This mixture
cannot be kindled by electricity; whereas a mixture of oxy-
muriatic acid and carbureted hydrogen, burn directly when
an electric spark is passed through them.
Its action on metals and their oxides has been but imper-
fectly examined. Neither the alkalies nor the earths have
any action on it whatever.
Sect. III. Of the Oxides of Azote.
Azote and oxygen form two different oxides, both gases,
and both discovered by Dr Priestley. The first has been
called nitrous oxide gas, the second nitrous gas, or nitric ox-
ide gas.
SECT. III. OXIDES OF AZOTE. 139
1. Nitrous Oxide Gas.
This gas was discovered by Dr Priestley in 1776 and called
by him dephlogisticated nitous gas. The associated Dutch
chemists examined it in 1793, and aacertained its composi-
ion. But for the best account of it we are indebted to Mr Davy.
It may be obtaind by exposing the salt called nitrate of
ammonia in a retort to a heat between 340˚ and 500˚. It
melts and emits abundance of gas, which may be collected in
jars of water.
Thus obtained, it has all the mechanical properties of air.
Its specific gravity is l.603, that of air being 1.000.
It supportts combustion better than common air, almost as
well as oxygen gas, but for a much shorter time. But com-
bustinles do not burn in it, unless previously in a state of ig-
nition.
It may be breathed for a short time, and produces effects
similar to intoxication.
Water absorbs nearly its own bulk of this gas, and aquires
a sweetish taste; but its other propeerties are mot perceptinly
altered. It may be driven off from the water unaltered by
means ol heat.
It is not altered by light, nor by a moderate heat. But
by a red heat it is decomposed and converted into nitric acid
and common air.
Oxygen, or common air, has no action on this gas.
Sulphur, if introduced into this gas while burning with a
blue flame, is immediately extinguished; but, if it be burn-
ing with a violent flame, it continues to burn for some time
witah great brillancy with a fine red flame. The produts
are sulphuric acid and azote.
Phosphorus, when touched with a wire white hot, burns
with great brilliancy in this gas. The products are azotic
gas, phosphoric acid and nitric acid.
140 OXIDES. CHAP. I
Charcoal may be kindled in it by means of a burning
glass. The products are carbonic acid gas, and azotic gas.
Hydrogen detonates with it by means of electricity. Ac-
cording to Mr Davy, 39 measures of nitrous oxide consume
40 measures of hydrogen, and after the combustion 41 mea-
sures of azotic gas remain. From this experiment it has
been concluded, that nitrous oxide is composed by weight of
63 azote.
37 oxygen
___
100
Sulphureted, phosphureted and carbureted hydrogen gas
likewise burn when mixed with nitrous oxide, and kindled.
Neither azote nor muriatic acid produce any effect upon
this gas.
Some of the metals as iron and zinc, burn or may be oxy-
dized in it.
It has the property of combining with alkalies, and of
forming a peculiar species of salt, to which the name of azo-
tites may be given. Mr Davy, to whom we are indebted for
the discovery of these compounds, did not sucesed in com-
bining nitrous oxide with ammonia and the earths, but he has
rendered it probable that such compounds are possinle.
2. Nitrous Gas.
This gas was accidentally obtained by Dr Hales, but its
properties were first investigated, and its nature ascertained
by Dr Priestly.
To obtain it, dissolve copper or silver in nitric acid diluted
with water, a gas separates, which may be collected in jars
over water, and is the gas in question.
It possesses the mechanical properties of common air. Its
specific gravity is 1.094, that of air being 1.000.
SECT. III. OXIDES OP AZOTE. 141
It is exccedingly noxious to animals, producing instant
suffocation whenever they attempt to breathe it.
Most combustible substances refuse to burn io it. But
pyrophorus burns in it with great splendour, and Hom-
berg's phosphorus takes fire in it spontaneously just as in
common air. Dr Henry has ascertained, that ammoniacal
gas, when mixed with it, detonates by means of electricity.
When mixed with common air or oxygen gas, a yellow
colour appears, and if the mixture be standing over water, its
bulk gradually diminishes very considerably. The yellow co-
lour is owing to the presence of nitrous acid which is form-
ed, and the diminution of bulk to the gradual absorption of
that acid by the water. The cause of this remarkable phe-
nomenon is obvious. The nitrous gas combines with the
oxygen, and forms nitrous acid. Hence the diminution of
bulk depends upon the quantity of oxygen present. There is
a good deal of difference in the result obtained by chemists
of the amount of the diminution of bulk, which ensues.
According to Dalton, 21 measures of oxygen gas unite
either with 36 measures of nitrous gas, or with 72 measures.
According to Gay-Lussac 100 measures of oxygen gas unite
either with 200 or with 300 measures of nitrous gas, accord-
ing to circumstances.
Nitrons gas, by eletricity, is converted into nitrous acid
and azote.
Water, according to Dr Priestley, absorbs about 1-10th
its bulk of this gas; according to Dr Henry about l-20th
of its bulk.
It is decomposed by phosphorus and charcoal, and proba-
bly also by sulphur at a very high temperature. Hydrogen
gas mixed with it burns with a green flame. This mixture,
according to Fourcroy, detonates when passed throgh a red
hot tube.
Neither azote nor muriatic acid produce any effect upon it.
146 ACIDS. CHAP. II
Several of the metals decompose it. When kept for some
time in contact with iron, its bulk diminises, and it is con-
ed into nitrous oxide
It is absorbed unchanged by a solution of green sulphate
or muriate of iron. The liquid acquires a deep brown co-
lour; and, when kept, becomes blue. The gas may be ex-
pelled unaltered by heat.
The following bodies convert this gas into nitrous oxide.
Alkaline sulphites, hydrogurted sulphurets, muriate of tin,
sufphureted hydrogen gas, iron or zinc filings moistened with
water.
From the analysis of Mr Davy, it appears to be composed
by weight of
57 oxygen.
43 azote.
___
100
According to Gay-Lussac nitrous gas is composed of eqal
bulks of oxygen and azotic gas united together, and its speci-
fic gravity is exactly the mean. Hence no change of bulk
takes place when they are combined. This would give us
nitrous gas composed by weight of
53 oxygen.
47 azote.
___
100
CHAP. II.
OF ACIDS.
The word acid, originally synonymous with sour, is at pre-
sent applied to all bodies possessed of the following proper-
ties.
\A0
SECT. ACIDS. 143
1. When applied io the tongue, they excite that seasation
which is called sour or acid.
2. They change the blue colours of vegetables to red.
3. They unite with water in almost ever proportion.
4. They combine with the alkalies, earths, and metallic
oxides, and form a class of bodies called salts.
Every acid does not possess the whole of these properties.
But all of them possess a sufficient number to distinguish
them from other bodies. The 2nd and 4th properties are
considered as the most important and essential.
It was at one time believed that there existed only one acid
in nature, and that all bodies owed their acidity to the pre-
sence of that acid.
This notion was long a favourite one among chemists, and
sulphuric and phosphoric acids were pitched upon as the uni-
versal acids. But the claims of neither could stand the test
of a rigid examination. At last Mr Lavoisier proved that
many substances were capable of combining with oxygen,
and by that means were converted into acids. Hence oxy-
gen was termed the acidifying principle.
All that can he meant by this appellation is only that many
acids contain oxygen as a constituent, and that when deprived
of oxygen, they lose their acid characters. In this sense the
appellation is correct enough. But it is not true that oxy-
gen itself possesses acid characters; neither has it been proved
that it exists in every acid. Many substances contain oxy-
gen which are entirely destitute of acid properties. Thus
water, alkalies, and alkaline earths contain it. Yet it would
be absurd to consider any of these bodies as acids. As the
acids are very numerous, and very heterogeneous in their pro-
perties, it will be of some importance to subdivide them into
classes. They may be arranged under three heads: 1. Acid
products. 2. Acid supporters. 3. combustible acids.
144 ACIDS. CHAP. II.
Class 1. Acid products.
aAl the acids belonging to this class possess the following
properties.
1. They may be formed by combustion. Of course their
base is a simple combustible.
2. They are incombustible.
3. They resist a violent heat without decomposition. But
to this there are some exceptions.
4. They are decomposed by the joint action of a combus-
tinle body and caloric.
5. Oxygen is an essential ingredient is all of them.
Some of the combustibles combine with two doses of oxy-
gen, and form two distinct acids. When that happens, the
acid containing the smallest dose of oxygen is distinguished
by the termination ous, while that which contains a maximum
of oxygen is distinguished by the termination ic. Thus sul-
phurous and sulphuric acids. The first conptains the least,
and the second the most oxygen.
The following table exhibits the names of the acid pro-
ducts, their bases, and the proportion of oxygen in each,
combined with 100 of the bases as far as it is known at
present.
Names. Bases. Propor-
tion of
oxygen to
100 base.
Sulphuric Sulphur. 136.5
Sulphurous 88.6
Phosphoric Phosphorus 114.7
Phosphorous 28?
Carbonic Carbon 257
Boracic Boracium 200
Fluoric Unknown
SECT. I. SULPHURIC ACID. 145
Sect. I. Of Sulphurie acid.
Sulphuric acid seems to have been discovered by the al-
chymists. It was long obtained by distilling the salt called
green vitriol, or sulphate of iron. Hence the names oil of
vitriol and vitriolic acid originally applied to it. It is now
procured by burning a mixture of sulphur and nitre in cham-
bers lined with lead, the bottom of which is covered with
water. The acid formed is dissolved by the water, and is
concentrated by distillation in glass retorts.
Sulphuric acid is liquid, somewhat of an oily consistency,
transparent and colourless as water, without any smell, and
of a very strong acid taste. It destroys the texture of ani-
mal and vegetable substances. Its specific gravity, when as
strong as possinle, is about 1.85. It changes all vegetable
blues to red, except indigo. It boils at 546˚. When ex-
posed to cold, it crystallizes or congeals. The tempera-
ture necessary depends upon the strength. When of the spe-
cific gravity 1.780, it freezes at 45˚. When stronger or
weaker, it requires a much greater degree of cold.
It has a strong attraction for water, and when exposed to
the atmosphere, imbines nearly 7 times it weight of that li-
quid. When the two liquids are mixed together, a considerable
heat is evolved. Thus 4 parts of acid and 1 of water raises
the Thermometer to about 300˚. The density of this mixture
is always considerably greater than the mean. From the ex-
periments of Kirwan, it appears that the strongest sulphuric
acid of commerce contains almost l-5th of water, the remain-
ning 4-5ths are pure acid.
From the most accurate experiments hitherto made, sulphu-
ric acid appears to be composed of
42.3 oxygen.
57.7 sulphur.
____
lOO.O
K
146 ACIDS. CHAP. II.
This acid is not altered by exposure to light nor heat.
Oxygen gas does not act upon it nor combine with it.
The simple combustibles have but little effect upon it at
the ordinary temperature of the atmosphere, but when assist-
ed by heat they all decompose it. When hydrogen gas and
the acid are passed through a red hot tube, water is formed
and sulphur deposited. Charecal absorbs oxygen from it
and readily converts it into sulphurous acid, or into sulphur,
if the heat be long continued. Phosphorus and boracium
produce the same effect. Sulphur, when boiled with it,
readily converts it into sulphurous acid.
Azote has no action on it; but it readily absorbs muriatic
acid, and forms a smoking compound, whih acts powerfully
upon some metals.
Sulphuric acid, when concentrated, has little action on the
metals. When diluted, it dissolves iron and zinc with rapidi-
ty, water is decomposed, and hydrogen gas emitted. When
heated, it oxidizes several of the metals, and sulphurous acid
is exhaled. On gold and platinum it produces no effect
whatever.
It unites readily with the alkalies, earths and metallic ox-
ides, and forms with them a class of bodies called sulphates.
It absorbs a good deal of nitrous gas, and acquires, in con-
secquence, a purplish colour.
This acid is of great importance both in chemistry and the
arts.
SECT. II. Of Sulphurous Acid.
The existence of this acid was pointed out by Stahl, but
Priestley was the first who procured it in a separate state.
It may be obtained by distilling, in a retort, a mixture of two
parts sulphuric acid and one part of mercury. An efferves-
SECT. II. SULPHUROUS ACID. 147
cence takes place, and a gas comes over which may be re-
ceived in jars over mercury.
It is colourless, and possesses the mechanical properties of
common air. It has a strong and suffocating odour, precise-
ly the same as that emmitted by burning sulphur. Its specific
gravity is 2.265, that of air being 1.000. It reddens vege-
table blues, and gradually destroys the colour altogether.
When strongly heated, sulphur is deposited and sulphuric
acid formed. When exposed to the temperature of -18˚,
it is condensed into a liquid.
Water absorbs 33 times its bulk of this gas. The liquid
has the smell of the gas, an acid and sulphureous taste, and
the specific gravity 1.0513. It may be frozen without part-
ing with the gas. But when heated the gas is expelled.
When this liquid is left to iteslf, it gradually absorbs oxygen
and the acid is converted into the sulphuric.
Sulphur and phosphorus seem to have no action on this
acid, but hydrogen and charcoal decompose it when assisted
by heat, and sulphur is evolved. Neither azote nor muriatic
acid produce any effect upon it.
It oxidizes and dissolves iron, zinc and manganese.
It combines with the salifiable bases, and forms salts called
sulphites.
Sulphuric acid absorbs it, and forms a singular compound
called glasial sulphuric acid, which readily becomes solid,
and smokes when exposed to the air.
Its constituents, according to my experiments, are
53 sulphur.
47 oxygen.
___
100
K2
148 ACIDS. CHAP II.
SECT. III. Of Phosphoric Acid.
This acid was first mentioned by Boyle, but its properties
were investigated many years after. It may be obtained by
burning phosphorus, or by dissolving phosphorus in nitric
acid, and evaporating the liquid to dryness.
In this state it is solid, colourless and transparent, not un-
like glass. It reddens vegetable blues, has no smell, but has
a very acid taste. When exposed to the air, it attracts mois-
ture and gradually runs into an oily-like fluid. Its specific
gravity, when in the state of glass, is 2.8516; when in the
liquid state 1.417.
It is very soluble in water, and is said to be capable of
crystallizing, but it is difficult to obtain it in that state.
Oxygen has no effect upon it. None of the simple com-
bustinles are known to be capable of deconposing it, except
charcoal. When strongly heated with this substance, phos-
phorus is disengaged. The simple incombustibles have no
effect on it.
It is capable of oxidizing and dissolving some of the me-
tals. But its action on these bodies is by no means strong.
It combines with the salifiable bases, and forms a class of
salts called phosphates.
According to the experiments of Rose, it is composed of
46.5 phosphorus,
53.5 oxygen.
____
100
Sect. IV. of Photphorous acid.
This acid was known earlier than the preceding. For a
long time they were confounded. Lavoisier was, perhaps,
SECT. V. CARBONIC ACID. 149
the first who accurately distinguished them. It may be ob-
tained by exposing phosphorus to the open air: it gradually
absorbs oxygen and runs into a liquid, which is the acid in
question.
It is a viscid colourless liquid; having a very acid taste,
and emitting the smell of garlic, especially when heated. It
combines with water in any proportion. When evaporated
to dryness and heated, it gives out phosphureted hydrogen
gas, which burns when it comes in contact with the air.
This continues for a long time, and at last the acid is convert-
ed into the phosphoric. If nitric acid be poured upon it,
this change takes place much more easily and speedily.
The action of the simple combustibles, fine incombustibles
and the metals on this acid, is similar to their action on phos-
phoric acid.
It combines with the differed salifiable bases, and forms
a class of salts called phosphites.
Sulphuric acid, by the assistance of heat, converts it into
phosphoric acid.
It has been ascertained that this acid contains less oxygen
than the phosphoric, but the actual proportion has not been
determined.
SECT. V. Of Carbonic Acid.
This acid was discovered by Dr Black. Its properties
were afterwards investigated by Mr Cavendish and Dr Piest-
ley, and its composition ascertained by Mr Lavoisier. It
was at first called fixed air. Mr Lavoisier, after ascertain-
ing its base, gave it the name which it now bears. Every
chemist almost of eminence, during the last 50 years, has
added something to our knowledge of the properties of this
remarkable substance.
K3
150 ACIDS. CHAP. II.
It may be obtained by burning cbarcoal, or more easily by
pouring muriatic acid on chalk in a glass retort, and receiving
the gas which is extricated in glass jars over water. This
gas is the acid in question.
It is invisinle, and possesses the mechanical properties of
air. No combustible will burn in it. It is unfit for respi-
ration. It affects the nostrils with a kind of pungent sensa-
tion, but, when diluted with air, it has no smell whatever.
Its specific gravity is 1.500, that of air being 1.OOO. It red-
dens very delicate vegetable blues.
Atmospheric air contains about 1/1060 of its bulk of this
gas.
It is not altered by passing it through a red hot tube, but
but when electric sparks are passed through it for a long time
its bulk increases, and a portion of carbonic oxide is evolved.
Water absorbs it when placed in contact with it. The ra-
pidity of the absorption is much increased by agitation. Wa-
ter absorbs its own bulk of this gas at the temperature of
41˚. The water acquires a sour taste, a sparkling appear-
ance, and the property of reddening vegetable blues. When
heated or frozen, the gas is extricated. It makes its escape
also if the liquid be left exposed to the open air.
Carbonic acid is not acted upon by oxygen; nor, as far as
is known, is it altered by any of the simple combustibles,
incombustibles or metals. But several of these bodies, as
charcoal, phosphorus and different metals, have the property
of decomposing it at a red heat, when it is in combination
with lime, barytes or strontian. In these cases a quantity of
carbonic oxide is usually evolved.
It combines with the salifiable bases, and forms a class of
salts called carbonates.
From the most exact experiments hitherto made, we may
consider this acid as composed very nearly of
SECT. VI. BORACIC ACID. 151
28 carbon.
72 oxygen.
___
100
Sect. VI. Of Boracic Acid.
This acid is obtained from the salt called borax, brought
to Europe from the east, where it is found chiefly at the bot-
tom of some lakes in Tinet and China. It was first ex-
tracted from borax by Homberg, and its nature was ascer-
tained by Baron. To obtain it, dissolve borax in hot water
and add sulphuric acid till the liquid assumes a sensinly acid
taste. As the liquid cools, it deposites white cryatalline
scales, which are boracic acid.
Thus obtained, it has the form of thin hexagonal scales of
a silvery whiteness. Its taste is sourish and bitterish. It has
no smell. It reddens vegetable blues. Its specific gravity,
while in scales, is 1.479, when melted 1.803.
It is not altered by light nor heat. In a red heat it melts
into a transparent colourless glass, which becomes somewhat
opake when exposed to the air, but does not attract mois-
ture.
Boiling water does not dissolve more than 0.02 of this
acid, and cold water still less.
Neither oxygen, the simple combustibles, incombustibles
or metals, produce any effect upon this acid. But when
heated with potassium it is decomposed, and its base bora-
cium separated.
From the experiments of Davy, we may conclude that
boracic acid it composed of about 33 boracium
67 oxygen.
___
100
K4
152 ACIDS. CHAP. II.
It is soluble in alcohol containtng it burns
with a green coloured flame. It disolves also in some of
tbe oils.
It is hardly capable of oxidizing any of the metals except
iron and zinc.
It combines with the salifiable bases, and forms a class of
salts called borates.
Sect. VII. Of Fluoric Acid.
This acid was discovered by Scheele. He obtained it
from a pretty common and beautiful mineral called fluor
spar, and in this country often Derbyshire spar. This mine-
ral is a compound of fluoric acid and lime. Dr Priestley
first obtained the acid in a separate state.
To procure this acid, pour sulphuric acid on the pounded
spar and apply heat. A gas comes over which must be re-
ceived over mercury. It is the acid in question.
This gas possesses the mechanical properties of air. It
does not support combustion, nor can animals breathe it. It
smokes when mixed with tfe atmosphere, and has a smell si-
milar to that of muriatic acid.
It is not altered by exposure to heat or light.
Water absorbs it rapidly. If glass vessels have been em-
ployed to procure it, a jelly is deposited as soon as it comes
in contact with the water. This jelly consists of silica which
the gas has dissolved from the glass, and which is held in so-
lution. No method has been yet discovered of obtaining
fluoric acid gas free from foreign matter. If leaden vessels
be used, the gas does mot assume the elastic form, at least I
could not procure it by means of these vessels. When fluor
spar and vitreous boracic acid are heated together, a gas is ob-
tained, which is a combination of the two acids, to which
SECT. VII. FLUORIC ACID. 153
Thenard and Gay-Lussac, who discovered ths compound gas,
have given the name of fluoboracic acid gas.
Neither oxygen, the simple combustibles, incombustibles
or metals, as far as is known, produce any effect upon this
gas. It does not act powerfully upon the metald.
The fluoboracic acid is absorbed by water, and forms a
very powerful acid liquid, nearly as heavy as sulphuric acid,
and capable of resisting as strong a heat before it is volati-
lized.
One of the most curious properties of fluoric acid is the
ease whith which it corrodes glass, when that substance is ex-
posed to its fumes. In consequence of this property, it has
been employed to etch upon glass.
It combines with the different bases, and forms a class of
salts called fluates.
All attempts to decompose this acid have failed, in conse-
quence, chiefly, of the impossinility of making experiments
on it in a state of purity
CLASS 2. Acid Supporters.
The acid supporters are distinguished by the following
properties:
1. They cannot be produced by combustion. Hence their
base is either a simple incombustible or a metal.
2. They support combustion. Hence they acidify the
combustible bases and oxidize the metals.
3. They are decomposed at a high temperature, their oxy-
gen making its escape in the state of gas.
The only acid supporters known at present are those which
have the simple incombustibles and arsenic for their bases.
From analogy I refer the whole of the metallic acids to this
head.
154 ACIDS. CHAP. II.
The followingtable exhibits a view of all the acid sup-
porters, of their bases, and of the proportion of their consti-
tuents, as far as that has been ascertained.
Names. Bases. Proportion of
oxygen to
100 base.
Nitric Azote 236
Nitrous
Oxymuriatic Muriatic acid 29
hyper-oxymuriatic 194
Arsenic Arsenic 53
Tungstic Tungsten 25
Molybdic Molybdenum 50
Chromic Chromium 100
Columbic Columbium
Oxygen is an essential constituent of all these acids, as
well as of those belonging to the first class.
SECT. I. Of Nitric Acid.
This acid seems to have been first obtained in a separate
state by Raymond Lully, one of the most celebrated of the
alchymists. It was called, at first, water of nitre, aqua for-
tis, spirit of nitre.
It may be obtained by distilling a mixture of three parts
nitre and one of sulphuric acid in a glass retort .
The acid thus obtained has a yellow colour; but, if kept
for a short time in a boiling heat, it becomes colourless. It
has a peculiar smell, it smokes when exposed to the atmo-
SECT. NITRIC ACID. 155
sphere. Its taste is extremely acid, and it is one of the most
corrosive substances known, tinging the skin instantly of an
indelinle yellow, and very soon destroying its texture entirely.
It convertts vegetable blues to red. Its specific gravity, when
strongest, never exceeds 1.583. It contains, mixed with it, a
considerable portion of water, from which it cannot be freed.
When strongest, this water amounts to about one-fourth of
the whole.
It boils at 248˚, and may be distilled over without altera-
tion. When cooled sufficiently it congeals, and the freezing
point varies exceedingly according to the strength of the acid.
There is a certain strength at which it congeals most easily,
and, if it be either stronger or weaker, the freezing point is
considerably lower.
Oxygen has no effect upon this acid; but all the simple
combustibles decompose it. When poured upon charcoal,
phosphorus or sulphur, at a high temperature, it sets them
on fire. When diluted, it effervesces with these bodies, and
acidifies them. Hydrogen gas does not act upon it at the
common temperature of the atmosphere, but when passed
with it trough a red-hot tube, it detonates, water is formed
and azotic gas disengaged. Boracium is readily converted by
it into boracic acid. When poured upon the volatile oils,
and even upon several of the fixed oils, it sets them on fire.
If it be previously mixed with a little sulphuric acid, it sets
almost all the oils on fire.
Azote has no action on this acid, but murtiatic acid forms
with it thee compound called aqua regia, or nitro-muriatic
acid.
It is capable of oxidizing all the metals except gold, pla-
tinum and titanium. With most of the oxides it cominnes,
though some, as the peroxides of tin and antimony, are inso-
luble in it. It even sets fire to some of the metals when
poured upon them in fusion.
It absorbs nitrous gas in great abundance, and becomes first yellow, then orange, then olive, and at last green, according to the proportion of the gas present. Acid thus contaminated with nitrous gas was formerly called dephlogisticated nitric acid, and nitrous acid; on the supposition that it was nitric acid deprived of a portion of its oxygen. When fully saturated with nitrous gas, it assumes a gaseous state, and is known by the name of gaseous vapour.
Nitric acid comobines with the different salifiable bases, and forma a clas of salts called nitrates.
It has been ascertained that this acid is a compound of oxygen and azote in the following proportions: 28.77 azote, and 70.23 oxygen.
Section II
Of Nitrous Acid.
When nitre, which is a compound of nitric acid and potash, is exposed to a red heat, it yields a considerable portion of oxygen gas. If the process be conducted with the proper precautions, and stopped in time, the nitre still retains the porperies of a neutral salt. But hte acid which it contains is obviously in a different state, since it has lost a considerable part of its oxygen. To this mnew state the term nitrous acid is applied.
In this state it was discovered by Scheele, but all attempts to obtain the acid by itself have failed. It is decomposed aparently whenever it is separated from the potash; for fumes of nitrous gas immediately make their appearance.
Section III.
Of Oxymuriatic Acid.
This acid was discovered by Scheele, and called by him dephlogisticated muriatic acid. It got its present name after its constiturents were ascertained.
It may be obtained by distilling a mixture of muriatic acid and the black oxide of manganese; or by mixing togehter three parts of common salt, and two parts of black oxide of manganese in a glass retort, and pourong over them two parts of diluted sulfuric acid. When this mixture is heated, a green coloured gas makes its appearance, which may be collected in glass vials over water. This gas is the acid in question.
This gas has a yellowish green colour, it odour is extremely offensive and suffocating, and cannot be breathed. When drawn into the lungs mixed with common air, it occasions a violent coughwhich lasts for some time, accompanied with a sense of oprression and weakness. It is capable of supporting combustion. Indeed many substances, as phosporus, antimony, &c.
take fire in it of their own accord, without beieng kindled. Its specific gravity is 2.766, that of air beeing 1.000.
It is not altered by exposure to light, or to a red heat.
Water absorbs it slowly, and aquires a green colour, and the smell and properties of the gas. It may be frozen without losing the gas, but it is easily extricated by heat. When this liquid is exposed to the light, the acid is decomposed, oxygen gas is exhaled, and muriatic acid remains in solution in the water.
It does not redden vegetable blues, but destroys them. This property has made oxymuriatic acid a very valuable article in bleaching.
It is not acted on by oxygen, but all the simpe combustibles decompose it. When confined with half its bulk of oxygen ga in a phial, the hydrogen is gradually converted into
Ende Philadelphia$$$
158 ACIDS. CHAP. II.
water, and muriatic acid remains behind. This mixture ex-
plodes by electricity.
Charcoal is said by some to burn in it when introduced
about the temperature of 90˚. Phosphorus takes fire in it,
and is converted into phosphoric acid. Sulphur is gradually
acted on by it, and a red liquid formed, composed of muria-
tic acid, oxygen and sulphur, to which the name of sulphu-
reted muriatic acid has been given. Boracinm is speedily
converted into boracic acid. Sulphureted, carbureted and
phosphureted hydrogen gases likewise decompose this acid,
but only the last of them burns spontaneously when mixed
with it.
Neither of the simple combustibles produces any effect
upon this gas.
It oxidizes all the metals with facility, and even sets fire to
several of them, and burns them.
Ammoniacal gas likewise takes fire spontaneously, and
burns with considerable splendour when mixed with this gas,
the result is water and sal ammoniac.
It seems capable of uniting with the different bases, when
they are presented to it in a dry state, but water in general
seems sufficient to prevent the combination from taking
place. The salts formed are called oxymiriates.
It reddens nitrous gas, converting it into nitric acid. Sul-
phurous and phosphorous acids are converted by it into sul-
phuric and phosphoric acids. Upon the other acids, al-
ready descrined, it produces no effect.
When nitric and muriatic acids are mixed together, a quan-
tity of oxymuriatic acid gas is separated.
From the analysis of Chenevix, it appears that this acid if
composed of
77.5 muriatic acid.
22.5 oxgen.
____
100.0
SECT. IV. HYPEROXYMURIATIC ACID. 159
SECT. IV. Of Hyperoxymuriatic Acid.
This acid was discovered by Berthollet. Its nature and
peculiarities were farther investigated by Chenevix.
If a solution of potash in six times its weight of water be put
into a Woulfe's bottle, and a current of oxymuriatic acid gas
be passed through it for a sufficient time, small brilliant crys-
tals are deposited in scales. These crystals have received
the name of hyperoxymuriate of potash. They possess cu-
rious and important properties. The liquid contains another salt
composed of muriatic acid and potash. From this last
fact it was inferred, that the acid in the first salt contained
more oxygen than exists in oxymuriatic acid. This was de-
monstrated by the experiments of Chevenix, who showed
that it is composed of
66 oxygen.
34 muriatic acid.
___
100
All attempts to procure this acid in a separate state have
failed. When sulphuric or nitric acid is poured upon the
salt, it is dissolved, assumes an orange colour, and a greenish
yellow vapour floats above the solution. When heat is ap-
plied to drive off the acid, a violent detonation takes place,
which shatters the vessel to pieces. When muriatic acid is
poured upon the crystals, an effervescence takes place and a
gas is separated intermediate in its properties between oxy-
muriatic acid and hyper-oxymuriatic acid.
When this salt is rubbed with sulphur, phosphorus or char-
coal, or when struck with these bodies on an anvil, a violent
detonation takes place, and the combustible substances are
burnt. The same phenomena tate place when the salt is
struck after being mixed with a variety of other combustible
160 ACIDS. CHAP. II.
substances. Gunpowder my be made of it more powerful
than common gunpowder, but the manufacture is attended
with risk, in consequence of the tendency which the ingredi-
ents have to detonate when rubbed.
SECT. V. Of Arsenic Acid.
This acid was discovered by Scheele. It may be formed in
the following manner: Mix in a retort one part of muriatic
acid, four parts of white oxide of arsenic, and 12 parts of ni-
tric acid of the specific gravity 1.25. Boil the mixture till
the oxide disappear, and nitrous fumes cease to be disengaged;
then evaporate to dryness, and expose the mass to a low red
heat. The matter thus obtained is solid arsenic acid.
It is a white solid mass nearly tasteless, of the specific gra-
vity 3.391. It is very fixed. It melts at a red heat, and is
converted into glass.
It dissolves slowly in cold, but rapidly in hot water, and
by cautious evaporation may be obtained in crystals. The
taste of the solution is acid, caustic and metallic.
Oxygen has no effect on it. The simple combustibles de-
compose it when assisted by heat, and sometimes take fire, in
consequence of its action on them, a proof that this acid is a
supporter of combustion.
The simple incombustibles have no action on it. It oxi-
dizes several of the metals, especially when assisted by heat.
It combines with the salifiable bases, and forms a class of
salts called arseniates.
It has no action on any of the acids already descrined.
From the analysis of Proust, it appears that this acid is
composed of
65 arsenic.
36 oxygen.
__
100
SECT. VI. TUNGSTIC ACID. 161
SECT. VI. Tungstic Acid.
The substance orignally called tungstic acid was disco-
vered by Scheele. It was not pure, being contaminated by
the acid employed in separating it.
The real tungstic acid is a yellow powder first descrined
by the Eluyarts. It is tasteless, insoluble in water, and has
no effect on vegetable blues. It is rather an oxide than an
acid. But it combines with the salifiable bases, and forms
a class of salts called tungstates.
Sect.VII. Of Molybdic Acid.
Thins acid was discovered by Scheele. It has been lately
examined by Bucholz.
It may be obtained by digesting nitric acid on molybdena
till the whole is converted into a white mass. Edulcorate
this mass with water, the residue is molybdic acid.
It is a white powder of the specific gravity 3.460. In
close vessels it melts and crystallizes when heated; but in open
vessels it sublimes, and may be collected in the form of bril-
iant yellow scales.
li is soluble in 960 parts of water. The solution is pale
yellow. It is tasteless, but reddens vegetable blues.
Molybdic acid is not affected by oxygen gas; but it is de-
composed by sulphur and charcoal, and several of the metals.
It combines with the salifiable bases, and forms a class of
salts called molybdates.
It dissolves in sulphuric acid. The solution is colourless
when hot, but becomes blue when cold. It dissolves also in
muriatic acid, but not in nitric acid.
L
162 ACIDS. CHAP. II.
According to the analysis of Bucholz, it is composed of
67 molybdenum.
33 oxygen.
__
100
SECT. VIII. Of Chromic Acid.
This acid was discovered by Vanquelin. It may be ob-
tained from the red lead ore of Sineria, by boiling the ore
with carbonate of soda, decanting off the fluid solution, and
saturating it with sulphuric acid. A red powder falls, which
is chromic acid.
It has a red or orange yellow colour, an acrid and metal-
lic taste; is soluble in water, and crystallizes in elongated
prisms of a ruby colour.
When heated it gives out oxygen gas, and is converted into
green oxide of chromium.
When heated with filings of tin and muriatic acid, it be-
comes at first yellowish brown, and afterwards assumes a beau-
tiful green colour. When treated with acids, and various
other combustibles, a green colour is also evolved.
Sect. IX. Of Columbic Acid.
This acid was discovered by Hatchet in an ore from Ame-
rica of a black colour, which he found in the British Mu-
seum. It was obtained by fusing the ore with potash, dis-
solving the potash in water, and adding nitric acid to the so-
lution. The columbic acid precipitated in flakes.
It is a powder of a white colour, and not very heavy. It
is tasteless, insoluble in water, but gives a red colour to ve-
getable blues.
Sulphuric acid dissolves it, and forms a colourless solution,
SECT. IX. COLUMBIC ACID. 163
from which the columbic acid is precipitated by water. It
is soluble also in muriatic acid, but not in nitric acid.
It combines with the salifiable bases, and forms a class of
salts called columbates.
CLASS 3. combustible Acids.
The acids belonging to this class may be distinguished by
the following properties.
1. If they be combined with potash, and distilled, they
are decomposed, charcoal is usually evolved, and a consider-
able quantity of heavy inflammable air extricated.
2. All of them contain at least 2 simple combustibles as
a base, namely carbon and hydrogen. Some of them also
contain azote. Oxygen usually enters into their composition,
though not perhaps always.
3. They do not seem capable of combining with different
doses of oxygen. Whenever the proportion of oxygen
changes, that of the other constituents varies also.
4. They are decomposed by the action of the more power-
ful acid supporters, and either converted into other combus-
tinle acids, or into oxide and acid products.
They may be divided into four orders. Those belong-
ing to the first crystallize, and may be volatilized without de-
composition. Those belonging to the second likewise crys-
tallize, but they cannot be volatilized without decomposition.
Those belonging to the third order are not crystallizable,
though they may be exhibited in the state of a dry mass.
Under the fourth order are placed three acids, which, from
the singularity of their properties, ought to be considered
apart.
The following table exhibits the names and component
parts of each of these acids, as far as is known at present.
L2
164 ACIDS. CHAP. II.
Order 1 Crystallizable, volatilizable.
Names. Constituents.
1. Acetic. carbon, hydrogen, oxygen.
2. Benzoic.
3. Sebacic.
4. Succinic.
5. Moroxylic.
6. Camphoric.
7. Oxalic?
Order II. Crystallizinle, not volatilizable.
1. Mellitic. carbon, hydrogen, oxygen.
2. Tartaric.
3. Citric.
4. Kinic.
5. Saclactic .
6. Uric carbon, hydrogen, azote, oxygen.
Order III. Not crystallizable.
1. Malic. carbon, hydrogen, oxygen.
2. Suberic.
3. Formic.
Order IV. Colorific.
1. Prussic. carbon, hydrogen, azate.
2. Gallic. carbon, hydrogen, oxygen.
3. Tannin.
carbon, hydrogen, oxygen.
SECT. I. Of Acetic Acid.
This has been the longest known of all the acids. It is
obtained by causing wine or beer to unergo a new fermen-
tation. They become sour, and are known by the name of
SECT. I. ACETIC ACID. 165
vinegar. When the vinegar is distilled, a transparent colour-
less liquid is obtained, called distilled vinegar, or sometimes
acetous acid. When this substance is combined with oxide
of copper, and the dry mass distilled, a liquid is obtained,
which contains the acid in a much more concentrated state.
It was formerly called radical vinegar, and acetic acid, by
way of eminence.
It is now known that the acid principle in all these three
liquids is precisely the same, and that they differ merely in
the concentration of that acid, or in consequence of containing
small quantities of some foreign ingredient. Hence the
term acetic acid is now applied to the acid in all cases.
Acetic acid is a liquid transparent and colourless like wa-
ter. It has a peculiar and well-known aromatic smell when
in the state of vinegar or distilled vinegar. In radical vinegar
this smell is not so agreeable, being mixed with a kind of
empyreumatic odour. When sufficiently concentrated, it may
be obtained in crystals, but the process is difficult, and re-
quires particular precautions to ensure success.
The specific gravity of distilled vinegar varies from 1.007
to 1.0095; that of radical vinegar is 1.080. But the strength
of the acid is not always proportional to its specific gravity,
owing to the presence of foreign bodies from which it is
very difficult to free it. It is very volatile, unites with wa-
ter in any proportion, and reddens vegetable blues.
Neither oxygen, the simple combustibles or incombusti-
bles, have any action on this acid. It oxidizes some metals;
but its action on these bodies is not violent. It combines
with metallic oxides, and forms with every one a soluble salt.
Indeed all the salts that contain acetic acid are soluble in
water. In this respect it agrees with nitric acid.
It combines with salifiable bases, and forms a class of salts
called acetates.
Sulphuric and nitric acids seem capable of decomposing it,
L2
166 CIDS. CHAP. II.
but the action of the other acids is not remarkable. It dis-
solves and combines with many vegetable bodies, and is, in
consequence, useful in vegetable analysis.
It is composed of oxygen, hydrogen and carbon, but the
proportion of these constituents has not been hitherto ascer-
tained in an unexceptionable manner.
Sect. II. Of Benzoic Acid.
This acid is obtained, by sublimation, from a resinous sub-
tance called benzoin.
It is a fine light white matter in small needles. It is not
brittle, but has a kind of ductility. Its taste is acrid, hot,
and somewhat bitter. Its odour is weak but aromatic. Its
specific gravity 0.667. It reddens the most delicate vege-
table blues.
It is easily volatilized by heat. It burns when kindled, and
leaves no residuum. It is not altered by exposure to the air.
Cold water dissolves no sensible quantity of it, but it dissolves
readily in hot water.
It is not acted upon by oxygen gas, or by any of the simple
combustibles or incombustibles; nor does it seem capable of
oxidizing any of the metals.
It combines with the salifiable bases, and forms a class of
salts called benzoates.
Several of the strong acids dissolve it; but it is precipita-
ted again unaltered by the infusion of water. Alcohol dis-
solves it copiously.
Sect. III. Of Sebacic Acid.
This acid was mentioned many years ago, but its nature
and properties remained unknown till it was lately examined
by Thenard. Berzelius has lately added considerably to our
SECT. IV. SUCCINIC ACID. 16?
knowledge of it. It may be prepared by the following pro-
cess.
Distil hog's lard; wash the product with hot water, sepa-
rate this water and drop into it acetate of lead. A flaky pre-
cipitate appears which is to be washed and dried, mixed with
sulphuric acid and heated. A melted substance, like fat,
swims on the surface. This substance is sebacic acid.
Sebacic acid is white, it has no smell; its taste is a plea-
sant sour, leaving in the mouth a very slight impression of
bitterness. It reddens vegetable blues. When heated it
melts like tallow, and, on cooling, concretes into in crystalli-
zed mass. It may be volatilized, but requires a higher tem-
perature than benzoic acid. Berzelius has shown that this
acid, in most of its properties, coincides with benzoic acid;
and that the two acids, if not absolutely the same, at least
approach very closely to each other.
Sect. IV. Of Succinic Acid.
This acid is obtained when amber is exposed to heat. It
sublimes in small needles, coloured by an oil, from which it
may be freed by digestion in nitric acid and subsequent crys-
tallization. Trommsdorf affirms, that when dry saclactic acid
is distilled, it yields abundance of succinic acid.
This acid is white, crystallizes in triangular prisms, has an
acid taste, and reddens vegetable blues. When heated, it
melts and then sublimes.
It is but little soluble in cold, but very soluble in hot wa-
ter. Alcohol acts nearly upon it as water. It dissolves in
sulphuric, nitric and muriatic acids, without undefgoing de-
composition.
It combines with the salifiable basea, and forms a class of
salts called succinates.
L 4
168 ACIDS. CHAP. II.
SECT. V. Of Moroxylic acid.
This acid was discovered by Klaproth in a saline exuda-
tion incrusting the bark of the white mulberry tree. This
salt was a compound of the acid in question and lime.
The acid was separated by dissolving the salt in water, and
precipitating the acid by means of acetate of lead. The pre-
cipitate was mixed with diluted sulphuric acid and digested.
Sulphate of lead was formed and moroxylic acid disengaged.
It crystallized in needles, which had the taste of succinic
acid, were not altered by exposure to the air, and dissolved
readily in water and in alcohol. When heated it sublimes,
and thus may be obtained quite pure.
SECT. VI. Of Camphoric Acid.
This acid was discovered by Kozegarten, but first accu-
rately descrined by Bouillon La Grange.
It is obtained by distilling a solution of camphor in nitric
acid, repeatedly adding nitric acid till it amounts to 24 times
the weight of the camphor. Crystals gradually make their
appearance, which consist of camphoric acid.
This acid is snow-white. Its crystals are parrallelepipeds
which effloresce in the air. Its taste is acid and bitter, it has
the smell of saffron, and reddens vegetable blues.
It dissolves in about 100 parts of cold water, but is more
soluble in hot water. It dissolves in alcohol. The salts
which it forms are called camphorates.
Sect. VII. Of Oxalic Acid.
This acid was discovered by Scheele, and first descrined
by Bergman. It is obtained by heating a solution of sugar
in nitric acid.
SECT. VIII. MELLITIC ACID. 169
It crystallizes in small four-sided prisms, terminated by di-
hedral summits. These crystals are composed of 77 parts
acid and 23 water. When exposed to heat it sublimes, but
at the same time is partly decomposed.
These crystals have a very acid taste, and redden vegetable
blues. They dissolve in their own weight of boiling water,
and in twice their weight of cold water. They dissolve, al-
so, readily in alcohol.
When exposed to dry air they effloresce; but in moist air
they are not altered. Neither oxygen, nor the simple com-
bustinles or incombustibles act on this acid. It oxidizes
some of the metals; but most of them are not affected by it.
It combines with the salifiable bases, and forms a class of
salts called oxalates.
Muriatic and acetic acids dissolve it, sulphuric acid decom-
poses it by the assistance of heat. Nitric acid converts it
into water and carbonic acid.
When combined with a base and distilled, it is decompo-
sed and converted into water, carbonic acid, carbonic oxide,
carbureted hydrogen, and charcoal. It is composed, accord-
ing to my experiments, of oxygen 64
carbon 32
hydrogen 4
____
100
SECT. VIII. Of Mellitic Acid.
This acid was discovered by Klaproth, in the mineral called
mellite or honeystone, which he found composed of alumina
the acid in question.
It is obtained by boiling the mineral powder in 72 times
its weight of water, filtering the liquid and evaporating suffi-
ciently. The mellitic acid crystallizes.
170 ACIDS. CHAP. II.
The crystals are needles, having a brownish colour, and a
sweetish sour taste. It is but moderately soluble in water.
Nitric acid does not seem to decompose it. It reddens ve-
getable blues. The salts which it forms are called mellates.
SECT.IX. Of Tartaric Acid.
This acid exists in the salt called tartar, from which it
was first obtained in a separate state by Scheele. The pro-
cess is this:
Dissolve tartar in water, and add chalk in powder as long
as an effervescence continues. A white powder precipitates.
Pour on this precipitate a quantity of sulphuric acid equal in
weight to the chalk employed, previoudy diluted with water,
and digest for a day or two. Then filter and evaporate the
liquid. The tartaric acid is obtained in crystals.
These crystals are white, transparent and hard. They are
very irregular four-sided prisms, composed of 84.5 real acid,
and 15.5 water.
It is not altered by exposure to the air. At 212˚, it melts
and becomes as liquid as water. At 250˚, it boils without
losing its transparency or aquiring colour. When cooled it
concretes into a hard mass, but the nature of the acid is
changed. It has now acquired the property of deliquescing
when exposed to the air. When distilled, this acid yields an
acid liquid formerly called pyrotartarous acid, but now known
to be the acetic disguised by means of an emypreumatic oil.
When combined with a base and distilled, tartaric acid is de-
composed and converted into water, carbonic acid, heavy in-
flammahle air, and charcoal.
It dissolves readily in water, and when the solution is di-
luted, the acid undergoes spontaneous deomposition.
None of the simple substances produce any striking effect
upon this acid. It combines with the salifiable bases, and
forms a class of salts called tartrates.
SECT. XI. KINIC ACID. 171
Sect. X. Of Citric Acid.
This acid exists in the juice of oranges and lemons, and
was first obtained pure by Scheele. His process was this:
Saturate lemon-juice with chalk. A precipitate falls.
Wash this precipitate, and pour on it as much sulphuric acid
as will saturate the chalk employed, previously diluted with
six times its weight of water. Digest, filter and evaporate
the liquid. The citric acid crystallizes.
This acid crystallices in rhomboidal prisms. The crystals
are not altered by exposure to the air. The taste is acid,
and vegetable blues are reddened by it. It dissolves in less
than its weight of water.
It is not acted on by the simple substances. It oxidizes a
few of the metals. It combines with the salifiable bases,
and forms a class of salts called citrates.
Sulphuric acid decomposes it. Nitric acid converts it in-
to oxalic acid, or into acetic acid, if used in excess.
Sect. XI. Of Kinic Acid.
This acid was discovered by Vauquelin, in a salt first ob-
tained from Jesalts bark, by Deschamps. This salt is a
compound of kinic acid and lime.
Vauquelin dissolved the salt in water, and precipitated
the lime by means of oxalic acid. The liquid was evapo-
rated to the consistence of a syrup, and then set aside. No
crystals formed in it, at first, but on being touched, it wholly
crystallized in diverging plates.
Its colour is somewhat brown, its taste very acid and bit-
ter. It was not altered by exposure to the air. It is very
soluble in water. It does not precipitate silver nor lead
176 ACIDS. CHAP. II.
from their solutions. When heated it is decomposed, and
charcoal remains behind.
Sect. XII. Of Saclactic acid.
This acid was discovered by Scheele, who formed it by di-
gesting sugar of milk in nitric acid. Fourcroy and Vauque-
lin ascertained, afterwards, that it is formed when gum is heat-
ed with nitric acid and the solution allowed to cool. A white
powder precipitates, which is the acid in question.
Saclactic acid thus obtained, is in the form of a white
gritty powder, with a slight acid taste. It is only slightly
soluble in boiling water. The solution has an acid taste, and
reddens vegetable blues.
The compounds which this acid forms, with the salifiable
bases, are called saccolates.
SECT. XIII. Of Uric Acid.
This acid was discovered by Scheele in urinary calculi, and
first called lithic acid. But this term was afterwards laid
aside, and uric acid substituted; because this acid constitutes
one of the ingredients of urine. For the best account of the
properties of this acid we are indebted to Dr Henry.
It is obtained by dissolving the calculi, composed chiefly
of it, in alkaline ley, and precipitating by means of muriatic
or acetic acids. The white powder which falls, when well
edulcorated, is pure uric acid.
It is a white powder, without taste or smell. It reddens
vegetable blues, and requires more than 1700 parts of cold
water to dissolve it.
It dissolves readily in fixed alkaline solutions; but not in al-
caline carbonates. It dissolves in nitric acid, and when the
solution is evaporated nearly to dryness, it assumes a fine
SECT. XIV. MALIC ACID. 173
pink colour, which becomes much deeper when water is ad-
ded, so as to have a near resemblance to carmine. The wa-
tery solution of this matter loses its red colour in a few hours,
and it cannot afterwards be restored.
Oxymuriatic acid readily converts the uric into the oxalic
acid.
When distilled, carbonate of ammonia is obtained, and a
saline sublimate, which Dr Henry has shown to be a com-
pound of ammonia with a peculiar acid.
Sect XIV. Of Malic Acid.
This acid was discovered by Scheele. It exists in apples,
and in a variety of vegetable substances. It is formed also
by the action of nitric acid on sugar.
Scheele obtained it by saturating the juice of apples with
potash, precipitating by acetate of lead, digesting the preci-
pitate in a sufficient quantity of sulphuric acid to separate
the lead; and then filtrating. The liquid contained pure ma-
lic acid.
When malic acid is obtained by the action of nitric acid
on sugar, it is colourless; but it very easily acquires a brown
colour by the action of heat, of even by keeping it in a liquid
state. When evaporated, it may be obtained in a solid state;
but it is not capable of crystallizing. Its taste is very acid,
and it dissolves readily in water. It is said to undergo spon-
taneous decomposition; but I have kept it more than two
years in a liquid state without observing any such change.
It bears a strong resemblance to the citric acid, but it does
not crystallize, forms a more soluble salt with lime, and pre-
cipitates mercury, lead and silver from nitric acid, which ci-
tric acid does not.
The compounds which it forms with the salifiable bases,
are called malates.
174 ACIDS. CHAP. II
SECT. XV. Of Suberic Acid.
This acid was obtained by Brugnatelli by digesting com-
mon cork in nitric acid. Its properties were afterwards more
investigated by Bouillon la Grange.
It does not crystallize; but may be obtained in powder or
in pellicles. Its taste is acrid and slightly bitter, it reddens
vegetable blues, attracts moisture when exposed to the air,
but is not very soluble in water. It may be sublimed with-
out decomposition. The other acids dissolve it incomplete-
ly. The salts which it forms are called suberates<(i>.
SECT XVI Of Formic Acid.
This acid exists in the formica rufa, or red ant. It was
noticed in a paper by Mr Ray in 1671, in consequence of
the observatious of Halse and Fisher. But its properties
were first investigated by Margraff. Fourcroy and Vauque-
lin endeavoured to prove that it was a mixture of acetic and
malic acids; but the experiments of Suersen have shown that
this opinion is not correct.
This acid may be obtained by infusing the ants in water,
distilling off the water as long as it comes over without any
burnt smell, saturating the water with potash, evaporating to
dryness, mixing the residue with as much diluted sulphuric
acid as is sufficient to saturate the potash employed, distilling
this mixture to dryness, rectifying the liquid that comes over
by a second distillation with a moderate heat. The liquid
now contains only pure formic acid.
This liquid is colourless like water. It has a peculiar
smell; it reddens vegetable blues, and has an acid taste. Its
specific gravity varies from 1.102 to 1.113, whereas the most
SECT. I. PRUSSIC ACID. 175
concentrated acetic acid is only 1.080. Notwithstanding
this superior weight, it is not capable of neutralizing so
much of the salifiable bases as acetic acid. Lowitz attempt-
ed, in vain, to procure this acid in crystals, though he suc-
ceeded easily with acetic acid. The compounds which it
forms with the different bases are called formates. There is
a striking analogy between them and the acetates.
CHAP. III.
OF COLORIFIC ACIDS.
Under this name I include three substances which possess
such peculiar properties that they ought to be considered se-
parately from the combustible acids. These are prussic acid,
gallic acid and tannin. The two first have always been
considered as acids. The last, though not acid, is so inti-
mately connected with the gallic, that they cannot well be
separated. These substances possess the following charac-
ters.
1. They unite with alkaline bodies, but do not seem ca-
pable of neutralizing them.
2. They act with great energy upon metallic solutions,
usually entering into combination with the oxide, and precipi-
tating it in the state of an insoluble powder.
3. They have a tendency to enter into triple compounds
with a variety of bodies, especially with metallic oxides and
alkalies
SECT. I. 0f Prussic Acid.
This important substance was accidentally discovered by a
chemist of Berlin in 1710. This chemist, Diesbach by
176 COLORIFIC ACIDS. CHAP. III.
name, found out the method of preparing prussian blue.
The nature of this pigment was examined by Brown. But
it was Macquer who first ascertained its nature in a satisfac-
tory manner. In consequence of his experiments, prussian
blue was considered as a compound of oxide of iron with a
peculiar acid. But no one was able to obtain this acid in a
separate state, or to ascertain its properties, till Scheele in
two admirable dissertations published in 1782 and 1783,
pointed out a method of procuring it, and gave a detailed ac-
count of its nature.
He procured the prussic acid in the following manner.
He boiled in a matrass a mixture of 10 parts prussian blue,
5 parts red oxide of mercury, and 30 parts of water, and fil-
tered the solution. The liquid was poured upon 2 1/2 parts of
clean iron filings, and at the same time 1 part of sulphuric
acid was added and the mixture shaken. The iron disap-
peared and a quantity of running mercury was precipitated in
its place. Distil off one-fourth of this liquid by a moderate
heat, what comes over consists of water holding prussic acid
in solution.
Prussic acid, thus obtained, is a colourless liquid like wa-
ter. It has a strong odour resembling that of the flowers of
the peach or of bitter almonds. Its taste is sweetish, acrid
and hot, and it is apt to excite cough. It does not alter the
colour of vegetable blues. When swallowed it proves a very
virulent poison.
It is very volatile, and evidently capable of assuming the
gaseous form, though hitherto it has scarcely been examined
in that state.
It is capable, when dry, of withstanding a red heat without
decomposition, but when water is present, it very readily un-
dergoes change.
It combines with the salifiable bases, and forms a class of
bodies called prussiates. But they have very little perma-
SECT.I. PRUSSIC ACID 177
nency, being decomposed by all other acids, and even by ex-
posure to the atmosphere.
It is capable also of forming triple compounds, in which it
ia combined with two bases at once, one of them an alkali or
earh, the other a metallic oxide. These compounds are
much more permanent, and are therefore usually employed
by chemists. The one in most frequent use is the triple
russiate of potash, a yellow coloured salt crystallizing in
cubes, and composed of prussic acid, potash and oxide of
iron.
Scheele succeeded in forming prussic acid by causing a
current of animoniacal gas to pass through red hot charcoal,
the experiment has been since repeated successfully by
others. Hence it is obvious, that this acid is composed of
the constituents of ammonia and charcoal united together, or
by hydrogen, azote and carbon. This has been further con-
firmed by Berthollet. Oxymuriatic acid has the property of
altering the nature of prussic acid, and renders it capable of
throwinb down iron from solutions green instead of blue.
To the acid thus altered, Berthollet gave the name of oxy-
prussic acid. When heat is applied to it, the whole is con-
verted into carbonate of ammonia.
Prussian blue may be formed by calcining a mixture of
potash and dried blood in a covered crucinle in a heat gradu-
ally rised to redness. The mass is dissolved in water, and
poured into a solution of sulphate of iron. A green coloured
precipitate falls, which becomes prussian blue when digested
in muriatic acid. The triple prussiate of potash was formerly
called phlogisticated alkali. It is still useful in detecting
different metals in solutions by the colour of the precipitate
which it occasions, especially iron, which it throws down of
a deep blue.
M
178 COLORIFIC ACIDS. CHAP. III.
Sect.II. Of Gallic Acid.
This acid forms one of the constituents of the substance
called nutgails, a concretion formed on the oak in conse-
quence of the puncture of insects. Nutgalls come to this
country chiefly from the Levant. They vary a good deal in
their appearance. Scheele first separated gallic acid from
nutgalls. An infusion of nutgalls left to itself for some time
becomes mouldy on the surface, and lets fall small crystals.
These crystals being pickes out, dissolved in water, and ob-
tained again by evaporation, constitute galli acid.
The acid obtained by this procees is never quite pure. If
the infusion of nutgalls be evaporated to dryness, and the
powdered residue be digested in pure alcohol, the alcohol,
when cautiously distilled to l-8th, leaves a residue behind it
nearly colourless, which is soluble in water, and yields by
evaporation gallic acid in needles much lighter coloured and
purer than that obtained by the first descrined process.
Gallic acid is white, usually with a shade of brown or yel-
low. It is crystallized in needles or transparent plates. Its
taste is acid and somewhat astringent, and when heated, it
exhales a peculiar, and rather unpleasant aromatic odour.
It is soluble in 1 1/2 parts of boiling, and in 12 parts of cold
water. When the solution is heated, the acid is decompo-
sed. When long kept, it becomes darker coloured, and the
acid is likcwise altered in its properties.
When heated, it sublimes, but its properties are somewhat
altered. When distilled, it yields, like other vegetable acids,
carbonic acid gas, and heavy inflammable air. Water is
also formed, and a portion of the acid escapes slightly modi-
fied in its nature.
It is not altered by exposure to the air. Neither oxygen
gas, the simple combustibles or incombustibles seem to pro-
SECT. III. TANNIN. 179
duce any effect upon it. The action of the metals is un-
known.
The compounds of this acid, with the salifiable bases, are
called ,gallates. They have scarcely been examined. When gal-
lic acid is dropt into lime, barytes or strontian water, it strikes
a bluish red colour, and occasions a daky precipitate. It
occasions a precipitate likewise when poured into the solu-
tions of yttria, glucina or zirconia in acids. Upon metallic
solutions it acts with considerable energy, changing their co-
lour and occasioning precipitates in many of them. Thus,
with iron it strikes a dark blue, or almost black colour.
When it precipitates metallic oxides, it seems to bring them
nearer to the metallic state, and sometimes reduces them al-
together. Thus gold is precipitated by it in the metallic
state.
SECT. III. Of Tannin.
Nutgalls, besides gallic acid, contain several constituents,
one of the most curious and important of these it tannin,
which is to occupy our attention in this section.
Tannin was first pointed out in vegetables by Deyeux,
though some of its properties had been noticed long before
by Lewis. Seguin first pointed out its great importance in
tanning, and hence the name was given it, by which it is at
present known. Proust endeavoured to obtain it in a sepa-
rate state. Mr Davy added to our knowledge of its proper-
ties. But it is to Mr Hatchet that we are indebted for the
most important set of new facts. He pointed out a method
of making it artifcially from almost all animal and vegetable
substances. As Mr Hatchet's tannins differs in several re-
spects from the tannin of nutgalls and other astringent sub-
stances, it will be proper to divide this section into two parts.
M 2
180 COLORIFIC ACIDS. CHAP. III.
1. Natural Tannin.
No unexecptionable method of obtaining tannin from
nut-galls, in a state of complete purity, has yet been discover-
ed. The best method is this:
Make an infusion of nut-galls in water, evaporate the infu-
sion to dryness, pulverize the residuum and digest the powder
in repeated portions of pure alcohol till that liquid ceases to
dissolve any thing. The residue is tannin tolerably pure.
It may be dissolved in water and precipitated by acetate of
lead. The edulcorated precipitate being mixed with water,
and a current of sulphureted hydrogen passed through it, the
lead combines with sulphur and remains insoluble; while the
tannin, thus set at linerty, dissolves in the water and may be
obtained by evaporating the liquid.
Tannin, thus obtained, is a brittle substance of a brown
colour, with an astringent taste like that of nut-galls. It dis-
solves readily in water, and the solution, according to Tromms-
dorf, is not liable to become mouldy. Pure alcohol does
not dissolve it; but it is soluble in alcohol diluted with a
little water, as for example in alcohol of 0.818 of specific
gravity, which contains 1-lOth of its weight of water.
It seems capable of combining with oxygen, but its pro-
perties are, by that means, completely altered; being, ac-
cording to Proust, a species of extractive.
The action of the simple combustibles on tannin is un-
known. The action of the metals is probably small, but it
combines with most of the metallic oxides, and forms com-
pounds which, for the most part, are insoluble in water.
Thus it strikes a deep blue or black with solutions of iron,
and if the solutions be diluted, the compound of tannin and
the oxide of iron precipitates.
SECT. III. TANNIN. 181
When a solution of glue, or gelatine as chemists term it,
is poured into an aqueous solution, a precipitate immediatdiy
falls. This precipitate consists of tannin and gelatine com-
bined together. It is insoluble in water, and composed, ac-
cording to Davy, of 54 gelatine and 46 tannin. This pro-
perty renders gelatine a very delicate test of tannin, which it
detects when it exists, even in small proportion, in vegetable
liquids.
The alkalies combine with tannin, and prevent it from pre-
cipitating gelatine till they are saturated with an acid.
The earths combine with tannin and form with it com-
pounds nearly insoluble. Hence they precipitate it from the
infusion of nut-galls.
Most of the acids combine with tannin, and form soluble
compounds with it. Arsenic, mriatic and sulphuric acids
precipitate it from water. The sulphuric acid gradually de-
composes it. Nitric acid also decomposes it, and a substance
is formed having the properties of malic acid.
Such are the properties of the tannin of nut-galls, as far as
they have been ascertained. The difficlty of obtaining it in
a state of purity renders some of them ambiguous, and has
induced chemists to employ the infusion of nut-galls in their
experiments rather than tannin.
This infusion is employed in considerable quantity by dy-
ers, and it forms the principle ingredient of common writing
ink. This liquor consists of a solution of sulphate of iron
in the infusion of nut-galls. No other salt of iron tried an-
swers so well as the sulphate. The deepest black is formed
when equal weights of nut-galls and of sulphate of iron are
employed. But it is not permanent unless the nut-galls
amount to about thrice the weight of the sulphate. The
best ink, according to Dr Lewis, who made many experi-
ments on the subject, may he made by means of the follow-
ing formula.
M 3
182 COLORIFIC ACIDS. CHAP. III.
Logwood, 1 ounce.
Nut-galls in powder, 3
Green vitriol, 1
Water, 1 or 2 quarts.
Boil the lobgwood and the nut-galls in water, adding new li-
quid in proportion to the evaporation, then strain through a
cloth and dissolve the green vitriol, adding at the same time
one ounce of gum arabic and a little sugar. Some recom-
mend the addition of a little cloves to prevent the ink from
moulding.
Tannin exists in many other substances besides nut-galls.
The barks of many trees, the substances called catechu and
kino, logwood, brazil wood, fustick and many other vegetable
bodies yield it in abundance. From the experiments of
Proust, it appears that it varies in its qualities in these bo-
dies, or that there are different species of tannin varying from
each other in several respects, especially in the colour which
they strike with iron. Some precipitate that metal black,
some green, and some flesh-red.
2. Artificial Tannin.
The important discovery, that a sucbstance capable or tan-
ning leather like the tannin of nut-galls, may be formed arti-
ficially, was made by Mr Hatchett in the course of a set of
experimems on the slow carbonization of vegetable bodies,
and detailed by him in various papers read to the Royal So-
ciety in 1805.
To form it, we have only to digest diluted nitric acid on
charcoal, till the whole, or nearly the whole, is dissolved,
and evaporate the solution to dryness; a brown coloured mat-
ter remains, which is artificial tannin. 1OO grains of char-
coal, by this process, were converted into 120 grains of arti-
SECT. III. TANNIN. 183
ficial tannin. A part of this increase is moisture, and it is
very difficult to get rid of the whole of the nitric acid, a por-
tion of which adheres to the tannin with great obstinacy.
Tannin, thus prepared, is a substance of a brown colour,
it has considerable lustre, and breaks with a vitreous frac-
ture. Its taste is very bitter and highly astringent. It has
no smell. It dissolves readily in cold water, forming a brown
coloured solution. Alcohol, of the specific gravity 0.800,
also dissolves it.
The solution is precipitated by gelatine very readily. The
precipitate is brown, and composed, according to Hatchett,
of 36 tannin and 64 gelatine.
Sulphuric and muriatic acids form a precipitate when
poured into solutions of artificial tannin. Nitric acid does
not decompose it nor alter its properties. This forms a
marked distinction between natural and artificial tannin.
The alkalies unite with it, and prevent it from precipitating
gelatine till they are saturated. The alkaline earths, and
most of the metallic oxides form insoluble compounds with
it. Hence it precipitates most of these bodies from their
solutions.
When distilled, artificial tannin yields water, a little nitric
acid, and a yellow coloured liquid; on raising the fire, am-
moniacal gas is disengaged with great rapidity, this is follow-
ed by carbonic acid gas, and a gas possessing the properties
of azote. A bulky charcoal remains behind. From these
results it is obvious that this substance consists of oxygen,
azote, hydrogen and carbon. The last constiuent, no doubt,
predominates.
Mr Hatchett has shown that every charcoal, both from
animal and vegetable substances, provided it be in the state
of charcoal, yields artificial tannin when digested with nitric
acid. He has pointed out two other methods of procuring
a substance possessed of similar properties. The first is by
M 4
134 COLORIFIC ACIDS. CHAP. III.
dissolving indigo and the resins or gum resins in nitric acid,
and digesting them for a considerable time in that liquid.
When the solution is evaporated to dryness, a yellow colour-
ed matter remains, which possesses the properties of artificial
tannin. The second method is by dissolving camphor and
the resins in sulphuric acid, digesting till the solution be-
comes black, and then precipitating by pouring it into cold
water. If the black powder which falls be digested in alco-
hol, a brown matter is taken up which possesses many of the
properties of artificial tannin.
SUCH are the properties of the colorific acids. They act
with most energy on metallic solutions, forming precipitates
which vary in their colour accoiding to the metal. It is this
property which renders them of so much importance in a
chemical point of view. The following table exhibits a
view of the colours which these bodies strike with the diffe-
rent metals, as far as is known.
Prussiate of Gallic Infusion of Artificial
Potash. Acid. Nut-galls. Tannin.
Gold Yellowish white Reduced Reduced Reduced
Platinum 0 0 0
Silver White Yellowis, brown Yellowis. brown Yellow
Mercury White Orange yellow Orange yellow Yellow
Palladium Olive
Rhodium 0
Iridium 0 0
Becomes colour- Becomes colour-
less less
Osmium Blue
Sect. III. TANNIN. 185
Prussiate of Gallic Infusion of Artificial
Potash. Acid. Nut-galls. Tannin.
Copper Greenish yellow Brown 0 Becomes olive Olive
Iron Blue Black Black Brown
Nickel Green White Grey
Tin White 0 Brown Blackishgrey
Lead White White White Brown
Zinc White 0 0 0
Bismuth White Orange Orange
Antimony 0 White White Yellow
Tellurium 0 Yellow
Arsenic White 0 0 Yellow?
Cobalt Brown yellow 0 Yellow white
Manganese Yellow white 0
Chromium Green Brown
Molybdenum
Uranium Brown red Chocolate
Tungsten Brown Straw yellow
Titanium Yellowis. brown Blood red
Columbium Olive Orange
Cerium White 0 0
186 COMPOUND combustibleS. CHAP. IV.
CHAP. IV.
OF COMPOUND combustibleS.
The compound combustibles are usually composed of car-
bon and hydrogen, or of carbon, hydrogen and oxygen.
They are very numerous, including almost all the animal and
vegetable bodies. But tbe progress of the investigation of
these bodies, and their importance in chemical investigations,
is not such as to warrant their introduction here. I shall de-
scrine only those compound combustibles which are of im-
portance as instruments of chemical analysis. These may be
comprehended under the five following heads. 1. Alcohol.
2. Ethers. 3. Volatile oils. 4. Fixed oils. 5, Bitumens.
Sect. I. Of Alcohol.
The liquid called alcohol, or spirit of wine, is obtained
when wine, beer, or other fermented liquors are subjected to
distillation. The ancients were unacquainted with it. We
do not know the discoverer of this liquid, but it was known
to the alchymists, and introduced by them into pharmaceuti-
cal preparations.
It is by the distillation of fermented liquors that ardent
spirits are obtained, and they receive various names according
to the nature of the substance employed. Thus brandy is
obtained from wine, rum from the fermented juice of the su-
gar cane, whisky and gin from the fermented infusion of malt
or grain. Now, ardent spirits consist almost entirely of 3
ingredients; namely water, pure spirit or akohol, and a little
oil or resin, to which they owe their flavour and colour.
When these liquids are re-distilled, the first portion that
SECT. I. ALCOHOL. 187
comes over is a fine light transparent liquid, kown in com-
merce by the name of rectified spirits. When as highly rec-
tified as possinle, the specific gravity of the liquid obtained
does not appear to be less than 0.820, and is generally more.
Alcohol, by this process, cannot be deprived of the whole of
the water with which it is combined. The best method of
gettitig rid of the wates is to expose a quantity of the salt
called muriate of lime to a red heat, to put it into a retort
while still warm, and to pour over it a portion of alcohol of
about 0.520, nearly equal to it in weight. The alcohol dis-
solves the salt, and much heat is evolved. This mixture is
to be exposed to heat and the alcohol distilled off. The salt
retains the water, and the alcohol comes over of the specific
gravity 0.791 at 63˚ or 0.796 at 60˚. In this state it is the
strongest alcohol that can be procured. It is, therefore,
called pure<(i>, or absolute alcohol. The alcohol of commerce
is never so strong as this, its specific gravity is seldom under
0.837.
Alcohol, thus procured, is a transparent liquid, colourless
as water, of a pleasant smell and a strong penetrating agree-
able taste. When swallowed it produces intoxication. It
cannot be frozen in the greatest degree of cold to which it
has been exposed, and it has been cooled down in thermo-
meter tubes to -91˚. It is very volatile, evaporating spon-
taneously at the common temperature of the atmosphere.
When heated to 173 1/2˚ it boils, and is converted into an
elastic fluid, possessing the mechanical properties of air, but
more than twice as heavy.
It combines with water in every proportion, and forms spi-
rits of different degrees of strength according to the quantity
of water present The common spirits of commerce are no-
thing else than such combinations of alcohol and water. The
proportion of alcohol present in these liquids is best judged
of by their specific gravity. The specific gtavity of pure
188 COMPOUND COMBUSTBLES. CHAP. IV.
alcohol is 0.796. That of water 1.000. Hence the lighter
a spirit is the stronger is it. Alcohol of O.820 contains
nearly 1-lOth of its weight of water; alcohol of 0.840 con-
tains 17/100 parts of water. What, in this country, is called
proof spirit, is of the specific gravity O920. It was under-
stood to be a mixture of equal bulks of alcohol and water.
This however is not the case. It contains 0.52 of its weight
of water. When spirits are weaker than 0.920, they are
said to be under proof; when stronger, to be above proof.
The spirits retailed in Scotland are, almost always, under
proof, and sometimes indeed very weak.
Neither common air nor oxygen gas act upon alcohol at
the common temperature, but in high temperatures the case
is different. When alcohol is kindled in the open air, it burns
all away without leaving any residuum. The flame is blue,
and if the vapours emitted be collected, they are found to
consist of carbonic acid and water, and the portion of water
formed is greater than the whole of the alcohol consumed.
When the vapour of alcohol is mixed with oxygen gas, it may
be kindled by an electric spark, provided the temperature be
above 70˚, a detonation takes place, the alcohol is consumed
and water and carbonic acid formed. When alcohol is pas-
sed, in the state of vapour, through a red-hot porcelain or
metallic tube, it is decomposed and a variety of new pro-
ducts evolved. These are, 1. a great quantity of inflam-
mable air, which, according to Saussure junior, consists of
oxygen, hydrogen, carbon and azote; 2. A little charcoal;
3. A little oil, partly in crystals, partly fluid; 4. A portion
of water holding, in solution, traces of acetic acid and am-
monia; 5. A little of an acid which resembles the benzoic.
By estimating the proportions of ingredients formed in these
decompositions, chemists have endeavoured to ascertain the
constituents of alcohol. The following is the result obtained
by Saussure junior, who has lately published an elaborate
SECT I. ALCOHOL. 189
set of experiments on the constituents of alcohol. It is
composed of
Oxygen, 37.85
Carbon, 43.65
Hydrogen, 14.94
Azote, 3.52
Ashes, 0.04
_____
100.00
Alcohol has little action on the simple combustibles.
On hydrogen and charcoal it seems to produce no effect.
But it dissolves a little phosphorus and sulphur. If phos-
phureted alcohol be dropt into water, a lambent flame is
observed playing on the surface of the liquid, and the phos-
phorus is disengaged.
Alcohol dissolves the fixed alkalies. It is by means of it,
indeed, that these bodies are obtained in a state of purity.
The earths are scarcely acted on by alcohol. It absorbs a
quantity of nitrous gas, which cannot afterwards be expelled
by heat.
The strong acids decompose alcohol. The rest combine
with it, and form a set of compounds hitherto but little exa-
mined. It dissolves also a considerable number of salts, es-
pecialiy the acetates, muriates and nitrates. The sulphates
are all insoluble in it. The colour of the flame of alcohol
is tinged by various bodies. Thus nitrate of strontian tinges
it purple; boracic acid and the cupreous salts tinge it
green, muriate of lime gives it a light red colour; nitre and
oxymuriate of mercury a yellow colour.
190 combustible COMPOUNDS. CHAP. IV.
Sect. II. Of Ethers.
When alcohol is acted upon by several of the acids, a fra-
grant liquid is formed, to which the name of ether has been
given. These ethers are named from the acid employed in
forming them. As they differ in their properties, it will be
requisite to descrine them separately.
1. Sulphuric Ether.
This liquid was known about the end of the 15th century,
and some of its properties descrined by Boyle; but the
attention of chemists was first drawn to it by a paper pub-
lished in the Philosophical Transactions for 1730, by a Ger-
man who called himself Dr Frobenius.
It may be obtained by distilling a mixture of equal parts
of alcohol and sulphuric acid in a glass retort, to which a
large receiver is attached. The ether condenses in the re-
ceiver. When first prepared it contains some sulphurous
acid, which is removed by putting some powdered chalk into
it, and agitating repeatedly in a close phial, till the sulphurous
acid smell is dissipated. The ether is then distilled a
second time. It still retains a portion of alcohol from which
it may be freed by adding to it dry muriate of lime as long
as it will dissolve that dry salt, and leaving, the solution in a
well corked phial. The muriate of lime dissolved in the al-
cohol gradually subsides, and the pure ether floats on the top.
It may be decanted off.
Ether thus obtained is a limpid and colourless fluid like
water. It has a peculiar and agreable smell, and a hot
pungent taste. Its specific gravity when pure is only 0.632
at 60˚; but the ether of commerce is seldom lower than
0.775, owing to the alcohol which it contains.
It is so volatlile that it cannot be poured from one vessel
4
SECT. II. SULPHURIC ETHER. 191
to another without considerable loss. When exposed to the
open air, it disappears in a very short time. It boils at 98˚,
and in a vacuum at -20˚. When evaporated, it produces a
considerable degree of cold, so that water may be easily
frozen by means of it even in summer. The specific gra-
vity of the vapour of ether, according to Dalton, is 2.25,
that of air being 1.00. When ether as exposed to a cold of
-46˚, it freezes and crystallizes.
Neither oxygen gas nor air produce any effect upon ether
at the common temperature of the atmosphere; but when
kindled in contact with these fluids, it burns with a strong
white flame, giving out a great deal of light and heat. The
products in this case are carbonic acid and water. It con-
sumes during its combustion about 7 times its bulk of oxy-
gen, supposing the ether in the gaseous state. When mixed
with oxygen gas in that proportion, it explodes very loudly
when an electric spark is passed through the mixture. Ya-
rious attempts have been made to estimate the oonstituents
of ether by consuming it with oxygen gas, and ascertaining the
products obtained. The following is the composition of
ether, according to the experiments of Saussure, junior.
Carbon, 58.20
Hydrogen, 22.14
Oxygen, 19.66
_____
100.00
These numbers indicate a much greater proportion of car-
bon and hydrogen, and a much smaller proportion of oxygen
in sulphuric ether than in alcohol.
When ether is passed through a red hot porcelain tube, it
is decomposed and converted into oil, charcoal, water, and a
great proportion of heavy inflammable gas.
Ether combines only in a small proportion with water.
192 combustible COMPOUNDR CHAP. IV.
Ten parts of that liquid dissolve about one part of ether.
But alcohol unites with ether in any proportion.
Ether dissolves a little phosphorus and sulphur, but does
not seem to act upon the other simple combustibles. It has
no action on the metals, but revives those metallic oxides
which readily part with their oxygen, as the oxides of gold
and silver. It dissolves the muriate of gold, and the oxymu-
riate of mercury.
It does not appear to have any action on the alkalies or
earths. It readily dissolves ammonia and nitrous gas.
Sulphuric acid seems capable of converting it into sweet oil
of wine. Oxymuriatic acid sets it on fire spontaneosly. The
action of the other acids has not been ascertained.
It dissolves the fixed and volatile oils, and bitumens, but
does not act upon gums.
From its constituents, as ascertained by Saussure, compared
with those of alcohol, it is obvious that, during the formation
of sulphuric ether, the alcohol is decomposed. This decom-
position, according to Fourcroy and Vauquelin, is owing to
the high temperature to which the alcohol is subjected in
consequence of being prevented from evaporating so easily
by the sulphuric acid with which it is combined.
2. Nitric Ether.
This ether is mentioned by some of the older chemists,
but its properties were almost unknown till it was lately exa-
mined by Thenard.
It may be formed by distilling a mixture of equal parts of
alcohol and nitric acid of the specific gravity 1.283 in a re-
tort, from which passes a tube that goes to the bottom of a
tail glass jar half filled with a saturated solution of common
salt in water. Several of these jars are connected together
SECT. II. ETHER. 193
by tubes, and from the last a tube passes to convey the gase-
ous products to the water trough. The ether condenses on
the surface of the liquid in these jars. It contains at first a
little nitrous and acetic acids, from which it is purified by agi-
tation with chalk is a closed phial till it ceases to redden ve-
getable blues.
Nitric ether thus prepared has a pale yellow colour, and a
very strong etherial odour. Its taste is strong and quite peculiar.
It is rather heavier than alcohol, but mich more volatile than
sulphuric ether. Hence it only moistens bodies for a mo-
ment, and produces a considerable cold by its evaporation.
The heat of the hand is sufficient to make it boil.
It dissolves in 48 parts of water, and communicates to
that liquid an odour like that of apples. It dissolves in alco-
hol in any proportion. It burns with a white flame, and as
brilliantly as sulphuric ether. When kept for some time,
both nitric and acetic acids are evolved in it. The same
acids make their appearance if the ether be heated, or if it
be agitated in water. When brought in contact with a little
of these acids, it instantly absorbs them and acquires the pro-
perty of reddening vegetable blues.
At the temperature of 70˚, it quintuples the bulk of gases.
At that temperature its vapour is capable of supporting a
column of mercury 28.74 inches high. Hence its boiling
point is obviously only a degree or two above 70˚.
From the analysis of Thenard, the constituents of nitric
ether are as follows:
Oxygen, 48.52
Carbon, 28.45
Azote, 14.49
Hydrogen, 8.54
______
100.00
N
194 COMPOUND combustibleS. CHAP. IY
It is probable that it contains nitric acid ready formed, as
one of its constituents, and that this acid is neutralized by the
spirit, and thus prevented from acting on vegetable blues.
It is obvious from the preceding account of its properties
that nitric ether differs entirely from sulphuric ether in its
nature.
3. Muriatic Ether.
After the discovery of sulphuric and nitric ether, various
attempts were made to procure muriatic ether and different
processes were suggested. Sometimes a mixture of alcohol,
and those metallic muriates that contain an excess of acid
were distilled, and sometimes alcohol was saturated with mu-
riatic acid gas and distilled. The nature of muriatic ether
was almost unknown till a set of experiments was made on
it by Gehlen in 1804. Thenard made another in 1807. To
the labours of these two chemists we are indebted for all the
knowledge we possess of this singular fluid.
It may be obtained by distilling in a retort equal bulks of
alcohol and muriatic acid, both as strong as possinle. From
the retort a tube passes into a Woulfe's bottle, partly filled
with water, and from the bottle another tube passes into the
water trough. The whole of the ether formed assumes the
gaseous form if the temperature be as high as 70˚, and may
be collected in jars over water. A mixture of acid and al-
cohol weighing 30 ounces troy, yields more than 1200 cubic
inches of this etherial gas.
This gas is colourless; it has a strong etherial smell, and
a sweetish taste. It produces no change on vegetable blues
or lime water. Its specific gravity is 2.219, that of air being
1.000. At the temperature of 64˚, water absorbs its own
bulk of this gas.
At the temperature of 52˚ it loses its gaseous form, and
SECT. II. ETHER. 195
becomes liquid ether. It may be obtained in that state by
passing it into a jar surrounded with ice. In its liquid state
it is colourless like water, and has the same smell and taste
as when gaseous. At the temperature of 41˚ its specific
gravity is 0.874. It has no effect on vegetable blues. It is
much more volatile than sulphuric or even nitric ether, as-
suming the gaseous form when not hotter than 64˚. It burns
with a green coloured flame, and a great quantity of muria-
tic acid is disengaged during the combustion. Thus it ap-
pears that muriatic acid is one of its constituents. But as
the presence of that acid cannot be detected before combus-
tion by the usual tests, it is obviously neutralized by the
other constituents of the ether. Thenard has endeavoured to
ascertain the constituents of this ether. The following are
the proportions which he found:
Muriatic acid, 29.44
Carbon, 36.6l
Oxygen, 23.3l
Hydrogen, 10.64
______
100.00
During the formation of muriatic ether, no gas whatever
is evolved except the ether, and no new product appears ex-
cept the ether itself. A portion of the muriatic acid disappears,
and exactly the same portion makes its appearance again
when the ether is burnt. These effects render it probable
that muriatic ether is a combination of muriatic acid and al-
cohol. But if any dependence can be put in the above ana-
lysis, and in Saussure's analysis of alcohol, it is obvious that
the alcohol in entering into the composition of muriatic
ether has been altered, as its constituents are not in the same
proportion as in pure alcohol.
N 2
196 COMPOUND combustibleS. CHAP. IV.
4. Acetic Ether.
Acetic ether was discovered in 1759 by the Count de
Lauraguais, who obtained it by distilling a mixture of alco-
hol and acetic acid. The process has been often repeated,
and has been improved since its original discovery. Thenard
has lately examined the properties of this ether.
He obtained it by distilling a mixture of strong acetic acid
and alcohol in a retort, and repeating the distillation 12 times.
No gas was found, nor any symptom of the decomposition
of either of the substances used exhibited. He then saturat-
ed the acid with potash, and by distilling the liquid off ace-
tate of potash, he got the ether in a separate state.
Acetic ether is limpid and colourless. It has an agreeable
odour of ether and acetic acid. It has a peculiar taste bear-
ing no resemblance to that of alcohol. It does not redden
vegetable blues. At the temperature of 44 1/2˚ its specific
gravity is 0.866. It boils at the temperature of 160˚. It
burns with a yellowjsh white flame, and acetic acid is deve-
loped. It undergoes no change by keeping. At the tem-
perature of 62˚ it requires more than 7 times its weight of
water to dissolve it. It seems from the preceding account
to be a kind of combination of acetic acid and alcohol, sub-
stances which it seems have the property of neutralizing each
other.
6. Phosporic Ethter.
From the late experiments of Boullay, it appears that ether
maybe formed also by means of phosphoric acid. This acid,
of the consistence of honey, was put into a retort, and heated
nearly to the temperature of boiling water. Alcohol was then
introduced by means of a funnel passing to the bottom of the
acid, and the mixture distilled. A liquid was obtained,
SECT III. VOLATILE OILS. 197
which, when rectified off muriate of lime, yielded an ether
possessing all the properties of sulphuric ether.
Besides these ethers, several others have been formed by
means of other acids. Indeed, from the late experiments of
Thenard, there is reason to believe that almost all the remain-
ing acids may be made to combine with alcohol, and to form
a liquid which might be denominated an ether, by distilling a
mixture of alcohol, sulphuric acid, and the acid in question.
From the preceding detail, it appears that there are two
kinds of ether essentially distinct: The first consisting of
sulphuric and phosphoric ethers is formed by the decomposi-
tion of alcohol, and contains no acid. All the others con-
tain an acid, and several of them seem to be combinations of
an acid and alcohol. Alcohol appears to have the property of
neutralizing acids, a property not suspected till lately; though
several other vegetable substances seem to possess the same
property.
SECT. III. Volatile Oils.
The term oil is applied to a number of liquids, wich,
when dropt upon paper, sink into it, and make it semitrans-
parent, or give it what is called a greasy stain. Chemists
have divided them into two classes, fixed and volatile.
Volatile oils, called also essential oils, are distinguished by
the following properties:
1. Liquid, often as liquid as water, sometimes viscid.
2. very combustible.
3. An acrid taste and a strong fragrant odour.
4. Volatilized at a temperature not higher than 212˚.
5. Soluble in alcohol, and imperfectly in water.
6. Evaporate without leaving any stain on paper.
Volatile oils are almost all obtanied from vegetables, and
they exist in every part of plants except the colyledons of
N3
198 COMPOUND combustibleS. CHAP. IV.
of the seed, where they have never been found. They are
sometimes obtained from plants by simple expression. But
in general they are procured by mixing the vegetable sub-
stance containing them with water, and distilling. The oil
comes over along with the water, and swims on its surface in
the receiver.
They are very numerous, but a detailed aocount of each
would not be interesting; a general account of their proper-
ties will be sufficient for our purpose.
Most of them are liquid. Some indeed are as liquid as
water, as oil of turpentine. Some are viscid, and some of
the consistence of butter, or even more solid.
Their colours are very various. Some are colourless like
water. Some yellow, brown, blue, green, &c.
Their odours are so various as to defy all description. It
is sufficient to say, that all the fragrance of the vegetable
kingdom resides in volatile oils. Their taste is acrid, and
sometimes they are even corrosive.
Their specific gravity is also various. Oil of turpentine,
the lightest oil known, is 0.792 and oil of sassafras, the hea-
viest, is 1.094.
They evaporate very readily in the open air, diffusing their
fragrant odour around. In close vessels the heat necessary
to distill them over appears to be greater. When cooled
they congeal; but the temperature necessary to produce this
effect varies in different oils. Some become solid at 50˚,
others not till cooled down to -17˚. Several of them yield
crystals of camphor and of benzoic acid when thus treated.
When exposed to the light, they acquire consistency, and
assiume a brown colour. Dr Priestley ascertained, that they
imbine oxygen with avidity. Probably these changes are
connected with that absorption. By long exposure several
of them assume the form of resins.
When heated sufficiently, they take fire, and burn with a
SECT. IV. VOLATILE OILS. 199
strong yellow flame, emitting a great quantity of smoke. The
products of the combustion, besides the soot deposited, are
water and carbonic acid.
When agitated in water, they render it milky, and com-
municate their peculiar odour. They dissolve in alcohol,
ether and fixed oils.
They dissolve a little phosphorus and sulphur, but do not
act on hydrogen or charcoal.
The alkalies and earths act but feebly on the volatile oils.
The conpounds formed have been called saponules. It is
probable that they assume the form of resins before they
combine with these bodies.
Sulphuric acid decomposes them, converting them first in-
to a kind of resin, and at last into charcoal. Concentrated
nitric acid sets them on fire. The diluted acid converts them
into a kind of yellow resin.
They scarcely act upon metals; but they have a tendency
to reduce some of the metallic oxides.
From the products obtained when the volatile oils are
burnt, it has been concluded that they are compounds of car-
bon and hydrogen. But no exact analysis of any of them has
hitherto been made.
Sect. IV. Of Fixed Oils.
The fixed oils, which are of so extensive utility, have been
known from the remotest ages. They may be distinguished
by the following properties.
1. Liquid, or easily become so when exposed to a gentle
heat.
2. An unctuous feel.
3. Very combustible.
4. A mild taste.
5. Boiling point not under 600˚
200 COMPOUND combustibleS. CHAP. IV.
6. Insoluble in water and alcohol.
7. Leave a greasy stain upon paper.
These oils, called also fat or expressed oils, are obtain-
ed partly from animals, partly from vegetables by simple
expression. They occur chiefly in the seeds of bicotyledi-
uous plants, and in the livers of animals. Whale oil, sper-
maceti oil, olive oil, and linseed oil may be mentioned as
examples of fixed oils.
Fixed oil is usually liquid with a certain degree of visco-
sity. It has usually a yellowish or greenish tinge. Its taste
is sweet or nearly insipid. When fresh it has no smell.
Many solid bodies also are obtained from vegetables
which have been hitherto confounded with the fixed oils, as
palm oil, shea butter, &c. From the late experiments of
Dr Bostoch, these substances seem to approach the nature
of wax rather more than that of fixed oils.
the fixed oils are all lighter than water. Their specific
gravity varies from 0.968 to 0.892.
Fixed oil does not begin to evaporate till heated above
212˚. As the heat encreases a pretty copions vapour may
be seen to rise. But the oil does not begin to boil till heat-
ed nearly to 600˚. It may be distilled over, but it is always
altered by the process. Some water and acetic acid seem to
be formed, heavy inflammable air is given out. The oil
deepens in colour and acquires a disagreeable taste and
smell.
Fixed oil when kindled burns with a yellowish white flame
and is decomposed. The products are carbonic acid and
water. When exposed to cold they congeal or crystallize
and at the same time their bulk diminishes very conside-
rably.
When exposed to the action of air, they undergo different
changes according to the nature of the oil. They gradually
absorb oxygen and become solid. Now there are some that
SECT. IV. FIXED OILS. 201
retain their transparency after they have become solid, while
others assume the appearance of tallow or wax. Those that
remain transparent are called drying oils; those that become
opake, are called fat oils.
The drying oils are used as a vehicle of paints and var-
nishes. Linseed, nut, poppy and hempseed oils belong to
this class. They acquire the property of drying oils more
completely after they have been boiled. For some purposes
it is common to set them on fire, and, after they have burnt
for some time, to extinguish them and continue the boilng,
till they have acquired the requisite viscidity. By this pro-
cess, they lose the property of leaving a greasy stain upon
paper, and acquire many properties in common with the re-
sins. In this way, nut-oil and linseed-oil are prepared for
printers ink. The oil, thus altered, still continues insoluble
in water and alcohol, but it readily unites with fixed oil.
The fat oils, when exposed to the air, gradually become
thick, opake and white, and assume an appearance very
much resembling wax or tallow. Olive-oil, oil of sweet-al-
amonds, of rape-seed and of ben, may be mentioned as ex-
amples of this class.
The action of the simple combustibles on the fixed oils is
not very remarkable. Hydrogen has no action. Charcoal
renders them purer when they are filtered through it; but se-
parates from them with such difficulty that it cannot be em-
ployed for that purpose with advantage.
They dissolve a little phosphorus and sulphur when assist-
ed by heat.
They are insoluble in water, alcohol and ether; but they
unite readily with each other, with volatile oils, with bitu-
mens and with resins.
The fixed alkalies combine with them readily, and form
with them the important compound called soap. Potash
forms with them only soft soap, while soda forms hard soap
202 COMPOUND combustibleS. CHAP. IV.
The earths likewise and metallic oxides combine with the
fixed oils, and form a kind of soap insoluble in water.
Sulphuric acid gradually decomposes the fixed oils, black-
ening their colour, and at last evolving charcoal. Nitric acid
acts with still greater energy. When poured suddenly on the
drying oils it sets them on fire. When sufficiently diluted, it
converts them all into substances similar to resins or tallow.
The fixed oils oxidize some of the metals, as copper and
mercury. They combine with various metallic oxides, as
those of arsenic, lead and bismuth, and are capable of form-
ing with several the viscid compomids called plasters.
They are liable, by keeping, to become rancid. They be-
come thick, acquire a brown colour, an acrid taste, and a
disagreeable smell. The oil, thus altered, converts vegetable
blues to red, and of course, contains an acid. This change
is, at present, ascrined to a decomposition of the mucilagi-
nous matter which is dissolved in all oils, or to the action of
that matter in the oil.
When oils are burnt, the only products are carbonic acid
and water. Lavoisier, from a set of experiments made in
this way on olive-oil, deduced its composition as follows.
Carbon, 79
Hydrogen 21
____
100
Many oils occur in the vegetable kingdom which are in-
termediate in their properties between the fixed and volatile
oils. Like the volatile oils they are soluble in alcohol; but,
like the fixed, they cannot be distilled over with that liquid.
Hence they may be obtained by digesting the substance con-
taining them in alcohol, and then separating the alcohol by
evaporation.
Many oils are formed when animal and vegetable bodies
are exposed to a heat above that of boiling water. These
SECT. V. BITUMENS. . fiOS
oils are called empyreumatic. They are usually dark-colour-
ed, have an acrid taste and a disagreeable smell, and possess
most of the properties of the volatile oils.
Sect. V. Of Bitumens.
The term bitumen has been often applied to all the in-
flammable substances which occur in the earth. But it is
better to limit it to those fossil bodies only which have a cer-
tain resemblance to oily and resinous substances. They may
be divided into two classes. The first set possess nearly the
properties of volatile oils; while the second set possess a pe-
culiar character. The first class may be called bituminous
oils. The second bitumens proper.
1. Bituminous Oils.
Only two species of bituminous oils have been hitherto
examined, namely naphtha and petroleum, and maltha or sea-
wax.
1. Naphtha, or peteoleum, is an oil of a brownish yellow
colour. When pure, fluid as water and pretty volatile. Its
specific gravity varies from 0.730 to 0.878. It has a pecu-
liar smell. When heated it may be distilled over without al-
teration. It unites with alcohol, ether, volatile and fixed oils,
and, as far as is known, possesses all the character of vola-
tile oils.
When found in the earth pure, it is distinguished by the
name of naphtha; when less fluid and darker coloured, it is
called petroleum. When petroleum is distilled, naphtha is
obtained from it.
2. Maltha, or sea-wax, is a solid substance found on the
Baikal lake in Sineria, it is white, melts when heated, and
on cooling assumes the consistence of white cerate. It dis-
204 COMPOUND combustibleS. CHAP. IV
solves in alcohol, and seems to possess the character of a so-
lid volatile oil.
2. Proper Bitumem,
The true bituminous substances may be distinguished by
the following properties:
1. They are either solid or of the consistence of tar.
2. Their colour is usually brown or black.
3. They have a peculiar smell, or at least acquire it
when rubbed. This smell is known by the name of the bi-
tuminous odour.
4. They become electric by friction, though not insu-
lated.
5. They melt when heated, and burn with a strong
smell, a bright flame, and much smoke.
6 They are insoluble in water and alcohol, but dissolve
most commonly in ether and in fixed and volatile oils.
7. They do not dissolve in alkaline leys nor form soap.
8. Acids have little action on them; the sulphuric scarce-
ly any: the nitric by long and repeated digestion, dissolves
them and converts them into a yellow coloured substance,
soluble both in water and alcohol.
The pure bitumens at present known are three, namely,
asphaltum, mineral tar, and mineral caoutchouc. United to
resin it forms a curious substance called retinasphaltum.
United to charcoal it forms the various species of pit-coal so
important as articles of fuel.
1. Asphaltum. This substance occurs in great abundance
in the island of Trinidad, on the shores of the dead sea, in
Albania and in other places. Its colour is black with a
shade of brown, red, or grey. It is heavier than water. It
is insoluble in acids, alkalies, water and alcohol; but soluble
in oils, petroleum and sulphuric ether.
SECT. V. BITUMENS. 205
2. Mineral tar. This substance is found in Barbadoes
and other places. It is named from its consistence and ap-
pearance. It seems to be a mixture of petroleum and as-
phaltum. Accordingly, when distilled, abundance of petro-
leuum is obtained, of a brown colour, but very fluid.
3. Mineral caoutchouc is a singular substance, hitherto
found only in Derbyshire. It is soft and elastic, not unlike
common caoutchouc or Indian rubber. Its colour is dark-
brown, with a shade of green or red. It resists the action
of almost all liquid menstrua. Neither alcohol, alkalies nor
nitric acid affect it. Even oils and petroleum are incapable
of dissolving it. When heated, it melts and continues after-
wards of the consistence of tar. In that state it is soluble
in oils. It burns with a bright flame and bituminous smell.
4. Retinasphaltum has hitherto been found only in Derby-
shire accompanying Bovey coal. Mr Hatchett discovered
its nature. It has a pale brown ochre yellow colour, is very
brittle, and breaks with a vitreous fracture. Its specific
gravity is 1.135. When heated it melts, smokes and burns
with a bright flame, and emits a fragrant odour. It is inso-
luble in water, but partially soluble in alcohol, potash and
nitric acid. It is composed of
Resin, 55
Asphaltum, 41
Earths, 3
____
99
5. Pit-coal, one of the most useful of all the mineral pro-
ductions, may be distinguished into three kinds. 1. Those
that still contain vegetable principles, strictly so called, and
thus give evident marks of their origin. Some yield extrac-
tive, others resin, besides charcoal and bitumen, which con-
stitute the greatest part of their contents. The term brown
coal, from their colour, haa been applied to the greater num-
206 COMBINATION OF EAERTHS. CHAP. I.
ber of coals belonging to this set. 2. Black coal. In them
no vegetable principle can be detected, they are composed of
bitumen and charcoal in various proportions, and are usually
mixed with more or less of earthy matter. 3. Glance coal.
Id this set no vegetable principle nor even bitumen is to be
found. The coal ooosists of charcoal pure, or contaminated
with some eart. These coals have a great deal of lustre.
They are heavy, and burn without emitting any flame or
smoke, and only when heated to redness.
DIVISION III.
OF SECONDARY COMPOUNDS.
By the term secondary compound, is meant a combination
of salifiable bases, or primary compounds with each other.
Thus acids combine with alkalies and form salts, earths com-
bine with fixed alkalies and form glass, oils combine with
fixed alkalies and form soap. The secondary compounds, as
far as we are at present acquainted with them, may be ar-
ranged under the five following classes.
1. Combinations of earths with each other and with
metallic oxides.
2. Combinations of earths with alkalies.
3. Combinations of acids with alkalies, earths and me-
tallic oxides.
4. Combinations of sulphureted hydrogen with alkalies,
eaitfas and metallic oxides.
5. Combinations of oils with alkalies, earths and metal-
lic oxides.
These combinations may be distinguished by the following
titles. 1. Combinations of earths; 2. Glass; 3. Salts; 4.
Hydrosulphurets; 5. Soaps.
CHAP. I. COMBINATIONS OF EARTHS 207
CHAP. I.
OF COMBINATIONS OF EARTHS.
This subject is in some measure new and has been but
imperfectly investigated. The following observations are all
that can be offered:
1. The earths require so violent a heat to melt them that
they are capable of resisting the most intense fires that we
can raised. But in several cases the fusion is much facilitated
by mixing various earths together. Thus alumina in a pure
state is infusinle, and so is a mixture of alumina and silica
or pure clay. But when lime is added to this substance it
melts with comparative facility. The oxide of iron also acts
as a solvent when mixed with other earthy bodies, and great-
ly facilitates their fusion.
2. The three alkaline earths, lime, barytes and strontian
resemble each other in their disposition to unite with the
other earths. Like the alkalies they combine with alumina
and silica, but shew no affinity for magnesia nor for each
other.
3. Magnesia has a marked affinity for alumina but for none
of the other earths. When magnesia and alumina are pre-
sent together in solutions, alkalies throw them down in com-
bination.
4. Alumina has an affinity for all the alkaline earths. It
has also an affinity for silver. These two earths are fre-
quently found combined in nature.
5. Silver has an affinity for the alkaline earths, for alumi-
na and for zirconia. Silver enters into fusion with all the
earths hitherto tried except alumina.
8
208 OF GLASS. CHAP. II.
6. Several of the earths are capable of combining like-
wise with metallic oxides. Hitherto only six metals in the
state of oxides have been found native combined with earths.
These are, 1. chromium; 2. nickel; 3. copper; 4. zinc;
5. manganese; 6. iron.
Chromium constitutes the colouring matter of the ruby
in which mineral it is combined with alumina and magnesia.
Nickel has been found only in one mineral the chrysoprase,
to which it gives a green colour. The same remark applies
to copper which has been found only in the smaragdite and
in a very small proportion. Zinc is sometimes found com-
bined with silica in the mineral called calamine, which is
frequently merely an oxide of zinc. The oxide of manga-
nese is a very frequent ingredient in dark coloured stones, as
schorl, ganrnet, &c. It is found also combined with barytes.
But it is the oxide of iron which constitutes by far the
most common metallic constituent of minerals. No less
than seven distinct colours besides various shades have been
observed in minerals containing iron. These arc white, black,
green, blue, red, yellow, brown.
The oxides of iron melt when heated with barytes, lime,
alumina or silica when they exceed the proportion of earth
considerably. They render mixtures of silica and alumina
fusinle at a very low heat.
CHAP. II.
OF GLASS.
Silica when mixed with the fixed alkalies and exposed to
a strong heat enters readily into fusion. It melts also when
heated along with some of the alkaline earths, as lime, pro-
vided a little alumina be present. These mixtures are very
2
CHAP. II OF GLASS. 209
ductile while in fusion and may be readily moulded into any
shape we please. If they be suddenly cooled below the tem-
perature at which they become solid, they retain their trans-
parency, and assume those peculiar properties which belong
to the substance called glass. Glass, then, is a combination
of the fixed alkalies or alkaline earths with silica, either alone
or conjoined with alumina, brought into complete fusion, and
then suddenly congealed. Metallic oxides are sometimes add-
ed; they assist the fusion like the alkalies, and communicate
frequently a peculiar colour to the vitreous mass.
When glass is in fusion, the substances which enter into its
composition may be considered as combined with each other,
so as to form a homogeneous mass similar to water holding
a variety of salts in solution. If it be cooled down very
slowly, the different tendency of the constituents to assume
a solid form at peculiar temperatures will cause them to se-
parate successively in crystals; just as the salts held in solu-
tion in water, assume the form of crystals as the liquid is
slowly evaporated. But if the glass be quickly cooled down
to the point of congelation, the constituents have not time to
separate in succession, and the glass remains the same homo-
geneous compound as while in a state of fusion; just as would
happen to a saline solution if suddenly exposed to a cold
capable of congealing it completely. Hence, it appears,
that the vitreous quality depends entirely upon the fusinility
of the mixture, and the suddenness with which it is cooled
down to the point of congelation. The substance, though
solid, is precisely the same as to its chemical composition, as
if it were still in fusion; the sudden cooling having fixed the
constituents before they had time to assume a new arrange-
ment.
All fusinle mixtures of the earths proper with fixed alka-
lies, alkaline earths or metallic oxides may be made at plea-
sure to assume the form of glass, or the appearance which
o
210 OF GLASS. CHAP. II
characterises stone or porcelain, according to the rate of cool-
ing; and glass may be deprived of its vitreous form merely
by fusing it and cooling it down with sufficient slowness to
enable the constituents to separate in succession. Sir James
Hall fount that glass (consisting of various earthy bodies)
always loses its vitreous state and assumes that of a stone, if
more than a minute or two elapses while it is cooling down
from complete fusion to the point at which it congeals.
There are different kinds of glass in common use for va-
rious purposes. The finest are plate glass and flint glass or
crystal. They are perfectly transparent, nearly colourless,
heavy and brilliant. They are composed of fixed alkali, pure
siliceous sand or calcinated flints, and litharge. Crown glass
is made without lead; it consists of fixed alkali and siliceous
sand, and is much lighter than flint glass. It has a distinct
greenish tinge from the oxide of iron present in the materials
employed in making it. Somtimes too great a proper-
tion of oxide of manganese is added, which gives it a purple
colour. Bottle glass is the coarsest and cheapest kind. It
consists cbiefly of lime fused with silica and a little alumina
and contains so much iron and manganese as to give it a dark
colour and to diminish its transparency very much. It is
much harder, stronger, and more difficultly fusinle than the
fine kinds of glass.
Glass answers well as a chemical vessel, as it is acted on
only by a small number of re-agents. Fluoric acid corrodes
it readily, so do the fixed alkalies whan assisted by heat. Wa-
ter when long boiled in it disengages some alkali from it, and
occasions the separation of silica in the state of a white
powder.
CHAP. III. OF SALTS. 211
CHAP. III.
OF SALTS.
The world salt was of originally confined to muriate of soda
or common salt, a substance, which has been knowa and in
common use from the remotest ages. The term was after-
wards generalized by chemists and applied to all bodies which
sapid, easily melted, soluble in water and not combustible.
At length it was confined to acids, alkalies, and the combina-
tion of these bodies with each other. At present the term
is applied to all the compounds which the acids form with
alkalies, earths amd metallic oxides.
Chemists have agreed to denominate the salts from the
acids which they contain. The alkali, earth or metallic oxide,
combined with that acid is called the base of the salt. Thus
common salt, being a compound of muriatic acid and soda, is
called a muriate and soda is called the base of common salt.
Hence it follows that there are as many genera of salts as
there are acids, and as many individual salts or species as there
are combinations of acids with a base. Silica and some of
the metallic oxides do not appear capable of combining with
acids. But to compensate this there are some acids which
combine with two bases at once, and form what are called
triple salts. Thus tartaric acid combines at once with po-
tash and soda. Some salts combine with an additional dose
of their acid, and others with an additional dose of their
base. The first render vegetables blue, the second usually
render them green. The first kind of salts are distinguished
by prefixing to the usual name the preposition super, the se-
cond by prefixing the preposition sub. Thus sulphate of
potash, denotes the salt in a state of perfect neutralisation
o 2
212 OF SALTS. CHAP. III.
without any excess either of acid or potash; supersulphate
of potash is the same salt with an excess of acid; subsul-
phate of potash is the same salt with an exeess of base.
As the different genera are denominated from the acids, it
is obvious that there must be as many genera as there are
acids. The termination of the names of these genera differs
according to the acid which constitutes them. When the
acid contains a maximum of oxygen, the termination of the
genus is ate, when it does not contain a maximum of oxy-
gen the termination of the genus is ite. Thus the salts which
contain sulphuric acid are called sulphates; those which
contain sulphurous acid are called sulphites. This distinc-
tion is of some consequence, because the salts differ very
much according as the acid is saturated with oxygen or not.
The ites are seldom permanent; when exposed to the air
they usually attract oxygen and are converted into ates.
Every particular species of salt is distinguished by subjoin-
ing to the generic term the name of its base. Thus the
salt composed of sulphuric acid and soda, is called sulphate
of soda. Triple salts are distinguished by subjoining the
names of both the bases connected by hyphens. Thus the
salt composed of tartaric acid, potash and soda is called
tartrate of potash-and-soda. Sometimes instead of this,
one of the bases is prefixed to the name by way of adjective.
Thus soda-muriate of rhodium means the triple salt com-
posed of muriatic acid, soda and the oxide of rhodium.
Sometimes the name of the base prefixed is altered a little;
as, ammonio-sulphate of magnesia (sulphate of magnesia-and-ammonia); ferruginous sulphate of zinc (sulphate of zinc-
and-iron.)
The salts naturally divide themselves into two classes.
Those which contain an alkali or earth for their base, derive
their chief properties from the acids, and are properly enough
characterised by the name of the acids applied to the names
SECT. I. ALKALINE AND EARTHY SALTS. 213
of the genera. But those which have for their base a me-
tallic oxide, derive their characteristic properties from that
base, and ought therefore to be arranged according to it.
We shall therefore divide this chapter into two sections, in
the first we shall treat of the salts with alkalitne and earthy
bases; in the second, of the salts with metallic bases:
Sect. I. Of Alkaline and Earthy Salts.
As the genera of these salts (derived tiom their acids)
are very numerous, it will be advantageous to the learner if
we subdivide them into sets according to their properties:
this is attempted in the following table:-
I. Incombustible Salts.
a. Not altered when heated with charcoal.
1. Muriates.
2. Fluates.
3. Borates.
4. Phosphates*.
b. Decompoied without combustion when heated with charcoal.
1. Sulphates.
2. Carbonates.
c. Set fire to charcoal or yield oxygen gas by heat.
1.Nitrates.
2. Nitrites.
3. Hyper-oxymuriates,
4. Arseniates.
5. Molybdates.
. The phosphates are decomposed when violently heated with charcoal, but
the temperature required is so high that the decomposition cannot be effected
in ordinary fires. Except the phpsphate of ammonia which is decomposed
prety easily.
o 3
214 ALKALINE AND EARTHY SALTS. CHAP. III
6. Tungstates.
7. Chromates.
8. Columbates*.
II. combustible Salts.
a. Acids partially dissipated by heat, leaving salts
in ate.
1. Sulphites.
2. Phosphites.
b. Acids entirely dissipated by heat, leaving the
base and charcoal.
+ Acids partly sublimed unaltered
1. Acetates.
2. Succinates.
3. Moroxylates.
4. Benzoates.
5. Camphorates.
++ Acids wholly decomposed
6. Oxalates.
7. Mellates.
8. Tartrates.
9. Citrates
10. Kinates.
11 Saccolates.
12. Urates.
13. Sebates.
14. Malates.
15. Formiates.
16. Suberates.
+++ Anomalous.
17. Gallates.
. The nitrate and hyperoxymuriate of ammonia are combustible alone.
They are completely dissipated when heated. The genera in italics are
placed from analogy only.
SECT. I. ALKALINE ANO EARTHY SALTS. 215
18. Prussiates.
Let us take a view of these genera in their order.
Genus I. Muriates.
The muriates are all soluble in water, and several of them
likewise in alcohol. When mixed with sulphuric acid they
effervesce, and white acrid fumes with the odour of muriatic
acid are exhaled. They are in number 12.
Sp. 1. Muriate of Potash. This salt crystallizes in ir-
regular cubes. Its taste is salt and rather bitter. It dis-
solves in thrice its weight of cold water. Little altered by
exposure to the air. In a red heat it melts and loses about
three per cent. of its weight. Not sensinly soluble in al-
cohol.
Sp. 2. Muriate of Soda or Common Salt. This salt has
been in common use as a seasoner of food from the ealiest
ages. It exists abundantly in sea water from which it is ob-
tained by evaporation. Mines of it occur also in different
parts of the world. It crystallises in cubes. Its taste is
unversally known, and is what strictly speaking is denomi-
nated salt. It dissolves in rather less than thrice its weight of
water, and is nearly equally soluble in cold and hot water.
It is insoluble in pure alcohol. It deliqueces somewhat
when exposed to moist air. In a red heat it melts and loses
about two per cent. of its weight. In a violent heat it eva-
porates.
Sp. 3. Muriate of Ammonia. This salt was named sal
ammoniac because it was found native near the temple of
Jupiter Ammon in Africa. It is usaally in the form of hard
elastic cakes. But by solution and evaporation it may be
ohtained crystallized in long four-sided pyramids. It deli-
quesces a little when exposed to moist air. It is soluble in
about thrice its weight of water, and in about 75 parts of
o 4
2l6 SALTS. CHAP. III.
alcohol. When heated, it sublimes without decomposition
in a white smoke.
Sp. 4. Muriate of Magnesia. Tis salt exists in sea-wa-
ter. It is not easily crystallized, but when its solution, pro-
perly concentrated, is exposed to a sudden cold, it may be
obtained in small needles. Its taste is very bitter, hot and
biting. It dissolves in about half its weight of water; and
in about twice its weight of pure alcohol. When exposed
to the air it speedily deliquesces. A strong heat decom-
poses it. When dried in a high temperature, it is very
caustic.
Sp. 5. Muriate of Ammonia-and-Magnesia. This salt is
obtained when the solutions of the two last salts are mixed
together. Its crystals are small and irregular, its taste bit-
ter and ammoniacal. It dissolves in about six times its
weight of cold water.
Sp. 6. Muriate of Lime. This salt is not easily procured
in crystals on account of its great solubily in water. Its
crystals are six-sided striated prisms, terminated by very sharp
pyramids. Its taste is very bitter and pungent. At the
temperatuce of 60˚, water dissolves four times its weight of
this salt, and it dissolves any quantity whatever, at the tem-
perature gf 100˚. Alcohol seems capable of dissolving
more than its own weight of this salt. This salt deliques-
ces very speedily when exposed to the atmosphere. When
heated it melts and loses its water of crystallization. In a
violent heat it loses also a portion of its acid, and then has
the property of shining in the dark. In that state it is called
the phosphorus of Homberg.
Sp. 7. Muriate of Barytes. This salt crystallises in four-
sided prisms, whose bases are squares; but it is obtained
more commonly in tables. It has a pungent and disagree-
able taste, and like all other preparations of barytes is poi-
sonous. It requires rather more than twice its weiglht of
SECT I. MURIATES. 217
water to dissolve it. It is not sensinly soluble in pure alco-
hol. It is not altered by exposure to the air. In a red heat
it melts but is not decomposed.
Sp. 8. Muriate of Strontian. This salt crystallizes in
long slender hexagonal prisms, usually so minute as to have
the appearance of needles. It dissolves in rather less than its
weight of cold water, while boiling water dissolves any
quantity of it whatever. It dissolves in about 24 parts of
pure alcohol. The crystals not much altered by expo-
sure to the air. When heated they undergo the watery fu-
sion, and in a red heat are converted to a white powder.
Sp. 9. Muriate of Alumina. This salt is always in the
state of a supermuriate. It hardly crystallizes, being always
either gelatinous or in the state of a white mass. Water dis-
solves about four times its weight of it. It speedily deli-
quesces in the air. Alcohol dissolves at least half its weight
of this salt. When heated it melts and loses its acid.
Sp. 10. Muriate of Yttria. This salt does not crystal-
lize, but runs to a jelly. It melts in a gentle heat, and attracts
moisture very rapidly from the atmosphere.
Sp. 11. Muriate of Glucina. This salt has a sweet taste
and readily crystallizes.
Sp. 12. Muriate of Zirconia. This salt is transparent and
crstallises in needles which effloresce in the air. It is very
soluble in water and in alcohol. Heat decomposes it with
facility.
The following table exhibits the composition of these salts
according to the most accurate experiments hitherto made
218 SALTS. CHAP. III.
Muriates of Constituents.
Acid. Base. Water.
Ammonia 100 58.4 75.4
Magnesia 100 89.8 99.3
Soda 100 114 14
Lime 100 118.3
Potash 100 185.7
Strontian 100 216.2 233
Barytes 100 314.5 87
Alumina 100 100 135
The three last species have not hitherto been analysed.
Genus II. Fluates.
Most of these salts are but sparingly soluble in water, and
hitherto have been but superficialy examined. When
sulphuric acid is poured on them, thej exhale acrid fumes,
which readily act upon glass and corrode it.
Sp. 1. Fluate of Potash. This salt is hardly known. It
is said to crystallize when pure. It has but little taste, dis-
solves readily in water, and melts when heated. It combines
readily with silica, and forms a white powder, loose like
chalk, containing an excess of acid.
Sp. 2. Fluate of Soda. This salt crystallizes in cubes.
Its taste is bitter and astringent, it is sparingly soluble in
water. When heated it decrepitates and melts into a trans-
parent globule.
Sp. 3. Fluate of Ammonia. This salt crystallizes and
may be sublimed without decomposition.
SECT. I. FLUATES. 219
Sp. 4. Fluate of Alumina. This salt does not crystal-
ize, but is easily obtained in the state of a jelly. Its taste is
astringent, and it always contains an excess of acid.
The remaining fluates are insoluble in water.
Sp. 5. Fluate of Magnesia. When this salt contains an
excess of acid, it may be obtaitned in dodecahedrons. Heat
does not decompose this salt.
Sp. 6. Fluate of Lime. This salt occurs native in abun-
dance, and is the only fluate that has been accurately exami-
ned. It is usually crystallized in cubes, sometimes in octahe-
drons. It has no taste, nor is it altered by exposure to the
air. Its specific gravity is 3.15. When heated, it decrepi-
tates and phosphoresces strongly. When strongly heated it
melts into a tansparent glass. According to my Analysis, it
il is composed of 32 2/3 acid and 67 1/3 lime.
Sp. 7. Fluale of Barites. This is a white tasteless
powder not hitherto examined.
Sp. 8. Fluate of Alumina-and-Soda. This salt has been
found in Greenland, and is called cryolite by mneraiogists.
Its colour is greyish white. It has some transparency. It
breaks into cubic fragments. Its specfic gravity is 2.950.
It is brittle and softer than fluate of lime. It is composed of
Acid an water, 40
Soda, 36,
Alumina, 24
____
100
Sp. 9. Fluate of Silica. Fluoric acid, as usually obtain-
ed, contains, in solution, a quantity of silica. When kept in
vessels not completely shut, it deposites small rhomboidal
crystals of silica.
220 SALTS. CHAP. III.
Genus III. Borates.
This genus has been very imperfectly examined. All the
fluates, before the blowpipe, melt into a glass. When boiled
in diluted sulphuric acid, they yield small scales of boracic
acid.
Sp. 1. Borate of Potash. This salt crystallizes in four-
sided prisms. It has been very little examined.
Sp. 2. Borate of Soda. This salt may be formed by sa-
turating borax with boracic acid. It is soluble in 2 1/2 times
its weight of hot water.
Sp. 3. Borax or Sub-borate of Soda. This salt is the
only one of the borates which has been accurately examined.
It is brought from the East Indies, and has been in common
use in Europe for ages. It seems even to have been known
to the ancients. It crystallizes in hexangular prisms, but is
usually in roundish semi-transparent lumps. Colour white.
Specific gravity 1.740. Taste styptic and alkaline. Con-
verts vegetable blues to green. Soluble in about 20 times
its weight of cold water, but more soluble in hot water.
When exposed to the air it effloresces slowly and slightly.
When heated it melts, loses its water of crystallization, and
is converted into a light porous substance called calcined bo-
rax. In a strong heat it melts into a transparent glass, still
soluble in water. It is said to be composed of
Acid, 39
Base, 17
Water, 44
____
100.
Sp. 4. Borate of Ammonia. This salt forms permanent
crystals, which resemble those of borax. Heat decomposes
it.
SECT. I. PHOSPHATES. 221
Sp. 5. Borate of Strontian. This salt is a white powder
and contains an excess of base.
The remaining borates are insoluble in water.
Sp. 6. Borate of Magnesia. This salt may be obtained
in small irregular crystals. It is soluble in acetic acid. Al-
cohol is said to decompose it. When heated it melts, and is
not decomposed.
Sp. 7. Borate of Lime. This is a white powder hardly
soluble in water, and tasteless.
Sp. 8. Borate of Barytes. An insoluble white powder,
hardly examined.
Sp. 9. Borate of Alumina. Scarcely soluble, and not
crystallizable.
Genus IV. Phosphates.
The salts belonging to this genus, when heated before the
blowpipe, melt into a globule of glass. They dissolve in ni-
tric acid without effervescence, and are precipitated from
that solution by lime-water or ammonia. They amount to
twelve.
Sp. 1. Phosphate of Potash. Of this salt there are two
varieties, the superphosphate long known, and phosphate,
not accurately discriminated till lately.
Variety 1. Superphosphate. This salt is formed by dis-
solving carbonate of potash in phosphoric acid till all effer-
vescence cease, and then evaporating the solution. It crystal-
lizes with difficulty in striated prisms. It is very soluble in
water, and deliquesces when exposed to the air. When heat-
ed it undergoes the watery fusion, loses its water of crystal-
lization, and is reduced to dryness. In a high temperature
it melts into a transparent glass.
Variety 2. Phosphate. This salt may be formed by satu-
rating the superphosphate with potash, and exposing the mix-
222 SALTS. CHAP. III.
ture to heat in platinum crucinle. It is usually in the state
of a white powder, tasteless and insoluble in cold water,
though it dissolves in hot water. It melts easily into a tran-
sparent bead, which becomes opake on cooling. It dissolves
in the nitric, muriatic and phosphoric acids, and is not preci-
pitated by alkalies; but when the solutions are concentrated,
a precipitate falls.
Sp. 2. Phosphate of Soda. This salt is usually prepared
by decomposing the superphosphate of lime from burnt
bones with carbonate of Soda. As sold by apothecaries, it
is much contaminated by sulphate of soda. It crystallizes in
rhomboidal prisms. Its taste is similar to that of common
salt. It dissolves in four times its weight of cold water. In
the air it effloresces. When heated it undergoes the watery
fusion; and, at a red heat, melts into a white enamel.
Sp. 3. Phosphate of Ammonia. This salt exists in urine.
It is also prepared artificially in the same way as the last spe-
cies. It crystallizes in four-sided prisms. Its taste is cool-
ing, salt and ammoniacal. It is soluble in four parts of cold
water. When beated it undergoes the watery fusion. In a
strong heat the ammonia is disengaged, and the posphoric
acid melts into a glass.
Sp. 4. Phosphate of Magnesia. This salt may be ob-
tained by mixing together concentrated solutions of phosphate
of soda and sulphate of magnesia; in a few hours crystals of
phosphate of magnesia are deposited. It crystallizes in six-
sided prisms with unequal sides. It has little taste, dissolves
in 15 parts of cold water, and falls to powder wben exposed
to the air. When heated strongly it melts into a transparent
glass.
Sp. 5. Phosphate of Soda-and-Ammonia. This salt,
known by the name of microcosmic salt, may be obtained
from urine. It possesses nearly the properties of a mixture
of the two preceding species.
SECT. I. PHOSPHATES. 223
Sp. 6. Phosphate of Ammonia-and-Magnesia. This
triple salt exists also is urine. Its crystals are four sided
transparent prisms, terminated by four sided pyramids. It
is tasteless; scarce soluble in water; and not liable to be
altered by exposure to the air. In a strong heat, it loses its
ammonia, and melts inta a transpareut glass.
The remaining, phosphates are insoluble in water.
Sp. 7. Phosphate of Lime. This salt constitutes the
basis of bones. It may be obtained by calcining bones,
dissolving them in muriatic acid, and precipitating by am-
monia. It is then in the state of a white powder; but it is
found native, crystallized in six-sided prisms, and is distin-
guished among mineralogists by the name of apatite. It
has no taste, is insoluble in water, and not altered by expo-
sure to the air. A red heat does not alter it; but in a very
violent temperature, it is converted into a kind of enamel.
It dissolves in the strong acids without effervescence, and
may be again precipitated by ammonia. The strong mine-
ral acids decompose it partially, and convert it into super-
phosphate of lime, which is an acid liquid which crystal-
lizes in thin brilliant plates.
Sp. 8. Phosphate of Bartytes. This is a white tasteless
powder, which, in a violent temperature, melts into a grey
enamel.
Sp. 9. Phosphate of Strontian. This is a white powder,
insoluble in water, but soluble in phosphoric acid. Befopre
the blowpipe, it fuses into a white enamel.
Sp. 10. Phosphate of Alumina. A white powder, but
tasteless and insoluble in water.
Sp. 11. Phosphate of Yttria. A gelatinous mass, inso-
luble in water.
Sp. 12. Phosphate of Glucina. A white tasteless inso-
luble powder.
224 SALTS. CHAP. III
The following table exhibits the constituents of the phos-
phtes, according to the experiments of Richter.
Phosphate of Acid. Base.
Alumina 100 53.6
Magnesia 100 62.8
Ammonia 100 68:6
Lime 100 81
Soda 100 87.7
Strontian 100 135.7
Potash 100 164
Barytes 100 222
Genus V. Phosphites.
The salts belonging to this genus have been but little ex-
amined by Chemists. When heated, they emit a phospho-
rescent flame. When strongly heated, they yield a little
phosphorus, and are converted into phosphates.
Sp. 1. Phosphite of Potash. This salt crystallizes in
four-sided prisms. Its taste is sharp and saline. It is solu-
ble in 3 parts of cold water. It is not altered by exposure
to the air.
Sp. 2. Phosphite of Soda. It crystallizes in rbomboids.
Its taste is cooling and agreeable. It dissolves in two parts
of cold water. It effloresces in the air. Before the blow-
pipe, it gives out a fine yellow flame, and melts into a glo-
bule which becomes opake in cooling.
Sp. 3. Phosphite of Ammonia. It crystallizes in four-
sided prisms. Its taste is sharp and saline. It dissolves in
two parts of cold water. It deliquesces a little. When
heated, it loses its base; emits phosphureted hydrogen gas,
and phosphoric acid remains.
Sp. 4. Phosphite of Ammonia-and-Magnesia. This
salt is sparingly soluble in water, and crystallizes.
Sp. 6. Phosphite of Alumina. This salt does not cry-
stallize, but forms a glutinous mass which dries gradually,
SECT, I. CARBONATES. 225
and does not afterwards attract moisture. It is very soluble
in water. Its taste is astringent.
The remaining phosphites are insoluble in water.
Sp. 6. Phosphite of Magnesia. This salt is usually in
the state of a white powder, or of small four-sided prisms.
It effloresces is the air. It is said to be soluble nn 400
parts of cold water.
Sp. 7. Posphite of Lime. This is a white tasteless
powder, insoluble in water, but soluble in phosphorous
acid, forming a snperphosphite, which may be obtained in
prismatic crystals by evaporation.
Sp. 8. Phosphite of Barytes. This is a white powder,
hardly soluble in water, unless there be an excess of acid.
Genus VI. Carbonates.
This is one of the most important of the saline genera.
When muriatic or nitric acid is poured on them, they effer-
vesce, and give out carbonic acid. When fully saturated
they do not affect vegetable blues, but the alkaline subcar-
bonates convert vegetable blues to green.
Sp. 1. Carbonate of Potash. Of this salt there are two
varieties, the carbonate and subcarbonate.
Variety 1. Carbonate. This salt may be formed by caus-
ing a current of carbonic acid to pass through a solution of
potash, till the salt crystallizes. It crystallizes in rhomboi-
dal prisms, with dihedral summits. It has a very slight al-
caline taste, and still gives a green colour to vegetable
blues. It is soluble in four parts of cold water. Alcohol
scarcely dissolves it. Exposure to air does not alter it.
Variety 2. Subcarbonate. This salt is obtained by ex-
posing the preceding to a strong red heat. It contains ex-
actly one half of the acid contained in the carbonate. It
is much more soluble in water; its taste is very alkaline and
P
226 SALTS. CHAP. III.
caustic; and when exposed to the air, it soon deliquesces
and runs into a liquid. The potash of commerce is always
in the state of a subcarbonate.
Sp. 2. Carbonate of Soda. Of this salt, like the pre-
ceding, there are two varieties.
Variety 1. Carbonate. This salt occurs native in Africa,
and may be formed by passing a current of carbonic acid
through a solution of soda, till it ceases to absorb any more.
It runs into a hard solid mass, which is not altered by expo-
sure to the air.
Variety 2. Subcarbonate. What is called carbonate of
soda in commerce, is nothing else than this salt. Its cry-
stals are octahedrons, having their apexes truncated, or.
more commonly flat rhomboidal prisms. It dissolves in two
parts of cold water. When exposed to the air, it efflores-
ces and falls to powder. When heated, it undergoes the
watery fusion, and melts in a red beat into a transparent li-
quid.
Sp. 3. Carbonate of Ammonia. Of this salt, also, there
are at least two varieties.
Variety 1. Carbonate. This salt may be obtained by
passing a current of carbonic acid through the subcarbonate
dissolved in water. It crystallizes in six-sided prisms; has
no smell, and much less taste than the subcarbonate. When
heated it sublimes, and is decomposed.
Variety 2. Subcarbonate. This salt crystallizes, but the
crystals are small and irregular. Its smell and taste are
similar to those of ammonia, though weaker. It is lighter
than water. It is soluble in less than twice its weight of
water. From the experiments of Davy, it would appear
that there are different varieties of this salt, containing vari-
ous proportions of acid, according to the temperatures in
which it has been prepared.
SECT. I. CARB0NATES. 227
Sp. 3. Carbonate of Ammonia-and-Magnesia. This
salt may be formed by mixing together aqueous solutions of
its two constituents. Its properties have not been examined.
The remaning carbonates are insoluble in water.
Sp. 5. Carbonate of Magnesia. Of this salt, there are
likewise two varieties.
Variety 1. Subcarbonate. This is a light white powder,
constituting the magnesia of commerce.
Variety 2. Carbonate. It may be formed by diffusing
the preceding variety in water, and passing a current of car-
bonic acid through the liquid. It crystallizes in six-sided
transparent prisms. It has little taste. It dissolves, when
in crystals, in 48 parts of cold water. It effloresces in the
air, and falls to powder.
Sp. 6. Carbonate of Lime. This salt, under the names
of marble, chalk, limestone, calcareuus spar, &c. exists in
great abundance in nature. It crystallizes in rhomboidal
prisms, with angles of 101 1/2˚ and 78,1/2˚; and no less than
616 different varieties of form have been observed and de-
scrined by mineralogists. It is tasteless, insoluble in water,
but soluble in a small proportion by means of carbonic acid.
When heated strongly, its loses its acid, and the escape of
the acid is greatly facilitated by the presence of vapour.
When suddenly heated, it melts without losing its acid, and
assumes a form bearing some resemblance to granular lime-
stone.
Sp. 7. Carbonate of Barytes. This salt is found native,
and distinguished by mineralogists by the name of Witherite.
It crystallizes in double six-sided and four-sided pyramids.
It is tasteless, insoluble in water, but poisonous. It is not
altered by exposure to the air. When made up into a ball
with charcoal, and violently heated, it loses its acid.
Sp. 8. Carbonate of Strontian. This salt also occurs
native, usually in semi-transparent striated masses, with a
P2
228 SALTS. CHAP. III.
greenish tinge. It is tastless, insoluble in water, and not
altered by exposure to the air. When violently heated it
loses its acid.
Sp. 9. Carbonate of Alumina. Water, containing car-
bonic acid gas, dissolves a little alumina; but when the alu-
mina is precipitated and dried, it appears, from the experi-
mets of Saussure, that it loses its acid. Carbonate of alu-
mina, then, cannot exist in a dry state.
Sp. 10. Carbonate of Yttria. A white, tasteless inso-
luble powder.
Sp. 11. Carbonate of Glucina. A white, soft, tasteless
powder, with greasy feel.
Sp. 12. Carbonate of Zirconia. A white tasteless pow-
der.
The following table exhibits a view of the composition
of these salts as far as it has been ascertained.
Carbonate of Acid. Base. Water.
Ammonia 100 33.9 44.6
Magnesia 100 50 50
Potash 100 95.3 37
Soda 100 97.4 59
Lime 100 122
Strontian 100 231
Yttria 100 305.5 150
Barytes 100 354.5
The subcarbonates appear to contain just one half of the
acid which exists in the carbonates.
Genus VII. Sulphates.
This genus of salts has been long known, and very care-
fully examined. Most of the salts in it crystallize. Their
taste is usually bitter. They are insoluble in alcohol, and
precipitated from water by alcohol. When heated to red-
ness, along with charcoal, they are converted into sulphu-
rets. all their solutions yield a white precipitate, insoluble
SECT. I. SULPHATES. 229
in cold sulphuric acid, when mixed muriatic of ba-
rytes.
Sp. 1. Sulphate of Potash. Of this salt there are two
varieties.
Variety 1. Sulphate. This salt is usually to be found in
considerable quantity in the potash of commerce. The cry-
stals are small, irregular, hard; and firm: usually six-sided
prisms. The taste is a disagreeable bitter. It dissolves in
about 16 times its weight of cold water. It is not altered
by exposure to the air. In a red heat if melts, and loses
about 1 1/2 per cent. of its weight.
Variety 2. Superphosphate. This salt may be obtained by
dissolving the preceding in sulphuric acid, and evaporating.
Its crystals are long, slender needles, or six-sided prisms.
Its taste is acid, and it reddens vegetable blue. When
heated it melts, and assumes the appearance of oil. A
strong red heat is necessary to drive off the excess of acid,
and convert it into sulphate.
Sp. 2. Sulphate of Soda. This salt is often called Glau-
ber's salt, from the name of the discoverer of it. There
are two varieties of it, like the preceding.
Variety 1. Sulphate. This salt crystallizes in six-sided
transparent prisms, temimated by dihedral summits. The
sides of the prisms are usually channeled. Its taste, at first,
has some resemblance to that of common salt, but it soon
becomes disagreeably bitter. It dissolves in less than thrice
its weight of cold water, and in less than its weight of boil-
ing water. When exposed to the air, it loses its water, ef-
floresces, and falls to powder. The loss of weight is about
0.56 parts. When heated, it undergoes the watery fusion.
In a red heat it melts, and, according to Kirwan, loses
part of its acid.
Variety 2. Supersulphate. This salt may be obtained by
dissolving the preceding variety in sulphuric acid, and eva-
P3
230 SALTS. CHAP. III.
porating the solution. It crystallizes in large transparent
rhombs, which effloresce in the air, and easily part with
their excess of acid.
Sp. 3. Sulphate of Ammonia. This salt crystallizes in
small six-sided prisms. It has a sharp bitter taste; is solu-
ble in twice its weight of cold water, and in its weight of
boiling water. When exposed to the air, it slowly attracts
moisture. When heated it decrepitates, then melts and
sublimes with some loss of its alkali. When heated nearly
to redness, the greatest part of it is decomposed.
Sp. 4. Sulphate of Magnesia. This salt was long known
by the name of Epsom salt, because it exists in the spring at
Epsom near London. It exists also in sea water. It crys-
tallizes in regular four sided prisms, surmounted by four sided
pyramids or dehedral summits. The crystals refract doubly.
Its taste is intensely bitter. It dissolves in its own weight of
cold water. In the air it effloresces. When heated it un-
dergoes the watery fusion, and before the blow-pipe melts
with difficulty into an opake vitreous globule.
Sp. 5. Sulphate of Potash-and-Ammonia. This salt crys-
tallizes in brilliant plates. Its taste is bitter, and it is not al-
tered by exposure to the air.
Sp. 6. Sulphate of Potash-and-Magnesia. This salt crys-
tallizes in rhomboidal prisms, and is not altered by exposure
to the air.
Sulphate of soda is also capable of forming triply salts
with ammonia and magnesia.
Sp. 7. Sulphate of Magnesia-and-Ammonia. This salt
crystallizes in octahedrons. Its taste is acrid and bitter. It is
decomposed by heat, and is less soluble in water than either
of its constituents.
Sp. 8. Sulphate of Alumina. This salt crystallizes in thin
plates soft and pliant, and of a pearly lustre. Its taste is
SECT. I. SULPHATES. 231
astingent. It is very soluble in water, and crystalizes with
difficulty.
Sp. 9. Alum. This is a triple salt, of which there are
four varieties, namely, 1. Sulphate of alumina-nnd-potash;
2. Sulphate of alumina-and-ammonia; 3. Supersulphate of
of ammonia-and-potash; 4. Supersulphate of alunina-and-
ammonia. The two last (especially the 3rd) constitute the
alum of commerce; the two first have been called alum
saturated with its earth, or aluminated alum.
The composition of common alum was first ascertained by
Vauquelin. It crystallizes in regular octahedrons. It is
white, and semitransparent. Its taste is sweetish and astrin-
gent, and it reddens vegetable blues. It dissolves in about
16 parts of cold water. In a gentle heat it undergoes the
watery fusion, and by continuing the heat it loses about 44
per cent. of water, and is called calcined or burnt alum. In
a violent heat a portion of the acid is converted into sulphu-
rous acid, and oxygen gas. This salt, according to the ana-
lysis of Vanquelin, is usually composed of
Sulphuric acid 30.52
Alumina 10.50
Potash 10.40
Water 48.58
______
lOO.OO
Alum sometimes contains a little sulphate of iron mixed
with it, which injures its qualities as a mordant.
The sulphates, or two first varieties, may be formed by
boiling alumina in a solution of alum. They are tasteless
powders, insoluble in water, and not altered by exposure to
the air.
Sp. 10. Sulphate of Yttria. This salt crystallizes in flat
six-sided prisms. It is not altered by exposure to the air.
Its taste is astringent and sweet. It has an amethyst red co-
232 SALTS. CHAP. III.
lour, and dissolves in about 30 parts of cold water. At a red
heat it is perfectly decomposed.
Sp. 10. Sulphate of Glucina. This salt is colourless. It
crystallizes in needles, its taste is very sweet, and somewhat
adstringent It is very soluble in water, and the solution does
not readily crystallize. When heated it undergoes the watery
fusion, and in a red heat is completely decomposed.
Sp 12. Sulphate of Zirconia. This salt is usually in the
form of a white powder; though it may be obtained also
crystallized in needles. It is tasteless, and insoluble in wa-
ter; not altered by exposure to the air, and easily decom-
posed by heat.
Sp. 13. Sulphate of Lime. This salt occurs native, and
is distinguished by names of gypsum and selenite. It is
found crystalllized in octahedrons, six-sided prisms, and in
lenses. It has litlle or no taste. It dissolves is about 460
parts of cold water. It is not altered by exposure to the air.
It dissolves in sulphuric acid. When heated it loses it wa-
ter of crystallization. When mixed with a little lime, it is
much used under the name of Plaster of Paris for forming
casts, moulds, &c.
Sp. 14. Sulphate of Barytes. This salt is found na-
tive, and distinguished by the names of ponderous spar,
heavy spar, baroselenite. It occurs crystallized in tables
with bevilled edges, in four-sided prisms, &c. It is white,
tasteless, insoluble in water, but soluble in hot sulphuric
acid. It melts when strongly heated into a white opake glo
bule. When made into a cake with flour, and heated to red-
ness, it is phosphorescent.
Sp. 15. Sulphate of Strontian. This salt, like the pre-
ceding, occurs native in considerable quantity. It is crystal-
lized in rhomboidal prisms. It is white, tasteleas, insoluble in
water, but soluble in hot sulphuric acid. In most of its pro-
perties it resembles the preceding salt, but its specific gra-
2
SECT. I. SULPHITES. 233
vity in much less. The specific gravity of sulphate of bary-
tes is at least 4.3, while that of sulphate of strontian does not
exceed 3.66.
The following table exhibits the compostion of the diffe-
rent sulphates as far as it has beea ascertanied.
Sulphate of Acid. Basr. Water.
Ammonia 100 26.05 57
Magnesia 100 57.92 182.1
Lime 100 76.70 55.8
Soda 100 78.32 246.0
Potash 100 130 20
Strontian 100 138
Barytes 100 203
Genus VIII. Sulphites.
The sulphites may be formed by passing a current of sul-
phurous acid gas through water, holding the different bases
in solution or suspension. They have a disagreeable sulphure-
ous taste. When heated they emit sulphurous acid and wa-
ter, and at last sulphur, and are converted into sulphates.
When they are exposed the air in a state of solution, they
are also gradually converted into sulphates.
Sp. 1. Sulphite of Potash. This salt crystallizes in rhom-
bodial plates, white and semitransparent. Its taste is pene-
trating and sulphureous. It dissolves in its own weight of
cold water. In the air it loses about 2 per cent. of its
weight, and is slowly altered; at least in six months it
still contained nearly the usual proportion of sulphurous acid.
Nitric acid speedily converts it into sulphate of potash.
234 SALTS. CHAP. III.
Sp. 2. Sulphite of Soda. This salt crystallizes in flat four
sided prisms. It is white and transparent. Its taste is cool
and sulphureous. It dissolves in four times its weight of cool
water. In the air it effloresces, and is converted into sul-
phate. When heated it undergoes the watery fusion.
Sp. 3. Sulphite of Ammonia. It crystallizes in six-sided
prisms. Its taste is cool and penetrating, and it leaves a sul-
phureous impression in the mouth. It dissolves in its own
weight of cold water. When exposed to the air it attracts
moisture, and is soon converted into sulphate. When heated,
a little ammonia is disengaged, and the salt then sublimes in
the state of supersulphite of ammonia.
Sp. 4. Sulphite of Magnesia. It crystallizes in the form of
depressed tetrahedrons. It is white and transparent. Its taste
is mild, but it leaves a sulphureous impression in the mouth.
When exposed to the air, it becomes opake, and is very slow-
ly converted into sulphite. It dissolves in 20 parts of cold
water. When heated it becomes ductile like gum, and loses
45 per cent. of its weight.
Sp. 5. Sulphite of Ammonia-and-Magnesia. This salt
crystallizes, and is less soluble in water than either of its con-
stituents.
Sp. 6. Sulphite of Lime. This salt is in the state of a
white powder, or if an excess of acid be added, it crystal-
lizes in six-sided prisms, terminated by six-sided pyramids. It
has little taste, dissolves in about 800 parts of water, and in
the air effloresces very slowly, its surface being changed into
sulphate.
Sp. 7. Sulphite of Barytes. This salt, like the preced-
ing may be obtained in crystals, by adding an excess of acid.
It crystallizes in needles. It is tasteless, and nearly insoluble
in water.
Sp. 8. Sulphite of alumina. This salt does not crystal-
lize. It is a white soft powder with an earthy and sulphu-
SECT. I. NITRATES. 235
reous taste. It is insoluble in water, and when exposed to
the air it is slowly converted into sulphate.
The following table exhibits the constituents of the sul-
phites as far as they have been ascertained.
Sulphite of Acid. Bate. Water.
Magnesia 100 41 115
Ammonia 100 48.3 18.3
Soda 100 58 164
Lime 100 97.9 10.5
Potash 100 125 4.6
Alumina 100 137.5 75
Barytes 100 151 5.1
Genus IX. Nitrates.
All the salts belonging to this genus are soluble in water,
and crystallize by cooling. When heated to redness, and
charcoal powder thrown over them, a violent combustion
is produced. Sulphuric acid disengages from them fumes
of nitric acid. When heated they are decomposed and yield
at first oxygen gas.
Sp. I. Nitrate of Potash or Nitre. This salt, which is
of great importance, is found in warm climates on the sur-
face of the earth. It is collected and purified by solution
and crystallization. Its crystals are six-sided prisms termi-
nated by six-sided pyramids. Its taste is sharp, bitterish
and cooling. It is very brittle. It dissolves in seven parts
of cold water, and in less than its own weight of boiling
water. Pure alcohol does not dissolve it. In a red heat it
236 SALTS. CHAP. III.
melts and congeals into an opake mass which has been call-
ed mineral criystal. When kept melted it gives out about
the third of its weight of oxygen gas. It detonates most
violently with charcoal. This salt constitutes the principal
ingredient of gun powder, which is a mixture of about se-
venty-six parts nitre, fifteen charcoal, and nine sulphur. The
constituents are ground to a fine powder, and then mixed
together with great care. The goodness of the powder de-
pends upon the intimate mixture. Those kinds of charcoal
are pitched upon which absorb the least moisture from the
air.
Sp. 2. Nitrate of Soda. This salt crystallizes in trans-
parent rhombs differing but little from cubes. It has a cool
sharp taste, and is. rather more bitter than nitre. It dis-
solves in three parts of cold water, and in less than its weight
of boiling water. When exposed to the air it rather at-
tracts moisture. Its phenomena with combustibles and heat
are the same as those of the preceding species.
Sp. 3. Nitrate of Ammonia. This salt crystallizes in
six-sided prismr terminated by six-sided pyramids. It has
a very acrid, bitter, disagreeable taste. It dissolves in twice
its weight of cold water, and in half its weight of boiling
water. In the air it very speedily deliquesces. When heat-
ed it undergoes the watery fusion, but even after the water
is driven off it continues liquid at the temperature of about
400˚, boils, and is decomposed, being converted into water
and nitrous oxide gas, in the proportion of about four parts
gas to three parts water. When heated nearly to redness, it
burns with a kind of explosion. Hence it was formerly
called nitrum flammans.
Sp. 4. Nitrate of Magnesia. This salt crystallizes in
rhomboidal prisms or smail needles. Its taste is very bitter
and disagreeable. It is soluble in little more than its weight
of cold water. In the air it deliquesces. When heated it
SECT. I. NITRATES. 237
undergoes the watery fusion, and speedily assumes the form
of a white powder. It scarcely detaonates with combustible
bodies.
Sp. 5. Nitrate of Lime. This salt crystallizes in six-sided
prismas terminated by long pyramids. Its taste is very acrid
and bitter. It dissolves in about the fourth part of its weight
of cold water, and boiling water dissolves any quantity of it
whatever. Boiling alcohol dissolves its own wheight of it.
It speedily deliquesces in the air. When heated it readily
undergoes the watery fusion. When deprived of its water
of crysallization it ofteh has the property of shining in the
dark. In this state it is called Baldwins phosphorus.
Sp. 6. Nitrate of Barytes. This salt crystallizes is re-
gular octahedrons or in small brilliant plates. Its taste is
hot, acrid and austere. It is soluble in about twelve parts
of cold water. When thrown upon burning coals, it decre-
pitates and is converted into a dry mass. When strongly
heated, the whole of its acid is dissipatad and pure barytes
obtained.
Sp. 7. Nitrate, of Strontian. This salt cryistallizes in re-
gular octahedrons not unlike the crystals of nitrate of barytes.
It has a strong pungent cooling taste. It is soluble in its
own weight of cold water, and in little more than half its
weight of boiling water. It is insuluble in alcohol. It de-
flagrates on hot coals. In a crucinle it melts when heated.
At a red heat it gives out its acid, and pure strontian remains
behind. combustibles thrown into it when red hot burn
with a lively red flame.
Sp. 8. Nitrate of Ammonia-and-magnesia. This salt
crystallizes in fine prisms. It has a bitter, acrid, ammo-
niacal taste. It dissolves in about eleven parts of cold wa-
ter. In the air it gradually attracts moisture and deli-
quesces.
238 SALTS. CHAP. III.
Sp. 9. Nitrate of Alumina. This salt crystallizes with
difficulty into thin soft plates which have but little lustre. It
has an acid and astringent taste, is very soluble in water and
soon deliquesces when exposed to the air. When evaporat-
ed, it is readily converted into a gummy mass of the consist-
ence of honey. It is easily decomposed by heat.
Sp. 10. Nitrate of Ytria. This salt scarcely orystallizes.
Its taste is sweet and astringent. It speedily deliquesces in
the air.
Sp. 11. Nitrate of Glucina. This salt may be obtained
in the state of a powder, but not in crystals. Its taste is
sweet and astringent. It is very soluble in water and speedi-
ly deliquesces in the air.
Sp. 12. Nitrate of Zirconia. This salt does not crystal-
lize, but may be obtained in the state of a viscid mass which
dries with difficulty. It has an astringent taste. It is very
sparingly soluble in water, and seems indeed to be partially
decomposed by that liquid. When heated it readily parts
with its acid and is decomposed.
The following table exhibits the composition of the ni-
trates as far as it has been ascertained:-
Nitrate of Acid. Base. Water.
Ammonia 100 40.38 35.1
Magnesia 100 47.64
Lime 100 65.70 18.7
Soda 100 73.43
Strontian 100 116.86 105.3
Potash 100 117.7 8.1
Barytes 100 178.12 34.3
SECT. I. HYPER0XYMURIATES. 239
Genus X. Nitrites.
When the crystallized nitrates are exposed to a sufficient
heat, they give out oxygen gas. If the process be stopped
in time the salts still continue neutral. But the nature of the
acid is obviously changed as it has lost oxygen. Hence by
this process the nitrates are converted into nitrites. The
properties of the nitrites have not hitherto been investigated,
except the nitrite of potash, examined by Bergman and
Scheele. It deliquesces when exposed to the air, and gives
out nitrous fumes, when treated with any acid, even the
acetic.
Genus XI. Oxymuriates.
When oxymuriatic gas is passed through the alkalies and
alkaline earths in a dry state, a combination takes place and
saline substances are formed, to which the name of oxymu-
riates is given. But when the bases are dissolved or sus-
pended in water, the oxymuriatic acid is decomposed and
converted into hyperoxymuriatic and common muriatic acid.
The oxymuriates have not, hitherto, been examined.
Genus XII. Hyperoxymuriates.
This genus of salts was discovered by Berthollet. But
except the first species, all the rest were nearly unknown till
examined by Chenevix in 1802. They are formed by passing
a current of oxymuriatic acid through the bases dissolved in
water. When heated nearly to redness, they give out oxygen
gas and are converted into muriates. When mixed with
combustibles and heated, triturated or struck upon an anvil,
they detonate with great violence.
240 SALTS. CHAP. III.
Sp. 1. Hyperoximuriate of Potash. This salt crystallizes
in flat rhomboidal prisms of a silvery whiteness. Its taste is
cooling, austere and disagreeable, somewhat analogous to
that of nitre. It dissolves in l6 parts of cold, and 2 1/2 of
boiling water. It is not sensinly altered by exposure to the
air. When heated nearly to redness, it gives out more than a
third of its weight of oxygen gas. It detonates loudly when
mixed with sulphur or phosphorus, and struck upon an anvil
or triturated in a mortar. The experiment ought not to be
tried with more than a grain of the mixture. It may be
made into gunpowder with sulphur and charcoal, but it is
liable to explode during the preparation.
Sp. 2. Hyperoxymuriate of Soda. This salt is not easily
obtained pure, because it is as soluble in water as the muriate
of soda, with which it is mixed in the preparation. It crys-
tallizes in cubes. It produces a sensation of cold in the
mouth, and has a taste different from that of common salt.
It dissolves in about three parts of cold water. In the air it
deliquesces slightly. It dissolves in alcohol.
Sp. 3. Hyperoxymuriate of Ammonia. This salt may be
formed by mixing carbonate of ammonia with an earthy hy-
peroxymuriate. It is very soluble in water and alcohol, and
is decomposed at a moderate temperature.
Sp. 4. Hyperoxymuriate of Magnesia. This salt resem-
bles the hyperoxymuriate of lime in its properties.
Sp. 5. Hyperoxymuriate of Lime. This salt may be
formed by passing a current of oxymuriatic acid gas through
lime diffused in water, and boiling phosphate of silver in the
solution, filtering and evaporating. Its taste is sharp and
bitter, it is very deliquescent, and dissolves copiously in al-
cohol.
Sp. 6. Hyperoxymuriate of Barytes. This salt may be
obtained in the same way as the preceding species. It is so-
luble in four parts of cold water.
SECT. 1. ARSENIATES, 241
Sp. 7. Hyperoxymuriate of Strontian. This salt may be
prepared like the preceding. It crystallizes in needles, deli-
quesces, and is soluble in alcohol.
The followng table exhibits a view of the constituents of
the hyperoxymuriates, as far as has been ascertanied.
Hyperoxymurate of Acid. Bse. Water.
Magnesia 100 42.80 23.83
Soda 100 44.78 6.35
Lime 100 51.25 29.89
Strontian 100 56.52 60.77
Potash 100 67.24 4.30
Barytes 100 89.78 22.98
Genus XIII. Arseniates.
When the salts belonging to this genus are heated along
with charcoal powder, they are decomposed and arsenic
sublimes.
Sp. 1. Arseniate of Potash. This salt does not crystal-
lize. It deliquesces, and changes vegetable blues to green.
The superarsenate of potash is a transparent white salt which
crystallizes in four-sided prisms, terminated by four-sided py-
ramids. It is soluble in water, and gives a red colour to ve-
getable blues.
Sp. 2. Arseniate of Soda. This salt crystallizes in six-
sided prisms. The superarseniate does not crystallize.
Sp. 3. Arseniate of Ammonia. This salt crystallizes in
rhomboidal prisms. With an excess of acid it crystallizes in
needles.
0
242 SALTS. CHAP. III.
Sp. 4. Arseniate of Magnesia. This salt does not crys-
tallize, but may be obtained in a solid gummy mass.
Sp. 5. Arseniate of Lime. This salt crystallises, and is
soluble in water.
Sp. 6. Arseniate of Barytes. This salt is insoluble in
water, and cannot be orystallized.
Sp. 7. Arseniate of Alumina. This salt is a white pow-
der insoluble in water.
Sp. 8. Arseniate of Yttria. This salt is likewise a white
powder, which does not crystallize.
Genus XIV. Arsenites.
The term arsenite has been applied to the combinations of
white oxide of arsenic with the slifiable bases. The alka-
line arsenites are yellow coloured masses with a nauseous
odour not crystallizable, formerly called livers of arsenic.
The earthy arsenites are white powders nearly insoluble in
water.
Genus XV. Molybdates.
If into a solution of a molybdate a cylinder of tin with some
muriatic acid be put, the liquid gradually assumes a deep
blue colour.
Sp. 1. Molybdate of Potash. This salt crystallizes in
small rhomboidal plates. It is bright and has a metallic
taste. It is soluble in hot water.
Sp. 2. Molybdate of soda. This salt crystallizes, and is
very soluble in water.
Sp. 3. Molybdate of Ammonia. This salt is soluble in
water, and does not crystallize.
Sp. 4. Molybdate of Magnesia. This salt also is soluble
in water, and does not crystallize.
SECT. I. TUNGSTATES 243
Sp. 5. Molybdate of Lime. This is a white insoluble
powder.
Genus XVI. Tungstates.
These salts are combinations of yellow oxide of tungsten
with the salifiable bases.
Sp. 1. Tungstate of Potash. This salt is soluble in wa-
ter, deliquesces and does not crystallize. Its taste is metallic
and caustic.
Sp. Tungstate of Soda. This salt crystallizes in elon-
gated hexahedral plates. Taste acrid and caustic. Soluble
in four partes of cold, and two parts of boiling water.
Sp. 3. Tungstate of Ammonia. This salt crystallizes in
needles or small plates. Its taste is metallic. It is soluble
in water, and does not deliquesce.
Sp. 4. Tungstate of Magnesia. This salt crystallizes in
small brilliant scales. It is soluble in water, and not altered
by exposure to the air.
Sp. 5.0 Tungstate of Lime. This salt is found native. It
is usually crystallized. The crystals are octahedrons. Co-
lour yellowish grey, semi-transparent. It is insoluble in wa-
ter, and not altered by exposure to the air.
Sp. 6. & 7. The tungstates of barytes and of alumina, are
white insoluble powders scarcely examined.
Genus XVII. Chromates.
This genus of salts has been but imperfectly examined.
The salts have usually a yellow colour. The alkaline chro-
mates and chromate of lime are soluble in water and crys-
tallize; chromate of barytes appears to be insonlbule.
0 2
244 Salts. CHAP. III.
Genus XVIII. Columbates.
This genus of salts has been very imperfectly examined.
We know only the columbate of potash which crystallizes
in scales. Its taste is acrid and disagreeable.
ORDER II.
combustible SALTS.
Genus I. Acetates.
The acetates are all soluble in water. Heat decomposes
them, driving off and destroying the acid. When mixed with
sulphuric acid and distilled, acetic acid comes over, easily dis-
tinguished by its smell.
Sp. 1. Acetate of Potash. This salt is usually obtained
in plates, but it crystallizes regularly in prisms. It has a
sharp warm taste. It deliquesces in moist air, but in dry air
undergoes but little alteration. It is soluble also in alcohol.
When heated it melts, and in a high temperature is decom-
posed.
Sp. 2. Acetate of Soda. This salt crystallizes in striated
prisms, not unlike those of sulphate of soda. It has a sharp
taste, inclining to bitter. It dissolves in rather less than three
times its weight of cold water. It is not affected by expo-
sure to the air. When heated it loses its water of crystalli-
zation, and is decomposed.
Sp. 3. Acetate of Ammonia. This salt, called formerly
spirit of Mindererus, cannot easily be crystallized by evapo-
ration, but it may be obtained in needles by slow sublima-
tion. Its taste is similar to that of a mixture of sugar and
SECT. I. ACETATES. 245
nitre. It is very deliquescent. It melts at 170˚, and su-
blimes at about 250˚.
Sp. 4. Acetate of Magnesia. This salt does not crystal-
lize. It has a sweetish taste. It is very soluble both in wa-
ter and alcohol. It deliquesces in the air.
Sp. 5. Acetate of Lime. This salt crystallizes in needles,
and has a glossy appearance like satin. Its taste is bitter and
acid. It is soluble in water, and not altered by exposure to
the air.
Sp. 6. Acetate of Barytes. This salt crystallizes in fine,
transparent, prismatic needles. Its taste is acid and some-
what bitter. It dissolves in little more than its weight of .
water, and rather effloresces in the air. Alcohol dissolves
about 1/100 of its weight of it.
Sp. 7. Acetate of Strontian. This salt crystallizes. Its
taste is not unpleasant. It dissolves in little more than its
weight of cold water. It gives a green colour to vegetable
blues.
Sp. 8. Acetate of Alumina. This salt crystallizes in
needles, is very deliquescent, and has an astringent taste.
Sp. 9. Acetate of Yttria. This salt crystallizes in six-
sided plates of an amethyst red colour; and is not altered by
exposure to the air.
Sp. 10. Acetate of Glucina. This salt does not crystal-
lize, but yields a gummy mass. Its taste is sweet and astrin-
gent.
Sp. 11. Acetate of Zirconia. This salt does not crystal-
lize, but may be obtained in the state of a powder which
does not attract moisture from the air. It taste is astringent.
It is very soluble in water and in alcohol.
The following table exhibits a view of the constituents of
these salts, as far as they have been ascertained.
2 3
246 SALTS. CHAP. III.
Acetates of Acid. Base.
Alumina 100 35.48
Magnesia 100 41.55
Ammonia 100 45.40
Lime 100 53.58
Soda 100 58.04
Strontian 100 89.80
Potash 100 108.45
Barytes 100 165.72
Genus II. Benzoates.
This genus of salts has been so superficially examined, that
a detailed description of the species cannot be given. All
the benzoates examined are soluble in water, crystallize and
have a sharp saline taste. The benzoates of ammonia and
alumina deliquesce, the others do not. Most of the species
form feather-shaped crystals.
GENUS III. Succinates.
This genus of salts is almost as little known as the pre-
ceding. Most of the succinates crystallize. Succinate of
magnesia is an exception; and succinates of barytes and
glucina, are nearly inssoluble in water.
Genus IV. Moroxylates.
Only two species of this genus have been examined, the
moroxylates of lime and ammonia, both of which crystal-
lize in needles, and are soluble in water.
SECT. I. CAMPHORATES. 247
Genus V. Camphorates.
The salts belonging to this genus have usually a bitterish
taste. When heated, they are decomposed, and the acid
commonly sublimes. Before the blowpipe, they burn with
a blue flame.
Sp. 1. Camphorate of Potash. This salt is white and
transparent, and crystallizes in hexagons. It dissolves in
100 parts of cold, and in four parts of hot water. Alcohol
also dissolves it, and burns with a deep blue flame. When
heated it melts, and the acid is volatilized.
Sp. 2. Camphorate of Soda. This salt is white and
transparent. Its crystals are irregular. It dissolves in ra-
ther more than 100 parts of cold, and in eight parts of hot
water. It is soluble in alkohol. It effloresces slightly in the
air.
Sp. 3. Camphorate of Ammonia. This salt does not
readily crystallize. It is opake, and has a sharp bitterish
taste. It dissolves in about 100 parts of cold, and three
parts of hot water. It is soluble in alcohol. When heat-
ed it sublimes.
Sp. 4. Camphorate of Magnesia. This salt does not cry-
stallize. It is white, opake, and has a bitter taste. It re-
quires abont 290 parts of water to dissolve it. Cold alco-
hol does not act on it, hot alcohol decomposes it, and dis-
solves the acid.
Sp. 5. Camphorate of Lime. This salt does not cry-
stallize. Cold water dissolves very little of it; hot water
dissolves about 1/100th part. It is insoluble in alcohol. In
the air it falls to powder. When heated it melts, and the
acid is volatilized.
Sp. 6. Camphorate of Barytes. This salt does not cry-
stallize. It has little taste. It is scarcely soluble in water
24
248 SALTS. CHAP. III.
or alcohol. It is not altered by exposure to the air. When
heated it melts, and the acid is volatilized.
Sp. 7. Camphorate of alumina. This salt is a white
powder, with an acid, bitter, astringent taste. It dissolves
in about 200 parts of cold water, and in a much smaller
quantity of hot water. Hot alcohol dissolves it readily.
Genus VI. Oxalates.
The salts belonging to this genus are easily decomposed
in a red heat; water, carbonic acid, carbonic oxids, carbu-
reted hydrogen and charcoal are evolved, and the acid de-
stroyed. The alkaline oxalates are soluble in water, and
crystallize. They combine with an excess of acid, and form
super-oxalates. The earthy oxalates are insoluble in water,
or nearly so. Lime water occasions a precipitate in the so-
lution of oxalates, provided there be no great excess of acid.
Sp. 1. Oxalate of Potash. This salt crystallizes in flat
rhomboids. Its taste is cooling and bitter. It dissolves in
thrice its weight of cold water. It absorbs a little moisture
from the atmosphere.
Sp. 2. Superoxalate of Potash. This salt is extracted
from sorrel, and usually sold under the name of the essential
salt of lemons. Its crystals are small opake parallelopipeds.
It has an acid, pungent, bitterish taste. It dissolves in about
10 times its weight of boiling water, but requires a much
greater quantity of cold water. It is not altered by expo-
sure to the air. It contains exactly double the quantity
of acid which the oxalate of potash contains.
Sp. 3. Quadroxalate of Potash. This salt was lately
discovered by Dr Wollaston, by digesting superoxalate of
potash in nutric or muriatic acids. One half of the alkali
is separated, and there remains behind a salt, which may be
SECT. I. OXALATES. 249
obtained in crystals, and which contains four times the pro-
portion of acid that exists in oxalate of potash.
Sp. 4. Oxalate of Soda. This salt crystallizes, and has
nearly the same taste with the oxalate of potash. When
heated it falls to powder, being deprived of its water of
crystallization.
Sp. 5. Oxalate of Ammonia. This salt crystallizes in
four-sided prisms, terminated by dihedral summits. Its
taste is bitter and unpleasant, somewhat similar to that of
sal-ammoniac. 100 parts of cold water dissolve 4 1/2 of this
salt. It is insoluble in alcohol. When distilled, carbonate
of ammonia is disengaged, a little acid sublimed, and some
charcoal left behind.
Sp. 6. Oxalate of Alumina. This salt does not cry-
stallize, and has a yellow colour. It has a sweet astringent
taste, is soluble in water, and sparingly soluble in alcohol.
It deliquesces in the air.
The remaining species are nearly insoluble in water.
Sp. 7. Oxalate of Magnesia. This is a tasteless white
powder, not sensinly soluble in water; yet oxalate of am-
monia does not occasion a precipitate when dropt into sul-
phate of magnesia.
Sp. 8. Oxalate of Lime. This is a white powder, insolu-
ble in water, which makes its appearance when oxalate of
ammonia is poured into any neutral salt with base of lime.
It is tasteless, and dissolves readily in acids.
Sp. 9. Oxalate of Barytes. This is an insoluble, taste-
less, white powder. With an excess of acid, it may be ob-
tained crystallized in needles.
Sp. 10. Oxalate of Strontian. This is a white, insolu-
ble, tasteless powder. The superoxalate of strontian is
also insoluble. It contains just double the proportion of
acid which the oxalate does.
250 SALTS. CHAP. III.
Sp. 11. Oxalate of Yttria. This is also a white, insolu-
ble, tastelesw powder.
The following table exhibits the composition of the oxa-
lates, as far as ascertained:
Oxlalates of Acid. Base.
Ammonia 100 34.12
Magnesia 100 35.71
Soda 100 57.14
Lime 100 60.00
Potash 100 122.86
Strontian 100 151.51
Barytes 100 142.86
Genus VII. Mellates.
This genus of salts has been but imperfectly examined.
The alkaline mellates are soluble in water, and crystallize.
The earthy do not appear soluble, and therefore are usually
in the state of flaky powders.
Genus VIII. Tartrates.
These salts, when exposed to a red heat, are decompo-
sed, and the base remains in the state of a carbonate, usu-
ally mixed with charcoal. The earthy tartrates are nearly
insoluble in water; the alkaline are soluble; but they com-
bine with an excess of acid, and are converted into super-
tartrates, which are much less soluble than the tartrates.
They readily combine with another base, and form triple
salts.
SECT. I. TARTRATES. 251
Sp. 1. Tartrate of Potash. Of this salt there are two
varieties. The first, containing an excess of acid, is usually
called tartar. The second, which is neutral, is called tar-
trate of potash, and formerly it was called soluble tartar,
from its greater solubility in water.
Variety I. Supertartrate of Potash, or Tartar. This
salt deposites itself on the sides of casks in which wine is
kept. It is purified by solution, and evaporations. It is
from it that tartaric acid is usually obtained. Its crystals
are small and irregular. Its taste is acid, and rather un-
pleasant. It is brittle, and soluble in about 6O parts of
cold water. It is not altered by exposure to the air, but
when kept dissolved in water is gradually decomposed.
When distilled, it gives out a great deal of heavy inflamma-
ble air, and carbonic acid gas; and an acid liquor is obtain-
ed, formerly called pyrotartarous acid, but now known to
be merely the acetic, contaminated with a little empyreuma-
tic oil. The tartar of commerce contains about 5 per cent,
of tartrate of lime.
Variety 2. Tartrate of Potash. This salt may be formed
by saturating the preceding with potash or its carbonate. Its
crystals are flat four-sided rectangular prisms, terminated by
dihedral summits. It dissolves in about its own weight of cold
water. Its taste is an impleasant bitter.
Sp. 2. Tartrate of Soda. This salt crystallizes in needles.
It is soluble in its own weight of cold water. It it capable
of forming a supertartrate.
Sp. 5. Tartrate of Anmonia. This salt crystallizes in
small polygonal prisms. It has a cooling bitter taste. It is
very soluble in water. It is said also to be capable of form-
ing a supertartrate.
Sp. 4. Tartrate of Potash-and-Soda. This salt may be
formed by saturating tartar with carbonate of soda. It
was formerly called Rochelle salt, and salt of Seignette. It
252 SALTS. CHAP. III.
crystallizes in large irregular prisms. It has a bitter taste, is
very soluble in water, and effloresces when exposed to the
air.
Tartar forms also a triple salt when neutralized by am-
monia.
Sp. 6. Tartrate of Magnesia. This salt is insoluble in
water, unless it contains an excess of acid. In that case it
crystallizes in six-sided prisms.
Tartar forms a triple salt when neutralized by magnesia.
Sp. 6. Tartrate of Lime. This salt is a white powder in-
soluble in cold water. It is difficult to free it from water by
heat. An excess of acid renders it soluble.
Tartar forms a triple salt when neutrallized by lime.
Sp. 7. Tartrate of Baryes. This salt is soluble; but its
properties have not been ascertained.
Sp. 8. Tartrate of Strontian. This salt crystallizes in
trriangular tables. It is insipid, and nearly insoluble in water.
Tartar forms triple salts when neutralised by barytes and
strontian.
Sp. 9. Tartrate of Alumina. This salt does not crystal-
lize, but forms a gummy mass soliuble in water. Its taste is
astringent. It does not deliquesce.
Tartar forms a triple salt when neutrallized by alumina.
Sp. 10. Tartrate of IYttria. This salt is soluble in water,
but not to a great degree.
The following table exhibits the composition of the tar-
trates as far as it has been ascertained.
SE. I. CITRATBS. 253
Tartrates of Acid. Base.
Alumina 100 31.06
Magnesia lOO 36.30
Ammonia 100 39.67
Lime 100 45.00
Soda 100 50.80
Strontian 100 78.60
Potash 100 72-41
Barytes 100 131.41
Genus IX. Citrates.
When barytes is poured into a solution of a citrate a pre-
cipitate appears. They are decomposed also by the mineral
acids, and by oxalic and tartaric acids. When distilled, they
yield traces of acetic acid. When kept dissolved in water the
acid is gradually decomposed.
Sp. 1. Citrate of Potash. This salt does not crystallize
easily. It is very soluble in water and readily deliquesces.
Sp. 2. Citrate of Soda. This salt cystallizes in six-sided
prisms, not terminated by pyramids. Its taste is salt and
cooUng, but mild. It dissolves in less than twice its weight of
water. When exposed to the air it effloresces slightly.
Sp. 3. Citrate of Ammonia. This salt crystallizes in elon-
gated prisms. Its taste is cooling, and moderately saline. It
is very soluble in water.
Sp. 4. Citrate of Magnesia. This salt is very soluble in
water. It does not crystallize.
Sp. 5. Citrate of Lime. This is a white powder scarcely
254 SALTS. CHAP- III.
soluble is water, but with an exess of acid it may be obtain-
ed in crystals.
Sp. 6. Citrate of Barytes. This salt is very imperfectly
soluble in water. It may be obtained in the state of a white
powder, or of silky flukes.
Sp. 7. Citrate of Strontian. Thk salt is soluble in wa-
ter. It may be obained in cyrstals; and is said to resemble
in its properties, the oxalate or tartrate of strontian.
GENUS X. Kinates.
Only one species of this genus of salts has been hitherto
examined, namely kinate of lime, obtained by macerating
yellow peruvian bark in water, and evaporating the solution.
It is white, crystallizes in rhomboidal plates, dissolves in about
five times its weight of cold waiter, and is insoluble in alco-
hol. When heated sufficiently, it is decomposed, and the
acid destroyed,
GENUS XI. Saccolates.
These salts have hitherto been too superficially examined
to admit of description. The alkaline saccolates are soluble
in water, but the earthy are insoluble in that liquid.
GENUS XII. Sebates.
From the observations of Berazelius, it appears that the se-
bates approach very nearly to the benzoates in their proper-
ties.
GENUS XIII. Urates.
For the best account of these salts we are indebted to Dr
SECT. I. GALLATES. 255
Henry. They are white powders destitute of taste, and im-
perfectly soluble in water. Urate of ammonia is the most
solulbe, and urate of barytes the least soluble.
GENUS XIV. Malates.
This genus of salts has also been imperfectly investigated.
The alkaline malates are soluble in water, and deliquesce
in the air. Malates of barytes and lime are nearly insoluble,
but the latter combines with an excess of acid, and forms a
supermalate of lime, which dissolves in water. This last salt
is common in the vegetable kingdom. Malate of strontian
dissolves in water, and malate of magnesia is very soluble in
that liquid.
GENUS XV. Formiates.
These salts resemble the acetates in their properties. But
they have been only superficially examined.
GENUS XVI. Suberates.
These salts have a bitter taste. They are all soluble in
water, except the suberate of barytes. The earthy suber-
ates scarcely crystallize. Most of these salts have an excess
of acid.
GENUS XVII. Gallates.
The gallic acid seems scarcely capable of forming perma-
nent salts with the salifiable bases. When the alkalies are
dropt into a sulution gallic acid, it assumes a green colour.
When the liquid is evaporated, the acid seems to be decom-
256 SALTS. CHAP. III
posed. Gallic acid occasions a blue or a red colour, when
dropt into lime, barytes or strontian water.
GENUS XVIII. Prussiates.
The prussic acid combines with the salifiable base, but
the compounds have little permanency, as the acid is sepa-
rated by mere exposure to the air, or by a heat of 120°.
Hence these salts have been but little examined. It is ca-
pable of combining with an alkali or earth, and with a me-
tallic oxide at the same time, and of forming triple salts,
which have a great deal of permanency. The oxide of iron
is the metallic oxide usually present. Of all these salts the
most important is the prussiate of potash-and-iron, or the
triple prussiate of potash, as it is in common use as a re-
agent. It crystallizes in cubes or parallelopipeds. It has
a yellow colour, and is semi-transparent. It contains about
one-fourth of its weight of oxide of iron. It has a bitter
taste, and is insoluble in alcohol, though soluble enough
in water.
Sect. II. Of Metalline Salts.
Acids combine only with the oxides of metals; they seem
incapable of uniting with metals themselves. Now most me-
tals form more than one oxide, and acids are usually capable
of combining with two oxides at least of the same metal.
The properties of the salt vary a good deal according to the
state of oxydizement of the oxide. Thus muriatic acid com-
bined with the protoxide of mercury forms a salt insoluble
in water, and which acts merely as a cathartic when taken
internally. The same acid combined with the peroxide of
mercury forms a salt which is soluble in water, and consti-
tutes one of the most virulent poisons known. To distin-
SECT. II. OF GOLD. 257
guish the state of oxidizement of the metal in these salts
therefore is necessary. At present I shall sytisfy myself with
denoting those metalline salts that contain protoxides by the
usual name; while to the names of those that contain a pero-
xide the syllables oxy will be prefixed. Thus muriate of
mercury is the compound of muriatic acid and protoxide of
mercury; oxy muriate of mercury is the compound of the
same acid and peroxide of mercury. As there are twenty-
seven metals, it is obvious that the genera of metalline salts
are twenty-seven.
Genus I. Salts of Gold.
The salts of gold are soluble in water, and the solution has
a yellow colour. Triple prussiate of potash occasions a
white precipitate in them, and the infusion of nutgalls gives
them a green colour, and occasions a brown precipitate which
is gold reduced. A plate of tin or muriate of tin occasions
a purple precipitate. Sulphate of iron precipitates the gold
in the metallic state.
Sp. 1. Muriate of Gold. This salt is easily obtained by '
dissolving gold in a mixture of one part nitric and four parts
muriatic acid. The solution takes place speedily, and with
effervescence. It has a yellow colour, and when sufficiently
concentrated, lets fall small yellow crystals of muriate of
gold. They are four-sided prisms or truncated octahedrons,
and exceedingly deliquescent. The taste of this salt is acerb
with a little bitterness. It tinges the skin of an indelinle
purple colour. It dissolves readily in alcohol, and seems
more soluble in ether than in water. Almost all the metals
throw down the gold from this salt, either in the metallic
state or in that of a purple oxide. Hydrogen, posphorus
and sulphurous acid, produce the same effect by depriving the
gold of its oxygen. Murate of tin occasions a beautiful
258 SALTS. CHAP. III.
powder called purple of cassius. It is employed as a paint,
and to give a red colour to glass and porcelain. According to
Proust, it is a compound of three parts of the oxide of tin,
and one part of gold in the metallic state. But it seems
more likely that the gold is in the state of protoxide.
Sp. 2. Nitrate of Gold. Nitric acid containing a consi-
derable proportion of nitrous gas in solution, dissolves gold,
especially, it be much divided, as is the case in gold leaf.
The solution has an orange colour, and cannot be evaporat-
ed to dryness without decomposition.
The other salts of gold have not hitherto been examined.
Genus II. Salts of Platinum
The solution of these salts in water has a brown or yel-
lowish brown colour. No precipitate is produced by prus-
siate of potash or infusion of nutgalls. Sal-ammoniac oc-
casions a copious yellow-coloured precipitate.
Sp. 1. Nitrate of Platinum. Nitric acid does not act
upon platinum, but it dissolves its peroxide, and forms a salt
not hitherto examined.
Sp. 2, Muriate of Platinum. This salt is obtained by
dissolving platinum in aqua regia, and evaporating the solu-
tion, which is of a dark brown colour and opake. Small
irregular crystals of muriate of platinum may be obtained,
not more soluble in water than sulphate of lime. This salt
has a disagreeable astringent metallic taste. Heat drives
off the acid, and reduces the oxide to the metallic state.
The properties of the remaining species have been but
imperfectly examined. Potash and ammonia are capable of
combining with the salts of platinum and forming compounds
very little soluble in water. Hence a precipitate takes place
when these alkalies are poured into solutions containing pla-
tinum.
SECT. II. OF SILVER. 259
Genus III. Salts of Silver.
The nitric is the only acid which dissolves silver with fa-
cility, but they all combine with its oxides and form salts,
most of which are but sparingly soluble in water, When
the salts of silver are exposed to the action of the blow-pipe
on chaicoal, a globule of silver is obtained. Muriatic acid
or amuriate occasions a white precipitate in their solutions
which becomes black when exposed to the light. The prus-
siates occasion a white precipitate, and the hydrosulphuret
of potash a black precipitate in these solutions.
Sp. 1. Nitrate of Silver. There are two species of this
salt; the first, which has been long known, is an oxynitrate;
the second, recently discovered by Proust, is a nitrate.
1. Oxynitrate. Nitric acid dissolves silver with facility,
nitrous gas being emitted. The solution is colourless and
transparent; very heavy and very caustic. It tinges the skin
of an indelinle black, and is often used as a cautery. When
evaporated sufficiently it deposites crystals of oxynitrate of
silver. They are usually in thin plates, transparent, and
have an intensely bitter and metallic taste. It does not de-
liquesce, but becomes brown in a strong light. When heat-
ed, it readily melts, and congeals, when cold, into a grey
mass crystallized in needles. In this state it is cast into small
cylinders, and used under the name of lunar caustic by Sur-
geons, to open ulcers, and destroy fungous excrescences.
It detonates when heated with combustibles, or when struck
with phosphorus upon an anvil, and the silver is reduced.
A moderate heat disengages the acid, and reduces the silver
to the metallic state. It is composed of about seventy per-
oxide of silver, and thirty nitric acid.
2. Nitrate. This salt may be formed by boiling powder
of silver in a saturated solution of oxynitrate of silver. A
R 2
260 SALTS CHAP. III.
pale yellow coloured liquid is obtained, which contains ni-
trate in solution. This salt is exceedingly soluble in water,
and is not easily crystallized. When sufficiently evaporated,
it congeals entirely into a solid mass. When exposed to the
air, or mixed with nitric acid, it speedily absorbs oxygen,
and is converted into oxynitrate.
Sp. 2. Hyperoxymuriate of Silver. This salt may be ob-
tained by boiling phosphate of silver in hyperoxymuriate of
alumina. It is soluble in two parts of warm water; as the
solution cools it crystallizes in small rhomboids, opake and
dull like nitrate of lead. It is soluble in alcohol. When
exposed to a moderate heat, oxygen gas is given out and
muriate of silver remains. When mixed with sulphur, and
struck upon an anvil, it detonates with prodigious vio-
lence.
Sp. 3. Muriate of Silver. This salt is easily obtained,
by pouring common salt into a solution of nitrate of silver.
It is at first a heavy white curdy precipitate, but it soon
blackens when exposed to the air. It is insoluble in water.
When heated to about 500°, it melts into a grey coloured
semi-transparent mass, having some resemblance to horn,
and formerly called luna cornea. When heated with potash,
or when boiled with water and iron filings, it is decomposed,
and the silver reduced to the metallic state. It dissolves in
ammonia; it is likewise soluble in muratic acid, and by that
means may be obtained in octahedral crystals. It is com-
posed of about eighteen acid, and eighty-two peroxide of
silver. One hundred parts of dry muriate of silver contain
about 76.6 parts of pure silver.
Sp. 4. Sulphate of Silver. This salt may be formed by
boiling powder of silver in sulphuric acid. A white mass
is obtained, soluble in diluted sulphuric acid, and yielding
crystals by evaporation. The crystals are small prisms.
They dissolve in about eighty-seven parts of water. They
SECT. II. OF SILVER. 261
dissolve also is nitric acid. They melt when heated, and
are easily decomposed, the silver being reduced. It is com-
posed of about 17.4 acid and 82.6 peroxide of silver.
Sp. 5. Sulphite of Silver. This salt may be obtained by
mixing sulphite of ammonia and nitrate of silver. It is a
white powder, scarcely soluble in water, and having an acrid
metallic taste. In the light it becomes brown. When heat-
ed it is decomposed, and the silver reduced.
Sp. 5. Phosphate of Silver. This is a white powder in-
soluble in water, but soluble in nitric acid.
Sp. 7. Carbonate of Silver. This is a white insoluble
powder, which becomes black when exposed to the light.
Sp. 8. Fluate of Silver. This is a white powder inso-
luble in water.
Sp. 9. Borate of Silver. This likewise is a white inso-
luble powder.
Sp. 10. Acetate of Silver. This salt crystallizes in small
prisms, easily soluble in water. When heated, it swells and
yields a portion of ethereal liquor. The silver is redu-
ced.
Sp. 11. Benzoate of Silver. This salt is soluble in wa-
ter, and does not deliquesce.
Sp. Id. Saccinate of Silver. This salt crystallizes in
thin oblong radiated prisms.
Sp. 13. Oxalate of Silver, This is a white powder,
scarcely soluble in water, insoluble in alcohol, but soluble
in nitric acid.
bp. J 4. Tartrate of Silver. This salt is soluble in
water.
Sp. 16. Citrate of Silver. This salt is insoluble in wa-
ter. It is decomposed by nitric acid.
Sp. 16. Saccolale of Silver. A white insoluble pow-
der.
Sp. 17. Malate of Silver. A white powder.
R 3
282 SALTS CHAP- III.
Sp. 18. Arseniate of Silver. An insoluble brown pow-
der.
Sp. 19. Chromate of Silver. A beautiful crimson pow-
der which becomes purple when exposed to the light.
Sp. 20. Molybdate of Silver. A white flaky powder.
Genus IV. Salts of Mercury.
Mercurial salts when strongly heated are volatilized, and
traces of mercury may sometimes be observed. The prus-
siates occasion in them a white precipitate, hydrosulphuret
of potash, a black precipitate, and infusion of nulgalls an
orange yellow precipitate.
Sp. 1. Nitrate of Mercury. There are two species of
this salt, first correctly distinguished by Bergman, namely the
nitrate and oxynitrate.
1. Nitrate. This salt is obtained by dissolving mercury
in diluted nitric acid without the assistance of heat. The
solution is colourless, very heavy and caustic. It tinges the
skin indelinly black. It crystallizes in transparent octahe-
drons having their angles truncated. Sulphurated hydrogen
gas, passed through the solution of this salt, reduces the mer-
cury which separates in combination with sulphur. Muriate
of tin throws down the base in the state of running mer-
cury.
2. Oxymuriate. This salt is formed when nitric acid
is made to dissolve mercury with the assistance of heat;
provided an excess of mercury be not present. By conti-
nuing the heat, the solution passes into a yellow coloured
crystalline mass. When diluted with water, a white or yel-
low powder separates which is a suboxynitrate of mercury.
Sp. 2. Hyperoxymuriate of Mercury. Mr Chenevix ob-
tained this salt by passing a current of oxymuriatic acid
through water, in which red oxide of mercury was diffused.
SECT. II. OF MERCURY. 263
By evaporating the solution, crystals of oxymuriate and hy-
peroxymuriate of mercury were deposited. The latter were
picked out and purified by a subsequent crystallizatiom. This
salt is soluble in about four parts of water.
Sp. 3. Muriate of Mercury. Of this salt there are two
species, both long known, namely the oxymuriate and mu-
riate: Both are of great importance.
1. Oxymuriate. This salt is usually called corrosive su-
blimate, or corrosive muriate of mercury. It was known to
the alchymists. A vast number of methods of preparing it
have heen made public. The most common method is to
mix together equal weights of dry oxynitrate of mercury,
decrepitated common salt, and calcined sulphate of iron.
One-third of a matrass or phial is filled with this mixture.
The vessel is placed in a sand-bath, and gradually heated to
redness. A cake of oxymuriate of mercury sublimes into the
upper part of the vessel. It may be formed directly by dis-
solving red oxide of mercury in muriatic acid.
It has usually the form of a white semi-transparent cake
composed of small prisms. Its specific gravity is 5.1398.
Its taste is excessively acrid and caustic, and it leaves for a
long time a very disagreeable styptic metallic impression on
the tongue. It is one of the most virulent poisons known.
It is soluble in about 20 parts cold and S parts boiling wa-
ter. Alcohol dissolves nearly half its weight of it. It is not
altered by exposure to the air. When heated it sublimes
very readily, and the fumes are very dangerous when inhaled.
It is soluble in sulphuric, nitric and muriatic acids, decom-
posed by the alkalies, and precipitated of a brick red colour.
The alkaline earths likewise decompose it, and ammonia
forms with it a triple compound. It is composed of about
19 parts of acid and 81 of peroxide of mercury.
2. Muriate. This salt is distinguished by the names of
calomel and mercurius dulcis. It is prepared by titrating
R 4
264. SALTS CHAP. III.
four parts of oxymuriate of mercury, and three parts of mer-
cury in a mortar, and then subliming the mixture in a ma-
trass. It is a dull white mass, which becomes yellowish
when reduced to powder. When slowly sublimed, it crys-
tallizes in four-sided prisms, terminated by pyramids. Its
specific gravity is 7.1758. It is insoluble in water. It is
tasteless. When rubbed in the dark it phosphoresces. It
requires a higher temperature to sublime it than oxymuriate
of mercury. Oxymuriatic acid and nitric acid convert it in-
to oxymuriate. It is composed of about 11 acid and 89 pro-
loxide of mercury.
Sp. 4. Sulphated Mercury. Of this salt, likewise, there
are two species, the sulphate and oxysulphate.
1. Sulphate. This salt may be obtained by boiling over
mercury, sulphuric acid diluted with its own bulk of water.
Very little sulphurous acid gas is disengaged. By evapora-
tion the salt is obtained in small prismatic crystals. It dis-
solves in 500 parts of cold water, and is not altered by expo-
sure to the air. The alkalies throw down a dark-coloured
sub-sulphate of mercury, when poured into a solution of this
salt. The sulphate of mercury is composed of 12 acid, 83
protoxide and 5 water.
2. Oxysulphate. When three parts of sulfphuric acid are
boiled on two parts of mercury, the whole, by continuing the
heat, is converted into oxysulphate. This salt crystallizes in
small prisms. When neutral, its colour is a dirty white; but,
when in the state of super-oxysulphate, it is of a fine white.
The neutral salt is not altered in the air, the super-oxysul-
phate deliquesces. It is composed of 31.8 acid, 63.8 per-
oxide, 4.4 water. When water is poured upon this salt, it
is decomposed and converted into super-oxysulphate which
dissolves, and sub-oxysulphate, which remains in the state of
a beautifnl yellow powder. This sub-salt is used as a pig-
4
SECT. II. OF MERCURY. 265
ment, and was formerly known by the name of turpeth mine-
ral. It is composed of 15 acid and 85 peroxide.
Sp. 5. Phosphate of Mercury. This salt may be formed
by mixing together the solutions of nitrate of mercury and
phosphate of soda. It is a white powder, insoluble in water,
lately introduced into medicine, and composed of 28.5 acid,
71.5 peroxide.
There seems to be no such salt as phosphite of mercury.
Sp. 6. Carbonate of Mercury. A white insoluble powder.
Sp. 7. Fluate of Mercury. A white insoluble powder-
Sp. 8. Borate of Mercury. A yellow insoluble powder.
Sp. 9. Acetated Mercury. Of this salt there are two
species, the acetate and oxacetate.
1. Acetate. This salt may be obtained by mixing toge-
ther solutions of nitrate of mercury and acetate of potash.
Its crystals are plates of a silvery whiteness. It has an acrid
taste, is insoluble in alcohol, and scarcely soluble in water.
2. Oxacetate. This salt may be formed by dissolving red
oxide of mercury in acetic acid. It is a yellow mass, which
does not crystallize, and soon deliquesces in the air.
Sp. 10. Succinate of Mercury. This salt crystallizes, and
is soluble in water.
Sp. 11. Benzoate of Mercury. A white powder, insolu-
ble in water, and very sparingly soluble in alcohol.
Sp. 12. Oxalate of Mercury. A white powder, scarcely
soluble in water, which blackens when exposed to the light.
It detonates when heated.
Sp. 13. Mellate of Mercury. A white powder.
Sp. 14. Tartrate of Mercury. An insoluble white pow-
der, becoming yellow when exposed to the air.
Sp. 15. Citrate of Mercury. A white mass, scarcely so-
luble in water.
Sp. 16. Prussiate of Mercury. This salt may be formed
boiling red oxide of mercury and prussian blue in water.
266 SALTS CHAP. III.
It crystallizes in four-sided prisms, terminated by four-sided
pyramids. Its taste is acrid and metallic. It is white, and
soluble in water.
Sp. 17. Arseniate of Mercury. A yellow insoluble pow-
der.
Sp. 18. Molybdate of Mercury. A white flaky powder.
Sp. 19. Chromate of Mercury. An insoluble powder, of
a fine purple colour.
Genus V. Salts of Palladium.
The salts of this metal are almost all soluble in water, and
the solution has a fine red colour. Prussiate of potash oc-
casions a dirty yellowish brown precipitate, hydrosulphuret
of potash, and the alkalies an orange-yellow precipitate when
poured into solutions of these salts. Neither nitrate of pot-
ash nor sal ammoniac occasions any precipitate in them.
Nitric, muriatic and sulphuric acid digested on palladium ac-
quire a red colour. But the true solvent of that metal is ni-
tro-muriatic acid. The salts of palladium are not yet suffi-
ciently known to admit of a particular description.
GENUS VI. Salts of Rhodium.
The solutions of these salts are red. Prussiate of potash,
hydrosulphuret of potash, sal ammoniac, and alkaline carbo-
nates occasion no precipitate in them. But the pure alkalies
throw down a yellow powder soluble in an excess of alkali.
GENUS VII. Salts of Iridium.
These salts are soluble in water. The solution is at first
green, but becomes red when concentrated in an open vessel.
Neither prussiate of potash nor infusion of nutgalls occasion
SECT II OF COPPER. 267
any precipitate, but they render the solutions of iridium co-
lourless.
GENUS VIII. Salts of Osmium.
This genus of salts is still entirely unknown.
GENUS IX. Salts of Copper.
Most of these salts are soluble in water. The solution is
blue or green, or at least it acquires these colours when ex-
posed to the air. When ammonia is poured into these solu-
tions, they assume a deep blue colour. Prussiate of potash
occasions a greenish yellow precipitate, hydrosulphuret or
potash a black precipitate, and gallic acid a brown precipi-
tate in these solutions. A plate of iron or zinc put into these
solutions precipitates the copper in the metallic stale.
Sp. 1. Nitrate of Copper. Nitric acid attacks copper
with some violence, nitrous gas is emitted, and the metal dis-
solved. By evaporation the salt crystallizes in parallelopi-
peds. It has a blue colour, its taste is acrid and metallic,
and it is exceedingly caustic. It is very soluble in water, and
speedily deliquesces in the air. When heated it undergoes
the watery fusion; and, if the heat be increased, the acid is
driven off and the black oxide of copper remains in a state of
purity. It detonates feebly on burning coals. It detonates
when mixed with phosphorus and struck upon an anvil.
When moistened and wrapt up in tin-foil, it sets the tin on
fire. It is composed of 16 acid, 67 oxide and 17 water.
Sp. 2. Hyper-oxymuriate of Copper. This salt may be
formed by passing a current of oxymuriatic acid through
water, containing oxide of copper diffused through it.
Sp. 3. Muriated Copper. Of this salt there are two spe-
cies, the muriate and oxymuriate<(i>.
268 SALTS CHAP. III-
1. Oxymuriate. This salt may be obtained by dissolving
copper in nitro-muriatic acid, and evaporating the solution.
Its crystals are rectangular parallelopipeds of a grass-green
colour. It is verv acrid and caustic. It is very soluble in
water, and soon deliquesces in the air. In a moderate heat
it melts. If the heat be increased, oxymuriatic acid is disen-
gaged, and muriate of copper remains. This salt is compo-
sed of 24 acid, 40 peroxide, 36 water.
2. Muriate. This salt was discovered by Proust. It
may be formed by putting copper filings into liquid oxymu-
riate of copper in a well-stopped phial, or by mixing equal
weights of black oxide of copper and copper in powder, and
dissolving them in muriatic acid in a well-stopped phial. It
crystallizes in octahedrons. Its solution in water is colour-
ess; when diluted, a white powder precipitates, which is a
submuriate of copper. When exposed to the air, it is very
speedily converted into oxymuriate. It is composed of 24.75
acid, 70.25 protoxide, 5 water.
Sp. 4. Sulphate of Copper. This salt has been long known,
and in commerce is distinguished by the names of blue vitriol
or blue copperas. It crystallizes in oblique parallelopipeds,
has a blue colour, a styptic metallic taste, and is employed as
a caustic. It is soluble in about four parts of cold water.
When exposed to the air, it effloresces very slightly. By
heat it is decomposed, and black oxide of copper remains.
It reddens vegetable blues, and is, in fact, a supersulphate.
The real sulphate crystallizes in four-sided prisms, termi-
nated by pyramids. This salt is composed of 33 acid, 32
oxide, and 35 water.
Sulphuric acid does not seem capable of combining with
protoxide of copper.
Sp. 5. Sulphite of Copper. When sulphite of soda and,
sulphite of copper are mixed, whitish green crystals of sul-
SECT. II. OF COPPER. 263
phite of copper are deposited. They are sparingly soluble
in water.
Sp. 6. Phosphate of Copper. A bluish green powder,
insoluble in water.
Sp. 7 Carbonate of Copper. A beautiful apple green
powder, insoluble in water. It is often found native, and is
distinguished by mineralogists by the name of malachite.
Sp. 7. Fluate of Copper. This salt crystallizes in cubes
of a blue colour.
Sp. 8. Borate of Copper. A green powder, scarcely so-
luble in water.
Sp. 9. Acetate of Copper. This salt was known to the
ancients. It is sometimes called verdigris. Though that
name is more frequently applied to a subacetate of copper.
It crystallizes in four-sided truncated pyramids. Its colour
is a beautiful bluish green. Its taste is metallic, and nau-
seous; and like all the salts of copper it is poisonous. It is
sparingly soluble in cold water, but boiling water dissolves
about one-third of its weight of it. It is soluble also in al-
cohol. When exposed to the air it effloresces. When dis-
tilled, it yields acetic acid in considerable quantity. It is
composed, according to Proust, of 61 acid and water, and
39 oxide of copper.
Sp. 11. Succinate of Copper. Small green crystals, not
yet examined.
Sp. 12. Benzoate of Copper. Deep green crystals, spa-
ringly soluble in water, and insoluble in alcohol.
Sp. 13. Oxalate of Copper. A green coloured salt,
scarcely soluble in water.
Sp 14 Tartrate of Copper. Bluish green crystals, spa-
ringly soluble in water.
Sp. 15. Citrate of Copper. Light green crystals.
Sp. l6. Arseniate of Copper. This salt is precipitated
in the state of a bluish white powder, when arseniate of
270 SALTS CHAP. III.
potash is poured into sulphate of copper. It is insoluble
in water, unless it contains an excess of acid. It has been
found native in Cornwall, in crystals, and has been analyzed
by Chenevix. There are five varieties of it, differing in the
proportion of acid and oxide, in the figure of their crystals
and in colour.
The oxide of copper likewise combines with white oxide
of arsenic, and forms a green powder, usually known by the
name of Scheele's green.
GENUS X. Salts of Iron.
Most of the salts of iron are soluble in water; the solu-
tion has a green, or yellowish, or reddish colour, according
to the state of oxydizement of the iron. Prussiate of po-
tash throws down from these solutions a blue powder, or at
least it becomes blue when exposed to the air. Hydrosul-
phuret of potash occasions a black precipitate. Gallic acid
and the infusion of nut galls, throws down a black or purple
precipitate.
Sp. 1. Nitrate of Iron. Diluted nitric acid acts with
great energy upon iron, a gas being extricated, which is a
mixture of nitrous gas and nitrous oxide. There are two
varieties of this salt.
1. Nitrate. This salt may be formed by dissolving iron
in nitric acid of the specific gravity 1.16. The action is
slow and little gas is extricated. The iron is in the state of
black oxide. The solution cannot be heated or concentrat-
ed without converting the iron into red oxide.
2. Oxynitrate. This salt may be formed by concentrat-
ing the preceding. The liquid assumes a red colour, and
the red oxide of iron at last precipitates. The salt may be
obtained in crystals, by keeping nitric acid in contact with
black oxide of iron. The oxide gradually dissolves and four-
SECT.II. OF IRON. 271.
sided prisms, nearly colourless are gradually formed. They
deliquesce in the air-
Sp 2. Hyperoxymuriate of iron. This salt may be form-
ed by passing a current of oxymuriatic acid through water,
having red oxide of iron mixed with it.
Sp. 3. Muriared Iron. Of this salt there are two spe-
cies, the muriate and oxymuriate.
1. Muriate. This salt may be formed by dissolving iron
filings in muriatic acid, without the contact of the extemal
air. The solution is green, and yields green coloured crys-
tals very soluble in water. The solution absorbs nitrous gas
in great abundance. When exposed to the air it absorbs
oxygen, and the salt is converted into oxymuriate.
2. Oxymuriate. This salt may be formed by exposing
the preceding to the atmosphere, or by dissolving red oxide
of iron in muriatic acid. The solution has a dark brown
colour; the salt does not crystallize, but when evaporated to
dryness leaves a yellow coloured mass which deliquesces,
and is soluble in alcohol. When heated, oxymuriatic acid
is given out; and black oxide of iron remains still combined
with muriatic acid.
Sp. 4. Sulphated Iron. Of this salt, likewise, there are
two species, the sulphate and oxysulphate.
1. Sulphate. This salt was known to the ancients, and
is used in considerable quantity in dyeing, and in the manu-
facture of ink. It is easily obtained by dissolving iron in
diluted sulphuric acid and evaporating the solution. It has
a green colour, sometimes very light, sometimes very dark.
In this last state it is preferred by artists. Upon what the
difference depends is not accurately known. It crystallizes
in rhomboidal prisms. It has a very styptic taste, and al-
ways reddens vegetable blues. It is soluble in two parts of
cold, and in less than its weight of boiling water. It is in-
soluble in alcohol. When an alkali is poured into a solu-
272 SALTS. CHAP. III.
tion of this salt, a white powder precipitates which is a sub-
sulphate of iron. Whenm heated it melts and loses its water
of crystallization. In a red heat it loses most of its acid,
and is converted into a red powder, known by the name of
colcother of vitriol, and used in polishing metallic bodies.
This salt is composed of 26.7 acid, 28.3 base, 45 water.
2. Oxysulphate. This salt may be formed by exposing
the solution of the preceding to the open air. It has a yel-
lowish red colour, does not crystallize and when evaporated
to dryness soon attracts moisture and becomes again li-
quid.
Sp 5. Sulphite of Iron. Iron dissolves in sulphurous
acid without the emission of much gas. The solution yields
crystals of sulphite, which are soon changed into sulphate by
exposure to the air.
Sp. 6. Phosphated Iron. Of this salt there are two spe-
cies, the phosphate and xyphosphate.
1. Phosphate. This salt may be obtained by mixing so-
lutions of phosphate of soda and sulphate of iron. It pre-
cipitates in the state of a blue powder. It is tasteless, inso-
luble in water, but soluble in nitric acid. It is found native,
crystallized in blue coloured prisms.
2. Oxyphosphate. This is a white powder insoluble in
water, but soluble in acids, and precipitated by ammonia.
When violently heated it melts into an ashcoloured globule.
When treated with a fixed alkali it loses a portion of its acid
and is converted into a brown coloured powder. In this
state it is a suboxyphosphate of iron. It is insoluble in wa-
ter, and nearly so in acids. But it dissolves in the serum of
blood, and is supposed by some to give the red colour to
blood.
Sp. 7. Carbonate of Iron. Thiy salt may be obtained
by precipitating sulphate of iron by an alkaline carbonate.
It has been found native, crystallized in rhombs, somewhat
SECT. II. OF IRON. 273
transparent, of a greenish yellow colour, and brittle. It is
composed of 36 acid, 59.5 protoxide and two water. Rust
is frequently a carbonate of iron. Hence it effervesces when
dissolved in acids.
Sp. 8. Fluate of Iron. Fluoric acid dissolves iron rea-
dily. The solution does not crystallize, but assumes the
form of a jelly.
Sp. 9. Borate of Iron. A yellow powder insoluble in
water.
Sp. 10. Acetated Iron. Of this salt ithere are two spe-
cies, the acetate and oxacetate.
1. Acetate. It may be obtained by dissolving sulphuret
of iron in acetic acid. It forms green coloured prismatic
crystals sufficiently soluble in water.
2. Oxacetate. A reddish brown liquid, which does not
crystallize, but is easily converted into a jelly, which deli-
quesces. This liquid is much used by calico-printers.
Sp. 11. Succinate of Iron. A brownish red powder,
insoluble in water, unless there be an excess of acid pre-
sent.
Sp. 12. Benzoate of Iron. Yellow crystals, with a sweet
taste, soluble in water and in alcohol.
Sp. 13. Oxalated Iron. Oxalic acid attacks iron rapidly
and combines with both its oxides.
1. Oxalate. Prismatic crystals of a green colour, very
soluble in water, with an execess of acid.
2. Oxygenized Oxalate. A yellow powder scarcely so-
luble in water, and incapable of crystallizing.
Sp. 14. Tartrated Iron. The tartrate cystallizes, and
is sparingly soluble in water; the oxytartrate is red, does
not crystallize, but runs into a jelly.
Sp. 15. Citrate of Iron. A browo coloured solution,
which deposists small crystals very soluble in water.
274 SALTS CHAP. III.
Sp. 16. Malate of Iron. A brown solution which does
not crystallize.
Sp. 17. Gallate of Iron. A deep blue or black powder,
insoluble in water.
Sp. 18. Prussiated Iron. The prussiate is a white pow-
der, the oxyruissiate, a deep blue powder; both insoluble
in water.
Sp. 19. Arseniated Iron. The arseniate is a green co-
loured salt, insoluble in water, found native, crystallizes in
cubes. The oxyarseniate is a brownish red powder, likewise
insoluble in water.
Sp. 20. Tungstate of Iron. An insoluble powder of a
grey colour.
Sp. 21. Molybdate of Iron. An insoluble brown
powder.
Sp. 22. Columbate of Iron. An insoluble mineral of
a dark brownish grey colour, and a lamellated structure.
GENUX XI. Salts of Tin.
Most of these salts are soluble in water, and the solution
is colourless, or has a brownish colour, according to cir-
cumstances. The prussiates, whep dropt into these solu-
tions occasion a white precipitate; hydrosulphuret of potash
occasions a brownish black, or a golden yellow precipitate;
corrosive sublimate occasions a black or a white precipitate;
infusion of nut galls occasions no precipitate in these so-
lutions.
Sp. 1. Nitrated Tin. Nitric acid acts with great violence
on tin, and speedily converts it into an oxide. When the
acid is much diluted, it forms a yellow coloured solution,
containing deutoxide of tin. But when the solution is left
to itself, or when it is concentrated by evaporation, the oxide
of tin is precipitated. When the acid is strong, it speedily
SECT. II. OF TIN. 275
converts the metal into peroxide without dissolving any of it .
During the action ammonia is formed and remains in combi-
nation with the acid.
Sp. 2 Muriated tin. Of this salt there are two species
the muriate and oxymuriate,
1. Muriate, Muriatic acid dissolves tin when assisted by
heat, and the salt formed is muriate of tin. By evapora-
tion it is obtained in needle-shaped crystals, soluble in water,
and somewhat deliquescent. It has a strong affinity for oxy-
gen and readily imbines it from the atmosphere, from oxy-
muriatic and nitric acids, and from various metallic oxides
and salts. Hence the remarkable changes which it produ-
ces on many metallic solutions.
2. Oxymuriate. This salt is commonly known by the
name of smoking liquor of Linavius. It may be formed by
triturating together amalgam of tin, and corrosive sublimate,
and distilling the mixture in a retort with a moderate heat.
At first some water comes over, then a white smoke passes
all of a sudden, which condenses into a colourless liquid,
which constitutes the salt in question. If this liquid be ex-
posed to the air, it smokes violently in consequence of its
great affinity for water. When mixed with about one-third
of its weight of water it crystallizes. Oxymuriate of tin
may be formed also by exposing a solution of muriate of tin
to the atmosphere, or by passing a current of oxymuriatic
acid gas through it. When evaporated, it yields small pris-
matic crystals which deliquesce. When heated, it sub-
limes.
Sp. 3. Sulphate of Tin. When tin is kept in sulphuric
acid, little action takes place. However, the tin is gradual-
ly oxydized, and sulphurous acid gas is emitted. The sul-
phate of tin, formed, may be obtained in the state of fine
needles by evaporation. It may be readily obtained by pour-
ing sulphuric acid into muriate of tin; a white powder pre-
S2
275 SALTS CHAP. III
cipitates, which is the sulphate, and which dissolves in wa-
ter and crystallizes.
The Oxysulphate of tin does not crystallize, but assumes
the form of a jelly.
Sp. 4. Sulphite of Tin. When tin is kept in sulphurous
acid, the acid is decomposed, oxide of tin dissolved, and
sulphuret tin precipitated.
Sp. 5. Phosphate of Tin. A white powder insoluble in
water.
Sp. 6. Carbonate of Tin. As far as known, this spe-
cies of salt does not exist.
Sp. 7. Fluate of Tin. A gelatinuos solution having a
very disagreeable taste.
Sp. 8. Borate of Tin. A white powder insoluble in wa-
ter.
Sp. 9. Acetated Tin. The acetate of tin crystallizes, the
oxacetate forms a gummy incrystallizable mass.
Sp. 10. Succinate of Tin. This salt crystallizes, and is
soluble in water.
Sp. 11. Benzoate of Tin. This salt is soluble in water,
but insoluble in alcohol.
Sp. 12. Oxalate of Tin. Prismatic cryslals, söluble in
water.
Sp. 13. Arseniate of Tin. A white insoluble powder.
Genus XII. Salts of Lead.
Many of these Salts are scarcely soluble in water. Those
that are, form colourless solutions, which have usually a
sweet taste. The prussiates occasion a white precipitate
in these solutions, hydrosulphuret of potash, a black pre-
cipitate, infusion of nutgalls, a white precipitate.
Sp. 1. Nitrated Lead. Of this salt there are two va-
rieties, the first composed of yellow oxide and nitric acid,
3
SECT. II. OF LEAD. 277
has long been known; we shall call it oxynitride; the se-
cond, or nitrate, has been lately discowered by Proust.
1. Oxynitrate. This salt is easily obtained by dissolving
lead in diluted nitric acid, and evaporating the solution.
The crystals are sometimes tetrahedrous, having theri opexes
truncated; sometimes octahedrons. They are opake and
white, and have a silvery lustre. Their taste is sweet and
harsh. They are not altered by exposure to the air They
dissolve in less than eight parts of boiling water. When
heated it decrepitates, and in a strong heat the acid is driven
off, whiel at the same time the oxide is partially reduced to
the metallic state. This salt is composed of 66 yellow oxide,
34 acid and water.
2. Nitrate. This salt is obtained by boiling lead in a so-
lution of oxynitrate. A portion of the lead is dissolved, and
the sollution aquires a yellow colour. When evaporated
the salt crystallizes in scales, and in small prisms. The
oxide in my trials appeared to be the yellow; but Buchholz
affirms that it contains less oxygen. This salt is composed of
81.5 oxide, 18.5 acid.
Sp. 2. Hyperoxymuriate of Lead. This salt is obtained
by passing in current of oxymuriatic acid through water, in
which oxide of lead is suspended. It is more soluble than
muriate of lead, and is easily decomposed.
Sp. 3. Muriate of Lead. Muriatic acid attacks lead
when assisted by heat. The muriate may be easily formed
by pouring muriate of soda into a solution of nitrate of lead.
The muriate precipitates in small prisms of a white colour
and a satin lustre. This salt dissolves in 22 parts of cold
water, and is considerably more soluble in hot water. It dis-
solves also in acetic acid. It is not altered by exposure to
the air. When heated it melts, and when cold congeals into
a semitransparent, greyish mass, formerly called plumbum
corneum. When strongly heated it is converted into a sub
S3
278 SALTS CHAP. III.
muriate of lead. The muriate of lead is composed of about
18 1/3 acid, 81 3/4 yellow oxide. 400 parts of the crystallized
salt contain about 76 parts of metallic lead.
The submuriate of lead may, be obtained in the state of a
white powder, by treating muriate of lead with a pure alkali.
When heated it assumes a fine yellow colour. It is inso-
luble in water. It is employed as a paint.
Sp. 4. Sulphate of Lead. This salt may be obtained by
pouring sulphuric acid or an alkalkine sulphate into nitrate of
lead. It is a white powder insoluble in water, in alcohol,
and in nitric and acetic acids. It is found native, crysttalized in
octahedrons. It is composed of about 25 acid and 48 yellow
oxide. A hundred parts of it, according to Kirwan, contain
71 of metallic lead. I may be heated to redness in a plati-
num crucinle without alteration, but when in contact with
charcoal, it melts, and the lead is reduced.
Sp. 5. Sulfite of Lead. This is a tasteless white pow-
der, insoluble in water. It is composed of about 74.5 oxide,
amd 25.5 acid.
Sp. 6. Phosphate of Lead. A white tasteless powder, in-
soluble in water, easily obtained by pouring phosphate of
soda into nitrate of lead. It is found native, usually of a
green or yellow colour, and is often crystallized in six-sided
prisms. It is soluble in nitric and muriatic acids, and from
the last solution muriate of lead precipitates. When heated
it melts, and assumes on cooling a regular polyhedral form.
It is composed of 18 acid and 82 yellowish oxide.
Sp. 7. Carbonate of Lead. This is a white powder inso-
luble in water, easily obtained by mixing solutions of nitrate
of lead, and an alkaline carbonate. It is found native, crys-
tallized jn six-sided prisms, and in tables. It is employed as
a paint under the name of white lead. It is composed of
16 1/3 acid, and 83 2/3 yellow oxide.
SECT. III. OF LEAD. 279
Sp. 8. Fluate of Lead. A white powder insoluble in wa-
ter, unless there be an excess of acid.
Sp. 9. Borate of Lead. A white insoluble powder.
Before the blowpipe, it melts into a colourless glass-
Sp. 10. Acetate of Lead. Of this salt there are t wo va-
rieties, the superacetate and acetate.
1. Superacetate. This salt has been long known. It is usual-
ly distinguished by the name of sugar of lead. It may be ob-
tained by dissolving acetate of lead in acetic acid. It is much
used by dyers and calico-printers. Its crystals are small
needles, with a glossy appeance like satin. It has a sweet,
and rather astringent taste. Water dissolves rather more
than 1/4th of its weight of this salt. It is not altered by ex-
posure to the air. When distilled, there comes over water
acidulated with acetic acid, then a yellow inflammable li-
quor, which has some of the properties of ether. The gasses
extricated are carbonic acid in cosiderable quantity, with a
very little heavy inflammable air. This salt is composed of
26 acid, 58 yellow oxide, 16 water.
2. Acetate. This salt may be obtained by boiling together in
water 100 parts of sugar of lead, and 15O parts of lithargê.
its taste is less sweet, it is less soluble in water than the pre-
ceding variety, and if crystallizes in plates. A solution of this
salt is employed by surgeons under the name of Goulard's
extract.
Sp. 11. Succinate of Lead. Slender foliated crystals,
scarcely soluble in water, but soluble in nitric acid.
Sp. 12. Benzoate of Lead. This salt forms white crys-
las soluble in water and alcohol, and decomposed by heat.
Sp. 13. Oxalate of Lead. Small crystals insoluble in al-
cohol, and scarcely soluble in water, unless there be an ex-
cess of water present.
Sp. 14. Tartrate of Lead. An insoluble white powder,
S 4
280 SALTS CHAP. III
decomposed by a moderate heat. It is composed of 37 acid
and 63 yellow oxide.
Sp. 15. Citrate of Lead. A whit powder, difficultly so-
luble in water.
Sp. 16. Malate of Lead. A white powder, which preci-
cipitates in fine light flakes, and is insoluble in water, but easily
soluble in acetic and weak nitric acid.
Sp. 17. Arseniate of Lead. A white powder, insoluble
in sater. It is composed of 35.7 acid and 63.3 yellow oxide.
Sp. 18. Molybdate of Lead. A white powder, insoluble
in water. It ocucrs native in rhomboidal plates, of a yellow
colour, and is composed of 35.7 acid; and 64.3 yellow oxide.
Sp. 19. Tungstate of Lead. A white insoluble powder.
Sp. 20. Chromate of Lead. This is a fine red powder,
with a shade o yellow, tasteless and insoluble in water. It occ-
curs native, crystallized in four-sided prisms, and is composed
of 34.9 acid, and 65.1 oxide.
Genus XIII. Salts of Nickel.
The salts belonging to this genus haive been but imper-
fectly examined. They are generally soluble in water, and
the solution has a fine green colour. Prussiate of potash dropt
into them occasions a dull green precipitate, hydrosulphuret
of potash a black precipitate, and the infusion of nutgalls a
greyish white precipitate.
Sp. 1. Nitrate of Nickel. This salt crystallises in rhom-
boidal prisms; has a fine green colour; when exposed to the
air at first deliquesces, and afterwards falls to powder, and
gradually loses the whole of its acid. It is composed of 55
acid, 25 oxide, and 20 water.
Sp. 2. Muriate of Nickel. This soalt may be obtained by
dissolving nickel in nitromuriatic acid, and evaporating the
SECT. II. OF ZINC. 281
solution. It crystallizes irregularly, has an apple green co-
lor, and deliquesces in air. When heated it loses its
water, and may be sublimed in the state of golden yellow
flowers, which become green by absorbing water from the
atmosphere. This salt is composed of 34 oxide, 11 acid,
and 55 water.
Sp. 3. Sulphate of Nickel. This salt has a fine green co-
loura, and crystallizes in six-sided prisms. It is very soluble
in water, and effloresces in the air. It is composed of 35
oxide, 19 acid, and 46 water.
Sp. 4. Carbonate of Nickel. This salt is obtained by pre-
cipitating nitrate of Nickel with carbonate of potash. It is a
green powder, composed of 56.4 acid and water, 43.6 oxide.
Sp. 5. Fluate of Nickel. A salt wich yields light-green
coloured crystals.
Sp. 6. Acetate of Nickel. A salt which forms rhomboi-
dal crystals of a green colour.
Sp. 7. Oxalate of Nickel. A green powder, scarcely so-
luble in water.
Sp. 8. Arseniate of Nickel. A soluble salt of an apple
green colour.
Sp. 9. Molybdate of Nickel. A white insoluble matter.
Genus XIV. Salts of Zinc.
Most of the salts of zinc are soluble in acids, and may be
formed directly by dissolving zinc in the different acids.
Their solutions are transparent and colourless. Prussiate of
potash occasions a white precipitate, and infusion of nut-
galls no precipitate.
Sp. 1. Nitrate of Zinc. Nitric acid dissolves zinc with
great rapidity. The solution yields flat four-sided prisms,
which deliquesce in the air. They are very soluble both in
282 SALTS CHAP. III.
water and alcohol. When heated they melt, and in a strong
heat the acid is driven off, and the oxide remains.
Sp. 1. Muriate of Zinc. Muriatic acid dissolves zinc
with rapidity. The solution does not crystallize, but yields
gelationous mass which deliquesces in the air. When heated
it sublimes, and forms a white coloured mass composed of
small needles. It is very soluble in water.
Sp. 3. Sulphate of Zinc. diluted sulphuric acid dissolves
zinc with rapidity. The solution, when concentrated, yields
crystals of sulphate of zinc. This salt was discovered at Ra-
melsberg in Germany, about the middle of 16th century,
and introduced into commerce under the name of whiate vi-
triol. Its crystals are four-sided flat prisms. Cold water
dissolves nearly 1 1/2 times its weight of it, and boiling water
dissolves any quantity whatever. When heated it melts, and
at a red heat it parts with most of its acid. It is composed of
28.2 oxidce, 25.8 acid, and 46 water. It contains an excess
of acid.
Sp. 4. Sulphite of Zinc. Sulphurous acid dissolves zinc,
and by evaporation two distinct sets of crystals are obtained.
The first of sulphureted sulphite, consisting of sulphite com-
bined with sulphur. Its crystals are four-sided prisms, solu-
ble both in water and alcohol. In the air they become white,
and deposite an insoluble powder. They absorb oxygen
very slowly when exposed to the athmosphere. The sulphite
of zinc also crystallises. It is less acrid but more styptic in
its taste than sulphurated sulphite. It is less soluble in wa-
ter, and insoluble in alcohol. When exposed to the air it is
speedily converted into sulphate.
Sp. 5. Phosphate of Zinc. This salt does not crystallize,
but yields, when evaporated, a mass like gum arabic.
Sp. 6. Carbonate of Zinc. This salt may be obtained by
precipitating sulphate of zinc by an alcaline carbonate. It
SECT. I. OF BISMUTH. 283
occurs native, and is known by the name of calamine. It is
composed of one part acid and two parts oxide.
Sp. 7. Fluate of Zinc. This salt is soluble in water
and does noQt crystallize.
Sp. 8. Borate of Zinc. A white powder inoaluble in
water.
Sp. 9 Acetate of Zinc. Acetic acid readily dissolves
zinc. The salt crystallizes in rhomboidal or hexagonal plates
of a talky appearance. Its taste is bitter and metallic. It
is soluble in water, and not altered by exposure to the air.
On live coals it burns with a blue flame.
Sp. 10. Succinate of zinc. Foliated crystals scarcely ex-
amined.
Sp. 11. Benzoate of Zinc. Needle-shaped crystals solu-
ble in water and alcohol.
Sp. 12. Oxalate of Zinc A white powder scarcely solu-
ble in water.
Sp. 13. Citrate of Zinc. Small brilliant crystals insoluble
in water.
Sp- 14. Arseniate of Zinc. A white powder, insoluble in
water.
The tungstate, molybdate, and chromate of zinc, are also in-
soluble in water. The first two are white, the last orange
red.
GENUS XV. Salts of Bismuth.
This genus of salts has been but imperfectly examined.
The solutions of them are usually colourless, and when wa-
ter is added to them, a white powder precipitates unless there
be a considerable excess of acid present. Prussiate of pot-
ash occasions a white precipitate, hydrosulphuret of potash
a black precipitate, and infusion of nutgalls an orange pre-
cipitate, when poured into these solutions.
284 SALTS CHAP. III.
Sp. 1. Nitrate of Bismuth. Nitric acid attacks bismuth
with great violence. The solution is colourless, and depo-
sits small white crystals, which are four-sided prisms. They
attract a little moisture in the air. They detonate feebly
on burning coals, loudly when triturated with phosphorus.
When dissolved in water they are decomposed, and a white
powder, which is a subnitrate of bismuth, is deposited.
Sp. 2. Muriate of Bismuth This salt may be obbtained
by dissolving bismuth in nitromuriatic acid, and evaporating
to dryness. It forms small prismatic crystals. It sublimes
when heated, and forms a white mass, which easily melts, for-
merly called butter of bismuth.
Sp. 3 Sulphate of Bismuth. This salt may be obtained
by heating a mixture of bismuth and sulphuric acid. A white
mass remains, decomposed by water.
Sp 4. Sulphite of Bismuth A white powder, insoluble
in water.
Sp. 5. Phosphate of Bismuth. Crystals soluble in wa-
ter, and not altered by exposure to the air. The subphos-
phate of bismuth is a white insoluble powder.
Sp, 6. Acetate of Bismuth. It may be obtained by mix-
inn solutions of nitrate of bismuth and acetate of potash, and
heating the mixture. Small talky crystals of acetate ob bis-
muth gradually precipitate.
Sp. 7. Succinate of Bismuth. Yellow crystallinea plates
soluble in water.
Sp. 8. Benzoate of Bismuth. Needle shaped crystals, not
altered by exposure to the air, soluble in water, and very
sparingly soluble in alcohol.
Sp. 9. Oxalate of Bismuth. A white powder, scarcely
soluble in water.
Sp. 10 Tartrate if Bismuth. A whiate insoluble powder.
Sp. 11. Arseniate of Bismuth. A white tasteless pow-
der.
SECT. II. OF ANTIMONY. 285
der, sometimes having a shade of green; insoluble in water
and nitric acid, but soluble in muriatic acid.
Sp. 12. Molybdate of Bismuth. A white insoluble pow-
der
Genus XVI. Salts of Antimony.
The oxides of antinomy combine but imperfectly with
acids, and the salts which they form have not been very care-
fully examined. Their solutions have usually a brownish
yellow colour, and in most cases a precipitate falls when they
are diluted with water. Prussiate of potash and infusion of
nutgalls throw down a white precipitate, hydrosulphuret of
potash an orange coloured precipitate.
Sp. 1, Nifrate of Antimony. Nitric acid attacks antimo-
ny slowly. Nitrous gas is emmitted, ammonia formed, and
the metal converted into white oxide. A portion of it is dis-
solved, but it does not yield crystals.
Sp. 3. Muriate of Antimony. Muriatic acid dissolves
animony wehn kept long in contact with it, and deposites
small needles. But it is nitro-muriatic acid that is the true
solvent of antimony. The solution has a yellow colour, and
contains, no doubt, oxymuriate of antimony. This salt was
formerly known by the name of butter of antimony. It was
prepared by titurating together one part of antimony and
two parts of oxymuriate of mercury and distilling the mix-
ture. The oxyimuriate of antimony passes over in the state
of a thick fatty mass of a greenish white colour, and often cry-
stallized in four-sided prisms. It is very caustik, becomes
coloured when exposed to the air, and melts at a moderate
temperature.
Sp. 3. Sulphate of Antimony. Sulphuric acid oxidizes
antimoniy at a boiling heat, and converts it into a white mass,
from which water separates the acid.
286 SALTS CHAP. III.
Sp. 4 Sulphite of Antimony. This oompound is preci-
pitated in the state of white powder, by pouring sulphurous
acid into the solution of antimony in muriatic acid. It has
an acrid and astringent taste, melts when heated and is de-
composed.
Sp. 5. Phosphate of Antimony. This salt is soluble in
water: it does not crystallize.
Sp. 6. Acetate of Antimony. Acetic acid dissolves the
oxides of antimony, and forms a salt which crystallizes, and
is soluble in water.
Sp.7. Oxalate of Antimony, Small crystalline grains,
scarcely soluble in water.
Sp. 8. Tartrate of Antimony. This salt does not crystal-
lize, but readily assumea the form of a jelly.
Sp. 9. Arseniate of Antimony. A white powder insolu-
ble in water.
Sp. 10. Tartrate of Potash-and-Antimony. This salt,
usually called tartar emetic, was first made known to chemists
in 1631. It may be prepared by mixing together equal
parts of peroxide of antimony and tartar, and boiling them in
ten times their weight of water, filtering the solution and
evaporating it till a pellicle forms on the surface. It depo-
sites regular crystals of tartar emetic. This salt is white,
crystallizes in regular tetrahedrons, and gradually effloresces
when exposed to the air. It dissolves in about 14 1/4 parts of
cold water, and in about two parts of boiling water. Heat
decomposes it by destroying the acid. It is composed of
35.4 tartaric acid, 39.6 peroxide of antimony, 16.7 potash
and 8.3 water.
GENUS XVII. Salts of Tellurium.
Tellurium is too scarce a metal to expect that its state
should be completely examined. The fixed alkalies throw
SECT. II. OF ARSENIC. 287
down, from their solutions, a white posder, which is re-dis-
solved by an excess of alkali. Prussiate of potash occasions
no precipitate, hydrosulphuret of potash throws down a
brown or blackish precipitate, and infusion of nutgalls a
flaky yellow precipitate.
Sp. 1. Nitrate of Tellurium. Nitric acid readily dissolves
tellurium. The solution is colourless, and not rendered tur-
bid by water. When concentrated, it yields small crystals in
needles.
Sp. 2. Muriate of Tellurium. Nitro-muriatic acid dis-
solves tellurium. Water throws down a white precipitate
from the solution, which is re-dissolved by adding more
water.
Sp. 3. Sulphate of Tellurium. Sulphuric acid dissolves
tellurium. Water precipitates a white powder from the so-
lution.
GENUS XVIII. Salts of Arsenic.
Arsenic is readily converted into an acid, and even its
white oxide has acid properties. Hence it does not form
permanent salts with acids. The acids however dissolve it.
Prussiate of potash occasions a white precipitate in these so-
lutions, and hydrosulphuret of potash a yellow precipitate,
while the infusion of nutgalls produces no change.
Spw 1. Nitrate of Arsenic. Nitric acid dissolves arsenic
with violence, and separates a white powder scarcely soluble
in water.
Sp. 2. Muriate of Arsenic. Muriatic acid dissolves ar-
senic when assisted by heat. It dissolves also the white
oxide, especially if a little nitric acid be added. The muriate
of arsenic may be obtained in small crystalline grains.
Sp. 3. Sulphate of Arsenic. Sulphuric acid oxidises ar-
senic by the assistance of heat, the sulphate is a white pow-
der very imperfectly soluble in water.
288 SALTS CHAP. III.
Sp. 4. Acetate of Arsenic. Acetic acid dissolves the
white oxide of arsenic, and deposits crystals scarcely soluble
in water.
Genus XIX. Salts of Cobalt.
Most of these salts are soluble in water, and the solutions
have a red colour, unless a great excess of acid be present.
Alkalies precipitate a blue powder, prussiate of potash
throws down a brownish yellow precipitate, hydrosulphuret
of potash a black precipitate, infusion of nutgalls a yellowish
white precipitate.
Sp. 1. Nitrate of Cobalt. Nitric acid dissolves cobalt
when assisted by heat, and yields red prismatic crystals, which
deliquesce in the air-
Sp. 2. Muriate of Cobalt. Muriatic acid dissolves co-
balt when assisted by the presence of a little nitric acid. The
solution is green, or, if there be no excess of acid, blue, but
it becomes red when diluted with water. This solution
forms the oldest and best kmown sympathetic ink. It is very
much diluted with water. Characters drawn with it on pa-
per in that state are colourless when cold, but acquires a fine
green colour when heated. When the muriate is heated, it
sublimes in grey coloured flowers which dissolve with great
difficulty in water. The solution consists of common mu-
riate of cobalt.
Sp. 3, Sulphate of Cobalt. Sulphuric acid dissolves the
peroxide of cobalt with difficulty. The solution is red, and
yields needle-form crystals, consisting of rhomboidal prisms,
terminated by dihedral summits. It is soluble in 24 parts of
cold water, insolutie in alcohol, and not altered by exposure
to the air. It is composed of 26 acid, 30 oxide, 44 water.
This salt readily combines with potash and ammonia, and
forms triple salts with each.
SECT. II. OF MANGANESE 289
GENUS XX. Salts of Manganese.
These salts are mostly soluble in water. Alkalies throw
down from them a red or white precipitate, which becomes
black when exposed to the air. Prussiate of potash occa-
sions a yellowish white precipitate, hydrosulphuret of potash
a white precipitate, gallic acid produces no change.
Sp. 1. Nitrate of Manganese. Nitric acid dissolves the
black oxide of Manganese with the assistance of heat, pro-
vided a little sugar be added. The solution is colourless,
and does not yield crystals.
Sp.2. Muriate of Manganese. Muriatic acid readily
dissolves black oxide of manganese, when assisted by heat,
abundance of oxymuriatic acid separating. The solution is
colourless and deposites small crystals of muriate of manga-
nese. These crystals are not easily formed. When obtained
they are harde, very soluble in water, and deliquesce, in the
air. Muriatic acid appears also to combine with red oxide
of manganese, and to form a red solution containing oxy-
muriate of manganese.
Sp. 3. Sulphated Manganese. Sulphuric acid readily dis-
solves the white and red oxides of manganese. Upon the
black it has no action, unless it be assisted by heat. In that
case, oxygen gas is emitted in abundance, and the oxide is
dissolved, being converted into red or white oxide, according
to circumstances. There are two combinations of sulphuric
acid and the oxides of manganese; one with the white, and
another with the red oxide.
1. Sulphate. The solution of this salt is colourless, and
yields, by evaporation, rhomboidal crystals. They have a
very bitter taste, and are decomposed by heat, which drives
off the acid.
T
290 SALTS CHAP. III.
2. Oxysulphate. The solution of this salt has a red co-
lour. It does not readily crystallize, but when evaporated,
easily passes into a jelly. When evaporated to dryness, it
yields red coloured saline crusts, very soluble in water, and
not altered by exposure to the air.
Genus XXI. Salts of Chromium.
The salts of chromium are but very little known. For
the few facts ascertained, we are indebted to Richter, Gordon
and Vauquelin. Prussiate of potash occasions a brown so-
lution in these salts, infusion of nutgalls a brown precipitate,
hydrosulphuret of potash a green precipitate, which a few
drops of nitric acid change to yellow.
When the oxide of chromium is obtained by precipitating
chromate of potash by means of a hydrosulphuret, it dissolves
readily in acids. The solutions have a green colour, and the
compounds are easily decomposed. Nitric acid seems to
convert the oxide into chromic acid. It does not appear that
these solutions are capable of affording crystals. The acids
hitherto tried and found capable of dissolving oxide of chro-
mium are the nitric, muriatic, sulphuric, phosphoric, sulphu-
rous, and oxalic.
GENUS XXII. Salts of Molybdenum.
The salts belonging to this genus are as imperfect at those
belonging to the preceding. None of them seem capable
of crystallizing. But many acids dissolve oxide of molybde-
num, and the solutions are remarkable for the changes of
colour to which they are liable.
Nitric acid dissolves molybdenum with difficulty. If
the quantity of metal be greater than the acid can dissolve,
the solution is blue; but when a small quantity of molybde-
SECT. II. OF URANIUM. 291
num is dissolved in a considerable proportion of acid, the so-
lution isIS yellowish brown.
Muriatic acid does not attack molybdenum, but it dissolves
its oxide and forms a blue coloured solution.
Sulphuric acid dissolves molybdenum when assisted by
heat, and forms a yellowish brown or a blue solution ac-
cording to the proportion of metal acted on.
Genus XXIII. Salts of Uranium.
Most of these salts are soluble in water, and the solution
has a yellow colour. The pure alkalies occasion in these a
jellow precipitate, prussiate of potash a brownish red pre-
cipitate, hydrosulphuret of potash a brownish yellow preci-
pitate, and infusion of nutgalls a chocolate coloured precipi-
tate.
Sp. 1. Nitrate of Uranium. Nitric acid readily dissolves
uranium and its oxides. The solution, when suffciently con-
centrated, yields crystals of nitrate either in hexagonal tables
or in four-sided flat prisms, with a lemon yellow colour and
greenish edges. Water dissolves more than twice its weight
of this salt, and alcohol more than thrice its weight of it.
These liquids, when hot, dissolve any quantity of the salt
whatever. Sulphuric ether dissolves about one-fourth its
weight of this salt. Nitrate of uranium deliquesces in a
moist atmosphere, but when kept at the temperature of 100,
it soon falls to powder. When heated it melts, and, by con-
tinuing the heat, is decomposed. This salt is composed of
61 oxide, 25 acid and 14 water.
By exposing the nitrate to a moderate heat, it is converted
into a lemon-yellow powder, insoluble in water, which is a
sub-nitrate of uranium.
Sp. 2. Muriate of Uranium. Deliquescent crystals of a
yellowish green colour, having the form of four-sided tables.
T 2
292 SALTS CHAP. III.
Sp. 3. Sulphate of Uranium. Sulphuric acid scarcely
acts upon uranium, but it gradually dissolves its oxide, and
the solution yields small crystals of a lemomopn-yellow colour in-
prisms or tables. This salt dissolves in less than its weight
of cold water, and in about half its weight of boiling water,
Alcohol dissolves 1/25th of its weight of it. Heat decompo-
ses it, driving off the acid and water, but a violent tempera-
ture is necessary. This salt is composed of
Acid, 18
Oxide, 70
Water, 12
____
100
Sp. 4. Acetate of Uranium. Acetic acid dissolves oxide
of uranium, and yields beautiful crystals in the form of long
slender transparent four-sided prisms, terminated by four-
sided pyramids.
Genus XXIV. Salts of Tungsten.
This genus of salts is still unknown. None of them,
from the difficulty of obtaining the metal in a state of purity,
having been hitherto examined.
Genus XXV. Salts of Titanium.
The salts of Titanium are, in general, soluble in water, and
the solution is colourless. The alkaline carbonates occasion
a flaky precipitate in these solutions, prussiate of potash a
yellowish brown precipitate, hydrosulphuret of potash a dirty
bottle-green, and the infusion of nutgalls a very bulky blood-
red precipitate. When a rod of tin is plunged into a solu-
tion of titanium, the liquid around it gradutilly assumes a fine
red colour. A rod of zinc occasions a deep blue colour.
SECT. II. OF COLUMBIUM. 293
Sp 1. Nitrate of Titanium. Nitric acid dissolves the
carbonate of titanium, and yields transparent crystals in the
form of elongated rhombs, having two opposite angles trun-
cated, so as to represent six-sided tables-
Sp. 2. Muriate of Titanium. Muriatic acid dissolves
the carbonate of titanium, and forms transparent cubic cry-
stals. From the experiments of Vauquelin and Hecht, it
appears that it is the peroxide of titanium only that combines
with muriatic acid.
Sp. 3. Sulphate of Titanium. Sulphuric acid dissolves
the carbcnate of titanium. The solution does not crystal-
lize; but yields, when evaporated, a white opake gelatinous
mass.
GENUS XXVI. Salts of Columbium.
This genus of salts has been but imperfectly examined.
Hatchett, Ekeberg and Wollaston are the only persons who
have hitherto made experiments on this scarce metal. Sul-
phuric, nitric and muriatic acids scarcely dissolve the oxide
of columbium. The oxalic, tartaric and citric acids dissolve
it readily. The solutions appear to be transparent and co-
lourless. Neither prussiate of potash nor hydrosulphuret of
potash occasion any precipitate in these solutions. But in-
fusion of nutgalls throws down an orange coloured precipi-
tate, provided there be no excess of acid present. But a
slight excess of acid prevents the precipitate from appearing.
Genus XXVII. Salts of Cerium.
The salts of cerium have either a white or a yellow co-
lour, according to the state of oxidizement of the metal.
Their solutions in water have a sweet taste. Hydrosulphu-
ret of potash throws down a white precipitate, prussiate of
T3
294 SALTS CHAP. III.
potash a milk-white precipitate, and infusion of nutgalls no
precipitate whatever. The oxalate of ammonia occasions a
white precipitate, which is insoluble in nitric and muriatic
acids.
Sp. 1. Nitrate of Cerium. Nitric acid dissolves white oxide
of cerium readily: the solution is colourless, crystallizes with
difficulty, retains an excess of acid, and has an austere and
sweet taste. It dissolves the red oxide with difficulty unless
heat be applied. The solution is yellow, and yields small
white crystals, which deliquesce when exposed to the air.
Both of these salts are soluble in alcohol. Heat decom-
poses them, leaving a red coloured oxide.
Sp. 2. Muriate of Cerium. Muriatic acid dissolves red
oxide of cerium when assisted by heat, oxymuriatic gas is ex-
haled, and the solution has a yellowish red colour, which be-
comes lighter the longer the heat is continued. The solu-
tion yields four-sided prismatic crystals of a yellowish white
colour. They are soluble in alcohol, and deliquesce when
exposed to the air. Their taste is astringent and sweet.
Heat decomposes this salt by driving off the acid and water.
Sp. 3. Sulphate of Cerium. Sulphuric acid dissolves the
red oxide of cerium by long digestion, an orange coloured so-
lution is obtained, which yields small octahedral and needle-
form crystals. The colour of these crystals is partly lemon
yellow, partly orange. They are scarcely soluble in water.
Their taste is acid and sweet. When exposed to the air they
soon fall into a vellow powder.
Sulphuric acid dissolves the white oxide of cerium very
readily. The solution is colourless, has a sweet taste, and
yields crystals of sulphate of cerium.
Sp. 4. Carbonate of Cerium. When white oxide of ceri-
um is precipitated from its solutions by an alkaline carbonate,
carbonate of cerium is obtained. It is a granular powder of
CHAP. IV. HYDROSULPURETS. 295
a silvery whiteness, insoluble in water, and composed of 23
acid, 65 oxode, and 12 water.
Sp. 5. Acetate of Cerium. Aeetsc- acid disiolves tli9
white oxide of cerium, and forms small sweet-tasted ci jijtals
JohiUe in water, but mcy spanugiy i,piubM , sUcahal.
CHAPTER IV.
OF HYDROSULPURETS.
Sulphureted hydrogen gas possesses many of the proper-
ties of an acid, and, like acids, it combines with the salifiable
bases, and forms a class of bodies called hydrosulphurets.
These bodies are of considerable importance, as they are fre-
quently employed in chemical analysis, and enable us to se-
parate the metallic oxides from alkalies and earths, because
they throw down almost the whole of them from their solu-
tions in an insoluble state.
The hydrosulphurets are soluble in water, and the solution
is colourless. When the solution is exposed to the air it be-
comes green or greenish yellow. After long exposure to the
air, the solution becomes again limpid and colourless, and on
examination is found only to contain the base of hydrosulphu-
ret combined with sulphuric acid. The solution of the hy-
drosulphurets precipitate almost all the metallic oxides from
their solutions; iron and lead black, antimony orange, arse-
nic yellow, &c.
The hydrosulphurets may be formed by dissolving or dif-
fusing the respective bases in water, and passing a current of
sulphureted hydrogen gas through the liquid till it ceases to
absorb any more. The excess of gas is then driven off by
heat; and the hydrosulphuret may be obtained in a solid
state if required by evaporation. The yellow colour which
T 4
296 HYDROSULPHURETS. CHAP. IV.
these solutions acquire when exposed to the air, is owing to
the decomposition of the sulphureted hyrdrogen by the gradual
absorption of oxygen from the atmosphere.
Sp. 1. Hydrosulphuret of Barytes, When sulphate of
barytes is converted into sulphuret by mixing it with charcoal,
and heating it red hot in a crucible, if boiling water be poured
upon the black mass, and filtered while hot, the green coloured
solution thus obtained yields by evaporation a great number of
crystals. These crystals are hydrosulphuret of barytes. They
are white, and have a silky lustre. They have the form of
scales, and the shape cannot easily be distinguished. This
substance is soluble in water, the solutionQ has a slight tint of
green, its taste is acrid and sulphureous, and when exposed to
the air, is readily decomposed.
Sp. 2. Hydrosulphuret of Strontian, It may be procured
by the same process as the preceding hydrosulphuret, and its
properties are nearly similar.
Sp. 3. Hydrosulphuret of Potatsh. This substance is form-
ed during the solution of sulphuret of potash, and may be
obtained by evaporation. It is transparent and colourless,
and crystallizes in large prisms, not unlike the figure of sul-
phate of soda. Its taste is alkaline, and extremely bitter.
When exposed to the air it soon deliquesces into a liquor of
a syrupy consistence, tinging green all bodies with which it
happens to come in contact. The crystals have no smell at
first, but when they have deliquesced, they emit a fetid odour.
They dissolve both in water and alcohol, and during the evo-
lution, the temperature sinks considerably. Acids drive off
the sulphureted hydrogen with a violent effervescence.
Sp. 4. Hydrosulphuret of Soda, The crystals of this sub-
stance are transparent and colourless, having the figure of
four-sided prisms terminated by quadrangular pyramids. Its
taste is alkaline, and intensely bitter. It is very soluble both
in water and alcohol, and during the solution cold is pro-
CHAP IV. HYDROSULPHURETS. 297
duced. When exposed to the air it deliquesces and aquires
a green colour. Acids drive off the sulphureted hydrogen.
Sp. 6. Hydrosulphuret of Lime. This substance may be
formed by passing sulphureted hydrogen gas through water,
having lime suspended in it. The solution is colourless, and
has an acrid and bitter taste.
Sp. 6. Hydrosulphuret of Ammonia. This compound
may be formed by passing sulphureted hydrogen through li-
quid ammonia. When equal parts of lime, sal ammoniac
and sulphur mixed with a litlle water are distilled in a retort,
a yellow liquid is obtained, usually distinguished by the name
of fuming liquor of Boyle, because first prepared by that
philosopher. This liquid is little else than hydrosulphuret of
ammonia holding an excess of ammonia in solution.
Sp. 7. Hydrosulphuret of Magnesia. This substance
may be formed by passing a current of sulphureted hydrogen
through water in which magnesia is diffused. Its proper-
ties have not been hitherto examined.
Sp. 8 and 9. Hydrosulphuret of Glucina and of Yttria.
From the experiments of Klaproth and Vauquelin, we know
that the hydrosulphurets do not precipitate glucina or yttria
from acids. Hence it is likely that they are capable of com-
bining with sulphureted hydrogen, though these combinations
have not hitherto been examined by chemists.
Neither alumina nor zirconia combine with sulphureted
hydrogen. Hence the hydrosulphurets precipitate these
earths from acids.
When the alkalies and alkaline earths are mixed with sul-
phur and water, and boiled in a glass vessel, a brown coloured
solution is obtained, formerly called liquid liver of sulphur.
At present the term hydrogureted sulphurets is applied to
these solutions. They are conceived to be combinations of
the alkaline bases with sulphur and sulphureted hydrogen at
298 HYDROSULPHURETS. CHAP. IV.
once, and therefore to be triple compounds. The propor-
tion of sulphureted hydrogen is often very small.
This hydrosulphurets precipitate almost all the metals
from their solutions. The precipitates vary in their colour
according lo the metal. The following table exhibits a view
of the colours of the various precipitaes in these cases, as far
as the subject has been investigated.
Metals Precipitated by
Hydrosulphuret of Potash Hydrogureted sulphuret of potash
Gold Black Black
Platinum Black Black
Silver Black Black
Mercury Brown black Brown, becoming black
Palladium Black
Copper Black Brown
Iron Black Black, bcoming yellow
Nickel Black Black
Tin Black Black
Lead Black White becoming black
Zinc White White
Bismuth Black Black
Antimony Orange Orange yellow
Tellurrium Black? Deep brown or black
Arsenic Yellow Yellow
Cobalt Black Black
Manganese White White
Chromium Green
Molybdenum Reddish brown
Uranium Brown Brownish yellow
Titanium Bottle-green Bluish green
Columbium Chocolade
Cerium Brown
SECT. I. ALKALINE SOAPS. 299
CHAPTER V.
OF SOAPS.
The fixed oils have the property of combining with alka-
lies, earths and metallic oxides, and of forming a class of
compounds which have received the name of SOAPS. As
these soaps differ from each other very materially, according
as their base is an alkali, an earth or a metallic oxide, it will
be proper to consider each set separately.
Sect. I. Of Alkaline Soaps.
All or most of the fixed oils are capable of combining
with the alkalies, and forming soap; but the differences
which they produce on the qualities of the soap have only
been observed in a few cases. We can only consider the
different species occasioned by different alkalies.
Sp. 1. Soap of Soda, or Hard Soap. The word soap
(sapo sapon) first occurs in the writings of Pliny and Galen,
and was obviously derived from the old German word secpe.
For the knowledge of this useful compound seems first to
have arisen among the Gauls and Germans.
Hard soap is made by mixing soda of commerce with a
sufficient quantity of lime and water to deprive it of its car-
bonic acid, drawing off the ley, and boiling it with a quan-
tity of olive oil or tallow amounting to six times the weight
of the soda used. When sufficiently boiled, a quantity of
common salt is added, which induces the soap to separate
from the water, and to float upon the surface. Though in
this country, where kelp is usually employed at least in part
to furnish the soda, the quantity of common salt present
from the beginning is usually suficient without any addition.
300 SOAPS. CHAP. V.
The soap is then poured into proper vessels, and when cold
cut into parallelopipedes. Whale oil has been tried, but found
improper for making hard soap. In this country tallow is
usually employed, in France and the south of Europe olive
oil is used. When oil or tallow alone is used, the soap has
a whitte colour; but it is usual to add a quantity of rosin,
which gives it a yellow colour and a softer consistance. It
is then called yellow soap.
The appearance and properties of common soap are so well
known that it is unnecessary to describe it. The various
uses to which it is applied are equally well known. It dis-
solves in alcohol, but is precipitated by the addition of water.
With water it readily mixes, though it does not, strictly speak-
ing, dissolve in that liquidy as most of it is separated by the
filter. A specimen of white soap analized by Darcet, Le-
lievre and Pelletier was composed of
60.94 oil
8.56 alkali
3O.50 water
_____
100.00
Sp. 2. Soap of Potash or soft Soap. When potash is
substituted for soda, the soap never hardens by cooling, but
remains always soft. Whale oil is said to be employed in
the manufacture of soft soap. A little tallow is also added,
which, by peculiar management, is dispersed through the
soap in fine white spots. The properties of soft soa are too
well known to need description. It is the only species of
soap with which the ancients were acquainted. It is but lit-
tle used in this country in comparison of hard soap.
Sp. 3. Soap of Ammonia. This soap may be formed by
digesting carbonate of ammonia on soap of lime. Its taste is
more pungent than that of common soap. It mixes sparingly
with water, but pretty soluble in alcohol. The substance
SECT. III. METALLIC SOAPS. 301
employed as an external application by surgeons under the
name of volatile liniment, is scarcely any thing else than this
soap.
Sect. II. Of Earthy Soaps.
The earthy soaps differ essentially from the alkaline in be-
ing insoluble in water, and therefore incapable of being used
as detergents. They are formed whenever a solution of com-
mon soap in water is mixed with that of an earthy salt.
Hence the reason that all waters holding an earthy salt in so-
lution are unfit for washing. They decompose the common
soap, and form a soap insoluble in water. Such waters are
called hard, and are very frequent, especially in pit wells.
All the earthy soaps are insoluble in alcohol, except soap
of magnesia, which dissolves both in alcohol and fixed oils.
The earthy soaps are all white, and require a considerable
heat to melt them.
Sect. III. Of Metallic Soaps.
The metallic soaps may be formed in the same way as the
earthy soaps. They are insoluble in water, and cannot be
used as detergents; but several of them are soluble in alco-
hol and in fixed oils. The greater number of them have
a white colour; but soap of cobalt is of a leaden colour,
soap of iron reddish brown and soap of copper green. Ber-
thollet who examined these soaps has recommended some of
them as paints.
Some of the metallic oxides, as those of mercury, lead
and bismuth, when mixed with fat oils and water and boiled,
form an intimate combination with the oil, used by surgeons
under the name of plaster. Litharge is the metallic sub-
stance commonly used for these compounds; and olive oil an-
302 VEGETABLE SUBSTANCES. DIV. IV,
wers better than any other hitherto tried. These plasters
soften when heated, and adhere very strongly to the skin when
spread thin upon linen or leather, but they may be drawn off,
by using the requisite force, without leaving any portion ad-
hering to the skin. In these properties their excellence con-
sists.
DIVISION IV.
OF VEGETABLE SUBSTANCES.
The substances hitherto found in the vegetable kingdom,
all of them at least which have been examined with any de-
gree of accuracy, may be reduced under four heads: I. Sub-
stances soluble in water, at least in some state or other, and
vhich, in general, are solid and not remarkably combustible.
II. Substances, either fluids, or which melt when heated, and
burn like oil. They are all insoluble in water; but, in ge-
neral, they dissolve in alcohol. III. Substances neither so-
luble in water nor alcohol nor ether, and which have a fibrous
or woody texture. IV. Substances which belong to the mi-
neral kingdom, which occur only in small quantify in vege-
tables, and may therefore be considered as extraneos or fo-
reign. The following table exhibits a view of the different
vegetable substances hitherto discovered, arranged under their
respective heads.
DIV. IV. VEGETABLE SUBSTANCES. 303
I. 1 Acids.
2 Sugar.
3 Sarcocoll.
4 Asparagin.
5 Gum.
6 Mucus.
7 Jelly.
8 Ulmin.
9 Inulin.
10 Starch.
11 Indigo.
12 Gluten.
13 Albumen.
14 Fibrin.
15 Bitter principle.
16 Extractive.
17 Tannnin.
18 Narcotic prineiplf.
II. Oleoform.
1 Fixed oil.
2 Wax.
3 Volatile oil.
4 Camphor.
5 Bird-lime.
6 Resins.
7 Guaiacum.
8 Balsams.
9 Gum resins.
10 Caoutchouc.
III. Fibraus.
1 Cotton.
2 Suber.
3 Wood.
IV. Extraneous.
1 Alkalies.
2 Earths.
3 Metals.
The properties of these differens substances form the subject
of the following chapters.
304 VEGETABLE SUBSTANCES. CHAP. I.
CHAP. I.
OF ACIDS.
The acids found ready formed in the vegetable kingdom,
are the following;
1 Acetic. 4 Citric. 7 Benzoic.
2 Oxalic. 5 Malic. 8 Prussic.
3 Tartaric. 6 Gallic. 9 Phosphoric.
The sulphuric, nitric and muriatic acids are likewise to be
found in vegetables combined with alkalies, but only in small
quantities.
1. Acetic acid has been detected in the sap of different
trees, in the acid juice of the cicer parietinum, and in the
sambucus niger.
2. Oxalic acid in the state of superoxalate of potash exists
in the leaves of the oxalis acetosella, oxalis corniculata, and
different species of rumex. It exists uncombined in the juice
of the cicer parietinum. In the state of oxalate of lime it is
found in rhubarb, and in the roots and barks of a great va-
riety of plants.
3. Tartaric acid is found in the pulp of the tamarind, in
the juice of grapes and mulberries; likewise io the rumex
acetosa, rhus coriaria, rheum rhapontikum, agave americana,
triticum repens, leontodon taraxacum. In most of these
plants it is in the state of supertartrate of potash.
4. Citric acid is found intermixed with other acids in the
juice of oranges and lemons, and in the berries of vaccinium
oxycoccos, vaccinium vitis idaea, prunus padus, solanum dul-<(i>
CHAP. I. ACIDS. 305
camara, rosa canina. Mixed with other acidss it is common
in many fruits. Citrate of lime is found in the onion.
5. Malic acid is very common in plants. It was found by
Scheele, unmixed with any other acid, in the fruits of the
following plants; the apple, berberis vulgaris, prunus do-
mestica, prunus spinosa, sambucus nigra, sorbus aucuparia.
Braconnot has found it in the leaves of most vegetables
which he examined. Vauquelin found it in the state of su-
permalat of lime in the following plants; sempervivum tec-
torum, sedum album, sedum acre, sedum telephium, arum ma-
culatum, and different species of crassula and mesembrian-
themum. Mixed with citric acid, it constitutes the acid of
the following fruits; gooseberries, currants, bleaberries, cher-
ries, strawberries, cloudberries, raspberries. Sometimes, as
in the tamarind, it is mixed with tartaric acid.
6. Gallic acid has been found in the bark of most
astringent tasted trees; as, elm, oak, horse-chesnut, beech,
willow, elder, plum, sycamore, birch, cherry tree, mouutain-
ash, poplar, hazel, ash, sumach.
7. Benzoic acid has been found only in a few vegetable
substances, to which the name of balsam has been given.
The chief of these are benzoin, balsam of tolu, storax, dra-
gon's blood.
8. Prussic acid has been found in the leaves of the lauro-
cerasus, in peach blossoms, in the flowers of the sloe, in the leaves of the bay-leaved willow (salix pentandra), and in
most bitter tasted kernels.
9. Phosphoric acid is very common in plants, but only in
small quantities, and it is usually combined with potash or
lime. Phosphate of potash exists in barley and other species
of corn, so does phosphate of lime. Both of these salts exist
in the leaves of many trees.
U
306 VEGETABLE SUBSTANCES. DIV. IV.
CHAP. II.
OF SUGAR.
Common sugar is obtained from the juice of the arundo
sacharifera or sugar cane, a plant cultivated from time im-
memorial in India and China. It was unknown in Europe
till after the conquests of Alexander the Great. The culti-
vation of the sugar cane was gradually introduced into Sicily
and Spain, and after the discovery of America, it was im-
ported to the West Indian islands, where it has been cultiva-
ted to a great extent. Sugar has, in consequence, become
a necessary of life among the modern nations of Europe.
The juice is extracted by passing the cane between iron
rollers, and immediately run into a flat copper cauldron, where
it is mixed with a little lime and heated to the temperature
of 140. A thick viscid scum collects on the surface, which
is left unbroken, and the clear liquid drawn from below and
introduced into a large boiler. Here it is boiled briskly, the
scum, as it forms, being constantly removed. From this first
boiler it is passed into a second, from that to a third and
fourth, in each of which the boiling is continued. When
sufficiently concentrated, it is poured into a large wooden
vessel called the cooler, where it crystallizes or grains as it
cools. From the cooler it is taken and put into hogsheads,
having a hole in the bottom, into which de stalk of a plan-
tain leaf is thrust. Through these holes the molasses drain
into a receiver. The sugar, thus cleared, is brought to this
country under the name of raw sugar. It is refined by so-
lution in water, clarified by bullock's blood, boiled down and
poured into earthen cones, having a hole in the apex which
is undermost. The base of the cone is covered with
moist clay. From this the water slowly penetrates through
CHAP. II. SUGAR. 307
the sugar, and carries off the impurities. In this state it is
white, and is known by the name of loaf sugar.
From the experiments of Proust, it appears that sugar
cane juice contains gluten, gum, extractive, a little malic
acid, sulphate of lime, and two species of sugar. The ob-
ject of the process is to remove all the substances except the
crystallizable sugar.
Sugar is a firm white substance of an extremely sweet
taste, but destitute of smell. It is but little altered by ex-
posure to the atmosphere, though in damp air it is liable to
become moist.
Cold water dissolves nearly its own weight of sugar, and
boiling water dissolves any quantity whatever. The solution
constitutes a thick, ropy, adhesive fluid called syrup. When
syrup is sufficiently concentrated, and kept in open vessels in
a hot place, the sugar gradually crystallizes. The crystals
are four or six-sided prisms, terminated by two-sided, and
sometimes by three-sided summits.
The specific gravity of white sugar is 1.6065. It is not
acted on by oxygen gas, by the simple combustibles, by azote
or by the metals. The alkaline earths combine with sugar
and form a compound which has a bitter and astringent taste.
Sugar facilitates the solubility of lime and strontian in water;
but barytes appears to act with more energy, and to occasion
decomposition of sugar. The fixed alkalies combine with
sugar, and form compounds similar to those formed by the
alkaline earths.
The acids dissolve sugar, and the more powerful mineral
acids decompose it. Nitric acid dissolves it with efferves-
cence, converts one-half of its carbon into carbonic acid, the
residue assumes the form of water and oxalic acid. A
quantity of malic acid is also evolved. 100 grains of sugar
yield, by this treatment, 58 grains of oxalic acid. Oxymu-
riatic acid, according to Chenevix, converts sugar into citric
U 2
308 VEGETABLE SUBSTANCES. DIV. IV.
acid. Sulphuric acid decomposes sugar, water and acetic
acid are formed, and a great quantity of charcoal evolved.
Sugar dissolves in about 16 parts of boiling alcohol. If
the solution be set aside, the sugar is gradually deposited in
elegant crystals,
The hydrosulphurets, sulphurets and phosphurets of alka-
lies and earths seem to have the property of decomposing su-
gar, and of bringing it to a state not very different from that
of gum.
When heat is applied to sugar, it melts, swells, becomes
brownish black, emits air bubbles, and emits the smell of ca-
romel. At a red heat it bursts into flames with a kind of
explosion. When distilled, there comes over water; an acid
liquid called pyromucous acid, now known to be the acetic
mixed with a little empyreumatic oil; an oil; and a bulky
charcoal remains in the retort. During the distillation a con-
siderable quantity of carbonic acid and heavy inflammable air
come over.
From the experiments of Lavoisier, compared with some
of my own, it appears that sugar is composed of
64 oxygen
28 carbon
8 hydroge
___
100
It appears from the recent researches of chemists, that
there exist various species of sugar differing from each other
in their properties. The most important of these are the
following: common sugar, liquid sugar, sugar of grapes, su-
gar of beet, manna.
Common sugar is the substance described in the preced-
ing part of this chapter. It is obtained from the sugar cane.
The properties of the sugar of the maple are not known
to differ from those of common sugar.
CHAP. II. SUGAR. 309
Liquid sugar was first pointed out by Proust. It exists in
a variety of fruits and vegetable juices. It does not crystal-
lize, and can only be exhibited in a liquid state. It is more
soluble is alcohol than common sugar. It exists in the juice
of the sugar-cane, and constitutes no inconsiderable portion
of molasses.
Sugar was first extracted from grapes by the Duc de Bul-
lion. They often yield, according to Proust, from 30 to 40
per cent, of sugar. He extracted it by saturating the acids
contained in the juice of grapes with potash, boiling it down
to one half, and setting it aside. Several of the salts subsid-
ed. The juice was then mixed with blood, heated, scummed,
filtered, and boiled down to a syrup. Crystals of raw sugar
gradually form which may be purified by repeating the pro-
cess. This sugar is white, but inferior in consistence to com-
mon sugar. It is not so sweet, and resembles sugar from
honey. Like it, the sugar of grapes crystallizes in sphericles.
It is less soluble than common sugar, and does not go so far
in sweetening liquids.
Sugar was first extracted from the beet by Margraff. Many
experiments were afterwards made upon the extraction by
Achard and other German philosophers, and attempts made
to substitute the sugar of beet for common sugar, but
it could not be obtained at a low enough price. It has
a greater resemblance to common sugar than the sugar
of grapes; but is distinguished by a certain nauseous bitter
taste, owning perhaps to the presence of some foreign sub-
stance.
Manna is the produce of various trees, but is chiefly obtain-
ed from the fraxinus ornus, a species of ash, which grows
abundantly in Sicily and Calabria. It partly exudes sponta-
neously during the summer months, and is partly obtained by
incisions. The juice gradually concretes into a solid mass,
rr it is dried in the sun or in stoves. Pure manna is very light,
510 VEGETABLE SUBSTANCES. DIV. VI.
and appears to consist of a congeries of fine capillary crys-
tals. Its taste is sweety and it leaves a nauseous impression
in the mouth. Hot alcohol dissolves it readily, and, on
cooling, deposites about 5-8ths of the manna in the state of
a fine light spongy crystalline mass, bearing some resemblance
to camphor. This deposite may be considered as pure man-
na. It has an agreeable sweet taste, and instantly melts on
the tongue like snow in warm water. When dissolved in ni-
tric acid, it yields oxalic acid. The saclactic appears also
when the manna is impure. Manna does not undergo the
vinous fermentation, and seems in consequeuce incapable of
furnishing alcohol. Manna itself seems to be formed from
uncrystallizable sugar by a species of fermentation.
The plants yielding sugar are very numerous. It seldom
exudes spontaneously from vegelables, though this is some-
times the case.
CHAP. III.
OF SARCOCOLL.
This substance, which has hitherto been coufounded with
the gum resins, though its properties are very different, ex-
udes spontaneously from the penaea sarcocolla, a shrub said
by botanical writers to be indigenous in the north-eastern
parts of Africa. It may be obtained pure by solution in al-
cohol, filtration and evaporation.
Pure sarcocoll has a brown colour, is semitransparent, and
very like gum in appearance. Its specific gravity is 1.2684.
It has a sweet taste, but leaves an impression of bitterness.
It dissolves readily both in water and alcohol. The solution
is yellow. It does not crystallize. When heated, it sof-
tens, but does not melt. It emits a slight smell of caromel.
CHAP. IV. ASPARAGIN. 311
When strongly heated it blackens, and assumes the consist-
ence of tar, emitting a heavy white smoke, having an acrid
odour. Nitric acid dissolves it, but does not convert it into
tannin. From these properties sarcocoll appeals to be inter-
mediate between gum and sugar.
CHAP. IV.
OF ASPARAGIN.
I give this name to a substance discovered in the juice of
asparagus by Vauquelin and Robiquet. The juice was eva-
porated to the consistence of a syrup, and set aside. Crys-
tals of asparagin formed in it spontaneously.
These crystals are white and transparent, and have the
figure of rhomboidal prisms. The greater angle of the
rhomboidal base is 130.
Asparagin is hard and brittle. Its taste is cool, and slight-
ly nauseous, so as to occasion a secretion of saliva.
It dissolves readily in hot water, but in cold water only
sparingly. Alcohol does not dissolve it.
The aqueous solution does not affect vegetable blues. Nei-
ther infusion of nutgalls, acetate of lead, oxalate of ammonia,
muriate of barytes, nor hydrosulphuret of potash occasion any
change in it. When triturated with potash no ammonia is
disengaged. The potash seems to render it more soluble in
water.
When heated it swells, and emits penetrating vapours, af-
fecting the eyes and nose like the smoke of wood. It leaves
a large portion of insipid charcoal, which, when incinerated,
gives scarcely a trace of residue.
Nitric acid dissolves it with the evolution of nitrous gas.
The solution has a yellow colour, and a bitter taste like that
U4
312 VEGETABLE SUBSTANCES. DIV. IV.
of animal sabstances in the same acid. Lime disengages from
it a considerable qluantity of ammonia.
CHAP. V.
OF GUM.
There is a thick transparent tasteless fluid, which some-
times exudes from certain species of trees. It is very adhe-
sive, and gradually hardens without losing its tranaparency,
but easily softens again when moistened with water. This
exudation is known by the name of gum. The gum most
commonly used is that which exudes from different species
of the mimosa, particularly the nilotica, and is known by the
name of gum arabic.
Gum is usually obtained in small pieces like tears, mode-
rately hard, and somewhat brittle when cold, so that it can
be reduced by pounding to a fine powder. When pure it is
colourless; but it has commonly a yellowish tinge, and it is
not destitute of lustre. It has no smell. Its taste is insipid.
Its specitic gravity varies from 1.3161 to 1.4817.
It is not altered by exposure to the air, but the light of the
sun makes it assume a white colour. Water dissolves it in
large quantities. The solution, which is known by the name
of mucilage, is thick and adhesive. It is often used as a
paste, and to give stiffness and lustre to linen. When eva-
porated, the gum is obtained unaltered. Mucilage may be
kept for years without undergoing putrefaction: at last,
however, the odour of acetic acid becomes perceptible in it.
When gum is exposed to heat it softens and swells, but
does not melt; it emits air bubbles, blackens, and at last
when nearly reduced to charcoal, emits a low blue flame.
CHAP. V. GUM. 313
A white ash remains, consisting chiefly of the carbonates of
lime and potash.
Gum does not appear to be acted on by oxygen gas, the
simple combustibles, azote or the metals. The only me-
tallic salts which occasion a precipitate when dropt into mu-
cilage, are nitrate of mercury, and acetate of lead, both of
which occasion a white precipitate. The supercetate of
lead occasions no change. When oxymuriate of iron is
poured into a strong mucilage, the whole is converted into a
brown semitransparent jelly, which is not readily dissolved
by water.
Neither the alkalies, alkaline earths, nor earthy salts occa-
sion any precipitate in mucilage; except silicated potash,
which throws down a white flaky precipitate, even though
very much diluted. The liquid remains transparent and co-
lourless. Silicated potash is by far the most delicate test of
gum that I have yet met with.
Liquid potash first converts gum into a substance not un-
like curd, and then dissolves it. The solution is of is light
amber colour, and transparent. When kept long, the gum
falls again in the state of curd. Alcohol throws down the
gum in white flakes, still soluble in water, but it retains the
potash obstinatly, and is much more friable than before.
Lime water and ammonia likewise dissolve gum, and it may
be afterwards separated little altered.
The vagetable acids dissolve gum without alteration, the
strong acids decompose it. When thrown into sulphuric
acid it blackens, and is decomposed. Charcoal is evolved,
amounting to nearly one-third of the gum; some artificial
tannin may be detected, and water and acetic acid are like-
wise formed. When gum is dissolved in strong muriatic
acid, in brown solution is obtained, which becomes perfectly
transparent when diluted with water, while at the same time
some charry matter falls. If the solution be saturated with am-
314 VEGETABLE SUBSTANCES. D1V IV.
monia evaporated to dryness, and the residue digested in al-
cohol, the alcohol assumes a deep brown colour, and dis-
solves the whole except a little sal ammoniac. The gum
now bears some resemblance to sugar in its properties, at
least when heated it melts, and gives out a very strong smell
of caromel.
Oxymuriatic acid, according to Vauquelin, converts gum
into citric acid. If nitric acid be slightly heated upon gum
till it has dissolved it, and till a little nitrous gas has exhaled,
the solution on cooling deposites saclactic acid. Malic acid
is formed at the same time, and if the heat be continued, the
gum is at last changed into oxalic acid.
Gum is insoluble in alcohol. It is precipitated from wa-
ter by alcohol. It is insoluble also in ether and in oils; but
when triturated with a little oil, it renders the oil miscible
with water.
Gum readily combines with sugar by mixing together the
solutions of both in water, and evaporating to dryness. Al-
cohol digested on the residuum, dissolves most of the sugar,
a matter remains which still has a sweetish taste and resem-
bles the substance of which the nests of wasps are formed.
When gum is distilled in a retort, the products are water
impregnated with acetic acid and oi1, or pyromucous acid, as
it was formerly called, a little empyreumatic oil, carbonic
acid gas, and heavy inflamable air. There remains in the
retort charcoal containing lime and phosphate of lime. Gum
yields also traces of iron when its ashes are examined, but no
fixed alkalih or sulphur can be detected.
The species of gum at present known are numerous, and
a more rigid examination of the vegetable kingdom will
doubtless discover a still greater number. The most re-
markable are gum arabic, gum senegal, gum tragacanth, and
cherry tree gums.
4
CHAP. V. GUMS. 315
Gum arabic exudes from the mimosa nilotica. It is the
species descrined in the preceding part of this chapter.
Gum senegal, brought from the island of that name on the
coast of Africa, often supplies the place of gum arabic in the
shops. It is in larger masses than the arabic, and its colour
is darker, but in other respects its properties are the same.
Gum tragacanth is the produce of the astragalus tragacan-
tha, a thorny shrub which grows in Candia, and other islands
of the Levant. It exudes about the end of June, from the
stem and larger branches, and soon dries in the sun. It is
in the state of whitish vermiform pieces, not nearly so trans-
parent as gum arabic, and is exceedingly different from it in
many of its properties. When put into water, it slowly im-
bibes a large quantity of the liquid, and forms a soft but not
fluid mucilage. If the quantity of water be more than the
gum can imbibe, the mucilage forms an irregular mass,
which does not unite with the rest of the liquid. When tra-
gacanth is treated with nitric acid, it yields abundance of sac-
lactic acid, malic acid, and oxalic acid, but not the least
trace of artificial tannin. When the mucilage of gum tra-
gacanth is triturated in a mortar with water, it forms a ho-
mogeneous solution. This solution forms a precipitate with
acetate and superacete of lead and oxymuriate of tin.
Nitrate of mercury throws down a slight precipitate; but
neither oxysulphate of iron, nor silicated potash produce
any effect. These properties show it to differ very materi-
ally from gum arabic in its properties.
The prunus avium, the common cherry and plum-trees,
and the almond and apricot likewise yield a gum which ex-
udes in great abundance from natural or artificial openings
in the stem. It is of a reddish brown colour, in large masses,
at first much softer than gum arubic, but, by keeping, it be-
comes very hard. When put into water it gradually swells,
and is converted into a semi-tansparent reddish brown jelly.
316 VEGETABLE SUBSTANCES. DIV. IV.
Part of it dissolves, but a part of it remains in the state of
jelly, and refuses to dissolve even when boiled in water for
some time. The gum dissoved is not precipitated by alco-
ho1 or by silicated potash. Acetate of lead produces no
inmediate effect, but on standing the whole becomes opake,
and a precipitate at last subsides. Oxymuriate of tin causes
the liquid to gelatinize immediately. The superacetate of
lead and the nitrite of mercury produce no effect. When
treated with nitric acid, it yields a portion of saclactic acid.
These properties show a marked difference between cherry-
tree gum and the other species.
CHAP.VI.
OF MUCUS.
The substances to which I give the name of mucus, have
been hitherto considered as varieties of gum; but, from the
recent experiments of Dr Bostock, it appears that their
properties differ so much from those of gum as to entitle
them to a separate place as vegetable principles. They are
very numerous; existing in the roots, leaves and seeds of a
great variety of plants. They scarcely ever separate sponta-
neously, but may be obtained artificially in a state of tole-
rable purhy. Only a few of them have been examined.
The rest are classed with these only from analogy.
Linseed yields mucus in a state of tolerable purity. When
it is infused in ten times its weight of water, a fluid is obtain-
ed of the consistence of white of egg, which has the adhesive
qualities of mucilage of gum arabic. When mixed with al-
cohol, the mucus is separated in white flocks, but the liquid
does not become opake and milky like mucilage of gum ara-
bic when mixed with alcohol. Acetate of lead throws down
CHAP. VII. JELLY. 317
a copious dense precipitate. Superacetate of lead and oxy-
muriate of tin render the liquid opeke, and also throw down
a precipitate. Nitrate of mercury occasions a very slight
precipitate, while muriate of gold, oxysulphate of iron and
silicated potash produce no sensible effect whatever. No
change is produced by the infusion of ńutgalls.
Quince seeds and the root of the hyacinth yield a mucus
with the same properties with some slight shades of diffe-
rence, owing probably to the presence of foreign bodies
mixed with it. The roots of the hyacinth, vernal squill,
white lilly, comfrey and salop, contain so much mucus that,
when dried, they may be substituted for gum arabic. The
leaves of the malva sylvestris, many of the fuci, and a good
many of the stringy lichens, contain likewise abundance of
mucus. In short, it is one of the most common of the ve-
getable principles. Probably there are few plants which do
not yield some portion of it.
CHAP. VII.
OF JELLY.
If we press out the juice of blackberries, currants and
many other fruits, and allow it to remain for some time in a
state of rest, it coagulates into a tremulous soft substance,
well known by the name of jelly. When it is washed with a
small quantity of water and then dried, we obtain it in a state
approaching to purity.
It is nearly colourless, scarcely soluble in cold water, but
very soluble in hot water, and, when the solution cools, it
again coagulates into a jelly. When long boiled, it loses the
property of gelatinizing, and becomes analogous to mucilage.
When dried it becomes transparent. When distilled it yields
318 VEGETABLE SUBSTANCES. DIV. IV.
the same products as gum. It seems very intimately con-
nected with gum; but, as it has never been obtained in a
state of complete purity, we are but imperfectly acquainted
with its properties.
CHAP. VIII.
OF ULMIN.
I give this name to a singular substance lately examined
by Klaproth. It exuded spontaneously from the trunk of a
species of elm, supposed to be the ulmus nigra, and was
sent to Klaprolh from Palermo in 1802.
Externally it has a good deal of resemblance to gum. It
is solid, hard, of a black colour, and has considerable lustre.
Its powder is brown. It dissolves readily in the mouth, and
has an insipid taste.
Water dissolves it. The solution has a brown colour.
Though very strong, it is not in the least adhesive or ropy, nor
does it answer as a paste. It is insoluble in alcohol and
ether, and is partially precipitated from water by alcohol.
When a few drops of nitric acid are added to the aqueous
solution of ulmin, it becomes gelatinous, loses its brown co-
lour and a light brown substance precipitates. This precipi-
tate is soluble in alcohol, and possesses the properties of a
resin. Oxymuriatic acid produces nearly the same effect.
Thus it appears that ulmin, by the addition of a little oxy-
gen, is converted into a resinous substance. This property
is very singular. Hitherto the volatile oils were the only
substances known to assume the form of resins. That a
substance soluble in water should assume the resinous form
with such facility is very remarkable.
CHAP. IX. INULIN. 319
Ulmin when burnt emits little smoke or flame, it leaves a
spongy but firm charcoal, which yields, when concentrated, a
little carbonate of potash.
CHAP. IX.
OF INULIN.
I give this name to a substance discovered by Rose in the
root of the inula helenium or elecampane. When the root
of this vegetable was boiled in water, the decoction, after
standing some hours, deposites the inulin in the form of a
white powder like starch.
It is insoluble in cold water. By trituration the inulin is
uniformly diffused, and glives the liquid an opal appearance,
but it soon falls down in the state of a white powder, leav-
ing the liquid quite transparent.
It dissolves readily in hot water. One part of inulin in
four parts of boiling water formed a solution which passed
readily through the filter. After some hours the greater part
of the inulin precipitates from the water in the form of a
white powder.
When the aqueous solution of inulin is mixed with an
equal bulk of alcohol, no change takes place for some time;
but the inulin soon separates and falls to the bottom in the
state of a bulky white powder. A solution of gum arabic,
when treated in this manner, remains milky for days without
any precipitate falling.
When thrown upon burning coals it melts as readily as su-
gar, and emits a thick white smoke not unpleasantly pungent,
and similar in odour to that of burning sugar. The residue
which is but small, sinks into the coal. Starch emits a simi-
lar smoke, but leaves a more bulky residue. When exposed
320 VEGETABLB iUBSTANCES. Div. IV
to a red heat, inulin burns with a vivid flame, and leaves a
very small coaly residue.
When distilled, inulin yields a brown acid liquid, having
the smell of pyromucous acid, but not a trace of oil.
When inulin is treated with nitric acid, it yields malic and
oxalic acids, or acetic acid if too much nitric acid be em-
ployed. But no saclactic acid is formed as happens with the
gums, neither is any of the waxy matter separated, which
makes its appearance when starch is digested in nitric acid.
CHAP. X.
OF STARCH.
If a quantify of wheat flour be formed into a paste, and
then held under a very small stream of water, knedding, con-
tinually till the water runs off from it colourless, the flour
by this process is divided into two distinct constituents. A
tough substance of a dirty white colour, called gluten, re-
mains in the hand; the water is at first milky but soon depo-
sites a white powder, which is known by the name of starch.
The starch obtained by this process is not quite free from
gluten. Hence it is not very white, and has not that crystal-
lized appearance which distinguishes the starch of commerce.
Manufacturers employ a more economical and more effica-
tious process. Wheat is steeped in water till it gives out a
milky juice when squeezed, it is then put into coarse linen
sacks which are subjected to pressure in a vessel of water
till the whole starchy matter is separated. The sack and its
contents are then removed. The water containing the starch
gradually ferments. Vinegar and alcohol are formed in it,
partly, no doubt, at the expence of the starch. The vine-
gar thus formed dissolves all the impurities, and leaves no-
CHAP X. STARCH. 321
thing behind but the starch. It is poured off, and the starch
being edulcorated with water, is dried with a moderate heat.
During the drying, it usually splits into columnar masses,
which have a considerable degree of regularity.
Starch was well known to the ancients. According to
Pliny, the method of manucturing it was discovered by the
inhabitants of Chios.
Starch has a fine white colour, and is usually concreted in
four-sided prisms. It has scarcely any smell, and very little
taste. When kept dry, it contuiues for a long time uninju-
red, though exposed to the air.
It does not dissolve in cold water, but very soon falls to
powder, and forms a kind of emulsion. It dissolves in boil-
ing water, and forms a kind of jelly, which may be diffused
through boiling water: but when the mixture is allowed to
stand a sufficient time, the starch slowly precipitates to the
bottom. The subsidence takes place even when 90 parts of
water are employed to dissolve one of starch; but, in that '
case, at least a month elapses before the starch begins to
precipitate. The solution is glutinous in proportion to the
quantity of starch. Linen dipt into it and suddenly dried,
acquires a considerable degree of stiffness. When the solu-
tion is evaporatcd to dryness, a brittle opake mass is obtain-
ed, differing in appearance from common starch, but exhibit-
ing nearly the same properties with re-agents. Hence the
apparent difference is probably owing to a portion of water
remaining united to the boiled starch. When the solution of
starch is left exposed to damp air, it soon loses its consisten-
cy, acquires an acid taste, and becomes mouldy on the sur-
face.
Starch does not dissolve, nor even fall to powder in alco-
hol. Neither does it dissolve in ether.
Neither oxygen gas nor the simple combustibles have any
marked action on starch. The metals and their oxides have
X
322 VEGETABLE SUBSTANCES. DIV. IV.
little affinity for it. Acetate of lead throws it down from
water, but the superacetate has no effect upon it. Accord-
ing to Dr Bostock, it is precipitated also by oxyimuriate of
tin; but in my trials, I obtained no precipitate with that salt
in a decoction containing one-ninetieth of its weight of starch.
No other metallic salt tried produced a precipitate in this
decoction.
Neither lime nor strontian water precipitate the decoction
of starch; but barytes water throws down a copious white
flaky precipitate. It is dissolved by muriatic acid, but ap-
pears again on standing, unless a considerable excess of acid
be added. Neither muriate of barytes nor silicated potash
occasion any precipitate in the decoction of starch.
When starch is triturated in a hot infusion of nutgalls, a
complete solution is effected. This solution is transparent, and
rather lighter coloured than the infusion of nutgalls employed.
When this solution cools it becomes opake, and a copious
curdy precipitate falls. A heat of 120 re-dissolves this pre-
cipitate and renders the solution transparent, but it is depo-
sited again as the liquid cools. This property is characteris-
tic of starch. The infusion of nutgalls throws it down from
every solution, but the precipitate is re-dissolved by heating
the liquid to 120. The precipitate is a compound of tannin
and starch, and is least soluble when composed of about
three parts starch and two parts tannin. It has a brownish
yellow colour, is semi-transparent, has an astringent taste,
and feels glutionous between the teeth like gum.
When potash is triturated with starch and a little water
added, the whole assumes, on standing, the appearance of a
semi-transparent jelly. On adding water, an opal coloured
solution is obtained, from which the starch is readily thrown
down by an acid. When muriatic acid is employed, a pecu-
liar aromatic odour is perceived. The decoction of starch
CHAP. X. STARCH. 323
is neither altered by potash, carbonate of potash nor ammo-
nia.
When starch is thrown into any of the mineral acids, at
first no apparent change is visible; but, if an attempt is made
to reduce the larger pieces, while in acids, to powder, they
resist it and feel exceedingly tough and adhesive, Sulphuric
acid dissolves it slowly, and at the same time a smell of sul-
phuric acid is emitted, and such a quantity of charcoal evol-
ved, that the vessel may be inverted without spilling, any of
the mixture. Diluted sulphuric acid dissolves starch when
assisted by heat, and the starch may be again precipitated by
means of alcohol.
Diluted nitric acid slowly dissolves starch, the acid ac-
quires a green colour, and a small portion of white matter
swims on the surface, on which the acid does not act. Al-
cohol throws down the starch from this solution. Concen-
trated nitric acid dissolves starch pretty rapidly, assuming a
green colour, and emitting nitrous gas. The solution is ne-
ver complete, nor do any crystals of oxalic acid appear un-
less heat be applied. In this respect starch differs from su-
gar, which yields oxalic acid even at the temperature of the
atmosphere. When heat is applied to the solution of starch
in nitric acid, both oxalic and malic acids are formed, but
the undissolved substance still remains. When separated by
filtration and afterwards edulcorated, this substance has the
appearance of a thick oil not unlike tallow; but it dissolves
readily in alcohol. When distilled, it yields acetic acid and
an oil having the smell and consistence of tallow.
Strong muriatic acid dissolves starch slowly and without
effervescence. When the starch does not exceed one-twen-
tieth of the acid, the solution is colourless and transparent;
but if we continue to add starch, a brown colour appears,
and the acid loses a portion of its fluidity. Its peculiar
smell is destroyed and replaced by the odour which may be
X
324 VEGETABLE SUBSTANCES. DIV. IV.
perceived in corn mills. Acetic acid does not dissolve starch.
The action of the other acids has not been tried.
Alcohol separates starch in part from its decoction. A
solution of potash in alcohol occasions a copious white pre-
cipitate, which ih re-dissolved on adding a sufficient quantity
of water. A solution of sulphuret of potash in alkohol oc-
casions a flaky precipitate in the decoction of starch. This
precipitate has sometimes an orange colour.
When starch is thrown upon a hot iron it melts, blackens,
frothes, swells and burns with a bright flame like sugar, emit-
ting, at the same time, a great deal of smoke; but it does
not explode, nor has it the caromel smell which distinguishes
burning sugar. When distilled it yields water impregnated
with an acid supposed to be the pyromucous, a little empy-
reumatic oil, and a great deal of carbonic acid and heavy in-
flammable air. The charcoal which it leaves burns easily
when kindled in the open air, and leaves very little ashes.
Starch is contained in a great variety of vegetable sub-
stances; most commonly in their seeds or bulbous roots, but
sometimes also in other parts. All the different species of
corn contain a great proportion of it. There are obviously
different varieties of starch possessing distinct properties.
But hitherto these varieties have not been examined with
such attention as to enable us to give a detailed description
of each.
CHAP. XI.
OF INDIGO.
This valuable pigment, one of the capital manufactures of
America, is obtained from the leaves of different species of
plants; the indigofera argentea or wild indigo, the indigofe-
CHAP.XI. INDIGO. 325
ra disperma or Guatimala indigo, and the indigofera tinctoria
or French indigo, which yields the greatest quantity of indi-
go, and is therefore preferred by the planter, though its qua-
lity is said to be inferior to that of the indigo obtained from
the two first species. In the West Indies the seeds are sown
in March, in trenches about a foot asunder, and the plant
comes into blossom, and is fit for cutting down in May. But
in South America, six months elapse before it can be cut.
In the West indies four cuttings are often obtained from the
same plant in the course of a year; but in America, never
more than two, and often only one. The produce constant-
ly diminishes after the first cutting, so that it is necessary to
renew the plants for seed every year.
The plants are cut down with sickles, and laid in strata in
the steeper till it is about three parts full. This is a large
cistern of wood or mason work about 16 feet square. Here
they are pressed down with planks, and loaded to prevent
them from swimming, and covered with water to the height
of four or five inches. Here they ferment, and the utmost
attention is required to the process. If they be allowed to
remain too long, the pigment is spoiled; and if the water be
drawn off too soon, much of the indigo is lost. The tempe-
rature of 80˚ is said to answer best. The water acquires a
green colour, a smell resembling that of ammonia is exhaled,
and bubbles of carbonic acid are emitted. When the fer-
mentation has continued long enough, the liquor is let out
into a second cistern, placed lower than the first; this cis-
tern is called the battery, and is commonly about 12 feet
square, and four and a half deep. Here it is agitated for 15
or 20 minutes, by means of levers driven by machinery, till
the flocculi beginning to separate give it a curdled ap-
pearance. A quantity of lime-water is now poured in, and
the blue flocculi are allowed to subside. The water is then
drawn off, and the pigment put to be drained in small linen
X 3
326 VEGETABLE SUBSTANCES. DIV. IV.
bags, after which it is put into little square boxes, and al-
lowed to dry in the shade.
Chevreul has shown that the indigo exists in the plant
chiefly in the state of a white matter, which becomes blue
when it combines with oxgen. Indigo may be obtained
also from other plants, the nerium tinctorium for example,
and the isatis tinctoria, or woad, a plant common enough in
Britain. But the quantity, obtained from this plant does
not exceed one-tenth of what may be procured from the in-
digofera.
Indigo is a fine light friable substance of a deep blue co-
lour. Its texture is very compact, and The shade of its sur-
face varies according to the manner in which it has been pre-
pared. The principal tints are copper, violet and blue. The
lightest indigo is the best; but it is always mixed with fo-
reign substances; scarcely one half even of the best indigo
of commerce consisting of the pure pigment. The follow-
ing substances were extracted by Chevreul from 100 parts of
Guatimala indigo.
Ammonia, a trace
Disoxygenized indigo 12
Green matter 30
Bitter matter a trace
Red matter 6
Carbonate of lime 2
Oxide of iron and alumina 2
Silica 3
Pure indigo 45
___
100
Pure indigo has neither taste nor smell. It is insoluble in
water in its usual state, but disoxygenized indigo is soluble
in that liquid, as are likewise some of the foreign bodies
CHAP. XI. INDIGO. 327
with which indigo is usually mixed. When heated, indigo
sublimes in a purple smoke, and may be obtained unaltered
crystallized in needles. This purple smoke is characteristic
of indigo.
Neither oxygen nor the simple combustible have any ac-
tion on common indigo; but disoxygenized indigo readily
combines with oxygen, and may be separated again from it
without decomposition. In this respect it differs from almost
all other vegetable substances, and approaches the proper-
ties of the simple combustibles and metals.
The fixed alkaline solutions have no effect upon indigo,
except it be newly precipitated from a state of solution. In
that case they dissolve it with facility. The solution has at
first a green colour, which gradually disappears, and the na-
tural colour of the indigo cannot be again restored. Hence
we see that the alkalies when concentrated decompose
indigo. Pure liquid ammonia acts in the same way. Even
carbonate of ammonia dissolves precipitated indigo, and de-
stroys its colour.
Lime water has scarcely any effect upon indigo in its
usual state, but it dissolves precipitated indigo. The solu-
tion is at first green, but it becomes gradually yellow.
When diluted sulphuric acid is digested over indigo, it
produces no effect except that of dissolving the impurities;
but concentrated sulphuric acid dissolves it readily. One
part of indigo, when mixed with eight parts of sulphuric acid,
evolves heat, and is dissolved in 24 hours. The solution of
indigo is well known in this country by the name of liquid
blue, Bancroft calls it sulphate of indigo. While concen-
trated, it is opaque and black; but when diluted, it assumes
a fine deep blue colour, and its intensity is such, that a single
drop of the concentrated sulphate is sufficient to give a blue
colour to many pounds of water. Bergman ascertained the
X 4
328 VEGETABLE SUBSTANCES. DIV. IV
effect of different reagents on this solution with great pre-
cision. His experiments threw light, not only on the pro-
perties of indigo, but upon the phenomena that take place
when it is used as a dye-stuff.
From his experiments, it is obvious that all those substan-
ces which have a very strong affinity for oxygen give a green
colour to indigo, and at last destroy it. Hence it is extreme-
ly probable, that indigo becomes green by giving out oxy-
gen. Of course it owes its blue colour to that principle.
This theory was first suggested by Mr Haussman, and still
further confirmed by Berthollet. Now it is only when green
that it is in a state capable of being held in solution by lime,
alkalies, &c. in which state it is applied as a dye to cloth.
The cloth, when dipt into the vat containing it thus dissolv-
ed, combines with it, and the blue colour is restored by ex-
posure to the atmosphere. It may be restored equally by
plunging the cloth into oxymuriatic acid. Hence the resto-
ration cannot but be ascribed to oxygen. Hence then the
reason that sulphurous acid, the vegetable acids, sulphate of
iron, give sulphate of indigo a green colour.
From these experiments, we see also that the colour of
indigo is destroyed by the addition of those substances which
part with oxygen very readily, as the black oxide of manga-
nese. In that case the indigo is destroyed, for its colour
cannot be again restored. When the sulphate of indigo is
poured into boiling water, it affords a green-coloured solu-
tion; but with cold water a deep blue solution. What is
called smoking sulphuric acid dissolves indigo much more
readily than the pure acid, and evolves much more heat dur-
ing the solution. Bucholz has shown, that by boiling sul-
phur in pure sulphuric acid, it acquires the property of dis-
solving indigo as readily as the smoking acid.
Nitric acid attacks indigo with great violence; the evolu-
4
CHAP. XI. INDIGO. 329
tion of the abundance off heat and nitrous gas. When of the
specific gravity 1.52, it even sets fire to indigo. When the
acid is diluted, the action is still violent, unless the propor-
tion of water be considerable. Mr Hatchett poured upoa
100 grains of indigo an ounce of nitric acid diluted with an
equal quantity of water. The action was so rapid, that he
found it necessary to add another ounce of water. When the
effervescence had nearly subsided, the liquid was placed on
a sand bath for some days, and evaporated to dryness. Water
poured upon the residuum dissolved a considerable portion
of it, and formed a beautiful deep yellow solution of an in-
tense bitter taste. This solution contains only a very small
portion of oxalic acid but with a solution of isinglass it
forms a copious yellow insoluble precipitate, and of course
contains a portion of artificial tannin. With ammonia crys-
tals precipitate, consisting of bitter principle combined with
ammonia.
When four parts of nitric acid are boiled upom one part of
indigo, the pigment soon loses its colour, and is dissolved.
The solution becomes yellow, and a thin layer of a resinous
matter appears on the surface. If the process be now stopt,
the resinous matter becomes thin by cooling. If this matter
be removed, and the solution evaporated to the consistence
of honey, redissolved in hot water and filtered, potash throws
down yellow spicular crystals, consisting of bitter principle
combined with potash. These crystals have the curious pro-
perty of detonating with a purple light when wrapt up in pa-
per and struck with a hammer; the resin, by treating it with
fresh nitric acid, may be converted into the same bitter prin-
ciple. If the process be stopt sooner than the point men-
tioned above, yellow crystals are obtained, which are more
soluble in water, and which sublime in white needles, hav-
ing all the properties of benzoic acid.
330 VEGETABLE SUBSTANCES. DIV. IV
Muriatic acid does not act upon indigo in its commo-
mon state, but it readily dissolves indigo precipitated from
the sulphate, and forms a blue coloured solution. The same
phenomena are exhibited by the phosphoric, acetic, tartaric
acids, and probably by all except the acid supporters.
Oxymuriatic acid destroys the colour of indigo as readyly
as nitric acid, and obviously for the same reason.
Alcohol dissolves a small portion of indigo, but it gradu-
ally precipitates again unless red matter be present, in which
case the solution is permanent.
Indigo is not acted upon by ether or oils, at least if the
experiments of Bergman be accurate.
When indigo is mixed with bran, woad, and other similar
substances which readily undergo fermentation, it assumes a
green colour during the fermentation, and is then easily dis-
solved by lime or potash. It is by this process that it is
usually rendered proper for dyeing.
CHAPTER XII.
OF GLUTEN.
If wheat-flour be kneaded into paste with a little water,
it forms a tenacious elastic, soft, ductile mass. This is to be
washed cautiously, by kneading it under a small jet of water
till the water no longer carries off any thing, but runs co-
lourless; what remains behind is called gluten. It was dis-
covered by Beccaria, an Italian philosopher, to whom we
are indebted for the first analysis of wheat-flour.
Gluten, when thus obtained, is of a grey colour, exceed-
ingly tenacious, ductile, and elastic, and may be extended to
twenty times its original length. When very thin, it is of a
whitish colour, and has a good deal of resemblance to animal
CHAP. XI. INDIGO. 331
tendon or membrane. Its smell is peculiar. It has scarce
any taste, and does not lose its tenacity in the mouth.
When exposed to the air, it gradually dries; and, when
completely dry, it is pretty hard, brittle, slightly transpa-
rent, of a dark brown colour, and has some resemblance to
glue.
Fresh gluten imbibes water, and retains a certain quantity
of it with great obstinacy. To this water it owes its elasti-
city and tenacity. When boiled in water it loses both these
properties.
When fresh gluten is macerated for a considerable time
in cold water, the liquid becomes opaque, and contains small
films suspended, which do not soon subside. By repeated
filtrations it becomes transparent; but it holds in solution
gluten, which renders it frothy, and gives it the property of
precipitating when mixed with oxymuriatic acid or the infu-
sion of nutgalls. Thus gluten is to a certain extent soluble
in cold water. When the water is heated, the gluten sepa-
rates in the state of yellow flakes.
When kept moist, it very soon begins to decompose, and
to undergo a species of fermentation. It swells, and emits
air-bubbles, which Proust has ascertained to consist of hy-
drogen and carbonic acid gases. It emits also a very offen-
sive odour, similar to what is emitted by putrefying animal
bodies. Cadet kept gluten in a vessel for a week in a
damp room. Its surface became covered with byssi, the fer-
mentation just mentioned had commenced, and the odour was
distinctly acid. In 24 days, on removing the upper crust,
the gluten was found converted into a kind of paste, of a
greyish white colour, not unlike bird-lime. In that state he
gave it the name of fermented gluten. It the gluten be still left
to itself, it gradually acquires the smell and the taste of cheese.
This curious fact was first ascertained by Rouelle junior. In
332 VEGETABLE SUBSTANCES. DIV.IV.
that state it is full of holes, and contains the very same juice
which distinguish some kinds of cheese. Proust ascertained
that it contains ammonia and vinegar; bodies which Vau-
quelin detected in cheese; and ammonia robs both equally of
their smell and flavour.
Fresh gluten does not sensibly dissolve in alcohol, which
even throws down fresh gluten from water; yet in certain
cases this liquid forms a solution of gluten in very small pro-
portion.
When the fermented gluten of Cadet is triturated with a
little alcohol into a mucilage, and then mixed with a suffi-
cient quantity of that liquid, a portion of it is dissolved. This
solution constitutes an excellent varnish, possessed of consi-
derable elasticity. It may be spread over paper or wood;
and when dry resists other bodies, as well as most varnishes.
In this state, too, it may be employed to cement china; and
triturated with paints, especially vegetable colours, it forms a
very good ground. When this solution is mixed with a suf-
ficient quantity of lime, it forms a very good lute; and bits
of linen dipt in it adhere very strongly to other bodies.
Ether does does not sensibly dissolve gluten.
Acids act upon gluten differently according to the peculiar
properties of each.
Concentrated acetic acid dissolves it readily in considerable
quantity, and without altering its nature. The solution is
muddy, but permanent; and the gluten may be thrown down
by means of alkalies. This acid dissolves the fermented glu-
ten of Cadet; and the solution may be substituted for the so-
lution in alcohol as a varnish; but it does not answer to mix
it with colours.
Concentrated sulphuric acid renders it violet coloured,
and at last black; inflammable air escapes, and charcoal,
water, and a portion of ammonia, are formed. When nitric
CHAP. XI. GLUTEN. 333
acid is poured on it, and heat applied, there is a quantify
of azotic gas emitted, and by continuing the heat, some little
oxalic acid is formed, and likewise malic acid, while a num-
ber of yellow-coloured oily flakes make their appearance in
the solution.
Muriatic acid dissolves gluten with facility when its action
is assisted by heat. When gluten is placed in oxymuriatic
acid it softens, and seems to dissolve, but soon coagulates
again into yellow-coloured flakes, which become transparent
and greenish coloured by drying. when heated, they exhale
oxymuriatic acid, and assume the appearance of common
gluten. This acid has the property of precipitating gluten
from water in the state of yellowish white flakes.
Alkalies dissolve gluten when they are assisted by beat.
The solution is never perfectly transparent. Acids precipi-
tate the gluten from alkalies, but it is destitute of its elasti-
city. Alkalies, when much concentrated, form with it a kind
of soap, converting it into oil and ammonia; which last is
dissipated during the trituration.
Gluten is precipitated from water, and from some of its
other solutions, by the infusion of nutgalls. The colour of
the precipitate is usually yellowish brown, and it does not
dissolve though the solution be heated.
When moist gluten is suddenly dried, it swells amazingly.
Dry gluten, when exposed to heat, cracks, swells, melts,
blackens, exhales a fetid odour, and burns precisely like fea-
thers or horn. When distilled, there come over water im-
pregnated with ammonia and an empyreumatic oil; the char-
coal which remains is with difficulty reduced to ashes.
334 VEGETABLE SUBSTANCES. DIV. IV.
CHAP. XII.
OF ALBUMEN.
Albumen is the term by which chemists have agreed to
denote the white of egg, and all glary tasteless substances
which, like it, have the property of coagulating into a white,
opaque, tough, solid substance, when heated a little under
the boiling point. This substance forms a constituent of
many of the fluids of animal bodies; and when coagulated,
it constitutes also an important part of their solids. Sub-
stances analogous to it had been noticed by chemists in the
vegetable kingdom. Scheele affirmed, as early as 1780, that
the greater number of plants contained a substance analogous
to curd. Fourcroy, about the year 1790, announced the ex-
istence of albumen in a variety of plants; but Proust has
since shown, that the substance which he took for albumen,
and which had been already examined by Rouelle, was
not possessed of the properties which characterise that ani-
mal matter. But Vauquelin has lately discovered albumen
in abundance in the juice of the papaw tree; so that its ex-
istence as a vegetable principle cannot be disputed.
The papaw tree, the carica papaya of botanists, grows in
Peru, &c. and in the Isle of France, where the milky juice
that exudes from it is said to be employed with efficacy
against the Guinea worm. Two specimens of this juice were
brought from that island to Paris by Charpentier de Cossi-
guy. In the one, the juice had been evaporated to dryness,
and was in the state of an extract; in the other, the juice
was preserved by being mixed with an equal bulk of rum.
Both were subjected to a chemical analysis by Vauquelin.
The first was of a yellowish white colour, and semitranspa-
CHAP. XIII. ALBUMEN. 335
rent. Its taste was sweetish. It had no smell, and was
pretty solid; but attracted moisture when kept in a damp
place. The second was reddish brown, and had the smell
and taste of boiled beef. When the first specimen was ma-
cerated in cold water, the greatest part of it dissolved. The
solution frothed with soap. The addition of nitric acid co-
agulated it, and rendered it white; and when boiled, it threw
down abundance of white flakes. These flakes were coagu-
lated albumen.
Other specimens of this juice, both in the liquid and dried
state, have been examined more recently by Vauquelin, and
likewise by Cadet.
The essential characters of albumen are the following:
In its natural state it is soluble in water, and forms a gla-
ry limpid liquid, having very little taste; which may be em-
ployed as a paste, and which forms a very shining varnish.
The solution is coagulated by acids, pretty much in the
same way as milk is coagulated by the same re-agents.
When not too much diluted, it is coagulated also when
heated to the temperature of 176.
Albumen dissolved in water is precipitated in the state of
brown flakes by the infusion of tan.
The solution is equally coagulated when mixed with alco-
hol.
Albumen is precipitated from water in the state of white
powder by the salts of most of the white metals; such as sil-
ver, mercury, lead, tin, &c.
The juice of the papaw possessed all these properties. It
therefore contained albumen. In few other vegetable pro-
ductions has this substance been yet found in such abundance,
or in a state in which its properties were so decidedly cha-
racteristic; but the resemblance between the curd of milk
and albumen is very close, as we shall see afterwards. Now
Proust has ascertained that almonds, and other similar ker-
336 VEGETABLE SUBSTANCES. DIV. IV.
nels from which emulsions are made, contain a substance
which has the properties of curd.
Albumen, when burnt, emits ammonia; and when treated
with nitric acid, yields azotic gas. It evidently, then, con-
tains azote. But as it is more properly an animal than a ve-
getable substance, I shall defer giving any farther account of
its properties till I come to treat of animal bodies.
CHAP. XIV.
OF FIBRIN.
That peculiar substance which constitutes the fibrous part
of the muscles of animals has been called fibrin by chemists.
A substance resembling it, as it exists in the blood, has been
detected by Vauquelin in the juice of the papaw tree; the
same juice which contained albumen in such plenty. Fibrin
then must be ranked among vegetable substances.
When the juice of the papaw is treated with water, the
greatest part dissolves; but there remains a substance insolu-
luble, which has a greasy appearance. It softens in the air,
and becomes viscid, brown and semitransparent. When
thrown on burning coals it melted, let drops of grease exude,
emitted the noise of meat roasting, and produced a smoke
which had the odour of fat volatilized. It left behind it no
residue. This substance was the fibrin. The resemblance
between the juice of the papaw and animal matter is so close,
that one would be tempted to suspect some imposition, were
not the evidence that it is really the juice of a tree quite un-
exceptionable.
The properties of fibrin are the following:
1. It is tasteless, fibrous, elastic, and resembles gluten.
2. It is insoluble in water and in alcohol.
CHAP. XV. BITTER PRINCIPLE. 337
3. It is not dissolved by diluted alkalies.
4. But acids dissolve it without difficulty.
5. With nitric acid it gives out much azotic gas.
6. When distilled it yields much carbonate of ammonia
and oil.
7. It soon putrefies when kept moist, becomes green; but
does not acquire any resemblance to cheese.
CHAP. XV.
OF THE BITTER PRINCIPLE.
Many vegetable substances have an intensely bitter taste,
and on that account are employed in medicine, by brewers,
&c. This is the case with the wood of the quassia amara
and excelsa, the common quassia of the shops, with the
roots of the gentiana lutea, common gentian; the leaves of
the humulus lupulus, or hop; the bark and wood of the spar-
tium scoparium or common broom; the flowers and leaves
of the anthemis nobilis or chamomile; and many other sub-
stances. Some of these bodies owe their bitter taste to the
presence of a peculiar vegetable substance differing from
every other, which may be distinguished by the name of the
bitter principle.
No chemical examination of this substance has been hi-
therto published; nor indeed are we in possession of any
method of separating it from other bodies, or of ascertain-
ing its presence. At the same time it cannot be doubted
that it possesses peculiar characters; and its action on the
animal economy renders it an object of importance.
I. When water is digested over quassia for some time, it
acquires an intensely bitter taste and a yellow colour, but
no smell. When water thus impregnated is evaporated to
Y
538. VEGETABLE SUBSTANCES. DIV. IV.
dryness in a low heat, it leaves a brownish-yellow sub-
stance, which retains a certain degree of transparency. It
continues ductile for some time, but at last becomes brittle.
This substance I shall consider as the bitter principle in a
state of purity. If it contain any foreign body, it must be
in a very minute proportion. This substance I find to pos-
sess the following properties:
1. Its taste is intensely bitter. Colour brownish yellow.
2. When heated, it softens, and swells, and blackens; then
burns away without flaming much, and leaves a small quan-
tity of ashes.
3. Very soluble in water and alcohol.
4. Does not alter the colour of infusion of litmus.
5. Lime-water, barytes-water, and strontian-water, occa-
sion no precipitate. Neither is any precipitate thrown
down by silicated potash, aluminated potash, or sulphate
of magnesia.
6. The alkalies occasion no change in the diluted solu-
tion of the bitter principle.
7 Oxalate of ammonia occasions no precipitate.
8. Nitrate of silver renders the solution muddy, and a
very soft flaky yellow precipitate falls slowly to the bottom.
9. Neither corrosive sublimate nor nitrate of mercury oc-
casion any precipitate.
10. Nitrate of copper, and the ammonial solution of
copper, produce no change; but muriate of copper gives
the white precipitate, which falls when this liquid salt is
dropt into water.
11. Sulphate and oxymuriate of iron occasion no change.
12. Muriate of tin renders the solution muddy, but oc-
casions no precipitate, unless the solution be concentrated;
in that case a copious precipitate falls.
13. Acetate of lead occasions a very copious white pre-
cipitate; but the nitrate of lead produces no change.
CHAP. XV. BITTER PRINCIPLE. 339
14. Muriate of zinc occasions no change.
15. Nitrate of bismuth produces no change, though
when the salt is dropt into pure water a copious white pre-
cipitate appears.
16. Tartar emetic produces no change; but when the
muriate of antimony is used, the white precipitate appears,
which always falls when this salt is dropt into pure water.
17. Muriate and arseniate of cobalt occasion no change.
18. Arseniate of potash produces no effect.
19. Tincture of nutgalls, infusion of nutgalls, gallic acid,
occasion no effect.
These properties are sufficient to convince us that the
bitter principle is a substance differing considerably from all
the other vegetable principles. The little effect of the dif-
ferent re-agents is remarkable. Nitrate of silver and ace-
tate of lead are the only two bodies which throw it down.
This precipitation cannot be ascribed to the presence of mu-
riatic acid; for if muriatic acid were present, nitrate of lead
would also be thrown down.
II. Besides this purest species of bitter principle, it is
probable that several others exist in the vegetable kingdom,
gradually approaching by their qualities to the nature of ar-
tificial tannin. The second species is distinguished from
the preceding, by the property which it has of striking a
green colour with iron, and of precipitating that metal
from concentrated solutions. Mr Chenevix separated a
portion of it from coffee by the following process: He di-
gested unburnt coffee in water, and filtered the liquid. It
was then treated with muriate of tin. The precipitate was
edulcorated, mixed with water, and treated with sulphureted
hydrogen gas. The tin was thus precipitated, and the sub-
stance with which it had been combined was dissolved by
the water. The liquid was then evaporated to dryness,
Y 2
340 VEGETABLE SUBSTANCES. DIV. IV.
The substance thus obtained posessed the following pro-
perties:
1. Semitransparent like horn, and of a yellow colour.
2. When exposed to the air it does not attract moisture.
3. Soluble in water and in alcohol. The solution in wa-
ter is semitransparent, and has a pleasant bitter taste. When
the alkaline solutions are dropt into it, the colour becomes
garnet red.
4. It is not precipitated from water by the alkaline car-
bonates. Sulphuric acid renders the solution brown, but
produces no further change. Neither muriatic acidy nor
phosphoric acid, nor the vegetable acids, produce any change
on this solution.
5. The muriates of gold, platinum, and copper, occasion
no change.
6. With solutions of iron it forms a fine, green coloured
liquid; and when concentrated, iron throws down a green-
coloured precipitate. Indeed it is almost as delicate a test
of iron as tan and gallic acid.
7. Muriate of tin throws down a copious yellow preci-
pitate. This precipitate, and that by iron, are soluble in all
acids, but they lose their colour.
8. Neither lime nor strontian water occasion any preci-
pitate in the aqueous solutions of this substance; but barytes
water occasions a brown precipitate.
9. Gelatine occasions no precipitate,
III. The Third species may be distinguished by the name
of artificial bitter principle, as it has been formed by the
action of nitric acid on various vegetable and animal sub-
stances. It was first obtained by Haussman while examin-
ing indigo, but he mistook its nature. Welther afterwards
formed it by digesting silk in nitric acid, ascertained its
properties, and gave it the name of yellow bitter principle;
he is therefore to be considered as the real discoverer Bar-
CHAP. XV. BITTER PRINCIPLE. 341
tholdi afterwards procured it by treating the white willow
with nitric acid. Mr Hatchett lately obtained it during his ex-
periments on artificiaa tannin, by treating indigo with nitric
acid; and about the same time Fourcroy and Vauquelin
procured it by the same means, and examined its properties
in detail. This substance possesses the following properties:
Its colour is a deep yellow, its taste intensely bitter. It
is soluble both in water and alcohol, and has the property
of dyeing silk, woollen cloth, and cotton, of a durable yel-
low colour. It crystallizes in elongated plates, and pos-
sesses many of the characters of an acid, combining readily
with alkaline substances, and forming crystallizable salts.
When potash is dropt into a concentrated solution of it,
small yellow prismatic crystals are gradually deposited, con-
sisting of bitter principle combined with potash. These
crystals were examined by Welther, but it was Fourcroy
and Vauquelin that ascertained their composition. They
have a bitter taste, are not altered by exposure to the air,
are less soluble than pure bitter principle. When thrown
upon hot charcoal they burn like gunpowder, and detonate
very loudly when struck upon an anvil, emitting a purple
light. Ammonia dropt into the solution of bitter principle
deepens its colour, and occasions a copious deposition of
fine yellow spicular crystals. These are a combination of
bitter principle and ammonia.
IV. Artificial tannin itself may be considered as ap-
proaching the bitter principle in many of its properties.
Its taste is always intensely bitter, and the colour of the
precipitates which it throws down from the metals, is simi-
lar to what takes place when artificial bitter principle is pre-
sent. It is indeed possible, that the bitter taste may be
360owing not to the tannin, but to a portion of artificial bitter
principle which may be always formed along with the
Y 3
342 VEGETABLE SUBSTANCES. DIV. IV.
tannin; but this has not been ascertained. It is well known
that the bitter taste very easily overpowers and conceals all
other tastes.
CHAP. XVI.
OF TANNIN.
Notwithstanding the numerous experiments made upon
the infusion of nutgalls, we are not in possesion of a pro-
cess capable of furnishing tannin in a state of purity. Hence
the obscurity which still hangs over its characters. The
properties of this substance, as far as known, and the dif-
ferent methods of procuring it hitherto proposed by che-
mists, have been detailed in a preceding part of this work.
Like most other vegetable substances, it seems to be sus-
ceptible of different modifications. The following are the
different species of tannin which have been hitherto noticed.
1. Tannin from nutgalls. This is the common species
described in this work under the name of tannin. It pre-
cipitates iron black, and forms a firm insoluble brown pre-
cipitate with glue. The bark of oak and most other astrin-
gent trees in this country, are supposed at present to con-
tain this species of tannin.
2. The tannin which constitutes so large a proportion of
catechu forms the second species. Its peculiar nature was
first observed by Proust. It was afterwards more particu-
larly examined by Mr Davy. It forms with iron an olive
coloured precipitate.
3. The tannin of kino constitutes a third species. This
substance is obtained from different vegetables. It was ori-
ginally imported, as is supposed, from Africa; but at pre-
CHAP. XVII. TANNIN. 343
sent the common kino of the shops is, according to Dr
Duncan, an extract from the coccoloba urifera, or sea-side
grape, and is brougt chiefly from Jamaica. But the finest
kino is the product of different species of eucalyptus particu-
larly the resinifera or brown gum-tree of Botany Bay. It is
an astringent substance of a dark red colour, and very brittle.
It dissolves better in alcohol than water. The solution in
the latter liquid is muddy; in the former transparent, and a
fine crimson if sufficiently diluted. It throws down gela-
tine of a rose colour, and forms with salts of iron a deep
green precipitate, not altered by exposure to the air.
4. The fourth variety of tannin is contained in sumach.
This is a powder obtained by drying and grinding the shoots
of the rhus coriaria; a shrub cultivated in the southern
parts of Europe. The tan, which it contains in abnndance,
yields a precipitate with gelatine, which subsides very slowly,
and remains in the state of a white magma without con-
sistence.
5. The fifth variety, according to Proust, is to be found
in the wood of the morus tinctoria, or old fustic, as the Bri-
tish dyers term it. This wood gives out an extract both to
alcohol and water, which yields a precipitate with gelatine.
A solution of common salt is sufficient to throw it down.
CHAP. XVII.
OF THE EXTRACTIVE PRINCIPLE.
The word extract was at first applied to all those sub- l
stances which were extracted from plants by means of wa-
ter, and which remained behind in the state of a dry mass
when the water was evaporated; consequently it included
gum, jell, and several other bodies. But of late it has
Y 4
344 VEGETABLE SUBSTANCES. DIV. IV.
been confined by many to a substance which exists in many
plants, and which may be obtained nearly in a state of pu-
rity, according to Hermbstadt, by infusing saffron in water
for some time, filtrating the infusion, and evaporating it to
dryness. But as the word extract occurs even in modern
authors in its original sense, I shall rather denote this
substance by the phrase extractive principle, to prevent
ambiguity.
The difficulty of obtaining the extractive principle in a
separate state, and the facility with which it alters its na-
ture, have hitherto prevented chemists from examining it
with that attention to which it is entitled. It was first par-
ticularly attended to by Rouelle; but it is to Fourcroy and
Vauquelin that we are chiefly indebted for ascertaining its
characters. The dissertation of Vauquelin in the Journal
de Pharmacie, is by far the best account of extractive
matter which has hitherto appeared. Many valuable facts
and curious observations were published by Hermbstadt also
in his dissertation on extract But unfortunately the term
has not been always taken by chemists in the same accepta-
tion. Parmentier has lately published a dissertation on the
extracts of vegetables taken in the loose and general sense
of the word, which contains much information.
The extractive principle possesses the following pro-
perties:
Soluble in water, and the solution is always coloured.
When the water is slowly evaporated, the extractive matter
is obtained in a solid state and transparent; but when the
evaporation is rapid the matter is opaque.
The taste of extractive is always strong; but it is very
different according to the plant from which it is obtained.
Soluble in alcohol, but insoluble in ether.
By repeated solutions and evaporations, the extractive
matter acquires a deeper colour, and becomes iusoluble in
CHAP. XVII. EXTRACTIVE PRINCIPLE. 345
water. This change is considered as the consequence of
the absorption of the oxygen of the atmosphere, for which
the extractive principle has a strong affinity. But if the so-
lution be left to itself, exposed to the atmosphere, the ex-
tract is totally destroyed in consequence of a kind of putre-
faction which speedily commences.
When oxymuriatic acid is poured into a solution contain-
ing extractive, a very copious dark yellow precipitate is
thrown down, and the liquid retains but a light lemon co-
lour. These flakes are the oxygenized extractive. It is
now insoluble in water; but hot alcohol still dissolves it.
The extractive principle unites with alumina, and forms
with it an insoluble compound. Accordingly, if sulphate
or muriate of alumina be mixed with a solution of ex-
tractive, a flaky insoluble precipitate appears, at least when
the liquid is boiled; but if an excess of acid be present, the
precipitate does not always appear.
It is precipitated from water by concentrated sulphuric
acid, muriatic acid, and probably by several other acids.
When the experiment is made with sulphuric acid, the
fumes of vinegar generally become sensible.
Alkalies readily unite with extractive, and form com-
pounds which are insoluble in water.
The greater number of metallic oxides form insoluble
compounds with extractive. Hence many of them, when
thrown into its solution, are capable of separating it from
water. Hence also the metallic salts mostly precipitate ex-
tractive. Muriate of tin possesses this property in an emi-
nent degree. It throws down a brown powder perfectly in-
soluble, composed of the oxide of tin and vegetable matter.
If wool, cotton, or thread, be impregnated with alum,
and then plunged into a solution of extractive, they are
dyed of a fawn colour, and the liquid loses much of its ex-
tractive matter. This colour is permanent. The same ef-
346 VEGETABLE SUBSTANCES. DIV. IV.
fect is produced if muriate of tin be employed instead of
alum. This effect is still more complete if the cloth be
soaked in oxymuriatic acid; and then dipt into the infusion
of extractive. Hence we see that the extractive matter re-
quires no other mordant than oxygen to fix it on cloth.
When distilled, extractive yields an acid liquid impreg-
nated with ammonia.
It cannot be doubted that there are many differrent species
of extractive matter; though the difficulty of obtaning each
separately has prevented chemists from ascertaining its na-
ture with precision. Extracts are usually obtained by treat-
ing the vegetable substance from which they are to be pro-
cured with water, and then evaporating the watery solution
slowly to dryness. All extracts obtained by this method
have an acid taste, and redden the infusion of litmus. They
all yield a precipitate while liquid if they are mixed with
ammonia. This precipitate is a compound of lime and in-
soluble extractive. Lime always causes them to exhale the
odour of ammonia. It has been ascertained that the ex-
tractive principle is more abundant in plants that have grown
to maturity than in young plants.
CHAP. XVIII.
OF THE NARCOTIC PRINCIPLE.
It has been long known that the milky juices which exude
from certain plants, as the poppy, lettuce, &c. and the infu-
sions of others, as of the leaves of the digitalis purpurea, have
the property of exciting sleep, or, if taken in large enough
dozes, of inducing a state resembling apoplexy, and terminat-
ing in death. How far these plants owe these properties to
certain common principles which they possess is not known;
CHAP. XVIII. NARCOTIC PRINCIPLE. 347
though it is exceedingly probable that they do. But as a
peculiar substance has been detected in opium, the most no-
ted of the narcotic preparations, which possesses narcotic
properties in perfection, we are warranted, till further expe-
riments elucidate the subject, to consider it as the narcotic
principle, or at least as one species of the substances belong-
ing to this genus.
Opium is obtained from the papaver album, or white pop-
py, a plant which is cultivated in great abundance in India
and the East. The poppies are planted in a fertile soil and
well watered. After the flowering is over, and the seed cap-
sules have attained nearly their full size, a longitudinal inci-
sion is made in them about sun-set for three or four evenings
in succession. From these incisions there flows a milky
juice, which soon concretes, and is scraped off the plant and
wrought into cakes. In this state it is brought to Europe.
Opium, thus prepared, is a tough brown substance, has a
peculiar smell, and a nauseous bitter acrid taste. It is a very
compound substance, containing sulphate of lime, sulphate
of potash, an oil, a resinous body, an extractive matter, glu-
ten, mucilage, &c. besides the peculiar narcotic principle, to
which, probably, it owes its virtues as a narcotic.
When water is digested upon opium, a considerable por-
tion of it is dissolved, the water taking up several of its con-
stituents. When this solution is evaporated to the consist-
ence of a syrup, a gritty precipitate begins to appear, which
is considerably increased by diluting the liquid with water.
It consists chiefly of three ingredients; namely, resin, oxyge-
ated extractive, and the peculiar narcotic principle, which
is crystallized. When alcohol is digested on this precipitate,
the resin and narcotic substance are taken up, while the oxy-
genized extractive remains behind. The narcotic principle
falls down in crystals as the solution cools, still however co-
348 VEGETABLE SUBSTANCES. DIV. IV
loured with resin. But it may be obtained tolerably pure
by repeated solutions and crystallizations.
Water is incapable of dissolving the whole of opium.
What remains behind still contains a considerable portion of
narcotic principle. When alcohol is digested on this resi-
duum, it acquires a deep red colour; and deposites, on cool-
ing, crystals of narcotic principle, coloured by resin, which
may be purified by repeated crystallizations. The narcotic
principle obtained by either of these methods possesses the
following properties.
Its colour is white. It crystallizes in rectangular prisms
with rhomboidal bases. It has neither taste nor smell.
It is insoluble in cold water, soluble in about 400 parts of
boiling water, but precipitates again as the solution cools.
The solution in boiling water does not affect vegetable blues.
It is soluble in 24 purts of boiling alcohol and 100 parts
of cold alcohol. When water is mixed with the solution
the narcotic principle precipitates in the state of a white
powder.
Hot ether dissolves it, but lets it fall on cooling.
When heated in a spoon it melts like wax. When distil-
led it froths and emits white vapours, which condense into a
yellow oil. Some water and carbonate of ammonia pass in-
to the receiver; and at last carbonic acid gas, ammonia, and
carbureted hydrogen gas, are disengaged. There remains a
bulky coal, which yields traces of potash. The oil obtained
by this process is viscid, and has a peculiar aromatic smell
and acrid taste.
It is very soluble in all acids. Alkalies throw it down
from these solutions in the state of a white powder.
Alkalies render it rather more soluble in water. When
they are saturated with acids, the narcotic principle falls
down in the state of a white powder, which is re-dissolved by
adding an excess of acid.
CHAP. XIX. OILS. 349
Volatile oils, while hot, dissolve it; but, on cooling, they
let it fall in an oleaginous state at first, but it gradually cry-
stallizes.
When treated with nitric acid, it becomes red and dissolves;
much oxalic acid is formed, and a bitter substance remains
behind.
When potash is added to the aqueous solution of opium,
the narcotic principle is thrown down; but it retains a por-
tion of the potash.
Its solubility in water and alcohol, when immediately ex-
tracted from opium, seems to be owing to the presence of
resin and extractive matter, both of which render it soluble.
It posseses the properties of opium in perfection. Dé-
rosne tried it upon several dogs, and found it more powerful
than opium. Its bad effects were counteracted by causing
the animals to swallow vinegar. This substance is known to
be of equal service in counteracting the effects of opium.
Dérosne supposes that the efficacy of vinegar may be owing
to the readiness with which it dissolves the narcotic prin-
ciple.
CHAP. XIX.
OF OILS.
There are two species of oils; namely, fixed and volatile;
bodth of which are found abundantly in plants.
1. Fixed oil is only found in the seeds of plants, and is
almost entirely confined to those which have two cotyledons;
as linseed, almonds, beech root, poppy seed, rape-seed, &c.
Sometimes, though rarely, it is found in the pulp which sur-
rounds the stone of certain fruits. This is the case with the
olive, which yields the most abundant and most valuable
350 VEGETABLE SUBSTANCES. DIV. IV.
species of fixed oil. the bicotyledonous seeds, besides oil,
contain also a mucilaginous substance; and they have all the
character of forming, when bruised in water, a milky liquid,
known by the name of emulsion.
The following is a list of the plants which yield the fixed
oils which usually occur in commerce.
1. Linum usitatissimum et perenne Linseed oil
2. Corylus avellana Nut oil
3. Juglans regia Nut oil
4. Papairer somniferam . . Poppy oil
5. Cannabis sativa Hemp oil
6. Sesamum orientale Oil of Sesamum
7. Olea Europea Olive oil
8. Amygdalus communis Almond oil
9. Guilandina Mohriga Oil of behen
10. Cucurbita pepo et melopepo Cucumber oil
11. Fagus sylvatica Beech oil
12. Sinapis nigra et arvensis Oil of mustard
15. Helianthus annuus et perennis Oil of sunflower
14. Brassica napus et campestris Rape seed oil
15. Ricinus communis Castor oil
16. Nicotiana tabacum et rustica Tobacco seed oil
17. Prunus domestica Plum kernel oil
18. Vitis vinifera Grape seed oil
19. Theobroma cacao Butter of cacao
20. Laurus nobilis Laurel oil
21. Arachis hypogaea Ground nut oil
2. Volatile oils are found in every part of plants except
the cotelydons of the seeds, where they never occur. The
root, the stem, the leaves, the flower, the rind or pulp of the
fruit of a variety of plants, are loaded with volatile oils, from
which they are extracted by expression or by distillation.
CHAP. XIX. OILS. 351
The number of these oils is so great that it baffles all descrip-
tion. Almost every plant which is distinguished by a pecu-
liar odour contains a volatile oil, to which it is indebted for
that odour.
The following table contains a pretty copious list of plants
which yield volatile oils. The part of the plant from which
it is extracted, and the English name of the oil, are added in
separate columns.
Plants Parts Oil of Color.
1. Artemisia absynthium Leaves Wormwood Green
2. Acorus calamus Root Sweet flag Yellow
3. Myrtus Pimenta Fruit Jamaica pep. § Yellow
4. Anethum graveolens Seeds Dill Yellow
5. Angelica archangelica Root Angelica
6. Pimpinella Seeds Anise White
7. Illicium anisatum Seeds Stellat. anise Brown
8. Artemisia vulgaris Leaves Mugwort
9. Citrus aurantium Rind of the fruit Bergamotte Yellow
10. Meloleuca Ieucodendra Leaves Cajeput Green
11. Eugenia caryophyllata Capsules Gloves § Yellow
12. Carum carvi Seeds Caraways Yellow
13. Amomum cardamomum Seeds Card. seeds Yellow
14. Carlina acaulis Roots White
15. Scandix chaerefolium Leaves Chervil Sulph. Yel.
16. Matricaria chamomilla Petals Chamomile Blue
17. Laurus cinnamomum Bark Cinnamon § Yellow
18. Citrus medica Rind of the fruit Lemons Yellow
19. Cochlearia officinalis Leaves Scurvy grass Yellow
20. Copaifera officinalis Extract Copaiba White
21. Coriandrum sativum Seeds Coriand. seed White
22. Crocus sativus Pistils Saffron § Yellow
23. Piper cubeba Seeds Cubeb peb. Yellow
24. Laurus culilaban Bark Culilaban Br. yel.
25. Cuminum cyminum Seeds Cummi Yellow
26. Inula helenium Roots Elecampane White
27. Anethum faeniculum Seeds Fennel White
§ The oils marked § sink in water.
They yield also a fixed oil
352 VEGETABLE SUBSTANCES. DIV. IV.
Plants Parts Oil of Color.
28. Croton elutheria Bark Cascarilla Vellow
29. Maranta galanga Roots Galanga Tellow
30. Hyssopus officinalis Leaves Hyssop Vellow
31. Juniperns communis Seeds Juniper Green
32. Lavendula spica Flowers Lavender Yellow
33. Laurus nobilis Berries Laurel Brownish
34. Prunus laurocerasus Leaves Lauroceras. §
35. Levisticum ligusticum Roots Lovage Yellow
36. Myristica moschata Seeds Mace Yellow
37. Origanum majorana Leaves Marjorum Yellow
38. Pistacia lentiscus Resin Mastich Yellow
39. Matricaria parthenium Plant Motherwort Blue
40. Melissa officinalis Leaves Balm White
41. Mentha crispa Leaves White
42. -- piperitis Leaves Peppermint Yellow
43. Achillea millfolium Flowers Millefoil Blue and green
44. Citrus aurantium Petals Neroli Orange
45. Origanum creticum Flowers Spanish hop Brown
40. Apium petroselinum Roots Parsley Yellow
47. Pinus sylvestris et abies Wood and resin Turpentine Colorless
48. Piper nigrum Seeds Pepper Yellow
49. Rosmarinus officinalis Plant Rosemary Colouriess
50. Mentha pulegium Flowers Pennyroyal Yellow
51. Genista canariensis Root Rhodium Yellow
52. Rosa centifolia Petals Roses Colourless
53. Ruta graveolens Leaves Rue Yellow
54. Juniperus sabina Leaves Savine Yellow
55. Salvia officinalis Leaves Sage Green
56. Santalum album Wood Santalum § Yellow
57. Laurus sassafras Root Sassafras Yellow
58. Satureia hortensis Leaves Satureia Vellow
59. Thymus serpillum Leaves And flower Thyme Yellow
60. Valeriana officinalis Root Valerian Green
61. Kaempferia rotunda Root Zedoary Greenish blue
62. Amomum Zinziber Root Ginger Yellow
63. Andropogon schaenanthum Sira Brown
Several of the gum resins, as myrrh and galbanum, yield
likewise an essential oil, and likewise the balsam of benzoin, &c.
CHAP. XX. WAX. 353
CHAPTER. XX.
OF WAX.
The upper surface of the leaves of many trees is covered
with a varnish, which may be separated and obtained in a
state of purity by the following process:
Digest the bruised leaves, first in water and then in alco-
hol, till every part of them which is soluble in these liquids,
be extracted. Then mix the residuum with six times its
weight of a solution of pure ammonia, and, after sufficient
maceration, decant off the solution, filter it, and drop into
it, while it is incessantly stirred, diluted sulphuric acid, till
more be added than is sufficient to saturate the alkali. The
varnish precipitates in the form of a yellow powder. It
should be carefully washed with water, and then melted over
a gentle fire.
Mr Tingry first discovered that this varnish possesses
all the properties of bees wax. Wax, then, is a vegetable
product. Several plants contain wax in such abundance as
to make it worth while to extract it from them. But let us,
in the first place, consider the properties of bees wax, the
most common and important species. This substance, as
Huber has demonstrated, contrary to the generally received
opinion, is prepared by the bees from honey or sugar, the lat-
ter yielding the greatest proportion of it.
Wax, when pure, is of a whitish colour; it is destitute of
taste, and has scarcely any smell. Bees wax indeed has a pretty
strong aromatic smell; but this seems chiefly owing to some
substance with which it is mixed; for it disappears almost
completely by exposing the wax, drawn out into thin ribands,
for some time to the atmosphere. By this process, which is
Z
354 VEGETABLE SUBSTANCES. DIV. IV.
called bleaching, the yellow colour of the wax disappears,
and it becomes very white. Bleached wax is not affected
by the air.
The specific gravity of unbleached wax varies from 0.9000
to O.9650; that of white wax from 0.8203 to 0.9662.
Wax is insoluble in water; nor are its properties altered
though kept under that liquid.
When heat is applied to wax it becomes soft; and at the
temperature of 142˚, if unbleached, or of 155˚ if bleached,
it melts into a colourless transparent fluid, which concretes
again, and resumes its former appearance as the temperature
diminishes. If the heat be still farther increased, the wax
boils, and evaporates; and if a red heat be applied to the va-
pour it takes fire and burns with a bright flame. It is this
property, which renders wax so useful, for making candles.
Wax is scarcely acted on by alcohol when cold, but boil-
ing alcohol dissolves it.
Ether has but little action on wax while cold; but when
assisted by heat, it takes up about one-twentieth of its weight
of it, and lets the greatest part precipitate on cooling.
Wax combines readily with fixed oils when assisted by heat,
and forms with them a substance of greater or less consisten-
cy according to the quantity of oil. This composition, which
is known by the name of cerate, is much employed by sur-
geons.
The volatile oils also dissolve wax when heated. This is
well known, at least, lo be the case with oil of turpentine. A
part of the wax precipitates usually as the solution cools, but
of a much softer consistence than usual, and therefore con-
taining oil.
The fixed alkalies combine with it, and form a compound
which possesses all the properties of common soap. When
boiled with a solution of fixed alkalies in water, the liquid
becomes turbid, and after some time the soap separates and
swims on the surface. It is precipitated from the alkali by
CHAP. XX. WAX. 356
acids in the state of flakes, which are the wax very little al-
tered in its properties.
The acids have but little action on wax; even oxymuriatic
acid, which acts so violently on most bodies, produces no
other change on it than that of rendering it white. This
property which wax possesses, of resisting the action of acids,
renders it very useful as a lute to confine acids properly in
vessels, or to prevent them from injuring a common cork.
Mr Lavoisier contrived to burn wax in oxygen gas. The
quantity of wax consumed was 21.9 grains. The oxygen
gas employed in consuming that quantity amounted to 66.55
grains. Consequently the substances consumed amounted to
88.45 grains. After the combustion, there were found in
the glass vessel 62.58 grains of carbonic acid, and a quantity
of water, which was supposed to amount to 23.87 grains.
These were the only products.
From this experiment he concluded that 100 parts of wax
are composed of
82.28 carbon
17.72 hydrogen
_____
100.000
The myrtle wax of North America is obtained from the
myrica cerifera. The myrica cerifera is a shrub which
grows abundantly in Louisiana and other parts of North
Aimerica. It produces a berry about the size of a pepper
corn. A very fertile shrub yields nearly seven pounds.
From the observations of Cadet, we learn that the wax forms the
outer covering of the berries. The wax thus obtained is of a
pale green colour. Its specific gravity is 1.0150. It melts
at the temperature of 109˚: when strongly heated it burns
with a white flame, produces little smoke, and during the
combustion emits an agreeable aromatic odour. Water does
not act upon it. Alcohol, when hot, dissolves one-tenth of
Z2
356. VEGETABLE SUBSTANCES. DIV. IV.
its weight, but lets most of it fall again on cooling. Hot
ether dissolves about one-fourth of its weight; and when
slowly cooled, deposites it in crystalline plates, like sperma-
ceti. The ether acquires a green colour, but the wax be-
comes nearly white. Oil of turpentine, when assisted by
heat, dissolves it sparingly. Alkalies act upon it nearly as
on bees wax. The same remark applies to acids. Sulphuric
acid, when assisted by heat, dissolves about one-twelfth of
its weight, and is converted into a thick dark brown mass.
The Chinese extract a wax from various vegetables, which
they manufacture into candles, and of which they form many
delicate ornaments which are brought to Europe.
CHAP. XXI.
CAMPHOR.
The substance called camphor, though unknown to the
Greeks and Romans, seems to have been long known in the
East. When it was first brought to Europe does not appear,
though it seems to have been introduced by the Arabians.
It comes to Europe chiefly from Japan. It is obtained
from the laurus camphora, a tree common in the East, by
distilling the wood along with water in large iron pots, on
which are fitted earthen heads stuffed with straw. The cam-
phor sublimes, and concretes upon the straw in the form of
a grey powder. It is afterwards refined in Holland by a se-
cond sublimation. The vessels are of glass, and somewhat
of the shape of a turnip, with a small mouth above loosely
covered with paper. According to Ferber, about one-fourth
of pounded chalk is mixed with crude camphor; but others
assure us that there is no addition whatever employed.
CHAP. XXI. CAMPHOR. 357
Camphor thus confined is a white brittle substance, having
a peculiar aromatic odour, and a strong hot acrid taste. Its
specific gravity is 0.9887.
It is not altered by atmospheric air; but it is so volatile,
that if it be exposed during warm weather in an open vessel,
it evaporates completely. When sublimed in close vessels it
crystallizes in hexagonal plates or pyramids.
It is insoluble in water; but it communicates to that li-
quid a certain portion of its peculiar odour.
It dissolves readily in alcohol, and is precipitated again by
water. According to Neumann, well rectified alcohol dis-
solves three-fourths of its weight of camphor. By distillation
the alcohol passes over first, and leaves the camphor. This
property affords an easy method of purifying camphor. Dis-
solve the camphor in alcohol, distil off the spirit, and melt
the camphor into a cake in a glass vessel.
Camphor is soluble also in oils, both fixed and volatile.
If the solution be made by means of heat, as it cools part of
the camphor precipitates, and assumes the form of plumose
or feather-like crystals.
Camphor is not acted on by alkalies, either pure or in the
state of carbonates. Pure alkaies indeed seem to dissolve
a little camphor; but the quantity is too small to be per-
ceptible by any other quality than its odour. Neither is it
acted on by any of the neutral salts wihch have hitherto been
tried. '
Acids dissolve camphor without effervescence, and in
general it may be precipitated unaltered from the recent so-
lution.
When heat is applied to camphor it is volatilized. If
the heat be sudden and strong, the camphor melts before
it evaporates; and it melts, according to Venturi, at the
temperature of 300˚; according to Romieu, at 421˚. It
catches fire very readily, and emits a great deal of flame as
z S
358 VEGETABLE SUBSTANCES. DIV. IV.
it burns, but it leaves no residuum. It is so inflammable
that it continnes to burn even on the surface of water.
When camphor is set on fire in a large glass globe filled
with oxygen gas, and containing a little water, it burns with
a vary bright flame, and produces a great deal of heat.
The inner surface of the glass is soon covered with a black
powder, which has all the properties of charcoal; a quan-
tity of carbonic acid gas is evolved; the water in the globe
acquires a strong smell, and is impregnated with carbonic
acid and camphoric acid.
There are several species of camphor which have been
examined by chemists, and which differ considerably from
each other in their properties, The most remarkable are
common camphor, the camphor of volatilek oils, and the
camphor obtained by treating oil of turpentine with mu-
riatic acid.
Common camphor, obtained by distillation from the
laurus camphora, is the substance which has been descri-
bed in the proceding part of this Chapter. In Borneo and
Sumatra camphor is procured from the laurus sumatrensis;
but as none of this camphor is brought to Europe, we do
not know how far it agrees with common camphor in its
properties.The laurus cinnnamomum likewise yields
camphor.
The second species of camphor seems to exist in a great
variety of plants, and is held in solution by the volatile oils
extracted from them. Neumann obtained it from oils of
thyme, majoram, cardomum; Hermann, from oils extracted
from various species of mint. Cartheuser obtained it from
the roots of the maranta galanga, kaempferia rotunda, amo-
num zinziber, laurus cassia, and rendered it probable that
it is contained in almost all the labiated plants. It hasn
been Supposed to exist in these plants combined with vo-
CHAP. XXI. CAMPHOR. 359
latile oil. Proust has shown how it may be extracted, in
cosiderable quantity, from many volatile oils.
From the observations of Mr John Brown, there is rea-
son to believe that the camphor from oil of thyme differs
from common camphor in several respects. It does not
appear to form a liquid solution either with nitric or sul-
phuric acid; nor is it precipitated from nitric acid in pow-
der like common camphor, but in a glutinous mass.
The artificial camphor yielded by oil of turpentine, when
saturated with muriatic acid gas, was discovered by Mr
Kind, apothecary in Eutin, while employed in making a
medicine called the liquor arthriticus Pottii. He put a
quantity of oil of turpentine into a Woulfe's bottle, and
caused a current of muriatic acid gas, separated from com-
mon salt by sulphuric acid, to pass through it. The salt
used was of the same weight with the oil of turpentine. At
first the oil became yellow, then brown, and at last be-
came almost solid, from the formation of a great number
of crystals in it, which possessed the properties of camphor.
The proportion of muriatic gas found to answer best, is
what can be separated by sulphuric acid and heat from a
quantity of common salt equal in weight to the oil of tur-
pentine employed. The camphor produced amounts nearly
to one-half of the oil of turpentine.
The camphor thus produced was very white; it had a pe-
culiar odour, in which that of the oil of turpentine could be
distinguished. When washed with water, it became beau-
tifuilly white, and gave no longer signs of containing an acid,
but still had the smell of oil of turpentine. Water con-
taining some carbonate of potash deprived it of part of this
odour, but not the whole. When mixed with its own
weight of charcoal powder, wood-ashes, quicklime, or por-
celain clay, and sublimed, it was obtained in a state of
purity.
z 4
360 VEGETABLE SUBSTANCES. DIV: IV.
Its smell when pure resembles that of common camphor,
but is not so strong. Its taste also resembles that of cam-
phor. It swims on water, to which it communicates its
taste, and burns upon its surface. It dissolves completely
in alcohol, and is precipitated by water. Citric acid, of
the specific gravity 1.261, had no action on it, though it
readily dissolves common camphor; but concentrated nitric
acid dissolves it with the disengagement of nitrous gas; and
water does not precipitate it from its solution as it does com-
mon camphor. Acetic acid does not dissolve it. When
heated it sublimes without decomposition; and when set on
fire it burns like camphor.
CHAP. XXII.
OF BIRD-LIME.
The vegetable principle to which I give the name of bird-
lime, was first examined by Vauquelin, who found it pos-
sessed of properties different from every other. It was-
found collected on the epidermis of a plant brought to Eu-
rope by Michaud, and called robinia viscosa by Cels; con-
stituting a viscid substance, which made the fingers adhere
to the young twigs. From the late analysis of bird-lime by
Bouillon la Grange, it is obvious that it owes its peculiar
properties to the presence of an analogous substance, which
indeed constitutes the essential part of that composition.
Hence the reason why I have given the name of bird-lime
to the principle itself.
Natural bird-lime (or that which exudes spontaneously
from plants), possesses the following properties:
Its colour is green; it has no sensible taste or smell;
is extremely adhesive; softens by the heat of the fingers,
CHAP. XXII. BIRD-LIME. 361
and sticks to them with great obstinacy. When heated it
melts, swells up, and burns with a considerable flame,
leaving a bulky charcoal behind it. It does not dissolve
in water; alcohol has but little action on it, especially
when cold. By the assistance of heat it dissolves a por-
tion of it; but on cooling, allows the greatest part to pre-
cipitate again. When exposed te the air it continues glu-
tinous, never becoming hard and brittle like the resins.
It combines readily with oils. Ether is its true solvent,
dissolving it readily without the assistance of heat. The
solution is of a deep green colour. The alkalies do not
combine with it; the effect of the acids was not tried.
These properties are sufficient to distinguish bird-lime from
every other vegetable principle.
Artificial bird-lime is prepared from different substances
in different countries. The berries of the misletoe are said
to have been formerly employed. They were pounded,
boiled in water, and the hot water poured off. At pre-
sent bird-lime is usually prepared from the middle bark of
the holly. The process followed in England, as described
by Geoffroy, is as follows: The bark is boiled in water
seven or eight hours till it becomes soft. It is then laid in
quantities in the earth, covered with stones, and left to fer-
ment or rot for a fortinght or three weeks. By this fer-
mentation it changes to a mucilaginous consistency. It is
then taken from the pits, pounded in mortars to a paste
and well washed with river water. Bouillon la Grange in-
forms us, that at Nogent le Rotrou bird-lime is made by
cutting the middle bark of the holly into small pieces, fer-
menting them in a cool place for a fortnight, and then boil-
ing them in water, which is afterwards evaporated. At
Commerci various other plants are used.
Its colour is greenish, its flavour sour, and its consist-
ence gluey, stringy, and tenacious. Its smell si similar to
362 VEGETABLE SUBSTANCES. DIV. IV.
that of linseed oil. When spread on a glass plate, and ex-
posed to the air and light it dries, becomes brown, loses its
viscidity, and may be reduced to powder; but when water
is added to it, the glutinous property returns. It reddens
vegetable blues.
When gently heated it melts, and emits an odour like
that of animal oils. When heated on red hot coals, it
burns with a lively flame, and gives out a great deal of
smoke, leaving a white ash, composed of carbonate of
lime, alumina, iron, sulphate, and muriate of potash.
Water has little action on bird-lime. When boiled in
water the bird-lime becomes more liquid, but recovers its
original properties when the water cools. The water, by
this treatment, acquires the property of reddening vegetable
blues, and when evaporated leaves a mucilaginous sub-
stance, which may be likewise separated by alcohol.
A concentrated solution of potash forms with bird-lime
a whitish magma, which becomes brown by evaporation,
while ammonia separates, The compound thus formed is
less viscid than bird-lime, and in smell and taste resembles
soap. In alcohol and water it dissolves almost completely
and possesses properties similar to those of soap.
Weak acids soften bird-lime, and partly dissolve it; strong
acids act with more violence. Sulphuric acid renders it
black; and when lime is added to the solution, acetic acid
and ammonia separate. Nitric acid cold has little effect;
but when assisted by heat it dissolves the bird-lime; and
the solution, when evaporated, leaves behind it a hard brittle
mass. By treating this mass with nitric acid, a new solu-
tion may be obtained, which by evaporation yields malic
and oxalic acids, and a yellow matter which possesses se-
veral of the properties of wax. Cold muriatic acid does
not act on bird-lime; hot muriatic acid renders it black.
CHAP. XXIII RESINS. 3635
Alcohol of the specific gravity 0.817 dissolves bird-lime
matter
similar to wax. The filtered liquid is bitter, nauseous, and
acid. Water precipitates a substance similar to resin.
Sulphuric ether dissolves bird-lime readily, and in great
abundance. The solution is greenish. When mixed with
water, an oily substance separates, which has some resem-
blance to linseed oil. When evaporated a greasy substance
is obtained, having a yellow colour and the softness of wax.
Oil of turpentine dissolves bird-lime readily.
CHAP. XXIII.
OF RESINS.
It is at present the opinion of chemists, that resins stand
in the same relatin to the volatile oils that wax does to
the fixed. Wax is considered as a fixed oil saturated with
oxygen; resins, as volatile oils saturated with the same
principle.
Resins often exude spontaneously from trees; they often
flow from artificial wounds, and not uncommonly are com-
bined at first with volatile oil, from which they are sepa-
rated by distillation, The reader can be at no loss to form
a notion of what is meant by resin, when he is informed
that common rosin furnishes a very perfect example of a
resin, and that it is from this substance that the whole ge-
nus derived their name: for rosin is frequently denominated
resin.
I. Resins may be distinguished by the following pro-
perties:
They are solid substances, naturally brittle; have a cer-
364 VEGTETABLE SUBSTANCES DIV. IV.
tain degree of transparency, and a colour most commonly
inclining to yellow. Their taste is more or less acrid, and
not like that of volatile oils; but they have no smell unless
they happen to contain some foreign body. They are all
heavier than water. They are all non-conductors of electri-
city, and when excited by friction, their electricity is
negative.
Their specific gravity varies considerably.
When exposed to heat they melt; and if the heat be in-
creased they take fire, and burn with a strong yellow flame
emitting at the same time a vast quantity of smoke.
They are all insoluble in water whether cold or hot; but
when they are melted along with water, or mixed with vo-
latile oil, and then distilled with water, they seem to unite,
with a portion of that liquid; for they become opaque, and
lose much of their brittleness. This at least is the case
with common rosin.
They are all, with a few exceptions, soluble in alcohol,
especially when assisted by heat. The solution is usually
transparent; and when the alcohol is evaporated, the resin
is obtained unaltered in its properties.
Several of them are soluble in fixed oils, especially in the
drying oils. The greater number are soluble in the volatile
oils; at least in oil of turpentine, the one commonly em-
ployed.
Mr Hatchett first examined the action of fixed alkalies
on resins, and ascertained, contrary to the received opinion
of chemists, that alkaline ?leys dissolve them with facility.
He reduced a quantity of common rosin to powder, and
gradually added it to a boiling lixivium of carbonate of
potash; a perfect solution was obtained of a clear yellow
colour, which continued after long exposure to the air. The
experiment succeeded equally with carbonate of soda, and
CHAP. XXIII. RESINS. 365
with solutions of pure potash, or soda. Every other resin
was dissolved as well as rosin.
These alkaline solutions of resins have the properties of
soap, and may be employed as detergents. When mixed
with an acid, the resin is separated in flakes, usually of a
yellow colour, and not much altered in its nature.
Ammonia acts but imperfectly upon resins, and does not
form a complete solution of any of those bodies hitherto
tried.
It was the received opinion of chemists that acids do
not act upon resins. Mr Hatchett first ascertained this opi-
nion also to be erroneous, and showed that most of the acids
dissolve resins with facility, producing different phenomena
according to circumstances.
When sulphuric acid is poured upon any of the resins in
powder, it dissolves them in a few minutes. At in first the so-
lution is transparent, of a yellowish brown colour, and of the
consistency of a viscid oil, and the resin may be precipitated
nearly unaltered by the addition of water. if the solution
be placed on a sand bath, its colour becomes deeper, sul-
phurous acid gas is emitted, and it becomes very thick, and
of an intense black.
Nitric acid likewise dissolves the resins with facility, but
not without changing their nature. Mr Hatchett was first
led to examine the action of this acid on resins, by observing
that resins are thrown down by acids from their solutions in
alkalies in the state of a curdy precipitate; but when nitric
acid is added in excess, the whole of the precipitate is re-dis-
solved in a boiling heat. He poured nitric acid of the spe-
cific gravity 1.38, on powdered rosin in a tubulated retort;
and by repeated distillation formed a complete solution of a
brownish yellow colour. The solution takes place much
sooner in an open matrass than in close vessels. The solu-
tion continues permanent, though left exposed to the air. It
366 VEGETABLE SUBSTANCES. DIV. IV.
becomes turbid when water is added; but when the mixture
is boiled, the whole is redissolved.
When the digestion of nitric acid upon a resinous sub-
stance is continued long enough, and the quantity of acid is
sufficient, the dissolved resin is completely changed; it is not
precipitated by water; and by evaporation, a viscid sub-
stance of a deep yellow colour is obtained, equally soluble
in water and alcohol, and seemingly intermediate between
resin and extractive. If the abstraction of nitric acid be re-
peated, this substance gradually assumes the properties of ar-
tificial tannin. Thus it appears that nitric acid gradually al-
ters the nature of resin, producing a suite of changes which
terminate in artificial tannin, upon which nitric acid has no
action.
Muriatic acid and acetic acid dissolve resin slowly, and it
may be precipitated again from them unaltered.
When resins are subjected to destructive distillation, we
obtain carbureted hydrogen and carbonic acid gas, a very
small portion of acidulous water, and much empyreumatic
oil. The charcoal is light and brilliant, and contains no al-
kali.
II. Having now described the general properties of resi-
nous bodies, it will be proper to take a more particular view
of those of them which are of the most importance, that we
may ascertain how far each possesses the general characters
of resins, and by what peculiarities it is distinguished from
the rest. The most distinguished of the resins are the fol-
lowing.
1. Rosin. - This substance is obtained from different
species of fir; as the pinus abies, sylvestris, larix, balsamea.
It is well known that a resinous juice exudes from the pinus
sylvestris, or common Scotch fir, which hardens into tears.
The same exudation appears in the pinus abies, or spruce fir.
These tears constitute the substance called thus, or common
CHAP. XXIII. RESINS. 367
frankincense. When a portion of bark is stripped off these
trees, a liquid juice flows out, which gradually hardens.
This juice has obtained different names according to the
plant from which it comes. The pinus sylvestris yields
common turpentine; the larix, Venice turpentine; the balsa-
mea, balsam of Canada, &c. All these juices which are
commonly distinguished by the name of turpentine, are con-
sidered as composed of two ingredients; namely, oil of tur-
pentine and rosin.
2. Mastich. - This resin is obtained from the pistacia len-
tiscus; a tree which grows in the Levant, particularly in the
island of Chios. When transverse incisions are made into
this tree, a fluid exudes, which soon concretes into yellowish
semitransparent brittle grains. It softens when kept in the
mouth, but imparts very little taste. When heated, it melts
and exhales a fragrant odour. Its taste is slight, but not un-
pleasant. In Turkey great quantities of it are said still to be
chewed for sweetening the breath, and strengthening the
gums. It is to this use of the resin as a masticatory that it
is supposed to owe its name. Mastich does not dissolve
completely in alcohol; a soft elastic substance separates dur-
ing the solution. The nature of this insoluble portion was
first examined by Kind, who found it possessed of all the
properties of caoutchouc. These experiments have lately
been repeated by Mr Mathews with a similar result. Mr
Brande, however, has observed, that when this insoluble sub-
stance is dried, it becomes brittle, in which respect it differs
from caoutchouc. He has observed also, that by passing a
current of oxymuriatic gas through the alcoholic solution of
mastich, a tough elastic substance is thrown down, precisely
similar to the original insoluble portion.
3. Sandarach. - This resin is obtained from the juniperus
commuis or common juniper. It exudes spontaneously,
and is usually in the state of small round tears of a brown
368 VEGETABLE SUBSTANCES. DIV. IV
colour, and semitransparent, not unlike mastich, but rather
more transparent and brittle. When chewed it does not
soften an mastich does, but crumbles to powder. Mr Mat-
thews found it almost completely soluble in eight times its
weight of alcohol. The residue was extraneous matter. It
does not dissolve in tallow or oil, as common resin does.
4. Elemi. - This resin is obtained from the amyris elemi-
fera; a tree which grows in Canada and Spanish America.
Incisions are made in the bark during dry weather, and the
resinous juice which exudes is left to harden in the sun. It
comes to this country in long roundish cakes wrapped in flag
leaves. It is of a pale yellow colour, semitransparent; at first
softish, but it hardens by keeping. Its smell is at first strong
and fragrant, but it gradually diminishes.
5. Tacumahac. - This resin is obtained from the fagara
octandra and likewise, it is supposed, from the populus bal-
samifera. It comes from America in large oblong masses
wrapt in flag leaves. It is of a light brown colour, very
brittle, and easily melted when heated. When pure it has
an aromatic smell between that of lavender and musk.
6. Animé. - This resin is obtained from the hymenaea
courbaril or locust tree, which is a native of North America.
Animé resembles copal very much in its appearance; but is
readily soluble in alcohol, which copal is not: this distin-
guishes them. It is said to be very frequently employed in
making varnishes. Alcohol dissolves it completely.
7. Ladanum or labdanum. This resin is obtained from
the cystus creticus, a shrub which grows in Syria and the
Grecian Islands. The surface of this shrub is covered with
a viscid juice, which, when concreted, forms ladanum. It is
collected while moist by drawing over it a kind of rake with
thongs fixed to it. From these thongs it is afterwards scrap-
ed with a knife. It is always mixed with dust and sand,
sometimes in great abundance. The best is in dark coloured
CHAP. XXIII. RESINS. 569
masses, almost black, and very softy having a fragrant odour
and a bitterish taste. The impurities even in the best kinds,
amount to about one-fourth.
8. Botany Bay resin. - This resin is said to be the pro-
duce of the acarois resinifera; a tree which grows abundant-
ly in New Holland, especially near Botany Bay. Specimens
of it were brought to London about the year 1799, where it
was tried as a medecine.
The resin exudes spontaneously from the trunk of the sin-
gular tree which yields it, especially if the bark be wounded.
It is at first fluid, but becomes gradually solid when dried in
the sun. It consists of pieces of various sizes of a yellow
colour, unless when covered with a greenish grey crust. It
is firm, yet brittle; and when pounded, does not stick to the
mortar nor cake. In the mouth it is easily reduced to pow-
der without sticking to the teeth. It communicates merely
a slight sweetish astringent taste. When moderately heated,
it melts; on hot coals it burns to a coal, emitting a white
smoke, which has a fragrant odour somewhat like storax.
When thrown into the fire, it increases the flame like pitch.
It communicates to water the flavour of storax, but is inso-
luble in that liquid. When digested in alcohol, two-thirds
dissolve: the remaining third consists of one part of extrac-
tive matter, soluble in water, and having an astringent taste;
and two parts of woody fibre and other impurities, perfectly
tasteless and insoluble. The solution has a brown colour,
and exhibits the appearance and the smell of a solution of
benzoin. Water throws it down unaltered. When distilled,
the products were water and empyreumatic oil, and charcoal,
but it gives no traces of any acid, alkali, or salt, not even
when distilled with water.
9. Copal. - This substance, which deserves particular at-
tention from its importance as a varnish, and which at first
sight seems to belong to a distinct class from the resins, is
A a
370. VEGETABLE SUBSTANCES. DIV. IV.
obtained, it is said, from the rhus copallinum, a tree which is
a native of North America; but the best sort of copal is
said to come from Spanish America, and to be the produce
of different trees. No less than eight species are enumerated
by Hernandez.
Copal is a beautiful white resinous substance, with a slight
tint of brown. It is sometimes opaque, and sometimes al-
most perfectly transparent. When heated it melts like other
resins; but it differs from them in not being soluble in alco-
hol, nor in oil of turpentine without peculiar management.
Neither does it dissolve in the fixed oils with the same ease
as the other resins. It resembles gum animé a little in ap-
pearance; but is easily distinguished by the solubility of this
last in alcohol, and by its being brittle between the teeth,
whereas animé softens in the mouth. The specitic gravity
of copal varies, according to Brisson, from 1.045 to 1.139.
Mr Hatchett found it soluble in alkalies and nitric acid with
the usual phenomena; so that in this respect it agrees with
the other resins. The solution of copal in alkalies he found
indeed opalescent, but it is nevertheless permanent. It de-
serves attention, that he found rosin, when dissolved in nitric
acid, and then thrown down by an alkali, to acquire a smell
resembling that of copal.
When copal is dissolved in any volatile liquid, and spread
thin upon wood, metal, paper, &c. so that the volatile men-
struum may evaporate, the copal remains perfectly transpa-
rent, and forms one of the most beautiful and perfect var-
nishes that can well be conceived. The varnish thus formed
is called copal varnish, from the chief ingredient in it. This
varnish was first discovered in France, and was long known
by the name of vernis martin. The method of preparing it
is concealed; but different processes for dissolving copal in
volatile menstrua have been from time to time made public.
CHAP. XXIII. RESINS. 371
Lac. - This is a substance deposited on different spe-
cies of trees in the East Indies, by an insect called chermes
lacca, constituting a kind of comb or nidus. It has been
imported into Europe, and extensively used from time imme-
morial; but it is only of late years that correct information
concerning it has been obtained. For what relates to the
natutal history of the insect, and the mode of forming the
lac, we are nidebted to Mr Ker, Mr Saunders and Dr Rox-
burgh. Though very often employed in the arts, it was ne-
glected by chemists. Mr Hatchett has lately examined it
with his usual address, and ascertained its composition and
properties.
There are various kinds of lac distinguished in commerce.
Stick lac is the substance in its natural state, encrusting small
twigs. When broken off and boiled in water it loses its red
colour, and is called seed lac. When melted and reduced to
the state of thin crust, it is called shell lac. Stick lac is of a
deep red colour, and yields to water a substance which is used
as a red dye. The other two varieties are brown.
Water dissolves the greatest part of the colouring matter
of lac, which varies from 15 to 1/2 per cent. Alcohol dis-
solves the greatest part of the resin, which constitutes the
chief ingredient in the composition of lac. Ether acts more
feebly. Sulphuric acid dissolves and gradually chars lac;
nitric acid dissolves, and then produces the same changes on
it as on other resinous bodies. Muriatic and acetic acids
likewise act as solvents. A solution of borax in water readi-
ly dissolves lac. The best proportions are 20 grains of bo-
rax, 100 grains of lac, and four ounces of water. This solu-
tion, mixed with lamp black, constitutes Indian hik; and
may indeed be employed for many of the purposes of varnish.
The fixed alkalies readily dissolve lac, but not the volatile.
When placed on a hot iron it melts, and emits a thick smoke
with an odour rather pleasant, leaving a spongy coal. When
A a 2
372 VEGETABLE SUBSTANCES. DIV. IV.
distilled, it yields water slightly acidulous, and a thick buty-
raceous oil. The gasses emitted are a mixture of carbonic
acid and carbureted hydrogen. Stick lac yields also some
carbonate of ammonia; but the other two varieties none.
The following Table exhibits the constituents of the different
varieties of lac, according to the analysis of Mr Hatchett.
Stick Lac. Seed Lac. Shell Lac.
Resin 68 88.5 90.9
Colouring matter 10 2.5 0.5
Wax 6 4.5 4.0
Gluten 5.5 2.O 2.8
Foreign bodies 6.5
Loss 4.0 2.5 1.8
100 100 100
The resin is less brittle than those bodies usually are. The
colouring matter possesses the properties of extractive; the
wax is analogous to myrtle wax, and the gluten closely re-
sembles the gluten of wheat.
11. Amber. - This substance is undoubtedly of vegetable
origin; and though it differs from resins in some of its pro-
perties, yet it agrees with them in so many others, that it
may, without impropriety, be referred to them.
Amber is a brittle, light, hard substance, usually nearly
transparent; sometimes nearly colourless, but commonly
yellow or even deep brown. It has considerable lustre. Its
specific gravity is 1.065; It is tasteless, and without smell,
except when pounded or heated, when it emits a fragrant
odour. When heated it softens; but, as far as is known,
cannot be melted without losing some of its weight, and al-
tering its appearance. In a strong heat it burns, leaving a
small quantity of ashes, the nature of which has not yet
been ascertained. Water has no action on it; but alcohol,
by long digestion, dissolves about one eighth of the amber,
CHAP. XXIII. RESINS. 373
and forms a coloured solution, which when concentrated be-
comes milky when mixed with water. The residiuum of
the amber is not acted on by alcohol. Though amber be
roasted before the action of the alcohol, the tincture is still
formed. Hence we learn that the resinous part of amber is
not expelled by a melting heat.
The weaker acids have no action on amber. Sulphuric
acid converts it into a black resinous mass. Nitric acid acts
upon it; when assisted by heat, nitrous gas is emitted.
Neither fixed nor volatile oils have any action on amber
unless it has been previously roasted or exposed to a melting
heat. When thus treated, it combines with oils, and the so-
lution forms amber varnish. The process recommended by
Nystrom is this: Amber is to be spread on a flat-bottomed
iron pan, and placed on an equal coal fire till it melt; it is
then to be withdrawn, covered with a plate, of copper and
iron, and allowed to cool. If the process be properly con-
ducted, the amber will have lost half of its weight. If the
fire be too strong, the amber will be scorched and rendered
useless. If it be too low, the amber will not melt, but be re-
duced to a brown crust, which answers well enough for a
varnish, provided it be exposed to heat till it is reduced to
one half of the orignal weight. One part of this roasted
amber is to be mixed with three parts of the linseed oil
(rendered drying by litharge and white vitriol), and the mix-
ture exposed to a gentle heat till the amber is dissolved: it
is then to be withdrawn from the fire, and when nearly cold
four parts of oil of turpentine are be added. The whole
is then allowed to settle, and the clear portion is passed
through a linen cloth.
A a 3
374 VEGETABLE SUBSTANCES. DIV. IV
CHAP- XXIV.
OF GUAIACUM.
This substance is obtained from the guaiacum officinale,
a tree which is a native of the West Indies, and yields a very
hard heavy wood. The resin exudes spontaneously, and is
also driven out artificially by heating one end of the wood
in billets previously bored longitudinally; the melted resin
runs out at the extremity farthest from the fire. This sub-
stance has been used in medicine for a considerable time,
having been originally recommended in venereal diseases.
Nothing is known concerning its original introduction into
Europe.
It was considered by chemists as a resin, till Mr Hat-
chett observed, that when treated with nitric acid it yielded
products very different from those of the resinous bodies.
This induced Mr William Braude to examine its chemical
properties in detail.
Guaiacum is a solid substance, resembling a resin in ap-
pearance. Its colour differs considerably, being partly
brownish, partly reddish, and partly greenish; and it always
becomes green when left exposed to the light in the open
air. It has a certain degree of transparency, and breaks with
a vitreous fracture. When pounded it emits a pleasant bal-
samic smell, but has scarcely any taste, although when
swallowed it excites a burning sensation in the throat.
When heated it melts, and diffuses at the same time a pretty
strong fragrant odour. Its specific gravity is 1.2289.
When guaiacum is digested in water a portion of it is dis-
solved, the water acquiring a greenish brown colour and a
CHAP. XXIV. GUAIACUM. 375
sweetish taste. The liquid, when evaporated, leaves a brown
substance which possesses the property of extractive.
Alcohol dissolves guaiacum with facility, and forms a
deep brown coloured solution. Water renders this solution
milky by separating the resin. Muriatic acid throws down
the guaiacum of an ash grey, and sulphuric acid of a pale
green colour. Acetic acid and the alkalies occasion no pre-
cipitate. Liquid oxymuriatic acid throws it down of a fine
pale blue, which does not change when dried. Diluted ni-
tric acid occasions no change at first; but after some hours
the liquid becomes green, then blue, and at last brown, and
at that period a brown coloured precipitate falls down. If
water be mixed with the liquid when it has assumed a green
or a blue colour, green and blue precipitates may be respec-
tively obtained.
Sulphuric ether does not act so powerfully on guaiacum
as alcohol. The solution obtained by means of it, exhi-
bits the same properties when treated with re-agents as that
in alcohol.
The alkaline solutions, both pure and in the state of car-
bonates, dissolve guaiacum with facility. Two ounces of
a staturated solution of potash dissolved about 65 grains of
guaiacum; the same quantity of ammonia only 25 grains; or
guaiacum dissolves in about 15 parts of potash and 35 parts
of ammonia.
Most of the acids act upon guaiacum with considerable
energy.
Sulphuric acid dissolves it, and forms a deep red liquid,
which deposites while fresh a lilac-coloured precipitate when
mixed with water. When heat is applied the guiuacum is
charred.
Nitric acid dissolves guaiacum completely without the as-
sistance of heat, and with a strong effervescence. When the
solution is evaporated, it yields a very large quantity of oxa-
A a 4
376 VEGETABLE SUBSTANCES. DIV. IV.
lic acid. No artificial tannin appears to be formed, but ra-
ther a substance possessing the properties of extractive. Di-
luted nitric acid converts guaiacum into a brown substance,
similar to the precipitate obtained by nitric acid from the
the alcoholic solution of guaiacum. This brown matter pos-
sesses the properties of a resin.
Muriatic acid acts but slightly, as the guaiacum soon melts
into a blackish mass, which is not acted upon.
When guaiacum is distilled, 100 parts of it yielded to Mr
Brande the following products;
Acidulous water 5.5
Thick brown oil 24.5
Ihin empyreumatic oil 30.k0
Charcoal 30.5
Gasses, consisting of carbonic acid
and carbureted hydrogen 9.5
____
1000
The coal when incinerated left three grains of lime, but
no alkaline substance.
CHAP. XXV.
OF BALSAMS.
The term balsam or balm was originally confined to a
thick fragrant juice obtained from the amyris gileadensis,
and afterwards applied by chemists to all substances which
possess the same degree of consistence and a strong smell,
whether natural or artificial. Bucquet restricted the term
to those resinous-like substances which yield benzoic acid
when heated. This new meaning of the word, which has
been adopted by chemists in general, has introduced into the
CHAP. XXV. GUAIACUM. 377
class of balsams several substances which were formerly con-
sidered as resins. The word balsam originally implied a
substance possessing a certain degree of fluidity; but now
there are two classes of balsams; the one fluid, and the other
solid and brittle.
A balsam, then, is a substance which possesses the gene-
ral properties of a resin, but which, when heated or digested
in acids, yields a portion of benzoic acid. Chemists, in ge-
neral, have considered them as combinations of a resin with
benzoic acid; but Mr Hatchett has made it probable, that
the acid is formed at the time of its separation.
They are insoluble in water; but when boiled in that li-
quid often give out a portion of benzoic acid. Alcohol and
ether dissolve them readily. The strong acids likewise dis-
solve them; and during the solution a portion of benzoic
acid is separated. Nitric acid, in some cases, evolves like-
wise traces of prussic acid. The alkalies act upon them
nearly as on the resins. They may be divided into two
classes; namely, liquid and solid balsams.
1. Liquid Balsams.
The liquid balsams at present known are four in number;
namely,
1. Copaiva 3. Peru
2. Tolu 4. Styrax.
1. Copaiva. - This balsam is obtained from the copaifera
officinalis; a tree which grows in South America, and some
of the West India islands. It exudes from incisions made in
the trunk of the tree. The juice thus obtained is transpa-
rent, of a yellowish colour, an agreeable smell, a pungent
taste, at first of the consistence of oil, but it gradually be-
comes as thick as honey. Its specific gravity is 0.950. When
378 VEGETABLE SUBSTANCES. DIV. IV.
mixed with water and distilled, there comes over with the wa-
ter a very large quantity of volatile oil. The residuum con-
sists of two substances; namely, the watery portion, and a
greyish yellow substance, lying at the bottom of the vessel,
which, on exposure to the air, dries, and becomes brittle
and transparent. When heated it melts, and possesses the
characters of a resin. When distilled it yielded a yellowish
thick oil, some acidulous thick water, and a gas; one-sixth
of which was carbonic acid, and the remainder seemed to
possess the characters of olefiant gas. From these facts,
which have been long known, it was concluded, that copaiva
is a compound of a resin and a volatile oil, which passes over
at a heat inferior to that of boiling water; but the experi-
ments of Schonberg have rendered it much more probable,
that the balsam is decomposed when distilled along with wa-
ter, and that both the oil and resin are new products.
Whether this balsam yields benzoic acid has not been as-
certained. Its properties are rather against the probability
of its doing so. Indeed it bears a striking resemblance to tur-
pentine in many respects; and ought, along with it, to con-
stitute a class of bodies intermediate between volatile oils and
resins, to which the name of turpentines might be given.
Balsam of Tolu. - This substance is obtained from the
toluifera balsamum, a tree which grows in South America.
The balsam flows from incisions made in the bark. It comes
to Europe in small gourd shells. It is of a reddish brown co-
lour and considerable consistence; and when exposed to the
air, it becomes solid and brittle. Its smell is fragrant, and
continues so even after the balsam has become thick by age.
When distilled with water, it yields very little volatile oil, but
impregnates the water strongly with its taste and smell. A
quantity of benzoic acid sublimes, if the disillation be conti-
nued.
CHAP. XXV. BALSAMS. 375|
Balsam of Peru. - This substance is obtained from the
myroxylon peruiferum, which grows in the warm parts of
South America. The tree is full of resin, and the balsam
is obtained by boiling the twigs in water. It has the con-
sistency of honey, a brown colour, an agreeable smell, and a
hot acrid taste. When boiled with water for some time, the
liquid separated by the filter reddens vegetable blues, and de-
posits crystals of benzoic acid on cooling. The water con-
tains no other substance. When distilled with water, it yields
a very small quantity of reddish limpid oil.
4. Styrax. - This is a semifluid juice, said to be obtained
from the liquidambar styraciflua, tree which grows in Vir-
ginia, Mexico, and some other parts of America. It is pre-
pared according to Mr Petiver, in the island of Cobross in
the Red Sea, from the bark of a tree called rosa mallos by
the natives, and considered by botanists as the same with the
American species. The bark of this tree is boiled in salt water
to the consistence of bird lime, and then put into casks, in
colour is greenish, its taste aromatic, and its smell agreeable.
It is easily volatilized by beat. When treated with water,
benzoic acid is dissolved. It is totally soluble in alcohol ex-
cept the impurities. When exposed to the air it becomes
harder, and absorbs oxygen. When distilled, it yields an
acidulous water, having the odour of benzoic acid, a limpid
colourless hot oil, a solid coloured oil, benzoic acid, and a
mixture of carbonic acid and carbureted hydrogen. The
charcoal is light, and contains some oil.
2. Solid Balsams.
The solid balsams at present known are only three in num-
ber, namely,
380 VEGETABLE SUBSTANCES. DIV. IV.
1. Benzoin
2. Storax
3. Dragon's blood.
1. Benzoin. - This substance is the produce of the styrax
benzoe, a tree which grows in Sumatra, &c. Benzoin is ob-
tained from this tree by incision; a tree yielding three or four
pounds. It is a solid brittle substance, sometimes in the form
of yellowish white tears joined together by a brown substance,
and sometimes in the form of a brown substance not unlike
common rosin. It has a very agreeable smell, which is in-
creased by heating the benzoin. It has little taste. Its spe-
cific gravity is 1.002.
Cold water has very little effect on benzoin, but boilng
water takes up a portion of benzoic acid.
Alcohol dissolves it when assisted by a gentle heat, and
forms a deep yellow solution inclining to reddish brown.
When this solution is diluted with water, the benzoin preci-
pitates in the form of a white powder.
Ether dissolves benzoin with facility, and the solution with
re-agents exhibits the same phenomena as the alcoholic.
Nitric acid acts with violence on benzoin, and converts it
into an of orange-coloured mass. When assisted by heat, the
acid dissolves the benzoin; and as the solution cools, crytals
of benzoic acid gradually separate.
Sulphuric acid dissolves benzoin, while benzoic acid su-
blimes; the solution is at first a deep red. By continuing
the digestion, a portion of artificial tannin is formed, and the
charcoal evolved amounts to 0.48 of the benzoin dissolved.
Acetic acid dissolves benzoin without the assistance of heat.
When heat is applied, the solution, as it cools, becomes tur-
bid; owing to the separation of benzoic acid.
Benzoin is dissolved by a boiling lixivium of the fixed al-
kalies; a dark brown solution is formed, which becomes tur-
CHAP. XXV. BALSAMS. 381
bid after some days exposure to the air. Ammonia likewise
dissolves benzoin sparingly.
When Mr Brande exposed 100 grains of benzoin in a re-
tort to a heat gradually raised to redness, the products were,
Benzoic acid 9.0
Acidulous water 5.5
Butyraceous and empyreumatic oil 6O.O
Charcoal 22.0
Carbureted hydrogen and carbonic acid 3.5
____
100.0
2. Storax. - This is the most fragrant of all the balsams,
and is obtained from the styrax officinalis, a tree, which grows
in the Levant, and it is said also in Italy. Sometimes it is
in the state of red tears; and this is said to be the state is
which it is obtained from the tree. But common storax is
in large cakes; brittle, but soft to the touch, and of a reddish
brown colour. This is more fragrant than the other sort,
though it contains a considerable mixture of saw-dust. It dis-
solves in alcohol. When distilled with alcohol or with wa-
ter, scarcely any oil is obtained. When distilled by the na-
ked fire, it seems from the experiments of Neumann, to yield
the same products as benzoin.
3. Dragon's blood. - This is a brittle substance of a dark
red colour, which comes from the East Indies. There are
two sorts of it; one in small oval drops or tears of a fine deep
red, which becomes crimson when the tears are reduced
to powder; the other is in larger masses, some of which are
pale red, and others dark. It is probably obtained from dif-
ferent kinds of trees; the calamus draco is said to furnish
most of what comes from India. The dracaena draco and
the pterocarpus draco are also said to furnish it.
Dragon's blood is brittle and tasteless, and has no sensible
smell. Water does not act upon it, but alcohol dissolves the
382 VEGETABLE SUBSTANCES. DIV. IV
greatest part, leaving a whitish red substance, partially acted
upon by water. The solution has a fine deep red colour,
which stains marble, and the stain penetrates the deeper the
hotter the marble is. It dissolves also in oils, and gives them
a deep red colour. When heated it melts, catches flame,
and emits an acid fume similar to that of benzoic acid. When
digested with lime, a portion of it becomes soluble in water,
and it acquires a balsamic odour. On adding muriatic acid
to the solution, a red resinous substance is precipitated, and
slight traces of benzoic acid only become perceptible. Ni-
tric acid acts upon it with energy, changes it to a deep yel-
low, a portion of benzoic acid is sublmed, and a brown mass
remains soluble in water, and possessing the properties of ar-
tificial tannin.
CHAP. XXVI.
OF CAOUTCHOUC.
About the beginning of the 18th century, a substance call-
ed caouchouc was brought as a curiosity from America.
It was soft, wwonderfully elastic, and very combustible. The
pieces of it that came to Europe were usually in the shape
of bottles, birds, &c. This substance is very much used in
rubbing out the marks made upon paper by a black lead
pencil; and therefore in this country it is often called Indian
rubber.
It is now known that there are at least two trees in South
America from which caoutchouc may be obtained; the hae-
vea caoutchouc and the jatropha elastica; and it is exceed-
ingly probable that it is extracted also from other species of
haevea and jatropha. Several trees likewise which grow in
the East Indies yield caoutchouc; the principal of these are
CHAP. XXVI. CAOUTCHOUC. 383
the ficus indica, the artocarpus integrifolia, and the urceola
elastica.
When any of these plants are punctured, there exudes from
it a milky juice, which, when exposed to the air, gradually
lets fall a concrete substance, which is caoutchouc.
If oxymuriatic acid be poured into the milky juice, the
caoutchouc precipitates immediately, and at the same time
the acid loses its peculiar odour. This renders it probale
that the formation of the caoutchouc is owing to its basis ab-
sorbing oxygen. If the milky juice be contained in a glass
vessel containing common air, it gradually absorbs oxygen,
and a pellicle of caoutchouc appears on its surface.
Caoutchouc, when pure, is of a white colour, and without
either taste or smell. The blackish colour of the caout-
chouc of commerce is owing to the method employed in dry-
ing it after it has been spread upon moulds. The usual way
is to spread a thin coat of the milky juice upon the mould,
and then to dry it by exposing it to smoke; afterwards ano-
ther coat is spread on, which is dried in the same way. Thus
the caoutchouc of commerce consists of numerous layers of
pure caoutohouc alternating with as many layers of soot.
Caoutchouc is soft and pliable like leather. It is exceed-
ingly elastic and adhesive; so that it may be forcibly stretch-
ed out much beyond its usual length, and instantly recover
its former bulk when the force is withdrawn. It cannot be
broken without very considerable force. Its specific gravity
is 0.9335.
Caoutchouc is not altered by exposure to the air; it is per-
fectly insoluble in water; but if boiled for some time its edges
become somewhat transparent, owing undoubtedly to the wa-
ter carrying off the soot; and so soft, that when two of them
are pressed and kept together fur some time, they adhere as
closely as if they formed one piece. By this contrivance
384 VEGETABLE SUBSTANCES. DIV. VI
pieces of caoutchouc may be soldered together, and thus made
to assume whatever shape we please.
Caoutchouc is insoluble in alcohol. This property was
discovered very early, and fully confirmed by the experiments
of Mr Macquer. The alcohol, however, renders it colour-
less.
Caoutchouc is soluble in ether. This property was ffirst
pointed out by Macquer. Berniard, on the contrary, found
that caoutchouc was scarcely soluble at all in sulphuric
ether, which was the ether used by Macquer, and that even
nitric ether was but an imperfect solvent. The difference in
the results of these two chemists was very singular; both
remarkable for their accuracy, and both were too well
aquainted with the subject to be easily misled. The mat-
ter was first cleared up by Mr Cavallo. He found that
ether, when newly prepared, seldom or never dissolved
caoutchouc completely, but if the precaution was taken to
wash the ether previously in water, it afterwards dissolved
caoutchouc with facility.
When the ether is evaporated, the caoutchouc is obtained
unaltered. Caoutchouc, therefore, dissolved in ether, may be
employed to make instruments of different kinds, just as the
milky juice of the haevea; but this method would be a great
deal too expensive for common use.
Caoutchouc is soluble in volatile oils; but, in general,
when these oils are evaporated, it remains somewhat gluti-
nous, and therefore is scarcely proper for those uses to which,
before its solution, it was so admirably adapted.
The acids act but feebly upon caoutchouc. Sulphuric
acid, even after a long digestion, only chars it superficially.
When treated with nitric acid, there came over azotic gas,
carbonic acid gas, prussic acid gas; and oxalic acid is said
to be formed. Muriatic acid does not affect it. The other
acids have not been tried.
CHAP. XXVII. CAOUTCHOUC. 385
Fabroni has discovered, that rectified petroleum dissolves
it, and leaves it unaltered when evaporated.
When exposed to heat it readily melts; but it never af-
terwards recovers its properties, but continues always of the
consistence of tar. It burns very readily with a bright
flame, and diffuses a fetid odour. In those countries where
it is produced, it is often used by way of candle.
When distilled it gives out ammonia. It is evident from
this, and from the effect of sulphuric and nitric acid upon
it, that it is composed of carbon, hydrogen, azote, and oxygen
but the manner in which they are combined is unknown.
CHAP. XXVII.
OF GUM RESINS.
This class of vegetable substances has been long distin-
guished by physicians and apothecaries. It contains many
active substances much employed in medicine; and they cer-
tainly possess a sufficient number of peculiar properties to
entitle them to be ranked apart. Unfortunately these sub-
stances have not yet attracted much of the attention of che-
mists. Their properties and constituents of course are but
imperfectly ascertained.
They are usually opaque, or at least their transparency is
inferior to that of the resins. They are always solid, and
most commonly brittlem and have sometimes a fatty appear-
ance.
When heated they do not melt as the resins do; neither
are they so combustible. Heat, however, commonly softens
them, and causes them to swell. They burn with a flame.
They have almost always a strong smell, which in several
B b
386 VEGETABLE SUBSTANCES. DIV. IV.
instances is alliaceous. Their taste also is often acrid, and
always much stronger than that of the resins.
They are partially soluble in water; but the solution is
always opaque, and usually milky.
Alcohol dissolves only a portion of them. The solution
is transparent; but when diluted with water it becomes milky;
yet no precipitate falls, nor is any thing obtained by filtering
the solution.
Vinegar and wine likewise dissolve them partially; and
the solution, like the aqueous, is opaque or milky.
According to Hermbstadt, they are insoluble in sulphu-
ric ether.
The action of alkalies on them has been examined only
by Mr Hatchett. All of them tried by that celebrated che-
mist dissolved readily in alkaline solutions when assisted by
heat. We may therefore consider them as soluble in alkalies
like resins.
Nitric acid acts upon them with energy; converting them
first into a brittle mass, and then, with the assistance of heat,
dissolving them.
Their specific gravity is usually greater than that of the
resins.
Their other properties still continue unknown. They all
either exude spontaneously from plants, or are obtained by
incisions. At first they seem to be in a liquid state; but
they gradually harden when exposed to the air and weather.
The gum resins which have been hitherto applied to any
useful purpose are the following:
1. Galbanum. It is obtained from the bubon galbanum,
a perennial plant, and a native of Africa. When this plant
is cut across a little above the root, a milky juice flows out,
which soon hardens and constitutes galbanum. It comes to
this country from the Levant, in small pieces composed of
tears, agglutinated together, of a yellowish or white colour.
CHAP. XXVII. GUM RESINS. 387
Its taste is acrid and bitter, and its smell peculiar. Water,
vinegar, and wine, dissolve part of it, but the solution is
milky. Alcohol dissolves about three-fifths.
2. Ammoniac. This substance is brought from the East
Indies. Nothing certain is known concerning the plant
which yields it; though from analogy it has been suspected
to be a species of ferula. It is in small pieces agglutinated
together, and has a yellowish white colour. Its smell is
somewhat like that of galbanum, but more pleasant. Its
taste is a nauseous sweet mixed with bitter. It does not
melt. Water dissolves a portion of it; the solution is milky,
but gradually lets fall a resinous portion. More than one-
half is soluble in alcohol. This portion is a resin.
According to the analysis of Braconnot ammoniac is com-
posed of the following ingredients:
70.0 resin
18.4 gum
4.4 glutinous matter
6.0 water
1.2 loss
____
100-0
3. Olinanum. This substance is obtained from the juni-
perus lycia, and is chiefly collected in Arabia. It is the
frankincense of the ancients. It is in transparent brittle
masses about the size of a chestnut. Its colour is yellow.
It has a bitterish nauseous taste; and when burnt diffuses
an agreeable odour. Alcohol dissolves three-fourths of it;
and water about three-eights.
4. Asafoetida. This substance is obtained from the feru-
la asafoetida, a perennial plant which is a native of Persia.
When the plant is about four years old, its roots are dug up
and cleaned. Their extremity being then cut off, a milky
juice exudes, which is collected. Then another portion is
B b 2
388 VEGETABLE SUBSTANCES. DIV. IV.
cut off, and more juice exudes. This is continued till the
roots are exhausted. The juice thus collected soon hardens
and constitutes asafoetida. It comes to Europe in smal
grains of different colours, whitish, reddish, violet, brown.
Pretty hard, but brittle. Its taste is acrid and bitter; its
smell strongly allicaceous and fetid. Alcohol dissolves
about three-fourths of this substance; and water takes up
nearly one-fourth if applied before the spirit.
5. Scammony - This substance is obtained from the con-
volvulus scammonia, a climbing plant which grows in Sy-
ria. The roots when cut yield a milky juice. This when
collected and allowed to harden constitutes scammony. Co- ANIMAL SUBSTANCES. DIV. V.
lour dark grey or black. Smell peculiar and nauseous: taste
bitter and acrid. With water it forms a greenish-coloured
opaque liquid. Alcohol dissolves the greatest part of it. It
is usually mixed with the expressed juice of the root, and
frequently also with other impurities, which alter its appear-
ance. In medicine it operates as a strong cathartic.
6. Opoponax. - This substance is obtained from the pas-
tinaca opoponax, a plant which is a native of the countries
round the Levant. The gum resin, like most others, is ob-
tained by wounding the roots of the plant. The milky juice,
when dried in the sun, constitutes the opoponax. It is in
lumps of a reddish yellow colour, and white within. Smell
peculiar. Taste bitter and acrid. With water it forms a
milky solution, and about one-half of it dissolves. Alcohol
acts but feebly.
7. Gamboge or Gumgutt. - This substance is obtained
from the stakagmitis gambogioides, a tree which grows wild
in the East Indies. In Siam it is obtained in drops by
wounding the shoots; in Ceylon it exudes from wounds in
the bark. It is brought to Europe in large cakes. Its co-
lour is yellow; it is opaque, brittle and breaks vitreous.
It has no smell, and very little taste. With water it forms
CHAP. XXVII. GUM RESINS. 389
a yellow turbid liquid. Alcohol dissolves it almost com-
pletely; and when mixed with water becomes turbid, unless
the solution contains ammonia.
Braconnet analysed it, and found it composed of one part
of a gum which possessed the properties of cherry tree gum,
and four parts of a reddish brittle resin which possessed the
characteristic properties of the resins.
8. Myrrh. - The plant from which this substance is ob-
tained is unknown. If we believe Bruce it belongs to the
genus of mimosa. It grows in Abyssinia and Arabia. It it
in the form of tears. Colour reddish yellow; when pure
somewhat transparent, but it is often opaque. Odour pecu-
liar. Taste bitter and aromatic. Does not melt when heat-
ed, and burns with difficulty.
From the analysis of Braconnot it appears that myrrh is
composed of about
23 resin
77 gum
___
100
The resin is reddish, has a bitter taste and the peculiar odour
of myrrh. The gum differs in its properties from every
other gummy substance hitherto examined. It has a dark
brown colour; is at first soluble in water, but by boiling the
liquid, or by exposing the gum to heat, it requires cohesive
properties, and becomes insoluble in water. When distilled
it yields ammonia, and when dissolved in nitric acid, azotic
gas is disengaged.
It deserves attention, that the gum resins, when subjected
to destructive distillation, yield all of them a portion of am-
monia; a proof that they all contain azote. In this respect
they agree with gum and extractive.
B B 3
390 VEGETABLE SUBSTANCES. DIV. IV.
CHAP. XXVIII.
OF COTTON.
Cotton is a soft down which envelopes the seeds of various
plants, especially the different species of gossypium, from
which the cotton of commerce is procured. These plants
are natives of warm climates; grow wild in Asia, Africa, and
America, within the tropics; and are cultivated in the East
and West Indies.
Though no correct chemical investigation of the proper-
ties of cotton has hitherto been made, yet as its obvious qua-
lities distinguish it sufficiently from every other vegetable sub-
stance, we must consider it as a peculiar vegetable priniple;
and I have introduced it here, in hopes that some person or
other will be induced to examine its nature in detail. The
following are the particulars at present known.
This substance is in threads differing in length and fine-
ness. No asperities can be discovered on the surface of these
threads; but if Lewenhoeck's microscopical observations are
to be trusted, they are all triangular, and have three sharp
edges. Cotton differs considerably in colour; but when
bleached it becomes of a fine white.
Cotton is tasteless and destitute of smell. It is complete-
ly insoluble in water, alcohol, ether, and oils, and in all the
vegetable acids.
The diluted alcaline leys have no perceptible action on
cotton; but when very strong they dissolve it if assisted by a
sufficient degree of heat. The new products obtained by
this solution have not been examined.
Cotton combines readily with tannin, and forms a yellow
or brown compound. Hence the infusion of galls, and
CHAP. XXIX. SUBER. 391
Other astringent substances, is often used as a mordant for
cotton.
Nitric acid decomposes cotton when assisted by heat, and
oxalic acid is formed; the other products have not been ex-
amined. Sulphuric acid likewise chars it. Oxymuriatic
acid gas bleaches it, and probably alters and dissolves it when
applied in a concentrated state.
Cotton is exremely combustible, and burns with a clear
lively flame. The ashes left behind, according to Neumann,
contain some potash. When distilled it yields a great por-
tion of acidulous water, and a small quantity of oil, but no
ammonia.
CHAPTER XXIX.
OF SUBER.
This name has been introduced into chemistry by Four-
croy, to denote
the outer bark of the quercus sube, or the
common cork; a substance which possesses properties diffe-
rent from all other vegetable bodies.
It is exceedingly light, soft, and elastic; very combustible,
burning with a bright white flame, and leaving a light black
bulky charcoal; and when distilled, it yields a little am-
monia.
When digested in water, a yellowish-coloured solution is
obtained, seemingly containing extractive, as nearly the same
proportion is takien up by alcohol. Sulphuric acid readily
chars it. Nitric acid gives it a yellow colour, corrodes, dis-
solves, and decomposes it; converting it partly into suberic
acid, partly into a substance resembling wax, partly into ar-
tificial tannin, and partly into a kind of starchy matter.
B B 4
392 VEGETABLE SUBSTANCES. DIV. IV.
CHAP. XXX.
OF WOOD.
All trees, and most other plants, contain a particular sub-
stance well known by the name of wood. If a piece of wood
be well dried, and digested, first in a sufficient quantity of
water and then of alcohol, to extract from it all the substan-
ces soluble in these liquids, there remains only behind the
woody fibre.
This substance, which constitutes the basis of wood, is
composed of longitudinal fibres, is easily subdivided into a
number of smaller fibres. It is somewhat transparent; is
perfecty tasteless; has no smell; and is not altered by expo-
sure to the atmosphere.
It is insoluble in water and in alcohol. The fixed alka-
lies, when assisted by heat, give it a deep brown colour, ren-
der it soft, and decompose it. A weak alkaline solution dis-
solves it without alteration; and it may be thrown down again
by means of an acid. By this property we are enabled to
separate wood from most of the other vegetable principles,
as few of them are soluble in weak alkaline leys.
When heated, it blackens without melting or frothing up,
and exhales a disagreeable acrid fume, and leaves a charcoal
which retains exactly the form of the original mass. When
distilled in a retort, it yields an acid liquor of a peculiar taste
and smell, distinguished by the name of pyrolignous, and for-
merly considered as a distinct acid; but Fourcroy and Vau-
quelin have lately ascertained that it is merely the acetic acid
combined with an empyreumatic oil.
CHAP. XXXI. ALKALIES. 393
CHAP. XXXI.
OF ALKALIES.
The only alkalies found in plants are potash and soda.
Ammonia may indeed be obtained by distilling many vege-
table substances, but it is produced during the operation.
One or other of these alkalies is found in every plant which
has hitherto been examined. The quantity indeed is usually
very small. From the experiments of Vauquelin, it is pro-
bable that the alkalies are combined in plants with acetic and
carbonic acids.
1. Potash is found in almost all plants which grow at a
distance from the sea. It may be extracted by burning the
vegetable, washing the ashes in water, filtrating the water,
and evaporating it to dryness. It is in this manner that all
the potash of commerce is procured.
In general, three times as much ashes are obtained from
shrubs, and five times as much from herbs, as from trees.
Equal weights of the branches of trees produce more ashes
than the trunk, and the leaves more than the branches.
Herbs arrived at maturity produce more ashes than at any
other time. Green vegetables produce more ashes than dry.
2. Soda is found in almost all the plants which grow in the
sea, and in many of those which grow on the shore. In ge-
neral, the quantity of soda which plants contain bears a much
greater proportion to their weight than the potash does which
is found in inland vegetables. 100 parts of the salsola soda,
for instance, yield 19.921 of ashes; and these contain 1.992
parts of soda; some of which, however, is combined with
muriatic acid. The plants from which the greater part of
394 VEGETABLE SUBSTANCES. DIV. IV.
the soda, or barilha as it is called, which is imported from
Spain, is extracted, are the salsola sativa<(i> and vermculata.
CHAP. XXXII.
EARTHS.
The only earths hitherto found in plants are the four fol-
lowing: lime, silica, magnesia, alumina.
1 . Lime is usually the most abundant of the earths of
plants, and the most generally diffused over the vegetable
kingdom. Indeed it is a very uncommon thing to find a
plant entirely destitute of lime: salsola soda is almost the
only one in which we know for certain that this earth does
not exist.
2. Silica exists also in many plants, particularly in grasses and
equisetums. Mr Davy has ascertained that it forms a part
of the epidermis, or outer bark of these plants; and that in
some of them almost the whole epidermis is silica.
3. Magnesia does not exist so generally in the vegetable
kingdom as the two preceding earths. It has been found,
however, in considerable quantities in several sea plants,
especially fuci; but the salsola soda contains a greater pro-
portion of magnesia than any plant hitherto examined. Mr
Vauquelin found that 100 parts of it contained 17.929 of
that earth.
4. Alumina has only been found in very small quantities
in plants.
The following table exhibits the quantity of earths and
metallic oxides in grains, obtained by Schraeder from 32
ounces of the seeds of the following kinds of corn; wheat
(triticum hybernum), rye (secale cereale), barley (kordeum
CHAP. XXXIII. METALS. 395
vulgare), oats (avena sativa), and likewise from the same
quantity of rye straw.
Wheat. Rye. Barley. Oats. Rye Straw.
Silica 13.2 15.6 66.7 144.2 152
Carbonate of lime 12.6 13.4 24-8 33.75 46.2
Carbonate of magnesia 13.4 14.2 25.3 33.9 28.2
Alumina 0.6 1.4 4.2 4.5 3.2
Oxide of manganese 5.0 3.2 6.7 6.95 6.8
Oxide of iron 2.5 0.9 3.8 4-5 2.4
___________________________________
47.3 48.7 131.5 227.8 328.8
CHAP. XXXIII.
OF METALS.
Several metallic substances have also been found in the
ashes of vegetables, but their quantity is exceedingly small;
so small, indeed, that without very delicate experiments their
presence cannot even be detected.
The metals hitherto discovered are iron, which is by far
the most common, manganese, and, if we believe some che-
mists, gold.
1. Iron has been found in many plants; the ashes of sal-
sola contain a considerable quantity of it.
2. Scheele first detected manganese in vegetables. Proust
found it in the ashes of the pine, calendula, vine, green oak,
and fig-tree.
3. With respect to the minute portion of gold extracted
from the ashes of plants by Kunkel, Sage, &c. it is probable
that it proceeded rather from the lead which they employed
in their processes than from the ashes.
396 ANIMAL SUBSTANCES. DIV. V.
DIVISION V.
OF ANIMAL SUBSTANCES.
When we compare animals and vegetables together, each
in their most perfect state, nothing can be easier than to dis-
tinguish them. The plant is confined to a particular spot,
and exhibits no mark of consciousness or intelligence; the
animal, on the contrary, can remove at pleasure from one
place to another, is possessed of consciousness, and a high
degree of intelligence. But on approaching the contiguous
extremities of the animal and vegetable kingdom, these strik-
ing differences gradually disappear, the objects acquire a
greater degree of resemblance, and at last approach each
other so nearly, that it is scarcely possible to decide whether
some of those species which are situated on the very boun-
dary belong to the animal or vegetable kingdom.
To draw a line of distinction, then, between animals and
vegetables, would be a very difficult task: but it is not ne-
cessary at present to attempt it; for almost the only animals
whose bodies have been hitherto examined with any degree
of chemical accuracy, belong to the most perfect classes, and
consequently are in no danger of being confounded with
plants. Indeed, the greater number of facts which I have
to relate apply only to the human body, and to those of a few
domestic animals. The task of analysing all animal bodies
is immense, and must be the work of ages of indefatigable
industry.
This part of the subject naturally divides itself into two
chapters. In the first chapter, I shall give an account of
SECT. I GELATINE. 397
the different ingredients hitherto found in animals, such of
them at least as have been examined with any degree of ac-
curacy, and, in the second, I shall treat of the different
members of which animal bodies are composed; which most
consist each of various combinations of the ingredients des-
cribed io the first chapter.
CHAP. I.
OF ANIMAL SUBSTANCES.
The substances which have been hitherto detected in the
animal kingdom, and of which the different parts of animals,
as far as these parts have been analysed, are found to be
composed, may be arranged under the following heads:
1. Gelatine
2. Albumen
3. Mucus
4. Fibrin
5. Urea
6. Saccharine matter
7. Oils
8. Resins.
9. Sulphur
10. Phosphorus
11. Acids
12. Alkalies
13. Earths
14. Metals.
These shall form the subject of the following sections.
SECT. I. OF GELATINE.
If a piece of the fresh skin of an animal, an ox, for in-
stance, after the hair and every impurity is carefully separat-
ed, be washed repeatedly in cold water till the liqid ceases
to be coloured, or to abstract any thing; if the skin, thus
purified, be put into a quantity of pure water, and boiled
for some time, part of it will be dissolved. Let the decoc-
398 ANIMAL SUBSTANCES. DIV. V.
tion be slowly evaporated till it is reduced to a small quan-
tity, and then put aside to cool. When cold, it will be found
to have assumed a solid form, and to resemble precisely that
tremulous substance well known to every body under the
name of jelly. This is the substance called in chemistry
gelatine. If the evaporation be still farther continued, by
exposing the jelly to dry air, it becomes hard, semitranspa-
rent, breaks with a glassy fracture, and is, in short, the sub-
stance so much employed in different arts under the name
of glue. Gelatine, then, is precisely the same with glue;
only that it must be supposed always free from those impu-
rities with which glue is so often contaminated.
Gelatine is semitransparent and colourless when pure.
Its consistency and hardness vary considerably. The best
kinds are very hard, brittle, and break with a glassy fracture.
Its taste is insipid, and it has no smell.
When thrown into water it swells very much, but does
not readily dissolve; and when taken out, it is soft and gela-
tinous; but when allowed to dry, it recovers its former ap-
pearance. If it be put in this gelatinous state into warm
water, it very soon dissolves, and forms a solution of an opal
colour, and the more opaque according to the quantity of
gelatine which it contains. Tremulous gelatine dissolves in
a very small portion of hot water, but as the solution cools,
it gelatinizes afresh. If this solution, as soon as it assumes
the tremulous form, be mixed with cold water and shaken, a
complete solution takes place.
Dry gelatine undergoes no change when kept; but in the
gelatinous state, or when dissolved in water, it very soon pu-
trefies; an acid makes its appearance in the first place (pro-
bably the acetic), a fetid odour is exhaled, and afterwards
ammonia is formed.
Acids dissolve gelatine with facility, even when diluted,
especially when assisted by heat, but we are still ignorant
SECT. I. GELATINE. 399
of the changes produced upon it by these agents exccept by
nitric acid. When this acid is digested on it, a small quan-
tity of azotic gas is disengaged, then abundance of nitrous
gas; the gelatine is dissolved, except an oily matter which
appears on the surface, and converted partly into oxalic and
malic acids.
Alkalies dissolve gelatine with facility, especially when
assisted by heat; but the solution does not possess the pro-
perties of soap.
None of the earths seem to combine with gelatine; at
least they do not precipitate it from its solution in water.
The metals in their pure state have no effect upon gela-
tine; but several of the metallic oxides, when agitated in a
solution of gelatine, have the property of depriving the wa-
ter of the greatest part of that body, with which they form
an insoluble compound. Several of the metallic salts like-
wise precipitate gelatine from water.
Gelatine is insoluble in alcohol. When alcohol is mixed
with a solution of gelatine, the mixture becomes milky; but
becomes again transparent when agitated, unless the solu-
tion be concentrated, and the quantity of alcohol consider-
able. Gelatine is most probably equally insoluble in ether;
though I believe the experiment has not been tried.
When the solution of tannin is dropt into gelatine, a co-
pious white precipitate appears, which soon forms an elas-
tic adhesive mass not unlike vegetable gluten. This preci-
pitate is composed of gelatine and tannin; it soon dries in
open air, and forms a brittle resinous-like substace, in-
soluble in water, capable of resisting the greater number of
chemical agents, and not susceptible of putrefaction.
Gelatine, does not, properly speaking, combine with oils,
but it renders them miscible with water, and forms a kind
of emulsion.
400 ANIMAL SUBSTANCES. DIV. V.
From the effects df ditferent re-agents on gelatine, and
from the decomposition which it undergoes when heated, we
see that it contains carbon, hydrogen, azote, and oxygen. But
what the proportion of these constitueuts are, cannot be ea-
sily ascertained. The phosphate of lime, and the traces of
soda, which it always yields, are most likely only held in so-
lution by it.
SECT. II. Of Albumen.
The eggs of fowls contain two very different substances:
a yellow oily-like matter, called the yolk; and a colorless
viscid liquid, distinguished by the name of white.
This last is the substance which chemists have agreed to de-
nominate albumen. The white of an egg, however, is not
pure albumen. It contains also some mucus, soda, and sul-
phur: but as albumen is never found perfectly pure, and as
no method is known of separating it without at the same
time altering the properties of the albumen, chemists are
obliged to examine it while in combination with these
bodies.
Albumen dissolves readily in water, and the solution has
the property of giving a green colour to vegetable blues, in
consequence of the soda which it contains. When albumen
is heated to the temperature of 165˚, it coagulates into a
white solid mass; the consistency of which, when other things
are equal, depends, in some measure, on the time during
which the heat was applied. The coagulated mass has pre-
cisely the same weight that it had while fluid. This proper-
ty of coagulating when heated is characteristic of albumen,
and distinguishes it from other bodies.
The taste of coagulated albumen is quite different from
that of liquid albumen: its appearance, too, and its proper-
SECT. II. ALBUMEN. 401
ties, are entirely changed; for it is no longer soluble, as be-
fore, either in hot or in cold water.
The coagulation of albumen takes place even though air
be completely excluded; and even when air is present, there
is no absorption of it, nor does albumen in coagulating
change its volume. Acids have the property of coagulating
albumen, as Scheele ascertained. Alcohol also produces, in
some measure, the same effect. Heat, then, acids and alco-
hol, are the agents which may be employed to coagulate al-
bumen.
It is remarkable, that if albumen be diluted with a suffi-
cient quantity of water it can no longer be coagulated by
any of these agents.
We see, therefore, that albumen ceases to coagulate when-
ever its particles are separated from each other beyond a cer-
tain distance. That no other change is produced, appears
evident from this circumstance, that whenever the watery so-
lution of albumen is sufficiently concentrated by evaporation,
coagulation takes place, upon the applicalion of the proper
agents, precisely as formerly.
It does not appear that the distance of the particles of al-
bumen is changed by coagulation; for coagulated albumen
occupies precisely the same sensible space as liquid albu-
men.
Albumen, then, is capable of existing in two states; the
one before it has been coagulated, and the other after it has
undergone coagulation. Its properties are very different
in each. It will be proper therefore to consider them sepa-
rately.
Albumen in its natural state, or uncoagulated, is a glary
liquid, having little taste and no smell. When dried sponta-
neously, or in a low heat, it becomes a brittle transparent
glassy like substance; which, when spread thin upon surfaces,
C c
402 ANIMAL SUBSTANCES. DIV. V.
forms a varnish, and is accordingly employed by bookbinders
for that purpose. When thus dried it has a considerable re-
semblance to gum arabic, to which also its taste is similar.
The white of an egg loses about four-fifths of its weight in
drying. It is still soluble in water, and forms the same glary
liquid as before.
From the experiments of Dr Bostock, it appears, that
when one part of this dry albumen is dissolved in nine parts
of water, the solution becomes perfectly solid when coagula-
ted by heat; but if the albumen amounts only to of the
1/12 of the
liquid, then, though coagulation takes place, the liquid does
not become perfectly solid, but may be poured from one ves-
sel to another.
When one grain of albumen is dissolved in 1000 grains of
water, the solution becomes cloudy when heated.
Uncoagulated albumen soon putrefies unless it be dried;
in which state it does not undergo any change. It putrefies
more readily when dissolved in a large quantity of water than
when concentrated. The smell of white of egg, allowed to
run into putrefaction, resembles that of pus.
It is insoluble in alcohol and ether, which immediately co-
agulate it, unless it be mixed with a very great proportion of
water; in which case even acids have no effect.
When acids are poured upon it, coagulation takes place
equally; but several of them have the property of dissolving
it again when assisted by heat. This at least is the case with
sulphuric acid. The solution is of a green colour, and does
not soon blacken even when boiled. It is the case also with
nitric acid, and probably also with muriatic acid. Nitric
acid first disengages some azotic gas; then the albumen is
gradually dissolved, nitrous gas emitted, oxalic and malic
acids formed, and a thick oily matter makes its appearance
on the surface.
SECT. II. ALBUMEN. 403
None of the earths form insoluble compounds, with al-
bumen; in this respect they resemble the alkalies. The case
is different with the metallic oxides.
Every metal tried, except cobalt, occasions a precipitate ;
but no precipitate ever appears when the oxide is held in
solution by an alkali or earth. The effect of the metallic
salts on albumen forms a striking contrast with their effect
on gelatine.
From the experiments of Dr Bostock, it appears that a
drop of the saturated solution of oxymuriate of mercury,
let fall into water containing 1/1000th part of its weight of al-
bumen, produces an evident milkiness, and a curdy precipi-
tate falls. It is therefore a very delicate test of the presence
of albumen in animal fluids.
If a solution of tannin be poured into an aqueous solution
of uncoagulated albumen, it forms with it a very copious
yellow precipitate of the consistence of pitch, and insoluble
in water. This precipitate is a combination of tannin and
albumen. When dry it is brittle, like over-tanned leather,
and is not susceptible of putrefaction. This property which
albumen has of precipitating with tannin was discovered by
Seguin.
The infusion of galls is by no means so delicate a test of
the presence of albumen as of gelatine. When an infusion of
galls containing 2 1/2 per cent. of solid matter, and water hold-
ing 1/1000 of albumen in solution, are mixed in equal quan-
tities, no effect is produced at first, but after some time a
precipitating matter appears and slowly subsides.
II. When albumen is coagulated either by heat, alcohol,
or acids, it is an opaque substance of a pearl white colour,
tough, and of a sweetish mucilaginous taste. It is no longer
soluble in water, and is not nearly so susceptible of decom-
position as uncoagulated albumen. Mr Hatchett kept it
for a month under water, and yet it did not become putrid.
c 2
404 ANIMAL SUBSTANCES. DIV. V.
When this substance was digested for some hours in wa-
ter, it gradually softened, and became white and opaque like
newly coagulated albumen. When water is made to act upon
it long, a small portion of it is taken up. The watery liquid
is not precipitated by the infusion of tan; but nitromuriate of
tin occasions a faint cloud.
According to Scheele, the mineral acids, when greatly di-
luted with water, dissolve a portion of coagulated albumen,
which is thrown down again by the same acids concentrated.
When coagulated albumen is steeped in diluted nitric acid,
the acid in about four weeks begins to acquire a yellow tinge,
which becomes gradually deeper; but the albumen, though
it becomes more opaque, is not dissolved. The yellow acid,
when saturated with ammonia, becomes of a deep orange co-
lour, but does not let fall any precipitate. When the albu-
men, thus treated, is immersed in ammonia, the liquid as-
sumes a deep orange colour, inclining to blood red. The
albumen is slowly dissolved, and the solution has a deep yel-
lowish brown colour. If the albumen, after being steeped
in nitric acid, be washed and then boiled in water, it is dis-
solved, and forms a pale yellow liquid, which gelatinizes
when properly concentrated. If the gelatinous mass be again
dissolved in boiling water, the solution is precipitated by tan
and by nitro-muriate of tin. Hence we see that nitric acid
has the property of converting coagulated albumen into ge-
latine.
Concentrated nitric acid dissolves coagulated albumen
with effervescence, especially when assisted by heat. It be-
comes orange brown when mixed with ammonia, but no pre-
cipitate falls.
It is readily dissolved by a boiling lixivium of potash; am-
monia is disengaged, and an animal soap is formed. This
soap, when dissolved in water, and mixed with acetic or
muriatic acid, lets fall a precipitate which is of a sapona-
SECT. III. MUCUS. 405
ceous nature. When heated gently some oil flows from it,
and a brownish viscid substance remains. The alkalies,
when diluted, and not assisted by heat, act upon it slowly
and imperfectly.
These properties indicate sufficiently that coagulated al-
bumen is a very different substance from uncoagulated al-
bumen.
III. From the effects of nitric acid on albumen; and its
products, when subjected to destruictive distillation, it has
been concluded that it consists of carbon, hydrogen, azote,
and oxygen, in unknown proportions. As it yields more
azotic gas to nitric acid, it has been considered as containing
more of that principle than gelatine. It is obvious, how-
ever, that it does not differ much from that body, as nitric
acid spontaneously converts it into gelatine. Mr Hatchett
has rendered it very probable that it is the first of the soft
part of animals that is formed, and that all the other soft
parts are formed from it.
SE CT. III. Of Mucus.
No word in chemistry hass been used with less precision
than mucus. Too many experimenters have made it serve as
a common name for every animal substance which cannot be
referred to any other class. Dr Bostock, in his excellent
papers on the Analysis of Animal Fluids, has endeavoured to
fix the meaning of the word by ascertaining the properties of
pure mucus. Fourcroy and Vauquelin have lately written
an elaborate paper on the same subject.
From Bostock's experiments it appears, that if the solid
matter obtained by evaporating saliva to dryness be re-dis-
solved in water and filtered, the solution will contain very
little except mucus. He obtained mucus, also, by macerat-
406 ANIMAL SUBSTANCES. DIV. V.
ing an oyster in water and evaporating the liquid. Mucus,
thus obtaintd, possesses the following properties:
1. It has much the appearance of gum arabic, excepting
that, in general, it is rather more opaque; like it, it has little
taste, dissolves readily in water, and forms an adhesive so-
lution.
2. When evaporated to dryness it is transparent, inelastic,
and has much the appearance of gum. It is insoluble in
water, but dissolves readily in all the acids though very much
diluted.
3. It does not dissolve in Alcohol nor in ether.
4. It does not coagulate when heated; nor when concen-
trated by evaporation does its solution assume the form of a
jelly.
5. It is not precipitated by the oxymuriate of mercury,
nor by the infusion of galls.
6. The acetate of lead occasions a copious white preci-
pitate when dropt into solutions containing mucus; the su-
peracetate produces a much less striking effect.
7. Nitrate of silver likewise occasions a precipitate in so-
lutions containing mucus.
8. When heated it assumes the appearance of horn, and
when distilled it yields the common products of animal sub-
stances. According to Fourcroy and Vauquelin, horn, nails,
hair, feathers, the epidermis, and the scales which form on
the skin consist chiefly of mucus.
Many of the substances called mucus have the property of
absorbing oxygen, and of becoming by that means insoluble
in water. They resemble vegetable extractive matter in this
respect.
SECT. IV. FIBRIN. 407
Sect. IV Fibrin.
If a quantity of blood, newly drawn, from an anmial, be al-
lowed to remain at rest for some time, a thick red clot gradual-
ly forms in it, and subsides. Separate this clot from the rest
of the blood, put it into a linen cloth, and wash it repeated-
ly in water till it ceases to give out any color or taste to the
liquid; the substance which remains after this process is de-
nominated fibrin. It has been long known to physicians
under the name of the fibrous part of the blood, but has not
till lately been accurately described.
It may be procured also from the muscles of animals. Mr
Hatchett, to whom we are indebted for a very interesting set
of experiments on this substance, cut a quantity of lean beef
into small pieces, and macerated it in water for fifteen days,
changing the water every day, and subjecting the beef to
pressure at the same time, in order to squeeze out the water.
As the weather was cold, it gave no signs of putrefaction
during this process. The shreds of muscle, which amounted
to about three pounds, were now boiled for five hours every
day for three weeks in six quarts of fresh water, which was
regularly changed every day. The fibrous part was now
pressed, and dried by the heat of a water bath. After this
treatment it might be considered as fibrin nearly as pure as
it can be obtained.
fibrin is of a white colour, has no taste nor smell, and
is not soluble in water nor in alcohol. When newly ex-
tracted from blood, it is soft and elastic, and resembles
very much the gluten of vegetables. Its colour deepens very
much in drying. That which is extracted from muscle by
boiling and maceration has a certain degree of transparency,
and is not ductile but brittle. Its colour does not deepen
nearly so much as the fibrin from blood.
C 4
405 ANIMAL SUBSTANCES. DIV. V.
It undergoes no change though kept exposed to the ac-
tion of air; neither does it alter speedily though kept cover-
ed with water. Mr Hatchett kept a quantity of the fibrin
which he had prepared from beef moistened with water dur-
ing the whole month of April; it aquired a musty but not
a putrid smell, neither were the fibres reduced to a pulpy mass.
Even when kept two months under water, it neither became
putrid, nor was converted into the fatty matter obtained by
macerating recent muscle.
When fibrin is exposed to heat, it contracts very suddenly,
and moves like a bit of horn exhaling at the same time the
smell of burning feathers. In a stronger heat it melts.
When exposed to destructive distillation, it yields water, car-
bonate of ammionia, a thick heavy fetid oil, traces of acetic
acid; carbonic acid, and carbureted hydrogen gas.
Acids dissolve fibrin with considerable facility. Sulphuric
acid gives it a deep brown colour; charcoal is precipitated,
and acetic acid formed. Muriatic acid dissolves it, and forms
with it a green-coloured jelly. The acetic, citric, oxalic, and
tartaric acids also dissolve it by the assistance of heat; and
the solutions, when concentrated, assume the appearance of
jelly. Alkalies precipitate the fibrin from acids in flakes, so-
luble in hot water, and resembling gelatine in its properties.
Diluted nitric acid occasions the separation of a good deal
of azotic gas, as was first observed by Berthollet. Mr Hat-
chett steeped a quantity of fibrin in nitric acid diluted with
thrice its weight of water for 15 days. The acid acquired a
yellow tinge, and possessed all the properties of the nitric
solution of albumen. The fibrin thus treated, dissolved in
boiling water, and when concentrated by evaporation, be-
came a gelatinous mass, soluble in hot water, and precipita-
ted by tan and nitro-muriate of tin, and therefore possessing
the properties of gelatine. Ammonia dissolves the greater
part of the fibrin after it has been altered by nitric acid.
SECT. IV. FIBRIN. 409
The solution is of a deep orange colour, similar to the solu-
tion of albumen treated in the same way. Boiling nitric acid
dissolves fibrin, except some fatty matter which swims on the
surface. The solution resembles that of albumen; except
that ammonia throws down a white precipitate, consisting
chiefly of oxalate of lime. During the solution, prussic acid
comes over, and carbonic acid gas mixed with nitrous gas; a
considerable portion of oxalic acid is formed besides the fat-
ty matter which swims.
The alkalies, while diluted, have but little effect upon fib-
rin; but when concentrated potash or soda is boiled upon it,
a complete solution is obtained of a deep brown colour pos-
sessing the properties of soap. During the solution ammo-
nia is disengaged. when the solution is saturated with mu-
riatic acid, a precipitate is obtained similar to that from ani-
mal soap, except that it sooner becomes hard and soapy when
exposed to the air.
The earthts, as far as is known, have little or no action on
fibrin. Neither has the action of the metallic oxides and
salts been examined.
Fibrin is insoluble in alcohol, ether, and oils. The effect
of other re-agents on it has not been examined.
From the properties above detailed, fibrin appears to be
composed of the same constituents as gelatine and albumen;
but it probably contains more carbon and azote and less oxy-
gen. The close resemblance which it bears to albumen is
very obvious from the experiments of Hatchett just detailed.
Nitric acid converts both into gelatne, and alkalies convert
both into a species of oil. Now, as all the soft parts of ani-
mals consist of combinations of these three genera, it follows,
as Mr Hatchett has observed, that all the soft parts of ani-
mals may be either converted into gelatine or animal soap,
both substances of the highest importance.
410 ANIMAL SUBSTANCES. CHAP. I.
Fibrin exists only in the blood and the muscles animals;
but it is a genus which includes as many species as there are
varieties in the muscles of animals; and the great diversity of
these substances is well known. The muscles of fish, of
fowl, and of quadrupeds, bear scarcely any resemblance to
each other.
Sect. V. Of Urea.
Urea may be obtained by the following process: Evapo-
rate by a gentle heat a quantity of human urine, voided six
or eight hours after a meal, till it be reduced to the consist-
ence of a thick syrup. In this state, when put by to cool, it
concretes into a crystalline mass. Pour at different times
upon this mass four times its weight of alcohol, and apply a
gentle heat; a great part of the mass will be dissolved, and
there will remain only a number of saline substances. Pour
the alcohol solution into a retort, and distil by the heat of a
sand-bath till the liquid, after boiling some time, is reduced
to the consistence of a thick syrup. The whole of the alco-
hol is now separated, and what remains in the retort crystal-
lizes as it cools. These crystals consist of the substance
known by the name of urea.
Urea, obtained in this manner, has the form of crystalline
plates crossing each other in different directions. Its colour
is yellowish white: it has a fetid smell, somewhat resembling
that of garlic or arsenic; its taste is strong and acrid, resem-
bling that of ammoniacal salts; it is very viscid and difficult
to cut, and has a good deal of resemblance to honey. When
exposed to the open an, it very soon attracts moisture, and
is converted into a thick brown liquid. It is extremely so-
luble in water; and during its solution a considerable degree
of cold is produced. Alcohol dissolves it with facility, but
scarcely in so large a proportion as water. The alcohol so-
SECT. V. UREA. 411
lution yields crystals much more readily on evaporation than
the solution in water.
When nitric acid is dropt into a concentrated solution of
urea in water, a great number of bright pearl-coloured crys-
tals are deposited, composed of urea and nitric acid. No
other acid produces this singular effect. The concentrated
solution of urea in water is brown, but it becomes yellow
when diluted with a large quantity of water. The infusion
of nutgalls gives it a yellowish brown colour, but causes no
precipitate; neither does the infusion of tan produce any pre-
cipitate.
when heat is applied to urea, it very soon melts, swells
up, and evaporates with an insupportably fetid odour. When
distilled, there comes over first benzoic acid, then carbonate
of ammonia in crystals, some carbureted hydrogen gas, with
traces of prussic acid and oil; and there remains behind a
large residuum, composed of charcoal, muriate of ammonia,
and muriate of soda. The distillation is accompanied with
an almost insupportably fetid alliaceous odour.
When the solution of urea in water is kept in a boiling
heat, and new water is added as it evaporates, the urea is
gradually decomposed, a very great quantity of carbonate of
ammonia is disengaged, and at the same time acetic acid is
formed, and some charcoal precipitates.
When a solution of urea in water is left to itself for some
time, it is gradually decomposed. A froth collects on its
surface; air bubbles are emitted which have a strong disa-
greeable smell, in which ammonia and acetic acid are distin-
guishable. The liquid contains a quantity of acetic acid.
The decomposition is much more rapid if a little gelatine be
added to the solution. In that case more ammonia is disen-
gaged, and the proportion of acetic acid is not so great.
When the solution of urea is mixed with one-fourth of its
weight of diluted sulphuric acid, no effervescence takes place;
412 ANIMAL SUBSTANCES. CHAP. I.
but, on the application of heat, a quantity of oil appears on
the surface, which concretes upon cooling; the liquid which
comes over into the receiver contains acetic acid, and a quan-
tity of sulphate of ammonia remains in the retortl dissolved in
the undistilled mass. By repeated distiliations, the whole of
the urea is converted into acetic acid and ammonia.
When nitric acid is poured upon crystallized urea, a vio-
lent effervescencd takes place, the mixture frothes, assumes
the form of a dark red liquid, great quantities of nitrous gas,
azotic gas, and carbonic acid gas, are disengaged. When
the effervescence in over, there remains only a concrete white
matter, with some drops of reddish liquid. When heat is
applied to this residuum it detonates like nitrate of ammonia.
Muriatic acid dissolves urea, but does not alter it. Oxy-
muriatic acid gas is absorbed very rapidly by a diluted solu-
tion of urea; small whitish flakes appear, which soon become
brown, and adhere to the sides of the vessel like a concrete
oil. After a considerable quantity of oxymuriatic acid had
been absorbed, the solution, left to itself, continued to effer-
vesce exceeding slowly, and to emit carbonic acid and azotic
gas. After this effervescence was over, the liquid contained
muriate and carbonate of ammonia.
Urea is dissolved very rapidly by a solution of potash or
soda, and at the same time a quantity of ammonia is disen-
gaged; the same substance is disenaged when urea is treat-
ed with barytes, lime, or even magnesia. Hence it is evi-
dent, that this appearance must be ascribed to the muriate of
ammonia, with which it is constantly mixed. When pure
solid potash is triturated with urea, heat is produced, a great
quantity of ammonia is disengaged; the mixture becomes
brown, and a substance is deposited, having the appearance
of an empyreumatic oil. One part of urea and two of pot-
ash, dissolved in four times its weight of water, when distil-
SECT. VI. SACCHARINE MATTER. 413
led, give out a great quantity of ammoniacal water; the resi-
duum contains acetate and carbonate of potash.
When muriate of soda is dissolved in a solution of urea in
water, it is obtained by evaporation, not in cubic crystals, its
usual form, but in regular octahedrons. Muriate of ammo-
nia, on the contrary, which crystallizes naturally in octahe-
drons, is converted into cubes, by dissolving and crystallizing
it in the solution of urea.
Sect. VI. Of Saccharine Matter.
Sugar has never been found in animals in every respect si-
milar to the sugar of vegetables; but there are certain ani-
mal substances which have so many properties in common
with sugar, that they can scarcely be arranged under any
other name. These substances are,
1. Sugar of milk.
2. Honey.
3. Sugar of diabetic urine.
3. Sugar of milk may be obtained by the following pro-
cess: Let fresh whey be evaporated to the consistence of ho-
ney, and then allowed to cool; it concretes into a solid mass.
Dissolve this mass in water, clarify it with the white of eggs,
filter and evaporate to the consistence of a syrup; it depo-
sites on cooling a number of brilliant white cubic crystals,
which are sugar of milk.
When pure it has a white colour, a sweetish taste, and no
smell. Its crystals are semitransparent regular parallelopi-
peds, terminated by four-sided pyraamids. Its specific gravi-
ty, at the temperature of 55˚is 1.543. At that tempera-
ture it is soluble in seven times its weight of water; but is
perfectly insoluble in alcohol. When burnt it emits the
odour of caromel, and exhibits precisely the appearance of
burning sugar. When distilled, it yields the same products
414 ANIMAL SUBSTANCES CHAP. I.
as sugar, only the empyreumatic oil obtained has the odour
of benzoic acid. When treated with nitric acid it yields sac-
lactic acid. From these experiments, it appears that sugar
of milk is specifically different from every kind of vegetable
sugar at present known.
2. Honey is prepared by bees, and perhaps rather belongs
to the vegetable than the animal kingdom. It has a white
or yellowish colour, a soft and grained consistence, a saccha-
rine and aromatic smell. By distillation it affords an acid
phlegm and an oil, and its coal is light and spongy like that
of the mucilages of plants. Nitric acid extracts from it ox-
alic acid, precisely as it does from sugar. It is very soluble
in water, with which it forms a syrup, and like sugar passes
to the vinous fermentation.
According to Proust, there are two kinds of honey; one
always liquid, and the other solid and not deliquescent.
They may be separated, he says, by means of alcohol.
3. The urine of persons labouring under the disease known
to physicians by the name of diabetes, yields, when evapo-
rated, a considerable quantity of matter which possesses pro-
perties analogous to sugar. This seems to have been first
observed by Willis. When treated with nitric acid, it yield-
ed the same proportion of oxalic acid as an equal quantity
of common sugar would have done, making allowance for
the saline substances present. No saclactic acid was form-
ed. Hence it follows that this substance is not analogous
to sugar of milk, but nearer common sugar in its proper-
ties. It has been supposed incapable of crystallizing regu-
larly like common sugar. But I have seen it prepared by
Dr Wollaston in small grains, having almost exactly the ap-
pearance of common white sugar.
3
SECT. VII. OILS. 415
SECT. VII. Of Oils.
The oily substances found in animals belong all to the
class of fixed oils. They differ very much in their consist-
ence, being found in every intermediate state from sperma-
ceti, which is perfectly solid, to train oil, which is com-
pletely liquid. The most important of them are the fol-
lowing:
1. Spermaceti. - This peculiar oily substance is found in
the cranium of the physeter macrocephalus, or spermaceti
whale. It is obtained also from some other species. At
first it is mixed with some liquid oil, which is separated by
means of a woollen bag. The last portions are removed by
an alkaline ley, and the spermaceti is afterwards purified by
fusion. Thus obtained, it is a beautiful white substance,
usually in small scales, very brittle, has scarcely any taste,
and but little smell. It is distinguished from all other fatty
bodies by the crystalline appearance which it always as-
sumes. It melts, according to the experiments of Bostock,
at the temperature of 112˚. When sufficiently heated it
may be distilled over without much alteration; but when dis-
tilled repeatedly it loses its solid form and becomes a liquid
oil.
2. Fat. - This substance is found abundantly in different
parts of animals. When pure it possesses the properties of
the fixed oils. Its consitence varies from tallow or suet,
which is brittle, to hog's lard, which is soft and semi-fluid.
To obtain fat pure, it is cut in small pieces, well washed in
water, and the membranous parts and vessels separated. It
is then melted in a shallow vessel along with some water, and
kept melted till the water is completely evaporated. Thus
purified it is white, tasteless, and nearly insipid.
416 ANIMAL SUBSTANCES. CHAP. I.
3. Train oil. - This liquid is extracted from the blubber
of the whale, and from other fish. It forms a very import-
ant article of commerce, being employed for combustion in
lamps, and for other purposes. It is at first thick; but on
standing, a white mucilaginous matter is deposited, and the
oil becomes transparent. It is then of a reddish brown co-
lour, and has a disagreeable smell.
4. Though all the oily bodies found in animal substances
belong to the class of fixed oils, yet there is a peculiar vola-
tile oil which makes its appearance, and which is doubtless
formed during the distillation of different animal bodies.
Though this oil has now lost that celebrity which drew the
attention of the older chemists to it, yet as its properties are
peculiar, a short account of it will not be improper. It is
usually called the animal oil of Dippel, because that che-
mist first drew the attention of chemists to it. It is usually
obtained from the gelatinous and albuminous parts of ani-
mals. The horns are said to answer best. The product of
the first distillation is to be mixed with water, and distilled
with a moderate heat; the oil which is first obtained is the
animal oil of Dippel.
It is colourless and transparent; its smell is strong and
rather aromatic; it is almost as light and as volatile as ether;
water dissolves a portion of it; and it changes syrup of vio-
lets green, owing, as is supposed, to its containing a little
ammonia. The acids all dissolve it, and form with it a
kind of imperfect soap. Nitrous acid sets it on fire. It
forms with alkalies a soap. Alcohol, ether, and oils unite
with it. When exposed to the air it becomes brown, and
loses its transparency. It was formerly used as a specific in
fevers.
SECT. VII. RESINS. 417
SECT. VII. Of Animal Resins
Substances resembling resins are found in different animal
bodies; and which, for that reason, may be called animal
resins. Their properties are somewhat different from the
vegetable resins, but they have not been all examined with
precision. The following are the most remarkable of these
substances.
1. Resin of bile. -Tlus substance may be obtained by
the following process: Into thirty-two parts of fresh ox bile
pour one part of concentrated muriatic acid. After the
mixture has stood for some hours, pass it through a filter, in
order to separate a white coagulated substance. Pour the
filtrated liquor, which has a fine green colour, into a glass
vessel, and evaporate it by a moderate heat. When it has
arrived at a certain degree of concentration, a green-colour-
ed substance precipitates. Decant off the clear liquid; and
wash the precipitate in a small quantity of pure water. This
precipitate is the basis of bile, or the resin of bile, as it is
sometimes called.
the resin of bile is of a dark brown colour; but when
spread out upon paper or on wood, it is a fine grass green:
its taste is intensely bitter.
When heated to about 122˚ it melts; and if the heat be
still further increased it takes fire and burns with rapidity.
It is insoluble in water, but soluble in alcohol; and water
precipitates it from that liquid.
It is soluble also in alkalies, and forms with them a com-
pound which has been compared to a soap. Acids, when
sufficiently diluted, precipitate it both from water and al-
kalies without any change; but if they be concentrated, the
precipitate is re-dissolved.
D d
418 ANIMAL SUBSTANCES. CHAP. I.
2. Ambergris. This substance is found floating on the
sea, near the coasts of India, Africa, and Brazil, usually in
small pieces, but sometimes in masses of fifty or one hun-
dred pounds weight. Various opinions bave been entertain-
ed concerning its origin. Some affirmed that it was the con-
crete juice of a tree; others thought it a bitumen, but it
it now considered as pretty well established, that it is a con-
cretion formed in the stomach or intestines of the physeter
macrocephalus, or spermaceti whale.
Ambergris when pure is a light soft substance which swims
on water. Its specific gravity varies from 0.78 to 0.92, ac-
cording to Brisson; Bouillon La Grange, who has lately
published an analysis of it, found its specific gravity from
0.849 to 0.844. Its colour is ash grey, with brownish yel-
low and white streaks. It has to agreeable smell, which
improves by keeping. Its taste is insipid.
According to Bouillon La Grange it is composed of-
52.7 adipocire
3O.8 resin
11.1 benzoic acid
5.4 charcoal
___
100.0
3. Castor. This substance is obtained from the beaver.
In each of the inguinal regions of that animal there are two
bags, a large and a small. The large one contains the true
castor; the small one a substance which has some resem-
blance to it, but which is in much less estimation. We are
indebted to Bouillon La Grange for a set of experiments
on it.
Castor is of a yellow colour; and when newly taken from
the animal it is nearly fluid. But by exposure to the at-
mosphere it gradually hardens, becomes darker coloured,
SECT. IX. ACIDS. 419
and assumes a resiuous appearance. Its taste is bitter and
acrid, and its odour strong and aromatic.
From the analysis of Bouillon La Grange, we learn that
castor contains the follbwing ingredients:
1. Carbonate of potash
2. Carbonate of lime
3. Carbonate of ammonia
4. Iron
5. Resin
6. A mucilaginous extractive matter
7. A volatile oil
The properties of the resin are analogous to those of the
resin of bile.
Sect. IX. Of Acids.
The acids which have been discovered ready formed, and
constituting a part of animal bodies, are the following:
1. Phosphoric 7. Rosacic
2. Sulphuric 8. Amniotic
3. Muriatic 9. Oxalic
4. Carbonic 10. Formic
5. Benzoic 11. Acetic
6. Uric 12. Malic.
1. The phosphoric acid is by far the most abundant of all
the acids found in animals. Combined with lime, it con-
stitutes the basis of bone; and the phosphate of lime is
found in the muscles, and almost all the solid parts of ani-
mals; neither are there many of the fluids from which it is
absent. In the blood, phosphoric acid is found combined
with oxide of iron; and in the urine it exists in excess, hold-
ing phosphate of lime in solution.
2. Sulphuric acid can scarcely be considered as a compo-
nent part of any of the substances belonging to the human
D d 2
420 ANIMAL SUBSTANCES. CHAP. I.
body. It is said, indeed, to occur sometimes in urine com-
bined with soda. It is, however, a very common consti-
tuent of the liquid contents of the inferior animals. Thus
sulphate of soda is found in the liquor of the amnios of
cows, and sulphate of lime occurs usually in the urine of
quadrupeds.
Muriatic acid occurs in most of the fluid animal sub-
stances, and is almost always combined with soda, constitut-
ing common salt.
4. Carbonic acid has been detected in fresh human urine
by Proust, and it occurs in the urine of horses and cows
abundantly, partly combined with lime.
5. Benzoic acid was first discovered in human urine by
Scheele; and Fourcroy and Vauquelin have found it abun-
dantly in the urine of cows. Proust has detected it in the
blood, the albumen of an egg, in glue, silk, and wool, in
the sponge, different species of algae, and even in mush-
rooms.
6. Uric or lithic acid was discovered by Scheele in 1776.
It is the most common constituent of urinary calculi, and
exists also in humab urine. That species of calculus which
resembles wood in its colour and appearance is composed
entirely of this substance. It was called at first lithic acid;
but this name, in consequence of the remarks made by Dr
Pearson on its impropriety, has been laid aside, and that of
uric acid substituted in its place.
7. Rosaic. During intermittent fevers urine deposites a
very copious precipitate, which has been long known to
physicians under the name of lateritious sediment. This se-
diment always makes its appearance at the crisis of fevers.
In gouty people, the same sediment appears in equal abun-
dance towards the end of a paroxysm of the disease; and if
this sediment suddenly disappears after it has begun to be
deposited, a fresh attack may be expected, Scheele consi-
SECT. IX. ACIDS. 421
dered this sediment as uric acid mixed with some phos-
phate of lime; and the same opinion has been entertained
by other chemists: but Proust affirms that it consists chiefly
of a different substance, to which he has given the name of
rosacic acid from its colour, mixed with a certain propor-
tion of uric acid and phosphate of lime. This rosacic acid,
he informs us, is distinguished from the uric by the facility
with which it dissolves in hot water, the violet precipitate
which it occasions in muriate of gold, and by the little ten-
dency which it has to crystallize.
8. Amniotic acid has been lately discovered by Vauque-
lin and Buniva in the liquor of the amnios of the cow, and
may be obtained in white crystals by evaporating that liquid
slowly. Hence they have given it the name of amniotic acid.
It is of a white and brilliant colour; its taste has a very slight
degree of sourness; it reddens the tincture of turnsole; it
is scarcely soluble in cold water, but very readily in hot wa-
ter, from which it separates in long needles as the solution
cools. It is soluble also in alcohol, especially when assist-
ed by heat.
9. Oxalic acid has hitherto been found only in a few uri-
nary calculi by Vauquelin and Fourcroy.
10. Formic acid has been hitherto found only in the for-
mica rufa, or red ant.
11. Acetic. This acid has been detected in urine by
Proust. It exists also in the formica rufa, or red ant, as
has been demonstrated by the experiments of Fourcroy and
Vauquelin. It appears also, from the labours of these phi-
losophers and of Thenard, that the acid found in milk is
the acetic, disguised a little by holding somne salts in solu-
tion.
12. Malic acid. This acid has been lately detected by
Fourcroy and Vauquelin in the acid liquid obtained from the
formica rufa. When this liquid is saturated with lime, if
D d 3
422 ANIMAL SUBSTANCES. CHAP. I.
acetate of lead be dropt into the solution, a copious preci-
pitate falls, which is soluble in acetic acid. Fourcroy and
Vauquelin exposed the precipitate to the proper trials, and
ascertained that it was malate of lead.
Sect. X. Of Alkalies, Earth, and Metals.
I. All the alkalies have been found in the fluids of ani-
mals.
1. Potash is rather uncommon in the human fluids; but
it has been detected in the milk of cows, and it has been
found abundantly in the urine of quadrupeds.
2. Soda exists in all the fluids, and, seems always to be
combined with albumen. Phosphate and muriate of soda
are also found. It is this alkali which gives animal fluids
the property of tinging vegetable blues green.
3. Ammonia has been detected by Proust in urine; and
it is formed in abundance during the putrefaction of most
animal bodies.
II. The only earths hitherto found in animals are lime,
magnesia, and silica.
1. Lime exists in great abundance in all the larger ani-
mals. Combined with phosphoric acid, it constitutes the
basis of bones, while shells are composed of carbonate of
lime. Phosphate of lime is found also in the muscles and
other solid parts, and it is held in solution by almost all the
fluids.
2. Magnesia has been detected in human urine by Four-
croy and Vauquelin, combined with phosphoric acid and am-
monia. It constitutes also sometimes a component part of the urinary calculi.
6. Silica has not hitherto been detected in any of the
componcnt parts of animals, except hair; but Fourcroy and
Vauquelin found it in urinary calculi.
SECT. X. PARTS OF ANIMALS. 423
III. The metals found in animals are two; namely, iron
and manganese.
1. Iron combined with phosphoric acid is a constituent
part of the blood. Its presence was first ascertained by
Manghini, who proved at the same time that it does not ex-
ist in the solid parts of animals. It is said to exist also in
bile.
2. Manganese has been found in human hair, but scarce-
ly in any other animal substance.
CHAP. II
PARTS OF ANIMALS.
The different substances which compose the bodies of ani-
mals may be arranged under the following heads:
1. Bones and shells
2. Horns and nails
3. Muscles
4. Skin
5. Membranes
6. Tendons and ligaments
7. Glands
8. Brain and nerves
9. Marrow
10. Hair and feathers
11. Silk and similar bodies.
Besides these substances, which constitute the solid parts
of the bodies of animals, there are a number of fluids, the
most important of which is the blood, which pervades
every part of the system in all the larger animals: The rest
are known by the name of secretions, because they are form-
ed, or secreted as thei anatomists term it, from the blood. The
principal animal secretions are the following:
1. Milk
2. Eggs
3. Saliva
4. Pancreatic juice
D d 4
424 ANIMAL SUBSTANCES. CHAP. II.
5. Bile
6. Cerumen
7. Tears
6. Liquor of the pericardium
9. Humours of the eyes
10. Mucus of the nose, &c.
11. Sinovia
12. Semen
13. Liquor of the amnios
14. Poisonous secretions
15. Air
Various substances are separated either from the blood or
the food on purpose to be afterwards thrown out of the bo-
dy as usless or hurtful. These are called excretions. The
most important of them are,
1. Sweat
2. Urine
3. Faeces.
Besides the liqids which are secreted for the different
purposes of healthy animals, there are others which make
their appearance only during disease, and which may there-
fore be called morbid secretions. The most important of
these are the following:
1. Pus
2. The liquor of dropsy
3. The liquor of blisters.
To these we must add several solid bodies, which are oc-
casionally formed in different cavides in consequence of the
diseased action of the parts. They may be called morbid
concretions. The most remarkable of them are the follow-
ing:
1. Salivary calculi
2. Concretions in the lungs, liver, brain, &c.
3. Intestinal calculi
4. Biliary calculi
5. Urinary calculi
6. Gouty calculi.
SECT. I. BONES, &c. 425
These different substances shall form the subjects of the
following sections:
SECT. I. Of Bones, Shells, and Crusts.
By bones are meant those hard, solid, well-known sub-
stances, to which the firmness, shape, and strength of ani-
mal bodies are owing; which, in the larger aninials, form as
it were, the ground-work upon which all the rest is built. In
man, in quadrupeds, and many other animals, the bones are
situated below the other parts, and scarcely any of them are
exposed to view; but shell-fish and snails have a hard co-
vering on the outside of their bodies, evidently intended for
defence. As these coverings, though known by the name of
shells, are undoubtedly of a bony matter, I shall include them
in this section.
The bones are the most solid parts of animals. Their
texture is sometimes dense, at other times cellular and po-
rous, according to the situations of the bone. They are white,
of a lamellar structure, and not flexible nor softened by heat.
Their specific gravity differes in different parts. That of adults
teeth is 2.2727; the specific gravity of childrens teeth is
2.0836.
The component parts of bones are chiefly four; namely,
the earthy salts, fat, gelatine, and cartilage.
1. The earthy salts may be obtained either by calcining
the bone to whiteness, or by steeping it for a sufficient length
of time in acids. In the first case, the salts remain in the
state of a brittle white substance; in the second they are dis-
solved, and may be thrown down by the proper precipitants.
These earthy salts are four in number: 1. Phosphate of lime,
426 ANIMAL SOLIDS. CHAP. II.
which constitutes by far the greatest part of the whole.
2. Carbonate of lime. 3. Phosphate of magnesia, lately
discovered by Fourcroy and Vauquelin. It occurs in the
bones of all the inferior animals examined by these indefati-
gable chemists, but could not be detected in human bones.
4. Sulphate of lime, detected by Mr Hatchett in a very mi-
nute proportion.
2. The proportion of fat contained in bones is various.
By breaking bones in small pieces, and boiling them for
some time in water, Mr Proust obtained their fat swimming
on the surface of the liquid. It weighed, he says, one-fourth
of the wheight of the bones employed. This proportion ap-
pears excessive, and can scarcely be accounted for without
supposing that the fat still retained water.
3. The gelatine is separated by the same means as the fat,
by breaking the bones in pieces and boiling them long enough
in water. The water dissolves the gelatine, and gelatinizes
when sufficiently concentrated. Hence the importance of
bones in making portable soups, the basis of which is con-
crete gelatine, and likewise in making glue. By this process
Proust obtained from powdered bones about one-sixteenth
of their weight of gelatine.
4. When bones are deprived of their gelatine by boiling
them in water, and of their earthy salts by steeping them in
diluted acids, there remains a soft white elastic substance,
possessing the figure of the bones, and known by the name of
cartilage. From the experiments of Hatchett, it appears
that this substance has the properties of coagulated albumen.
Like that substance, it becomes brittle and semitransparent
when dried, is readily soluble in hot nitric acid, is converted
into gelatine by the action of diluted nitric acid; for it is so-
luble in hot water, and gelatinises on cooling, and ammonia
dissolves it and assumes a deep orange colour.
SECT. I. BONES, &c. 427
Ox bones, according to the analyis of Foucroy and Vau-
quelin, are composed of
51.0 solid gelatine
37.7 phosphate of lime.
10.0 carbonate of lime
1.3 phosphate of magnesia
____
100.0
From the calcined bones of horses and sheep, fowls, and
fishis, they extracted about one-thirtysixth part of phosphate
of magnesia.
The only bone hitherto observed altogether destitute of
cartilage is the enamel of the teeth. When the raspings of
bones are steeped in diluted acids, the cartilage alone re-
mains undissolved. Now, when the raspings of enamel are
treated in this manner, Mr Hatchett observed that the whole
was dissolved without any residuum whatever. If we be-
lieve Fourcroy and Vauquelin, the enamel of teeth is com-
posed of
72.9 phosphate of lime
27.1 gelatine and water
____
100.0
But the most complete analysis of teeth has been made by
Mr Pepys, and his results agree exactly with those of Hat-
chett. He found the enamel of the teeth composed of
78 phosphate of lime.
6 carbonate of lime
16 loss and water
___
100
2. Shells.
Under the name of shells I include all the bony coverings
of the differeut species of shell fish. Egg shells, also, from
428 ANIMAL SOLIDS. CHAP. II.
the similarity of their texture, belong to the same head. For
almost all the knowledge of these substances that we pos-
sess, we are indebted to the late important dissertations of
Mr Hatchett. A few detached facts, indeed, had been ob-
served by other chemists; but his experiments gave us a
systematic view of the constituents of the whole class.
Shells, like bones, consist of calcareous salts united to a
soft animal matter; but in them the lime is united chiefly to
carbonic acid, whereas in bones it is united to phosphoric
acid. In shells the predominating ingredient is carbonate of
lime; whereas in bones it is phosphate of lime. This con-
stitutes the characteristic difference in their composition.
Mr Hatchet has divided shells into two classes. The first
are usually of a compact texture, resemble porcelain, and
have an enamelled surface, often finely variegated. The shells
belonging to this class have been distinguished by the name
of porcelaneous shells. To this class belong the various spe-
cies of voluta, cypraea, &c. The shells belonging to the se-
cond class are usually covered with a strong epidermis, bo-
low which lies the shell in layers, and composed entirely of
the substance well known by the name of mother-of- pearl.
They have been distinguished by the name of mother-of-pearl
shells. The shell of the fresh water muscle, the haliotis iris,
the turbo olearius, are examples of such shells. The shells
of the first of these classes contain a very small portion of
soft animal matter; those of the second contain a very large
portion. Hence we see that they are exremely different in
their composition.
1. Porcelaneous shells, when exposed to a red heat,
crackle and lose the colour of their enamelled surface. They
emit no smoke or smell; their figure continues unaltered,
their colour becomes opaque white, tinged partially with pale
gray. They dissolve when fresh with effervescence in acids,
and without leaving any residue, but if they have been burnt,
SECT. I. BONES, &c. 429
there remains always a little charcoal. The solution is trans-
parent, gives no precipitate with ammonia or acetate of lead;
of course it contains no sensible portion of phosphate or sul-
phate of lime. Carbonate of ammonia throws down an
abundant precipitate of carbonate of lime. Porcelaneous
shells, then, consist of carbonatle of lime cemented together
by a small portion of an animal matter, which is soluble in
acids, and therefore resembles gelatine.
2. Mother-of-pearl shells when exposed to a red heat
crackle, blacken, and emit a strong fetid odour. They ex-
foliate, and become partly dark grey, partly a fine white.
When immersed in acids they effervesce at first strongly; but
gradually more and more feebly, till at last the emission of
air-bubbles is scarcely perceptible. The acids take up only
lime, and leave a number of thin membranous substances,
which still retain the form of the shell. From Mr Hatchett's
experiments we learn that these membranes have the proper-
ties of coagulated albumen. Mother of pearl shells, then,
are composed of alternate layers of coagulated albumen and
carbonate of lime, beginning with the epidermis, and ending
with the last formed membrane.
Pearl, a well known globular concretion which is formed
in some of these shells, resembles them exactly in its struc-
ture and composition. It is a beautiful substance of a bluish
white colour, iridescent, and brilliant. It is composed of
concentric and alternate coats of thin membrane and carbo-
nate of lime. Their iridescence is obviously the consequence
of the lamellated structure.
3. Crusts.
By crusts we understand those bony coverings of which
the whole external surface of crabs, lobsters, and other si-
milar sea animals are composed. Mr Hatchett found them
composed of three ingredients: 1. A cartilaginous substance,
430 ANIMAL SUBSTANCES CHAP. II.
possessubg the properties of coagulated albumen; 2. Carbo-
nate of lime; 3. Phosphate of lime. By the presence of
this last substance they are essentially distinguished from
shells, and by the great excess of carbonate of lime above
the phosphate they are equally distinguished from bones.
Thus the crusts lie intermediate between bones and shells,
partaking of the properties and constitutiott of each. The
shells of the eggs of fowls must be referred likewise to the
class of crusts, since they contain both phosphate and car-
bonate of lime. The animal cement in them, however, is
much smaller in quantity. From the experiments of Ber-
niard and Hatchett, it is extremely probable that the shells
of snails are composed likewise of the same ingredients,
phosphate of lime having been detected in them by these
chemists.
Sect. II. Of Horns, Nails, and Scales.
In the last Section I treated of those hard parts of animals
which were inflexible and incapable of being softened by
heat, and which contained a great portion of calcareous
salts; but there is another set of hard parts which possess
considerable elasticity, which are softened by heat, and which
contain but a very small portion of calcareous matter. This
set comprehends the substances well known under the names
of horn, nails, and scales.
1. Horns are well known substances that are attached to
the foreheads of oxen, sheep, and various other animals.
They are not very hard, as they may be easily cut with a
knife or rasped with a file; but they are so tough, as not to
be capable of being pounded in a mortar. When in thin
plates they have a degree of transparency, and have been
sometimes substituted for glass is windows. When heated
SECT. II. HORNS; &c. 431
sufficiently they become very soft and flexible, so that their
shape may be altered considerably. Hence they may be
gradually squeezed into a mould, and wrought into various
forms, as is well known. When strongly heated in a Papin's
digester, they are said to be converted into a gelatinous mass,
which possesses the properties of gelatine.
The quantity of earthy matter which they contain is ex-
ceedingly small. Mr Hatchett burnt 500 grains of ox horn.
The residuum was only 1.5 grain, and not the half of this
was phosphate of lime. Seventy-eight grains of the horn of
the chamois left only 0.5 of residue, of which less than the
half was phosphate of lime. They consist chiefly of a mem-
branous substance, which possesses the properties of coa-
gulated albumen; and probably they contain also a little ge-
latine.
2. The nails, which cover the extremities of the fingers,
are attached to the epidermis, and come off along with it.
Mr Hatchett has ascertained that they are composed chiefly
of a membranous substance, which possessed the properties
of coagulated albumen. They seem to contain also a little
phosphate of lime. Water softens but does not dissolve
them; but they are readily dissolved and decomposed by
concentrated acids and alkalies. Hence it appears that nails,
agree with horn in their nature and composition. Under
the head of nails must be comprehended the talons and
claws of the inferior animals, and likewise their hoofs, which
differ in no respect from horn.
3. Scales of animals are of two kinds; some, as those of
serpents and other amphibious animals, have a striking re-
semblance to horn; while those of fish bear a greater re-
semblance to mother-of-pearl. The composition of these
two kinds of shells is very different.
The scales of fish, are composed of different membranous
laminae. When immersed for four or five hours in nitric
2
432 ANIMAL SOLIDS. CHAP. II.
acid, they become transparent, and perfectly membranaceous.
The acid, when saturated with ammonia, gives a copious
precipitate of phosphate of lime. Hence they are composed
of alternate layers of membrane and phosphate of lime. To
this structure they owe their brilliancy. Mr Hatchett found
the spicula of the shark's skin to be similar in its compo-
sition, but the skin itself yields no phosphate of lime.
The horny scales of serpents, on the other hand, are com-
posed alone of a horny membrane, and are destitute of phos-
phate of lime. They yielded, when boiled, but slight traces
of gelatine; the horn-like crusts which cover certain insects
and other animals appear, from Mr Hatchett's experi-
ments, to be nearly similar in their composition and nature.
Sect. III. Of the Muscles of Animals.
After the hard parts of animals have been examined, it
remains for us to consider the composition of the soft parts.
Of these, the muscles naturally claim our attention in the
first place, as being the most important.
The muscular parts of animals are known in common
language by the name of flesh. They constitute a consi-
derable portion of the food of man.
Muscular flesh is composed of a great number of fibres
or threads, commonly of a reddish or whitish colour; but its
appearance is too well known to require any description.
Hitherto it has not been subjected to any accurate chemical
analysis.
When a muscle is cut in small pieces, and well washed
with water, the blood and other liquids contained in it are
separated, and part of the muscular substance also is dis-
solved. The muscle, by this process, is converted into a
white fibrous substance, still retaining the form of the ori-
SECT. III. HORNS, &c. 433
ginal body. The water assumes the colour which results
from mixing water with some blood. When heated it coa-
gulates; brown flakes swim on the surface, consisting of a1-
bumen combined with the colouring matter of the blood:
some fibrin likewise precipitates. If the evnporation be con-
tinued, more albumen precipitates, and at last the whole as-
sumes the form of a jelly. When evaporated to dryness,
and treated with alcohol, the gelatine thus formed, together
with a little phosphate of soda and of ammonia, remains un-
dissolved; but the alcohol dissolves a peculiar extractive
matter, first observed by Thouvenel. This matter may be
obtained by evaporating the alcohol to dryness. It has a
reddish brown colour, a strong acrid taste, and aromatic
odour.
If the muscle, after being thus treated with cold water, be
boiled for a sufficient time in water, an additional portion of
the same substances is separated from it. Some albumen
collects on the surface in the form of scum, accompanied
with some melted fat. The water, when sutfficiently concen-
trated by evaporation, assumes the form of a jelly. When
evaporated to dryness, and treated with alcohol, the gelatine
and phosphoric salts remain, while the extractive matter of
Thoutvenel is dissolved, and may be obtained by evaporating
to dryness.
The muscle, thus treated with water, is left in the state
of grey fibres, insoluble in water, and becoming brittle when
dry. This substance possesses all the properties of fibrin.
From these facts, ascertained by Thouvenel and Four-
croy, it appears that the muscles are composed chiefly of
fibrin, to which they owe their fibrous structure and their
form, and that they contain also
2. Albumen
3. Gelatine
4. Extractive
5. Phosphate of soda
6. Phosphate of ammonia
7. Phosph. of lime and carb. of dc.
E e
434 ANIMAL SOLIDS CHAP. II.
For the discovery of the last ingredients we are indebted to
Mr Hatchett, who found that 500 parts of beef muscle left,
after combustion, a residuum of 25.6 parts, consisting chiefly
of these salts.
The muscles of different animals differ exceedingly from
each other in their appearance and properties, at least as ar-
ticles of food; but we know little of their chemical dif-
ferences. The observations of Thouvenel alone were di-
rected to that object, and they are imperfect. The flesh of
the ox contains, according to him, the greatest quantity of
insoluble matter, and leaves the greatest residuum when
dried; the flesh of the calf is more aqueous and mucous: the
land and water turtle yields more matter to water than the
muscle of the ox; but Thouvenel ascribes the difference to
foreign bodies, as ligaments, &c. mixed with the muscle of
the turtle: snails yield to water a quantity of matter inter-
mediate between that given by beef and veal: with them the
muscles of frogs, cray fish, and vipers, agree nearly in this
respect; but the muscles of fresh water fish, notwithstanding
their softness, yield a considerably smaller proportion.
SECT. IV. Of the Skin.
The skin is that strong thick covering which envelopes
the whole external surface of animals. It is composed
chiefly of two parts: a thin white elastic layer on the out-
side, which is called epidermis or cuticle; and a much thick-
er layer, composed of a great many fibres closely interwo-
ven, and disposed in different directions; this is called the
cutis, or true skin. The epidermis is that part of the skin
which is raised in blisters.
1. The epidermis is easily separated from the cutis by
maceration in hot water. It possesses a very great degree
of elasticity.
SECT. IV. SKIN. 435
It is totally insoluble in water and in alcohol. Pure fixed
alikalies dissolve it completely, as does lime likewise, though
slowly. Sulphuric and muriatic acids do not dissolve it, at
least they have no sensible action on it for a considerable
time; but nitric acid soon deprives it of its elasticity, and
causes it to fall to pieces.
If the cuticle be tinged with nitric acid, the application of
ammonia to it is well known to give it instantaneously a
deep orange colour. Now, as Hatchett has shown that this
change is also produced upon coagulated albumen in the
same circumstances, and as the epidermis resembles that sub-
stance in all the properties above detailed, it can scardely be
doubtee that it is any thing else than a peculiar modification
of coagulated albumen.
2. The cutis is a thick dense membrane, composed of
fibres interwoven like the texture of a hat. When it is ma-
cerated for some hours in water, and agitation and pressure
are employed to accelerate the effect, the blood, and all the
extraneous matter with which it was loaded, are separated
from it, but its texture remains unaltered. On evaporating
the water employed, a small quantity of gelatine may be ob-
tained. No subsequent maceration in cold water has any
farther effect. When distilled it yields the same products as
fibrin. The concentrated alkalies dissolve it, converting it
into oil and ammonia. Weak acids soften it, render it trans-
parent, and at last dissolve it. Nitric acid converts it into
oxalic acid and fat, while, at the same time, azotic gas and
prussic acid are emitted. When heated it contracts, and
then swells, exhales a fetid odour, and leaves a dense char-
coal, difficult to incinerate. By spontaneous decomposition
in water or moist earth, it is converted into a fatty matter
and into ammonia, which compose a kind of soap. When
allowed to remain long in water, it softens and putrefies, be-
ing converted into a kind of jelly. When long boiled in wa-
E e 2
436 ANIMAL SOLIDS. CHAP. II.
ter it becomes gelatinous, and dissolves completely, consti-
tuting a viscid liquor, which, by proper evaporation. is con-
verted into glue. Hence the cutis of animals is commonly
employed in the manufacture of glue.
From these facts the cutis appears to be a peculiar modi-
fication of gekatine, enabled to resist the action of water, part-
ly by the compactness of its texture, and partly by the visci-
dity of the gelatine of which it is formed; for those skins
which dissolve most readily in boiling water afford the worst
glue. Mr Hatchett has observed that the viscidity of the
gelatine obtained from skins is nearly inversely as their flexi-
bility, the supplest hides always yielding the weakest glue;
but this glue is very soon obtained from them by hot water.
The skin of the eel is very flexible, and affords very readily
a great proportion of gelatine. The skin of the shark also
readily yields abundance of gelatine; and the same remark
applies to the skins of the hare, rabbit, calf and ox; the dif-
ficulty of obtaining the glue and its goodness always increas-
ing with the toughness of the hide. The hide of the rhino-
ceros, which is exceedingly strong and tough, far surpasses
the rest in the difficulty of solution and in the goodness of
its glue. When skins are boiled, they gradually swell and
assume the appearance of horn: then they dissolve slowly.
3. As to the rete mucosum, or the mucous substance, si-
tuated between the cutis vera and epidermis, its composition
cannot be determined with precision, because its quantity is
too small to admit of examination. It is known that the
black colour of negroes depends upon a black pigment, situ-
ated in this substance. Oxymuriatic acid deprives it of its
black colour, and renders it yellow. A negro, by keeping
his foot for some time in water impregnated with that acid,
deprived it of its colour, and rendered it nearly white; but
zn a few days the black colour returned again with its former
SECT V. MEMBRANES &c. 437
intensity. This experiment was first made by Dr Beddoes
on the fingers of a negro.
Sect. V. Of Membranes, Tendons, Ligaments, and
Glands.
These substances have not hitherto been subjected to a rigid
chemical analysis. But from the properties which have been
obsered, they appear to have a closer resemblance to the
skin than to any other animal substance.
1. The membranes are thin semitransparent bodies which en-
velope certain parts of the body, especialy the viscera; such
as, the dura and pia mater, the plura, the peritoneum, the
periosteum, &c. These substances are soft and pliable;
when macerated in water, they swell, and become somewhat
pulpy; and by continued decoction in hot water they are al-
most completely dissolved, and the solution concretes into
gelatine. They are convertible of course into the same sub-
stance as the cutis by decoction; hence we must consider
their composition as similar. Like hides they may also be
tanned and converted into leather. From the experiments of
Mr Hatchett, it appears that they contain no phosphate of
lime as a constituent part, and scarcely any saline ingredients;
for when calcined they leave but a very inconsiderable resi-
duum. Thus 250 grains of hog's bladder left only 0.02
grain of residuum.
2. The tendons are strong, pearl-coloured, brilliant bodies,
which terminate the muscles, and attach them to the bones,
and are known in common language by the name of sinews.
When boiled they assume the form of a semitransparent ge-
latinous substance, of a pleasant taste, well known in boiled
meat. If the decoction be continued they dissolve complete-
ly, and are converted into gelatine. From these facts we
E e 3
438 ANIMAL SOLIDS CHAP. II.
are authorized to conclude, that the composition of the ten-
dons is similar to that of the membranes and cutis.
3. The ligaments are strong bands which bind the bones
together at the different joints: they are fibrous substances,
very dense and strong, and somewhat elastic. When boiled
they yield a portion of gelatine, but they resist the action of
water with great obstnacy, and after a great deal of boiling
retain their form, and even their strength. The ligaments,
then, differ essentially from the two last species. How far
they resemble coagulated albumen remains to be ascertained.
It is not unlikely that they will form a genus apart.
4. The glands are a set of bodies employed to form or to
alter the different liquids which are employed for different
purposes in the animal body. There are two sets of them:
the conglobate, which are small, scattered in the course of
the lymphatics; and the conglomerate, such as the liver, kid-
neya, &c. Furcroy supposes the first of these to be com-
posed of gelatine; but this is not very probable. The struc-
ture of the large glands has been examined by anatomists
with great care; but we are still ignorant of their composi-
tion. Indeed the present state of chemistry scarcely admits
of an accurate analysis of these complicated bodies.
Sect. VI. Of The Brain and Nerves.
The brain and nerves are the instruments of sensation, and
even of motion; for an animal loses the power of moving a
part the instant that the nerves which enter it are cut.
The brain and nerves have a strong resemblance to each
other; and it is probable that they agree also in their com-
position. But hitherto no attempt has been made to analyse
the nerves. The only chemists who have examined the na- ture of brain are Mr Thouret and Mr Fourcroy.
SECT. VI. BRAIN AND NERVES. 439
The brain consists of two substances, which differ from
each other somewhat in colour, but which, in other respects,
seem to be of the sane nature. The outermost matter, ha-
ving some small resemblance in colour to wood ashes, has
been called the cineritious part; the innermost has been cal-
led the medullary part.
Brain has a soft feel, not unlike that of soap; its texture
appears to be very close; its spicific gravity is greater than
that of water.
When brain is triturated in a mortar with diluted sulphuric
acid, part is dissolved; the rest may be separated, by filtra-
tion, in the form of a coagulum. The acid liquor is colour-
less. By evaporation, the liquid becomes black, sulphurous
acid is exhaled, and crystals appear; and when evaporated to
dryness, a black mass remains behind. When this mass is
diluted with water, a quantity of charcoal separates, and the
water remains clear: The brain is completely decomposed,
a quantity of ammonia combines with the acid and forms sul-
phate of ammonia, while charcoal is precipitated. The wa-
ter, by evaporation and treatment with alcohol, yields sul-
phates of ammonia and lime, phosphoric acid, and phos-
phates of soda and ammonia. Brain therefore contains
Phosphate of limeM
____________ soda
____________ ammonia.
Traces also of sulphate of lime can be discovered in it.
The quantity of these salts is very small; altogether they do
not amount to 1/130th part.
Diluted nitric acid, when triturated with brain, likewise
dissolves a part, and coagulates the rest. The solution is
transparent. When evaporated till the acid becomes concen-
trated, carbonic acid gas andl nitrous gas are disengaged; an
effervescence takes place, white fumes appear, an immense
E e 4
440 ANIMAL SOLIDS CHAP. II.
quantity of ammonia is disengaged, a bulky charcoal remanis
mixed with a considerable quantity of oxalic acid.
When brain is gradually evaporated to dryness by the heat
of a water bath, a portion of transparent liquid separates at
first from the rest, and the residuum, when nearly dry, ac-
quires a brown colour; its weight amounts to about one-
fourth of the fresh brain. It may still be formed into an
emulsion with water, but very soon separates again spontane-
ously.
When alcohol is repeatedly boiled upon this dried resi-
duum till it ceases to have any more action, it dissolves about
five-eighths of the whole. When this alcohol cools, it depo-
sites a yellowish white substance, composed of brilliant
plates. When kneaded together by the fingers, it assumes
the appearance of a ductile paste: at the temperature of
boiling water it becomes soft, and when the heat is increased
it blackens, exhales empyreumatic and ammoniacal fumes,
and leaves behind it a charry matter. When the alcohol is
evaporated, it deposites a yellowish black matter, which red-
dens paper tinged with turnesole, and readily diffuses itself
through water.
Pure concentrated potash dissolves brain, disengaging a
great quantity of ammonia.
Sect. VII. Marrow.
The hollows of the long bones are in living animals filled
with a peculiar species of fat matter, to which the name of
marrow has been given. In some bones this matter is a
good deal mixed with blood, and has a red colour; in others,
as the thigh bones, it is purer, and has a yellow colour. Va-
rious experiments on this matter were made by the older
chemists, showing it to be analogous to animal fats, and
pointing out some of its peculiarities. Berzelius has lately
SECT. VII. MARROW. 441
examined it in detail, and published the results of his experi-
ments. The marrow on which his trials were made was ob-
tained from the thigh bone of an ox.
Marrow, freed from its impurities, has a white colour with
a shade of blue; its taste is insipid and rather sweetish. It
softens by the heat of the hand, and melts when heated to
113˚. When cooled slowly it crystallizes in sphericles like
olive oil. It burns with a flame like tallow. When distilled
it gives first a transparent fluid yellowish oil, accompanied by
carbonic acid gas, water, and heavy inflammable air. After-
wards there comes over a white solid oil, accompanied by a
less copious evolution of gaseous bodies, and which does not
become dark coloured, as happens when tallow is distilled.
This had already been observed by Neumann. This solid
oil has a disagreeable smell, amounts to 0.8 of the marrow
distilled, reddens vegetable blues, and when boiled in water
gives out a portion of sebacic acid, which Berzelius considers
as benzoic acid.
The empyreumatic oil combines readily with alkalies and
their carbonates. With the latter it forms a snow white
soap, insoluble in water, though it increases in bulk when
placed in contact with that liquid. It combines also with
the earths, and forms soaps likewise insoluble in water.
The water which comes over during the distillation of
marrow is colourless, has a fetid and sour smell, and an em-
pyreumatic taste. It contains a little acetic acid, empyreu-
matic oil, and probably benzoic acid; but exhibits no traces
of ammonia.
The gaseous products amount to one-tenth of the marrow
distilled. They contain no sulphur nor phosphorus, and
consist of carbonic acid and heavy inflammable air, which
burns with a white flame, and seems to contain oil in solu-
tion.
442 ANIMAL SOLIDS CHAP. II.
The charry matter in the retort amounts to 0.05 of the
marrow distilled. It is dark brown, heavy end brilliant. It
is incinerated with difficulty, and leaves an ash consisting of
phosphate of lime, carbonate of lime, and some soda.
Marrow combines with alkalies and forms soap. Boliling
alcohol and ether dissolve a small portion of it, which preci-
pitates again as the solution cools.
Marrow, from the thighbone of an ox, was found by Ber-
celius to be composed of the following substances:
Pure marrow 0.96
Skins and blood-vessels O.O1
Albumen \
Gelatine |
Extractive > O.O3
Peculiar matter |
Water /
____
1.00
From the preceding detail it appears, that pure marrow is a
species of fixed oil, possesing peculiar properties, and ap-
proaching somewhat to butter in in nature.
SECT. VIII. Of Hair and Feathers.
These substances cover different parts of animals, and are
obviously intended by Nature to protect them from the cold.
For this, their softness and pliability, and the slowness with
which they conduct heat, render them peculiarly proper.
1. Hair is usually distinguished into various kinds, accord-
ing to its size and appearance. The strongest and stiffest of
all is called bristle: of this kind is the hair on the backs of
hogs. When remarkably fine, soft, and pliable, it is called
wool; and the finest of all is known by the name of down.
SECT. VIII. HAIR. 443
But all these varieties resemble one another very closely in
their composition.
Vauquelin has lately published a curious set of experi-
ments on the analysis of human hair of various colours.
Though hair is ihsoluble in boiling water, he obtained a so-
lution by raising the temperature of the liquid in a Papin's
digester. If the heat thus produced was too great, the hair
was decomposed, and ammonia, carbonic acid, and an em-
pyreumatic oil formed. Sulphureted hydrogen is always
evolved, and its quantity increases with the heat. When hair
is thus dissolved in water heated above the boiling point, the
solution contains a kind of bituminous oil, which is deposited
very slowly. This oil was black when the hair dissolved was
black, but yellowish red when red hair was employed.
When the solution is filtered to get rid of this oil, the li-
quid which passes through is nearly collorless. Copious
precipitates are formed in it by the infusion of nutgalls and
oxymuriatic adid. Silver is blackened by it, and acetate of
lead precipitated brown. Acids render it turbid, but the
precipitate is re-dissolved by adding these liquids in excess.
Though very much concentrated by evaporation, it does not
concrete into a jelly.
Water containing only four per cent. of potash dissolves
hair, while hydrosulphuret of ammonia is evoked. If the
hair be black, a thick dark-coloured oil, with some sulphur
and iron, remains undissolved; if the hair be red, there re-
mains a yellow oil, with some sulphur and an atom or two
of iron. When acids are dropt into this solution, they throw
down a white matter soluble in an excess of acid.
Sulphuric and muriatic acids become red when first pour-
ed on hair, and gradually dissolve it. Nitric acid turns hair
yellow and dissolves it, while an oil separates, which is red
or black according to the colour of the hair dissolved. The
solution yields a great deal of oxalic acid, and coatains, be-
444 ANIMAL SOLIDS. CHAP. II.
sides, bitter principle, iron, and sulphuric acid. Oxymuria-
tic acid first whitens hair, and then reduces it to a substance
of the consistence of turpentine, and partly soluble in alco-
hol.
When alcohol is digested on black hair, it extracts from it
two kinds of oil. The first, which is white, subsides in white
shining scales as the liquor cools; the second is obtained
by evaporating the alcohol. It has a greyish green colour,
and at last becomes solid. From red hair alcohol likewise
separates two oils; the first white as from black hair, and the
other as red as blood. When the red hair is deprived of
this oil, it becomes of a chestnut colour. Hence its red co-
lour is obviously owing to the red oil.
When hair is incinerated, it yields iron and manganese,
phosphate, sulphate, and carbonate of lime, muriate of soda,
and a considerable portion of silica. The ashes of red hair
contain less iron and manganese: those of white hair still
less; but in them we find magnesia, which is wanting in the
other varieties of hair. The ashes of hair do not exceed
0.015 of the hair.
From the preceding experiments of Vauquelin, we learn
that black hair is composed of the nine following substances:
1. An animal matter, constituting the greatest part.
2. A white solid oil, small in quantity.
3. A greyish green oil, more abundant.
4. Iron; state unknown.
5. Oxide of manganese.
6, Phosphate of lime,
7. Carbonate of lime, very scanty.
8. Silica.
9. Sulphur.
The colouring matter of hair appears from Vauquelin's
experiments to be an oil. The oil is blackish green in black
hair, red in red hair, and white in white hair. Vauquelin sup-
SECT. IX. BLOOD. 445
poses that sulphureted iron contributes to the colour of dark
hair; and ascribes to the presence of an excess of sulphur
the property which white and red hair have of becoming
black with the oxides of the white metals. The sudden
change of colour in hair from grief, he thinks, is owing to the
evolution of an acid.
2. Feathers seem to possess nearly the same properties
with hair. Mr Hatchett has ascertained that the quill is
composed chiefly of coagulated albumen. Though feathers
were boiled for a long time in water, Mr Hatchett could ob-
serve no traces of gelatine.
Having given the preceding account of the solids which
compose animal bodies, I proceed next to the fluid which cir-
culates through living bodies, namely blood; and to the various
secretions formed from the blood, either in order to answer
some important purpose to the animal, or to be evacuated as
useless; that the blood thus purified may be more proper for
answering the ends for which it was destined. Many of
these substances have been examined with more care by
chemists than the animal solids.
Sect. IX. Of Blood.
Blood is a well-known fluid which circulates in the veins
and arteries of the more perfect animals. It is of a red co-
lour, has a considerable degree of consistency, and an unctu-
ous feel, as if it contained a quantity of soap. Its taste is
slightly saline, and it has a peculiar smell.
The specific gravity of human blood is, at a medium,
1.0527.
When blood, after being drawn from an animal, is allowed
to remain for some time at rest, it very soon coagulates into
a solid mass of the consistence of curdled milk. This mass
4 ANIMAL FLUIDS CHAP. II.
gradually separates into two parts; one of which is fluid, and
is called serum; the, other, the cuagulu, has been called
cruor, because it alone retains the red colour which
distinguishes blood. This separation is very similar to the sepa-
ration of curdled milk into curds and whey.
1. The serum is of a light greenish yellow colour; it has
the taste, smell, and feef of the blood, but its consistence is
not so great. Its mean specific gravity is about 1.0287. It
converts syrup of violets to a green, and therefore contains
an alkali. On examination, Rouelle found that it owes this
property to a portion of soda. When heated to the tempe-
rature of 156˚ the serum coagulates, as Harvey first disco-
vered. It coagulates also when boiling water is mixed with
it; but if serum be mixed with six parts of cold water, it
does not coagulate by heat. When thus coagulated, it has a
grayish white colour, and is not unlike the boiled white of an
egg. If the coagulum be cut into small pieces, a muddy fluid
may he squeezed from it, which has been termed the serosity.
After the separalion of this fluid, if the residuum be careful-
ly washed in boiling water and examined, it will he found to
possess all the properties of coaglated albumen. The se-
rum, therefore, contains a considerable proportion of albu-
men. Hence its coagulation by heat, and the other pheno-
mena which albumen usually exhibits.
If the coagulated serum be heated in a silver vessel, the
surface of the silver becomes black, being converted into a
sulphuret. Hence it is evident that it contains sulphur; and
Proust has ascertained that it is combined with ammonia in
the state of a hydrosulphuret.
If serum be mixed with twice its weight of water, and, af-
ter coagulation by heat, the albumen be separated by filtra-
tion, and the liquid be slowly evaporated till it is considera-
bly concentrated, a number of crystals are deposited when
the liquid is left standing in a cool place. These crystals,
SECT. X. BLOOD. 447
first examined by Rouelle, consist of carbonate of soda, mu-
riate of soda, besides phosphate of Soda and phosphate of
lime. The soda exists in the blood in a caustic state, and
seems to be combined with the gelatine and albumen. The
carboinc acid combines with it during evaporation.
2. The cruor, or clot as it is sometimes called, is of a red
colour, and possesses considerable consistence. Its mean
specific gravity is about 1.245. If this cruor be washed
carefully by letting a small jet of water fall upon it till the wa-
ter runs off colourless, it is partly dissolved, and partly re-
mains upon the searce. Thus it is separated into two por-
tions: namely, 1. A white, solid, elastic substance, which has
all the properties of fibrin; 2. The portion held in solution
by the water, which consists of the colouring matter, not
however in a state of purity, for it is impossible to separate
the cruor completely from the serum.
Bucquet proved that this watery solution contained albu-
men and iron. Menghini had ascertained, that if blood be
evaporated to dryness by a gentle heat, a quantity of iron may
be separated from it by the magnet. The quantity which he
obtained was considerable; according to him, the blood of a
healthy man contains above two ounces of it. Now, as nei-
ther the serum nor the fibrin extracted from the cruor con-
tains iron, it follows of course, that the water holding the co-
louring matter in solution must contain the whole of that
metal.
This watery solution gives a green colour to syrup of vio-
lets. When exposed to the air, it gradually deposites flakes,
which have the properties of albumen. When heated, a
brown-coloured scum gathers on its surface, if it be evapo-
rated to dryness, and then mixed with alcohol, a portion is
dissolved, and the alcoholic solution yields by evaporation a
residuum, which lathers like soap in water, and tinges vege-
table blues green; the acids occasion a precipitate from its
448 ANIMAL FLUIDS. CHAP. II.
solution. This substance is a compound of albumen and
soda. Thus we see that the watery solution contains albu-
men, iron, and soda.
Fourcroy and Vauquelin have ascertained that the iron is
combined with phosphoric acid, and in the state of sub-
phosphate of iron; thus confirming an opinion which had
been maintained by Sage, and announced as a fact by Gren.
Such are the propertied of blood, as far as they have been
hitherto ascertained by experiment. We have seen that it
contains the following ingredients:
1. Water 6. Subphosphate of iron
2. Fibrin 7. Muriate of soda
3. Albumen 8. Phosphate of soda
4. Hydrosulph. of ammonia 9. Phosphate of lime
5. Soda
Besides benzoic acid, which has been detected by Proust.
SECT. X. Of Milk.
Milk is a fluid secreted by the female of all those animals
denominated mammalia, and intended evidently for the nou-
rishment of her offspring.
The milk of every animal has certain peculiarities which
distinguish it from every other milk. But the animal whose
milk is most made use of by man as an article of food, and
with which, consequently, we are best acquainted, is the cow.
Chemists, therefore, have made choice of cow's milk for
their experiments.
Milk is an opaque fluid, of a white colour, a slight pecu-
liar smell, and a pleasant sweetish taste. When newly drawn
from the cow, it has a taste very different from that which it
requires after it has been kept for some hours. It reddens
vegetable blues.
SECT. X. MILK. 449
When milk is allowed to remain for some time at rest,
there collects on its surface a thick unctuous yellowish co-
loured substance, known by the name of cream.
After the cream is separated, the milk which remains is
much thinner than before, and it has a bluish white colour.
If it be heated to the temperature of 100˚, and a little rennet,
which is water digested with the inner coat of a calf's sto-
imach and preserved with salt, be poured into it, coagulation
ensues; and if the coagulum be broken, the milk very soon
separates into two substances; a solid white part, known by
the name of curd, and a fluid part called whey. Thus we
see that milk may be easily separated into three parts, name-
ly, cream, curd, and whey.
1. Cream is of a yellow colour, and its consistence increases
gradually by exposure to the atmosphere. In three or four
days it becomes so thick that the vessel which contains it
may be inverted without risking any loss. In eight or ten
days more, its surface is covered over with mucors and byssi,
and it has no longer the flavour of cream, but of very fat
cheese.
Cream possesses many of the properties of an oil. It is
specifically lighter than water; it has an unctuous feel, stains
clothes precisely in the manner of oil; and if it be kept fluid,
it contracts at last a taste which is very analogous to the ran-
cidity of oils. These properties are sufficient to show us that
it contains a quantity of oil; but this oil is combined with a
part of the curd, and mixed with some serum. Cream, then,
is composed of a peculiar oil, curd, and serum. The oil
may be easily obtained separate by agitating the cream for
considerable time. This process, known to every body, is
called churning. After a certain time, the cream separates
into two portions: one fluid, and resembling creamed milk;
the other solid, and called butter<(i>.
F f
450 ANIMAI FLUIDS. CHAP.II.
Butter is of a yellow colour, possesses the properties of an
oil, and mixes readily with other oily bodies. When heated
to the temperature of 96˚ it melts, and becomes transparent;
if it be kept for some time melted, some curd and water or
whey separate from it, and it assumes exactly the appearance
of oil. But this process deprives it in a great measure of its
peculiar flavour.
Butter may be obtained by agitating cream newly taken
from milk, or even by agitating milk newly drawn from the
cow. But it is usual to allow cream to remain for some time
before it is churned. Now cream, by standing, acquires a
sour taste; butter therefore is commonly made from sour
cream. When very sour cream is churned, every one must
have perceived, that the butter milk, after the churning, is not
nearly so sour as the cream had been. The butter, in all
cases, is perfectly sweet; consequently the acid which had
been evolved has in a great measure disappeared during the
progress of churning. It has been ascertained that cream
may be churned, and butter obtained, though the contact of
atmospheric air be excluded. On the other hand, it has
been affirmed, that when cream is churned in contact with
air, it absorbs a considerable quantity of it.
In many cases there is a considerable extrication of gas
during the churning of water. From the phenomena, it can
scarcely be doubted that this acid is carbonic acid.
2. Curd, which may be separated from creamed milk by
rennet, has many of the properties of coagulated albumen. It
is white and solid; and when all the moisture is squeezed out,
it has a good deal of brittleness. It is insoluble in water;
but pure alkalies and lime dissolve it readily, especially when
assisted by heat; and when fixed alkali is used, a great quan-
tity of ammonia is emitted during the solution. The solution
of curd in soda is of a red colour, at least if heat be employ-
ed; owing, probably, to the separation of charcoal from the
SECT. X. MILK. 451
curd by the action of the alkali. The matter dissolved by
the alkali may be separated from it by means of an acid; but
it has lost all the properties of curd. It is of a black colour,
melts like tallow by the application of heat, leaves oily stains
on paper, and never acquires the consistence of curd.
Curd, as is well known, is used in making cheese; and the
cheese is the better the more it contains of cream, or of that
oily matter which constitutes cream. It is well known to
cheesemakenrs, that the goodness of it depends in a great mea-
sure on the manner of separating the whey from the curd. If
the milk be much heated, the coagulum broken in pieces, and
the whey forcibly separated, as is the practice in many parts
of Scotland, the cheese is scarce good for any thing; but the
whey is delicious, especially the last squeezed out whey, and
butter may be obtained from it in considerable quantity:-a
full proof that nearly the whole creamy part of the milk has
been separated with the whey. Whereas if the milk be not
too much heated (about 100˚ is sufficient), if the coagulum
be allowed to remain unbroken, and the whey be separated
by very slow and gentle pressure, the cheese is excellent; but
the whey is almost transparent, and nearly colourless.
Good cheese melts at a moderate heat; but bad cheese,
when heated, dries, curls, and exhibits all the phenomena of
burning horn. From this it is evident, that good cheese con-
tains a quantity of the peculiar oil which constitutes the dis-
tinguishing characteristic of cream; hence its flavour and
smell. Proust has found in cheese an acid which he calls
the caseic acid, to which he ascribes several of the peculiar
properties of cheese.
3. Whey, after being filtered, to separate a quantity of
curd which still continues to float through it, is a thin pellu-
cid fluid, of a yellowish green colour and pleasant sweetish
taste, in which the flavour of milk may be distinguished. It
always contains some curd; but nearly the whole may be se-
F f 2
452 ANIMAL FLUIDS. CHAP. II.
parated by keeping the whey for some time noiling; a thick
white scum gathers on the surface, which in Scotland is
known by the name of float whey. When this scum, which
consists of the curdy part, is carefully separated, the whey,
after being allowed to remain at rest for some hours, to give
the remainder of the curd time to precipitate, is decanted off
almost as colourless as water, and scarcely any of the pecu-
liar taste of milk can be distinguished in it. If it be now
slowly evaporated, it deposites at last a number of white-co-
loured crystals, which are sugar of milk. Toward the end
of the evaporation, some crystals of muriate of potash and of
muriate of soda make their appearance. According to
Scheele, it contains also a little phosphate of lime, which
may be precipitated by ammonia.
The recent experiments of Fourcroy and Vauquelin, The-
nard, and Bouillon La Grange, have added considerably to
our knowledge of the constituents of whey. It always red-
dens vegetable blues, containing a portion of acetic acid.
The lactic acid of Scheele is nothing else than this acid hold-
ing an animal matter in solution. It contains likewise some
phosphate of magnesia and phosphate of iron, as Fourcroy
and Vauquelin have discovered. Sulphate of potash, like-
wise, and a peculiar extractive matter, have been separated
from it.
Thus we see that cow's milk is composed of the following
ingredients:
1. Water. 7. Muriate of soda.
2. Oil. 8. Muriate of potasn.
3. Curd. 9. Sulphate of potash
4. Extractive. 10. Phosphate of lime.
5. Sugar of milk. 11. Phosphate of magnesia.
6. Acetic acid. 12. Phosphate of iron.
SECT. XI. SALIVA. 453
The milk of all other animals, as far as has hitherto been
examined, consists nearly of the same ingredients: but there
is a very great difference in their proportion.
Sect. XI. Of Saliva.
The fluid secreted in the mouth, which flows in consider-
able quantity during a repast, is known by the name of sa-
liva.
Saliva is a limpid fluid like water; but much more viscid
it has neither smell nor taste. Its specific gravity, according to Hamberger, is 1.1067; according to Siebold, 1.080.
When agitated, it froths like all other adhesive liquids; indeed
it is usually mixed with air, and has the appearance of froth.
It neither mixes readily with water nor oil; but by tritura-
tion in a mortar it may be so mixed with water as to pass
through a filter. It has a great affinity for oxygen, absorbs
it readily from the air, and gives it out again to other bodies.
When boiled in water, a few flakes of albumen precipitate.
From the experiments of Dr Bostock, we learn that this al-
bumen is not in a state of solution. It is separated by the
filter, and subsides of its own accord when the liquid is dilu-
ted with water. In his analysis, this coagulated albumen
amounted to 0.4 of the solid matter contained in the saliva
examined.
When saliva is evaporated, it swells exceedingly, and leaves
behind it a thin brown-coloured crust: But if the evapora-
tion be conducted slowly, small cubic crystals of muriate of
soda are formed. The viscidity of saliva, the property which
it has of absorbing oxygen, and of being inspissated, announce
the presence of mucus as a component part. This is fully,
confirmed by the effect of neutral acetate of lead, which pro-
duces a copious precipitate in saliva. Dr Bostock considers
F f 3
454 ANIMAL FLUIDS. CHAP. II.
the mucus as constituting about one-half of the solid contents
of saliva.
When saliva is distilled in a retort, it froths very much:
100 parts yield 80 parts of water nearly pure, then a little
carbonate of ammonia, some oil, and an acid, which perhaps
is the prussic. The residuum amounts to about 1.56 part,
and is composed of muriate of soda, phosphate of soda, and
phosphate of lime.
The acids and alcohol inspissate saliva; the alkalies disen-
gage ammonia; oxalic acid precipitates lime; and the nitrates
of lead, mercurry, and silver, precipitate phosphoric and mu-
riatic acids.
From these facts, it follows that saliva, besides water,
which constitutes at least four-fifths of its bulk, contains the
following ingredients:
1. Mucilage. 4. Phosphate of soda.
2. Albumen. 5. Phosphate of lime.
3. Muriate of soda. 6. Phosphate of ammonia.
But it cannot be doubted that, like all the oter nnimal fluids,
it is liable to many changes from disease, &c, Brugnatelli
found the saliva of a patient labouring under an obstinate ve-
nereal disease impregnated with oxalic acid.
SECT. XII. Of Bile.
Bile is a liquid of a yellowish green colour, an unctuous
feel, bitter taste, and peculiar smell, which is secreted by the
liver; and in most animals considerable quantities of it are
usually found collected in the gall bladder.
I. Ox bile is a liquid of a yellowish green and sometimes
of a deep green colour. Its taste is very bitter, but at the
same time sweetish. Its smell is feeble, but peculiar and
disagreeable. It does not act on vegetable blues. Its con-
sistence varies very much. Sometimes it is a thin mucilage;
SECT. XII. BILE. 455
sometimes very viscid and glutinous; sometimes it is perfect-
ly transparent, and sometimes it contains a yellow coloured
matter which precipitates when the bile is diluted with water.
WheD an acid is added to bile, even in a minute quantity,
it acquires the property of reddening vegetable blues. The
addition of a little more acid occasions a precipitate, and sul-
phuric acid occasions a greater precipitate than any other
acid. This precipitate consists of a yellow coloured matter
often visible in bile, and which is insoluble in water. It con-
tains also a little resin which gives it a bitter taste. Acids do
not throw down the whole resin from bile. Yet if the resin
be dissolved in soda, it is readily precipitated by all the acids;
a proof that the resin is not kept in solution in bile by soda.
When superacetate of lead is poured into bile a copious
white precipitate falls, consisting of the resin combined with
the oxide of lead. The superacetate of commerce does not
readily throw down the whole resin; but if eight parts of
common sugar of lead and one part of litharge be united to-
gether by digestion in water, a salt is formed which readily
throws down the whole of the resin. If the precipitate be
treated with diluted nitric acid the lead is separated, and the
resin remains behind in a state of purity. It is a green co-
loured, bitter tasted substance, possessing most of the pro-
perties of resins. It has been already described in the pre-
ceding Chapter. One hundred parts of bile contain about
three parts of resin.
If acetate of lead be poured into bile thus deprived of its
resin by the superacetate, a new and more copious precipi-
tate falls, consisting of the oxide of lead united to a peculiar
substance, which gives bile most of its characters. This sub-
stance was first described in detail by Thenard, who has
given it the name of picromel. The compound, consisting
of oxide of lead and picromel, is soluble in acetic acid. If
a current of sulphureted hydrogen gas be passed through the
F f 4
456 ANIMAL FLUIDS. CHAP. II.
solution, the lead is separated; and by filtering and evapora-
ting the liquid dryness, picromel is obtained in a sepa-
rate state. When bile, mixed with muriatic acid and filter-
ed, is set aside for some months in an open vessel, I have
seen the picromel separate of its own accord. It is a white
solid substaqce in small globules. It has a sweet. and at the
same time an acrid taste, and is often somewhat bitter from
retaining a portion of the resin. It facilitates the solution of
resin in water: three parts of picromel and one part of resin
dissolve in water.
By evaporating a quantity of bile to dryness, calcining it,
and proceeding in the usual way, Thenard ascertained the
proportion of salts which it contained. The following was
the result of his analysis of 800 parts of bile.
700.0 water.
24.0 resin.
60.3 picromel.
4.5 yellow matter.
4.0 soda.
2.0 phosphate of soda.
3.2 muriate of soda.
0.8 sulphate of soda.
1.2 phosphate of lime.
oxide iron, a trace.
____
8OO.0
Such are the properties and the cgonstituents of ox bile,
as far as they have been examined by Thenard. From the
experiments of the same chemist it appeara, that the bile of
the calf, the dog, the sheep, and the cat, resmble that of
the ox exactly, both in their properties and their consti-
tuents.
SECT. XII. BILE. 457
3. The bile of the sow differs entirely from that of all these
animals. It contains neither albumen, nor animal matter, nor
picromel, but is merely a soap, as it contains a great quanti-
ty of resin and of soda, and is decomposed with facility by
all the acids, even by vinegar. It contains traces also of se-
veral salts; but Thenard did not ascertain their nature.
4. The bile of the common hen, of the turkey, and the
duck, has a good deal of resemblance to that of quadrupeds.
But it differs in the following particulars: 1. It contains a
considerable quantity of albumem; 2. The picromel has no
sensible sweet taste, but is very acrid and bitter; 3. It con-
tains very little soda; 4 The resin is not precipitated by
common superacetate of lead; but superacetate, boiled with
one-fourth of its weight of litharge, occasions it to precipi-
tate.
5. The bile of the thornback and salmon is yellowish white.
When evaporated it leaves a matter which has a very sweet
and slightly acrid taste. It appears to contain no resin. The
bile of the carp and the eel is very green, very bitter, contains
little or no albumen, but yields soda, resin, and a sweet acrid
matter similar to that which may be obtained from salmon
bile.
6. Human bile differs considerably from that of all other
animals examined, its taste is not very bitter. It is seldom
completely liquid, but usually contains some yellow matter
suspended in it. When evaporated to dryness it leaves a
brown matter amounting to about 1/11th of the original weight.
All the acids decompose human bile, and throw down a co-
pious precipitate consisting of albumen and resin. The fol-
lowing were the proportions of the constituents obtained by
Thenard from 11OO parts of human bile:
1000.O water.
from 2 to 10 yellow insoluble matter.
yellow matter in solution, a trace
458 ANIMAL FLUIDS. CHAP. II
42.0 albumen.
41.0 resin.
5.6 soda.
4.5 phosphate of soda, sulphate of soda, muriate of so-
da, phosphate of lime, oxide of iron.
SECT. XII. Of the Cerumen of the Ear.
Cerumen is a viscid yellow-coloured liquid secreted by the
glands of the auditory canal, which gradually becomes con-
crete by exposure to the air.
It has an orange-yellow colour and a bitter taste. When
slightly heated upon paper, it melts, and stains the paper like
an oil; at the same time it emits a slightly aromatic odour.
On burning coals it softens, emits a white smoke, which re-
sembles that given out by burning fat; it afterwards melts,
swells, becomes dark-coloured, and emits an ammoniacal
and empyreumatic odour. A light coal remains behind.
When agitated in water, cerumen forms a kind of emul-
sion, which soon putrefies, depositing at the same time white
flakes.
Alcohol, when assisted by heat, dissolves five-eighths of
the cerumen; the three-eighths wich remain behind have
the properties of albmuen, mixed however with a little oily
matter. When the alcohol is evaporated, it leaves a deep
orange residuum of a very bitter taste, having a smell and a
consistence analogous to turpentine. It melts when heated,
evaporates in a white smoke without leaving any residuum,
and in short resembles very strongly the resin of bile. Ether
also dissolves this oily body; but it is much less bitter and
much lighter coloured. When the albuminous part of ceru-
men is burnt, it leaves traces of soda and of phosphate of
lime. From these facts Vauquelin considers cerumen as
composed of the following substances:
SECT. XIV. TEARS AND MUCUS. 459
1. Albumen.
2. An inspissated oil.
3. A colouring matter.
4. Soda.
5. Phosphate of lime.
SECT. XIV. Of Tears and Mucus.
The liquid called tears is transparent and colourless like
water; it has scarcely any smell, but its taste is always per-
ceptinly salt. Its specific gravity is somewhat greater than
that of distilled water. It gives to paper stained with the
juice of the petals of mallows or violet a permanently green
colour, and therefore contains a fixed alkali. It unites with
water, whether cold or hot, in all proportions. Alkalies
unite with it readily, and render it more fluid. The mineral
acids produce no apparent change upon it. Exposed to the
air, this liquid gradually evaporates, and becomes thicker.
When nearly reduced to a state of dryness, a number of cu-
bic crystals form in the midst of a kind of mucilage. These
crystals possess the properties of muriate of soda; but they
tinge vegetable blues green, and therefore contain an excess
of soda. The mucilaginouts matter acquires a yellowish co-
lour as it dries.
When alcohol is poured into this liquid, a mucilaginous
matter is precipitated in the form of large white flakes. The
alcohol leaves behind it, when evaporated, traces of muriate
of soda and soda. The residuum which remains behind,
when inspissated tears are burnt in the open air, exhibits
some traces of phosphate of lime and phosphate of soda.
Thus it appears that tears are composed of the following
ingredients:
1. Water.
2. Mucus
3. Muriate of soda.
4. Soda.
5. Phosphate of lime.
6. Phosphate of soda.
460 ANIMAL FLUIDS. CHAP. II
The saline parts amount only to about 0.01 of the whole,
or probably not so much.
2. The mucus of the nose has also been examined by
Fourcroy and Vauquelin. They found it composed of pre-
cisely the same ingredients with the tears. As this fluid is more
exposed to the action of the air than the tears, in most cases it
mucilage has undergone less or more of that change which
is the consequence of the absorption of oxygen. Hence the
reason of the greater viscidity and consistence of the mucus
of the nose; hence also the great consistence which it acquires
during colds, where the action of the athmosphere is assisted
by the increased action of the parts.
3. As to the mucus which lubricates the alimentary canal,
the trachea, the bronchiae, the urethra, and all the different
cavities of the body, nobody has hitherto subjected it to ana-
lysis, because it cannot be obtained in sufficient quantity. It
is viscid, and no doubt contains a mucilaginous substance,
similar to that contained in the saliva, the tears, and the mu-
cus of the nose; as, like these liquids, it is liable to become
much more thick by exposure to the air.
Sect. XV. Liquor of the Pericardium.
This is is a liquor which lubricates the heart. It has been
lately examined by Dr Bostock, having been obtained from
the pericardium of a boy who had died suddenly.
It had the colour and appearance of the serum of the
blood. Evaporated to dryness, it left a residue amounting
to 1/12th of its weight. When exposed to the heat of boiling
water, it became opaque and thready. It was copiously pre-
cipitated by oxymuriate of mercury before boiling; but when
boiled, evaporated to dryness, and re-dissolved, the solution
was not affected by oxymuriate of mercury. These experi-
ments show us that it contained albumen. When saturated
SECT. XVI. HUMOURS OF THE EYE. 461
with oxymuriate of mercury, infusion of galls produced no
effect; indicating the absence of gelatine. It was copiously
precipitated by neutral acetate of lead, even after being
boiled to dryness and the residue re-dissolved in water. Ni-
trate of silver indicated the presence of muriatic acid. Dr
Bostock, from his experiments, considers it composed of
Water 92.0
Albumen 5.5
Mucus 2.0
Muriate of soda 0.5
____
100.0
Sect. XVI. Of the Humours of the Eye.
The eye is one of the most delicate and complicated or-
gans in the body; at the same time its structure, and the uses
of its parts, are better understood than almost any of the
other instruments of sensation. It is composed of several
concentric coats, which have not been chemically examined;
but, from the experiments of Hatchett on similar substances,
we may consider it as probable that they possess the pro-
perties of coagulated albumen. The internal part of the eye
is chiefly filled with three transparent substances, which have
been called humours by anatomists; namely, 1. The aqueous
humour, immediately behind the cornea; 2. The crystalline
humour or lense; and, 3. The vitreous humour, behind the
lense, and occupying the greatest part of the eye.
1. The aqueous humour of the eye of the sheep is a clear
transparent liquid like water, which has very little smell or
taste when fresh. Its specific gravity is 1.0090 at the tem-
perature of 60˚. It appears to be water slightly impregna-
ted with the following substances:
1. Albumen. 2. Gelatine. 3. Muriate of soda.
462 ANIMAL FLUIDS. CHAP. II
2. The vitreous matter possesses the very same properties
as the aqueous; even its specific gravity is the same, or on-
ly a very little greater.
3. The crystalline lense is solid: densest in the centre, and
becoming less solid towards the circumference. It is com-
posed of concentric coats, and is transparent. Its specific
gravity is 1.1000. When fresh it has little taste. It putre-
fies very rapidly.
It is almost completely soluble in water. The solution
is partly coagulated by heat, and gives a copious precipitate
with tannin both before the coagulation and after it. It
gives no traces of muriatic acid. Hence it is composed of
albumen and gelatine united to water. According to Nicho-
las, the quantity of gelatine diminishes as we approach the
centre of the lense, where it is very small. He detected
phosphate of lime likewise in every part of the lense.
The humours of the human eye are composed of the same
ingredients as those of the sheep; the only perceptible dif-
ference consists in their specific gravity. The specific gra-
vity of the human aqueous and vitreous humours is 1.0053;
that of the crystalline 1.0790.
The humours of the eyes of oxen resemble those of the
sheep in their composition. The specific gravity of the
aqueous and vitreous humours is 1.0088; that of the crystal-
line 1.0765.
Sect. XVII. Of Sinovia.
Within the capsular ligament of the different joints of the
body there is contained a peculiar liquid, intended evidently
to lubricate the parts, and to ifacilitate their motion. This
liquid is known among anatomists by the name of sinovia.
The sinovia of the ox, when it has just flowed from the
joint, is a viscid semitransparent liquid; of a greenish white
SECT. XVII. SINOVIA. 463
colour, and a smell not unlike frog-spawn. It very soon ac-
quires the consistence of jelly; and this happens equally
whether it be kept in a cold or a hot temperature, whether
it be exposed to the air or excluded from it. This consist-
ence does not continue long; the sinovia soon recovers again
its fluidity, and at the same time deposites a thready-like
matter.
Sinovia mixes readily with water and imparts to that li-
quid a great deal of vicidity. The mixture froths when
agitated; becomes milky when boiled, and deposites some
pellicles on the sides of the dish; but its viscidity is not di-
minished.
When alcohol is poured into sinovia, a white substance
precipitates, which has all the properties of albumen. One
hundred parts of sinovia contain 4.52 of albumen. The li-
quid still continues as viscid as ever; but if acetic acid be
poured into it, the viscidity disappears altogether, the liquid
becomes transparent, and deposites a quantity of matter in
white threads, which possesses the following properties:
1. It has the colour, smell, taste, and elasticity of vegetable
gluten. 2. It is soluble in concentrated acids and pure al-
kalies. 3. It is soluble in cold water; the solution froths.
Acids and alcohol precipitate the fibrous matter in flakes.
One hundred parts of sinovia contain 11.86 of this matter.
Margueron found that 100 parts of sinovia contained about
0.71 of soda.
When sinovia is exposed to a dry atmosphere, it gradually
evaporates, and a scaly residuum remains, in which cubic
crystals, and a white saline efflorescence are apparent. The
cubic crystals are muriate of soda. One hundred parts of
sinovia contain 1.75 of this salt. The saline efflorescence is
carbonate of soda.
From the analysis of Mr Margueron, it appears that sino-
via is composed of the following ingredients:
464 ANIMAL FLUIDS. CHAP. II
11.86 fibrous matter.
4.52 albumen.
1.75 muriate of soda.
.71 soda.
.70 phosphate of lime.
80.46 water.
_____
100.00
Sect. XVIII Of Semen.
The peculiar liquid secreted in the testes of males, and
destined for the impregnation of females, is known by the
name of semen.
Semen, when newly ejected, is evidently a mixture of two
different substances: the one fluid and milky, which is sup-
posed to be secreted by the prostate gland; the other, which
is considered as the true secretion of the testes, is a thick
mucilaginous substance, in which numerous white shining fi-
laments mav be discovered. It has a slight disagreeable
odour, an acrid irritating taste, and its specific gravity is
greater than that of water. When rubbed in a mortar it be-
comes frothy, and of the consistence of pomatum, in conse-
quence of its enveloping a great number of air-bubbles. It
converts paper stained with the blossoms of mallows or vio-
lets to a green colour, and consequently contains an alkali.
As the liquid cools, the mucilaginous part becomes trans-
parent, and acquires greater consistency; but in about twen-
ty minutes after its emission, the whole becomes perfectly li-
quid. This liquefaction is not owing to the absorption of
moisture from the air, for it loses instead of acquiring weight
during its exposure to the atmosphere; nor is it owing to
the action of the air, for it takes place equally in close
vessels.
SECT. XVI. SEMEN. 465
When oxymuriatic acid is poured into semen, a number of
white flakes precipitate, and the acid loses its peculiar odour.
These flakes are insoluble in water, and even in acids. If
the quantity of acid be sufficient, the semen acquires a yellow
colour. Thus it appears that semen contains a mucilaginous
substance analogous to that of the tears, which coagulates by
absorbing oxygen. Mr Vauquelin obtained from 10O parts
of semen six parts of this mucilage.
When semen is exposed to the air about the temperature
of б0˚, it becomes gradually covered with a transparent pel-
licle, and in three or four days deposites small transparent
crystals, often crossing each other in such a manner as to re-
present the spokes of a wheel. These crystals, when viewed
through a microscope, appear to be four-sided prisms, termi-
nated by very long four-sided pyramids. They may be sepa-
rated by diluting the liquid with water, and decanting it off.
They have all the properties of phosphate of lime. If, after
the appearance of these crystals, the semen be still allowed
to remain exposed to the atmosphere, the pellicle on its sur-
face gradually thickens, and a number of white round bodies
appear on different parts of it. These bodies also are phos-
phate of lime, prevented from crystallizing regularly by the
too rapid abstraction of moisture. Mr Vauquelin found that
100 parts of semen contain three parts of phosphate of lime.
If, at this period of the evaporation, the air becomes moist,
other crystals appear in the semen, which have the proper-
ties of carbonate of soda. The evaporation does not go on
to complete exsiccation, unless at the temperature of 77˚,
and when the air is very dry. When all the moisture is eva-
porated, the semen has lost 0.9 of its weight; the residuum
is semitransparent like horn, and brittle.
Thus it appears that semen is composed of the following
ingredients:
G g
466 ANIMAL FLUIDS. CHAP. II
90 water.
6 mucilage.
3 phosphate of lime.
1 soda.
___
100
Sect. XIX. Of Animal Poisons.
Several animals are furnished with liquid juices of a poi-
sonous nature, which, when poured into fresh wounds, occa-
sion the disease or death of the wounded animal. Serpents,
bees, scorpions, spiders, are well known examples of such
animals. The chemical properties of these poisonous juices
deserve peculiar attention; because it is only from such an
ittvestigatin that we can hope to explain the fatal changes
which they induce on the animal economy, or to discover an
antidote sufficiently powerful to counteract their baneful in-
fluence. Unfortuuately the task is difficult and perhaps
surpasses our chemical powers. For the progress already
made in the investigation, we are indebted almost entirely to
the labours of Fontana.
1. The poison of the viper is a yellow liquid, which lodges
in two small vesicles in the animal's mouth. These commu-
nicate by a tube with the crooked fangs, which are hollow,
and terminate in a small cavity. When the animal bites, the
vesicles are squeezed, and the poison is forced through the
fangs into the wound.
This poisonous juice occasions the fatal effects of the vi-
per's bite. It has a yellow colour, has no taste; but when
applied to the tongue occasions numbness. It has the ap-
pearance of oil before the microscope, but it unites readily
with water. It produces no change on vegetable blues.
SECT. XIX. POISONS. 467
When exposed to the open air, the watery part gradually
evaporates, and a jellowish-brown substance remains, which
has the appearance of gum arabic. In this state it feels vis-
cid like gum between the teeth; it dissolves readily in water,
but not in alcohol; and alcohol throws it down in a white
powder from water. Neither acids nor alkalies have much
effect upon it. It does not unite with volatile oils nor sul-
phuret of potash. When heated it does not melt, but swells,
and does not inflame till it has become black. These pro-
perties are similar to the properties of gum, and indicate the
gummy nature of this poisonous substance. Fontana made
a set of experiments on the dry poison of the viper, and a si-
milar set on gum arabic, and obtained the same results.
From the late observations of Dr Russel, there is reason
to beleve that the poisonous juices of the other serpents are
similar in their properties to those of the viper.
This striking resemblance between gums and the poison of
the viper, two substances of so opposite a nature in their ef-
fects upon the living body, is a humiliating proof of the small
progress we have made in the chemical knowledge of these
intricate substances. The poison of the viper, and of ser-
pents in general, is most hurtful when mixed with the blood.
Taken into the stomach it kills if the quantity be consider-
able. Fontana has ascertained that its fatal effects are pro-
portional to its quantity, compared with the quantity of the
blood. Hence the danger diminishes as the size of the ani-
mal increases. Small birds and quadrupeds die immediately
when they are bitten by a viper; but to a full-sized man the
bite seldom proves fatal.
Ammonia has been proposed as an antidote to the bite of
the viper. It was introduced in consequence of the theory
of Dr Mead, that the poison was of an acid nature. The
numerous trials of that medicine by Fontana robbed it of all
its celebrity; but it has been lately revived and recommend-
G g 2
468 ANIMAL FLUIDS. CHAP. II
ed by Dr Ramsay as a certain cure for the bite of the rattle-
snake.
The venom of the bee and the wasp is also a liquid
contained in a small vesicle forced through the hollow tube
of the sting into the wound inflicted by that instrument.
From the experiments of Fontana, we learn that it bears a
striking resemblance to the poison of the viper. That of the
bee is much longer in drying when exposed to the air than
the venon of the wasp.
3. The poison of the scorpion resembles that of the viper
also. But its taste is hot and acrid, which is the case also
with the venom of the bee and the wasp.
4. No experiments upon which we can rely have been
made upon the poison of the spider tribe. From the rapi-
dity with which these animals destroy their prey, and even
one another, we cannot doubt that their poisoin is sufficiently
virulent.
SECT. XX. Of Sweat.
A quantity of matter is constantly emitted from the skin;
this matter is invisible, and is distinguished by the name of
perspiration. Several experiments were made by Lavoisier
and Seguin to ascertain its amount. Mr Cruickshanks made
numerous trials to determine its nature, and it has been late-
ly subjected to a chemical examination by Theuard.
1. Mr. Cruickshanks put his hand into a glass vessel, and
luted its mouth at his wrist by means of a bladder. The in-
terior surface of the vessel became gradually dim, and drops
of water trickled down. By keeping his hand in this manner
for an hour, he collected 30 grains of a liquid, which pos-
sessed all the properties of pure water. On repeating the
same experiment at nine in the evening (thermometer 62˚),
he collected only 12 grains. The mean of these is 21 grains.
SECT. XX. SWEAT. 469
But as the hand is more extposed than the trunk of the body, it
is reasonable to suppose, that the perspiration from it is greater
than that from the hand. Let us therefore take 30 grains per
hour as the mean and let us suppose, with Mr Cruick-
shanks, that the hand is 1/50th of the surface of the body: The
perspiration in an hour would amount to 1880 grains, and
in 24 hours to 43,200 grains, or seven pounds six ounces
troy. This is almost double of the quantity ascertained by
Lavoisier and Segnin. Hence we may conclude that more
matter is perspired through the hand than the other parts of
the body, provided Mr Cruickshanks's estimate of the ratio
between the surface of the hand and body be not erroneous.
He repeated the experiment again after hard exercise, and
collected in an hour 48 grains of water. He found also, that
this aqueous vapour pervaded his stocking without difficulty;
and that it made its way through a shamoy leather glove, and
even through a leather boot, though in a much smaller quan-
tity than when the 1eg wanted that covering.
2. Besides water, it cannot be doubted that carbon is also
emitted from the skin; but in what state, the experiments
hitherto made do not enable us to decide. Mr Cruickshanks
found that the air of the glass vessel in which his hand and
foot had been confined for an hour contained carbonic acid
gas; for a candle burned dimly in it, and it rendered lime-
water turbid.
3. Besides water and carbon, or carbonic acid gas, the
skin emits also a particular odorous substance. That every
animal has a peculiar smell, is well known: the dog can dis-
cover his master, and even trace him to a distance, by the
scent. A dog, chained some hours after his master had set
out on a journey of some hundred miles followed his foot-
steps by the smell, and found him on the third day in the
midst of a crowd. But it is needless to multiply instances
of this fact; they are too well known to every one. Now
G g 3
470 ANIMAL FLUIDS. CHAP. II.
this smell must be owing to some peculiar matter which is
constantly emitted; and this matter must differ somewhat ei-
ther in quantity or some other property, as we see that the
dog easily distinguihes the individual by means of it. Mr
Cruickshanks has made it probable that this matter is an oily
substance; or at least that there is an oily substance emitted
by the skin. He wore repeatedly, night and day for a month,
the same vest of fleecy hosiery during the hottest part of the
summer. At the end of this time be always found an oily
substance accumulated in considerable masses on the nap of
the inner surface of the vest, in the form of black tears.
When rubbed on paper, it makes it transparent, and hardens
on it like grease. It burns with a white flame, and leaves
behind it a charry residuum.
4. Berthollet has observed the perspiration acid; and he
has concluded that the acid which is present is the phospho-
ric: but that has not been proved. Indeed the late experi-
ments of Thenard have proved that the acid in perspired
matter is not the phosphoric; but the acetic. He employed
the method practised by Mr Cruickshanks to collect this
matter. Different persons wore clean flannel waistcoats next
their skin for ten days, the waistcoats had been first washed
with soap, then in pure water, then in water acidulated with
muriatic acid, and lastly in a great quantity of pure water.
He steeped the waistcoats in hot distilled water, and thus se-
parated from them the perspired matter. The liquid was
put into a retort, and concentrated to the consistence of a
syrup. The liquid winch came over had a disagreeable
smell, and reddened infusion of litmus. Kept in an open
vessel it retained its transparency, but lost its odour. The
residue in the retort had no smell. It was strongly acid, and
tasted distinctly of common salt, while at the same time an
acrid and hot flavour could be distinguished. When evapo-
rated to dryness and strongly heated, the acid which it con-
SECT. XXI. URINE. 471
tained was dissipated or destroyed, and the residue consisted
of common salt, charcoal, and minute traces of phosphate of
lime, and oxide of iron. The same destruction of the acid
took place if it was previously saturated with potash before
it was heated to redness, and in that case the potash was con-
verted into a carbonate. When saturated with an alkali, and
distilled along with phosphoric acid, it yielded an acid which
possessed all the characters of the acetic.
5. The small quantity of animal matter which Thenard
found in the perspired matter, possessed characters which in-
duced him to consider it as similar to gelatine in its nature.
Sect. XX.I-Of Urine.
Fresh urine differs considerably in its appearance accord-
ing to the state of the person and the time at which it is
voided. In general, healthy urine is a transparent liquid of
a light amber colour, an aromatic odour resembling that of
violets and a disagreeable bitter taste. Its specific gravity
varies, according to Mr Cruickshanks, from 1.005 to 1.033.
When it cools, the aromatic smell leaves it and is succeeded
by another, well known by the name of urinous smell.
1. Urine reddens paper stained with turnsole and with
the juice of radishes, and therefore contains an acid. This
acid has been generally considered as the phosphoric, but
Thenard has shown that it is in reality the acetic.
2. If a solution of ammonia be poured into fresh urine, a
white powder precipitates, which has the properties of phos-
phate of lime.
3. If the phosphate of lime precipated from urine be ex-
amined, a little magnesia will be found mixed with it.
Fourcroy and Vauquelin have ascertained that this is owing
to a little phosphate of magnesia which urine contains, and
G G 4
472 ANIMAL FLUIDS. CHAP. II
which is decomposed by the alkali of lime employed to pre-
cipitate the phosphate of lime.
4. Proust informs us that carbonic acid exists in urine,
and that its separation occasions the froth which appears
during the evaporation of urine.
5. Proust has observed, that urine kept in new casks de-
posits small crystals which effloresce in the air and fall to
powder. These crystals possess the properties of the carbo-
nate of lime.
6. When fresh urine cools, it often lets fall a brick-colour-
ed precipitate, which Scheele first ascertained to be crystals
of uric acid. All urine contains this acid, even when no sen-
sible precipitate appears when it cools.
7. During intermitting fevers, and especially during dis-
eases of the liver, a copious sediment of a brick-red colour
is deposited from urine. This sedtment containes the rosacic
acid of Proust.
8. If fresh urine be evaporated to the consistence of a sy-
rup, and muriatic acid be then poured into it, a precipitate
appears which possesses the properties of benzoic acid.
9. When an infusion of tannin is dropt into urine, a white
precipitate appears, having the properties of the combination
of tannin and albumen or gelatine. Their quantity in healthy
urine is very small, often indeed not sensible. Cruickshanks
found that the precipitate afforded by tannin in healthy urine
amounted to the 1/240th part of the weight of the urine.
1O. If urine be evaporated by a slow fire to the consist-
ence of a thick syrup, it assumes a deep brown colour, and
exhales a fetid ammoniacal odour. When allowed to cool,
it concretes into a mass of crystals, composed of all the com-
ponent parts of urine. If four times its weight of alcohol
be poured into this mass, at intervals, and a slight heat be
applied, the greatest part of it is dissolved. The alcohol
SECT. XXI. URINE. 473
which has acquired a brown colour, is to be decanted off,
and distilled in a retort in a sand heat, till the mixture has
boiled for some time, and acquired the consistence of a sy-
rup. By this time the whole of the alcohol has passed off,
and the matter, on cooling, cystallizes in quadrangular
plates which intersect each other. This substance is urea,
which composes 9/20ths of the urine, provided the watery part
be excluded. To this substance the taste and smell of urine
are owing. It is a substance which characterizes urine, and
constitutes it what it is, and to which the greater part of the
very singular phenomena of urine are to be ascribed.
11. According to Fourcroy and Vauquelin, the colour of
urine depends upon the urea: the greater the proportion of
urea, the deeper the colour. but Proust has detected a re-
sinous matter in urine similar to the resin of bile; and to this
substance be ascribes the colour of urine.
12. If urine be slowly evaporated to the consistence of a
syrup, a number of crystals make their appearance on its
surface; these possess the properties of the muriate of soda.
13. The saline residuum which remains after the sepa-
ration of urea from crystallized urine by means of alcohol
has been long known by the names of fusible salt of urine
and microcosmic salt.
When these salts are examined, they are found to have the
properties of phosphates. The rhomboidal prisms consist
of phosphate of ammonia united to a little phosphate of so-
da; the rectangular tables, on the contrary, are phosphate of
soda united to a small quantity of phosphate of ammonia.
Urine, then, contains phosphate of soda and phosphate of
ammonia.
14. When urine is cautiously evaporated, a few cubic
crystals are often deposited among the other salts; these crys-
tals have the properties of muriate of ammonia.
474 ANIMAL FLUIDS. CHAP. II.
15. When urine is boiled in a silver bason, it blackens the
bason; and if the quantity of urine be large, small crusts of
sulphuret of silver may be detached. Hence we see that
urine contains sulphur.
Urine, then, contains the following substances:
1. Water. 10. Albumen.
2. Acetic acid. 11. Urea.
3. Phosphate of lime. 12. Resin.
4. Phosphate of magnesia. 13. Muriate of soda.
5. Carbonic acid. 14. Phosphate of soda.
6. Carbonate of lime 15. Phosphate of ammonia.
7. Uric acid. 16. Muriate of ammonia.
8. Rosacic acid. 17. Sulphur.
9. Benzoic acid.
These are the only substances which are constantly found
in healthy urine; but it contains also occasionally other sub-
stances. Very often muriate of potash may be distinguished
among the crystals which fom during its evaporaion. The
presence of this salt may always be detected by dropping
cautiously some tartaric acid into urine. If it contains mu-
riate of potash, there will precipitate a little tartar, which
may be easily recognised by its properties.
Urine sometimes also contains sulphate of soda, and even
sulphate of lime. The presence of these salts may be ascer-
tained by pouring into urine a solution of muriate of barytes;
a copious white precipitate appears, consisting of the barytes
combined with phosphoric acid, and with sulphuric acid, if
any be present. This precipitate must be treated with a
sufficient quantity of muriatic acid. The phosphate of ba-
rytes is dissolved, but the sulphate of barytes remains unal-
altered.
SECT. XXII. URIN. 475
SECT. XXII.-Of Morbid Concretions.
Hard substances occasionally make their appearance in
different parts of the animal body, both in the solids and the
cavities destined to cortain the fluids. In the first case they
are denominated concrtions or ossifications; in the second
calculi. Their formation is an irregularity in the animal
oeconomy, and they often produce the most excruciating dis-
eases. They may be divided into five classes; namely,
1. Ossifications; 2. Intestinal concretions; 3. Biliary cal-
culi; 4. Urinary calculi; 5. Gouty calculi.
1. Ossifications.
Under this name may be comprehended all the concre-
tions which make their appearance in the solid parts of the
animal body. The following are the most remarkable of
these:
1. Small concretions sometimes form in the pineal gland.
They consist of phosphate of lime.
2. Small concretions sometimes form in the saivary
glands. These likewise consist of phosphate of lime.
3. Pulmonary concretions are occasionally coughed up
by consumptive patients. They consist sometimes of phos-
phate of lime, sometimes of carbonate of lime, and some-
times of a mixture of both.
4. Hepatic concretions are composed of phosphate of
lime, and a tough animal membrane.
5. The concretions which sometimes form in the prostate-
gland are composed of phosphate of lime.
2. Intestinal Conretions.
Concretios somtimes form in the stomach and intestines
chiefly of the inferior animals. Some of these have been ce-
476 ANIMAL FLUIDS. CHAP. II.
lebrated under the name of bezoars for their medical virtue.
A great many of them have been analyzed, and no fewer
than eight species have been ascertained.
The first species consists of concretions composed of su-
perphosphate of lime, the second of phosphate of magnesia,
the third of ammonio-phosphate of magnesia; the fourth of
the yellow matter of bile; the fifth of a green-coloured re-
sinous matter; the sixth of small fragments of the boletus ig-
niarius; the seventh of balls of hair felted together, and the
8th of woody fibre.
3. Biliary Calculi.
Hard bodies sometimes form in the gall bladder and gall
ducts, and occasion painful diseases. Four kinds of these
calculi have been distinguished; the first kind is composed of
a matter resembling spermaceti in appearance, soluble in
hot alcohol, and crystallizing as the alcohol cools. This
matter has been called adiposire. The second kind are an-
gular, because a number of them exist in the gall bladder to-
gether. They are composed of adiposire, with a thin exter-
nal crust of yellow matter of bile. The third kind are of a
brown colour, and are supposed to be composed of the alter-
ed yellow matter of bile. The gall-stones of oxen usually
are of this kind. The fourth kind does not flame, but gra-
dually waste away at a red heat.
4. Urinary Calculi.
It is well known that concretions not unfrequently form in
the urinary bladder, and occasion one of the most dismal dis-
eases to which the human species is liable. These bodies have
been carefully and repeatedly examined by modern chemists,
who have found them to be very various in their composi-
SECT. XXII. MORBID CONCRETIONS. 477
tion. No less than nine distinct substances have been found
These being mixed in different proportions, occasion great
variation in the composition of the calculi. The following
are the substances:
1. Uric acid.
2. Phosphate of lime.
3. Phosphate of magnesia-and-ammonia.
4. Oxalate of lime.
5. Muriate of ammonia.
6. Magnesia.
7. Phosphate of iron.
8. Silica.
9. Urea.
The four first of these constitute by far the most common
and abundant ingredients of urinary calculi.
5. Gouty Concretions.
It is well known that concretions occasionally make their
appearance in joints long subject to the gout. These con-
cretions, from their colour and softness, are usually distin-
guished by the name of chalk-stones. They are usually
small; though they have been observed of the size of an egg.
All of them hitherto examined have been found composed
of uric acid and soda, so that they consist of the salt called
urate of soda.
478 AFFINITY BOOK III
BOOK III.
OF AFFINITY.
Having taken a view of the different substances which
constitute the objects of chemistry, it remains for us to make
a few remarks on the force by which different bodies are
united together, and kept in combination. This force has
received the name of affinity.
All the grat bodies which constitute the solar system are
urged toward each other by a force which preserves them in
their orbit abd regulates their motions. This force has re-
ceived the name of attraction. Newton demonstrated that
this force is the same with gravitation, or the force by which
a heavy body is urged towards the earth.
When two bodies are brought within a certain distance,
they adhere together, and require a considerable force to
separate them. Hence it appears that bodies are not
only attracted towards the planetary bodies, but towards
each other. In all cases we find the particles of matter unit-
ed together in masses, differing indeed in magnitude, but con-
taining all of them a considerable number of particles. These
particles remain united, and cannot be separated without the
application of a considerable force.
Thus we see that there is a certain unknown force which
urges bodies towards each other, a force which acts not only
upon large masses of matter, but upon the particles of which
bodies are composed. Attraction, therefore, as far as we
know, extends to all matter, and exists mutually between al1
matter.
BOOK III. AFFINITY. 479
The change which attraction produces on bodies is a di-
minution of their distance. Now the distances of bodies
from each other are of two kinds, either too small to be per-
ceived by our senses, or great enough to be easily perceived
and estimated. Hence the attractions of bodies as far as re-
gards us naturally divide themselves into two classes. 1.
Those which act at sensible distances from each other. 2.
Those which act at insensible distances. It is to the second
of these attractions that the term chemical affinity has been
given.
Chemical affinity then is the attraction which exists be-
tween the particles of bodies which urges them towards each
other and keeps them united. Now the particles of matter
are of two kinds, either homogeneous or heterogeneous. By
homogeneous particles are meant the particles which com-
pose the same body; by beterogeneous those which compose
different bodies. Thus the particles of iron are homogeneous;
but a particle of iron and a particle of lead are heteroge-
neous.
Homogeneous affinity urges the homogeneous particles to-
wards each other, and keeps them united. It is usually
denoted by the term cohesion, and sometimes by adhesion
when the surfaces of bodies only are referred to.
Heterogeneous affinity urges heterogeneous particles to-
wards each other, and keeps them at insensible distances,
and of course is the cause of the formation of new integrant
particles composed of a certain number of heterogeneous
particles.
Affinity, like sensible attraction, varies with the mass, and
the distance of the attracting bodies; but the rate at which
it varies remains still unknown. The characteristic marks
of affinity may be reduced to the three following.
1. It acts only at insensible distances, and of course af-
fects only the particles of bodies.
480 GASES. CHAP. I.
2. Its force is always the same in the same particles, but
it is different in different particles.
3. This difference is modified considerably by the mass.
Thus, though A have a greater affinity for C than B has, if
the mass of B be considerably increased while that of A re-
mains unchanged, B becomes capable of taking a part of C
from A. Let us now take a particular view of gases, li-
quids and solids, that we may ascertain in what way they
unite, and how far their combinations are influenced by the
state of the bodies themselves.
CHAP. I.
OF GASES.
im-
pression, and have their parts easily moved. Their elasticity
varies with the pressure, and hence it follows that their par-
ticles mutually repel inversely as the distances of their cen-
tres from each other. The gaseous bodies at present known
(including some vapours) amount to 23. The following table
exhibits their names and their specific gravity.
Gases. Sp. gravity.
Air 1.000
Oyamuriatic acid 2.766
Nitric acid 2.427
Sulpourous acid 2.265
Vapour of ether 2.230
Vapour of alcohol 2.100
Muriatic acid 1.929
BOOK III. AFFINITY. 481
Gazes. Sp. gravity.
Hyperoxymuriatic acid -
Fluoric acid -
Nitrous oxide 1.603
Carbonic acid 1.500
/ 1.106
Sulphureted hydrogen <
\ 1.236
Oxygen 1.093
Nitrous gas 1.094
Azote 0.978
Carbonic oxide 0.956
Olefiant gas 0.909
Steam 0.700
Ammonia 0.600
Carbureted hydrogen 0.600
Arsenical hydrogen 0.529 «
Phosphureted hydrogen -
Prussic acid -
Hydrogen 0.084
The gases usually contain water. This liquid in most
of them is in the state of vapoor, and only loosely united.
Hence it may be separated by cold or by substances which
have a strong affinity for water, as sulphuric acid, dry muri-
ate of lime, and the dry fixed alkalies. From the experi-
ments of Saussure we learn, that a hundred cubic inches of
air saturated with moisture at the temperature of 57˚ con-
tain 0.35 of a grain troy of moisture. But muriatic acid
contains at least one-fourth of its weight of water in a state
of intimate combination, from which it cannot be deprived
without losing its elastic form.
When gaseous bodies are brought into contact with each
other, they mix equably, how mumch soever they differ in spe-
cific gravity, and when once mixed, they never after separate.
By this mixture, neither the bulk nor the specific gravity of
H H
482 GASES. CHAP. I.
the gaseous bodies is altered. This mutual mixture seems
to be analogous to what happens when liquids are mixed
together, and seems explicable in the same way. It seems
to be owing to a weak attraction which exists between the
particles of all gaseous bodies. Mr Dalton affirms, that it
is owing entirely to the difference between the size of the
particles of different gases.
Several gases have the property of uniting intimately with
each other; and of forming new products possessing peculiar
properties. The following table exhibits a view of those
that unite upon simple mixture widi the products which
they form.
Products.
/ Nitrous acid.
Oxygen with nitrous gas <
\ Nitrc acid.
Ammonia with vapour Liquid ammonia.
muriatic acid Muriate of ammonia.
fluoric acid Fluate of ammonia.
carbonic acid Carbonate of ammonia.
sulphurous acid Sulphite of ammonia.
sulphureted hydrogen Hydrosulphuret of am-
monia.
The following are die gases which combine only in parti-
cular circumstances with the products which they form:
Products.
Oxygen with hydrogen Water.
carbonic oxide Carbonic acid.
azote Nitric acid.
muriatic acid Oxymuriatic acid.
oxymuriatic acid Hyperoxymuriatic acid.
sulphurous acid Sulphuric acid.
nitrous oxide Nitric acid.
The combination of the first two sets is produced by com-
bustion, and may be accomplished either by a red heat or by
the electric spark. Oxygen and azote unite slowly by means
BOOK III. AFFINITY. 483
of electric sparks, but without combustion. Little is known
of the way in which the remaining sets combine.
From the experiments hitherto made it follows, that when
gaseous bodies unite, they unite either in equal bulks of each,
or two or three parts by bulk of one, unite with one part by
bulk of the other. The following table exhibits a view of
the proportions of the different constituents by bulk of vari-
ous compounds formed by the union of elastic fluids.
Compounds. Constituents by bulk.
Muriate of ammonia 100 ammoniacal 100 muriatic acid gas
Carbonate of ammonia . 100 ditto 100 carbonic acid gai
Subcarbonate of ammoiria 100 ditto 50 ditto
Water 100 hydrogen gas 50 oxygen gas
Nitreous oxide 100 azotic gas 50 ditto
Nitreous gas 100 ditto 100 ditto
Nitric acid 100 ditto 200 ditto
Nitric acid 200 nitrous gas 100 ditto
Nitrous acid 300 ditto 100 ditto
Ammonia 100 azotic gas 300 hydrogen
Sulphuric acid 100 sulphurous acid 50 oxygen
Oxymuriatic acid 300 muriatic acid 100 ditto
Carbonic acid 100 carbonic oxide 50 ditto
Some gases, when mixed together, have the property of
mutually decomposing each other. The following is a list
of these gases.
Oxygen with phosphureted hydrogen
Oxymuriatic acid with ammonia
phosphureted hydrogen
hydrogen
carbureted hydrogen
carbonic oxide
olefiant gas
sulphureted hydrogen
sulphurous acid
nitrous gas
Sulphureted hydrogen with nitrous gas
sulphurous acid
II h 2
484 GASES. CHAP. I.
Many gases decompose each other by combustion produ-
ced either by electric sparks, or by a red hot body. The
following are the principal of these gases.
Oxygen with sulphurated hydrogen
carbureted hydrogen
olefiant gas
vapour of ether
- - - alcohol
Nitrous oxide with hydrogen
phosphureted hydrogen
sulphureted hydrogen
carbonic oxide
carbureted hydrogen
olefiant gas
vapour of ether
- - - alcohol
Nitrous gas with hydrogen
sulphurous acid
Hydrogen with sulphurous acid
carbonic add
Vapour of water with carbureted hydrogen
olefiant gas
muriatic acid
Water absorbs a certain portion of all the gases. Some
of them are absorbed only in small quantity by that liquid,
others in large quantity. The following table exhibits the
bulk of each gas absorbed by 100 parts of water freed from
air by boiling, as determined by the experiments of Dr Henry
and Mr Dalton.
BOOK III. AFFINITY. 385
Gases. Aborption according to
Henry. Dalton.
Carbonic acid 108 100
Sulphureted hydrogen 106 100
Nitrous oxide 86 100
__________________________
Olefiant gas - 12.5
__________________________
Nitrous gas 5 3.7
Oxygen gas 3.7 3.7
Posphureted hydrogen 2.14
Carbureted hydrogen 1.4 3.7
__________________________
Azotic gas 1.53 1.56
Hydrogen 1.61 1.56
Carbonic oxide 2.01 1.56
Dr Henry's numbers are the result of experiment: Mr
Dalton's of experiment modified a little by a happy genera-
liztion. He conceives that the degree of the absorption of
each of the four sets into which the gases are divided by the
horizontal lines in the preceding table may be represented as
follows:
First set Water absorbs its own bulk = 1 / 1 ^3
Second set - 1/8th its bulk = 1 / 2 ^3
Third sjet - 1/27 - = 1 / 3 ^3
Fourth set - 1/64 - = 1 / 4 ^3
From this generalization, which holds at least very nearly,
it follows that the density of the gases, after absorption, is
either the same as before it, or at least some submultiple of
it, and the distance between their particles is either the same
as before, or twice, thrice, or four times as great.
Dr Henry has shown, that whatever be the density of the
gas, the bulk of it absorbed is always the same. If carbonic
acid gas be reduced by pressure to twice the usual density,
water still continues to absorb its own bulk of it. Hence by
486 GASES. CHAP. I.
increasing the pressure, water may be made to absorb any
quantity of a gas whatever.
The gases still retain their elasticity after they have been
absorbed by water, accordingly they make their escape if the
water be placed under the exhausted receiver of an air pump.
The proportion of a gas absorbed by water depends very
much upon its purity. Thus water absorbs its own bulk of
pure carbonic acid gas; but if the carbonic acid gas be
mixed with common air, the proportion of it absorbed is
much diminished. Water impregnated with a gas must be
inl contact with a portion of the very gas absorbed, otherwise
that gas soon makes its escape altogether.
As the temperature increases, the absorbability of the
gases by water diminishes, no doubt in cobsequence of the
increased elasticity of the gases.
This absorption of the gases by water is probably the con-
sequence of an affinty between them and that liquid. Hence
the determinate proportion of each absorbed, and most of
the other phenomena, admit of an easy explanation.
The alkaline and acid gases are very absorbable by water,
and of course are acted on by a strong affinity. The follow-
ing table exhibits a view of the bulk of each gas absorbed
by one measure of water.
Oxymuriatic acid 1.5 +
Sulphurous acid 53
Fluoric acid 175 +
Muriatic acid 516
Ammoniacal gas 780
When a cubic inch of water is saturated with these gases,
its bulk increases. The following table exhibits the bulk of
water when thus saturated, supposing the original bulk to
have been 1.
BOOK III. AFFINITY. 487
Saturated with
Oxymuriatic acid 1.002 +
Sulphtirouf add 1.040
Muriatic acid 1.500
Anunoniacal 1.666
Thus the water undergoes an expansion. so that the densi-
ty of the gases absorbed is not in reality so great as it ap-
pears to be. The following table exhibits the real densities
of these gases in the water.
Oxymuriatic acid 1.5
Sulphurous 31.7 = 3 ^3 nearly.
Muriatic S44.0 = 7 ^3
Ammonia 468.0 = 8^ ^3
That these gaseous bodies combine chemically with water,
cannot be doubted.*
The simple gases have the property of combining with
different solid bodies, and of formmg compounds sometimes
gaseous, sometimes liquid, and sometimes solid. Oxygen
combines with two dozes of carbon, forming carbonic acid
and carbonic oxide, both gazes; the first a product of com-
bustion, the second a combustible oxide. It combines with
three dozes of phosphorus, forming oxide of phosphorus,
phosphorous acid and diphosphoric acid, all of which are solid
bodies. It unites likewise with three doses of sulphur, and
forms oxide of sulphur, sulphurous acid, and sulphuric acid:
the first a solid, the second a gas, the third a liquid. It
combines in various proportions with the metals, and all the
metallic oxide are solids.
Hydrogen appears to combine in at least two proportions
with each of the other simple combustibles. It unites also
with several of the metals, but the proportions have not been
ascertained.
488 LIQUIDS. CHAP. II.
CHAP. II.
OF LIQUIDS.
A liquid is a fluid, not sensibly elastic, the parts of
which yield to the smallest impression, and move easily upon
each other. All liquids have a certain cohesive force by
which their particles are retained together, and this force is
much greater in mercury than in water. The following
table exhibits a list of liquids with their relative specific gra-
vities.
Water 1.000
Ethers 0.632 to O.9OO
Petroleum 0.730 to 0.878
Volatde oils 0.792 to 1.094
Alcohol 0.796
Fixed oils 0.913 to 0.968
Supersulphureted hydrogen -
Nitric acid 1.583
Sulphuric acid 1.885
Phosphuret of sulphur -
Oxymuriate of tin -
Mercury 13.568
Most substances are rendered liquid by heat; but these
are the only bodies that are permanently liquid in this coun-
try.
Some liquids may be mixed, and of course combine in
any proportion whatever. In this respect they resemble the
gases. The following is a list of these liquids:
Watcr with alcohol.
nitric acid.
sulphuric acid.
BOOK III. AFFINITY. 489
Alcohol with ether.
Sulphuric acid with nitric acid.
Fixed oils with petroleum.
volatile oils.
fixed oils.
Volatile oils with petroleum.
volatile oils.
These liquids, when once combined, form a homogeneous
compound, and do not afterwards separate again. The union
is attended with the evolution of heat, and with a certain
degree of condensation, for the specfic gravity in always
greater than the mean.
The following table exhibits a list of those liquids that
unite with each other only in certain proportions:
Water with ether.
volatile oils.
oxymuriate of tin.
Alcohol with volatile oils.
petroleum.
phosphuret of sulphur.
Ether with volatile oils.
petroleum.
Volatile oils with petroleum.
The following table exhibits a list of the most remarkable
liquids that do not sensibly combine:
Water with petroleum.
fixed oils.
supersulphureted hydrogen.
Fixed oils with alcohol.
ether.
Mercury with water.
alcohoL
ether.
volatile oils.
petroleum.
490 SOLIDS. CHAP. III.
No doubt the action of liquids on each other depends
upon thwr affinity. The first class have the greatest affinity
for each other; that of the second is greater, and that of the
third is less than the cohesion of the particles of each.
Water has the property of combining with a very great number of solid bodies. It combines with them in two
ways. In the first way the solid retains its solidity while the
water loses its liquid form. Such combinations are called
hydrates. In this way water combines with sulphur, metal-
lic oxides, earths, alkalies, many acids, all salts, hydrosul-
phurets, and many animal and vegetable substances. In the
second way, the water dissolves the solid, and the whole be-
comes liquid. In this way it acts upon many acids, alkalies,
earths, salts, and vegetable substances.
These combinations are all chemical, and the hydrates ap-
pear to be the most intimate. Their specific gravity is always
greater than the mean, while the specific gravity of saline so-
lutions is usually less than the mean.
The action of the other liquids on solids has been hither-
to but imperfectly investigated.
CHAP. III.
OF SOLIDS.
Solids are bodies composed of partices that cohere to-
gether, and cannot be moved among themselves without the
exertion of a force sufficient to destroy the cohesion of the
body. They are very numerous, and their specific gravity
varies more than that of gases or liquids. The following
table exhibits the specific gravity of the most remarkable
solids:
BOOK III. AFFINITY. 491
Sp. gravity.
Charcoals O.223 to 1.526
Vegetable bodies 0.240 to 1.354
Salts 0.273 to 7.176
Earths 0.346 to 4.842
Solid acids O.667 to 3.391
Earthy compounds 0.68O to 4.815
Bitumens and solid oils 0.892 to 1.357
Fixed alkalies 1.336 to 1.708
Phosphorus 1.770
Carburets of iron 1.987 to 7.840
Sulphur 1.990
Glass 2.732 to 3.329
Carbon 3.518 to 3.531
Metallic sulphurets 3.225 to 10.000
Metals and alloys and oxides 0.6OO to 23.00
The following solids combine with each other in any pro-
portion whatever:
Sulphur with phosphorus.
Carbon with iron?
Metals with most metals.
Protoxide of antimony with sulphuret of antimony.
Earths with earths.
Earths with some metallic oxides.
Some earths with fixed alkalies.
Fixed alkalies with solid oils.
Solid oils with each other and with bitumen.
All these combinations are produced by means of heat;
unless they be brought into fusion, or at least one of them,
they do not combine.
The following table exhibits the principal solids which
have been observed to unite only in determinate proportions:
492 SOLIDS. CHAP. III.
Sulphur whh metals.
some metallic oxides.
earths.
fixed alkalies ?
Phosphorus with carbon.
metals.
some earths.
Acids with alkalies.
earths.
metallic oxides.
These combinations are more intimate than the pr eced-
ing, they have been more accurately examined, and are bet-
ter known. They never take place unless one of the bodies,
at least, be brought first into a liquid state, either by means
of heat, or by solution in water.
The salts are the most important of these combinations,
and a vast number of experiments have been made in order
to ascertain the proportions in which their constituents
combine. The following table exhibits the general result of
these experiments. The numbers represent the weight of
the different acids and bases which neutralize each other re-
spectively:
Acids. Bases.
Sulphurous 50 Barytes 63
Oxalic 39.5 Strontian 37
Nitric 34 Potash 38
Sulphuric 31 Soda 23.8
Phosphoric 22 Lime 21.8
Muriatic 18 Magnesia 17.6
Cainonic 16,5 Ammonia 9
Phosphorous 16
Suppose we wish to form sulphate of barytes-from the
above table, it appears that we must unite together 31 parts
by weight of sulphuric acid, and 63 parts of barytes.
BOOK III. AFFINITY. 493
From various experiments hitherto made, it appesrs that
the supersalts contain twice as much acid, an the subsalts
twice as much base, as the neutral salts. Suppose that a
given quantity of sulphate of potash is composed of 100
potash, united with x of sulphuric acid, then supersulphate
of potash is composed of 100 potash, united with 2 x sul-
phuric acid. The triple salts appear to consist of two dif-
ferent salts united together. Thus alum may be considered
as a compound of sulphate of potash and sulphate of alu-
mina.
According to the old doctrine of affinity delivered by
Bergman, all bodies capable of combining have an affinity
for each other. This affinity is a constant force, which may
be represented by numbers. Affinity is elective; that is
to say, if a has a stronger affinity for m than b has, and if m
be combined with b, forming a compound which we may
represent by mb; a, upon being mixed with this compound,
has the property of separating b completely from m, and
taking its place so as to form a compound, ma, while b is
entireiy disengaged. This doctrine has been lately called in
question by Berthollet, and the greatest part completely re-
futed. According to Berthollet, affinity is not elective, and
never occasions decomposition, but only combination. The
decompositions which take place, are owing to other causes,
such as insolubility, elasticity, &c. though this new opinion
renders Bergman's tables of decomposition, of little compara-
tive value; yet as they are in some cases useful, and are
often referred to, it has been thought worth while to sub-
join them to this work.
494 TABLE OF DECOMPOSITIONS.
TABLE OF CHEMICAL DECOMPOSITIOMS.
I.
ALKALIES.
_____________
Sulphuric acid
Nitric
Muriatic
Phosphoric
Fluoric
Oxalic
Tartaric
Arsenic
Succinic
Citric
Formic
Benzoic
Acetic
Saclactic
Boracic
Sulphurous
Carbonic
Prussic
II.
BARYTES AND STRONTIAN
Sulphuric
Oxalic
Succinic
Fluoric
Phosphoric
Saclactic
Nitric
Muriatic
Suberic
Citric
Tarrtaric
Arsenic
Benzoic
Acetic
Boracic
Sulphurous
Nitrous
Carbonic
Prussic
III.
LIME.
Oxalic
Sulphuric
Tartaric
Succinic
Phosphoric
Saclactic
Nitric
Muriatic
Suberic
Fluoric
Arsenic
Citric
Malic
Benzoic
Acetic
Boracic
Sulphurous
Nitrous
Carbonic
Prussic
IV.
MAGNESIA
Oxalic
Phosphoric
Sulphuric
Fluoric
Arsenic
Saclactic
Succinic
Nitric
Muriatic
Tartaric
Citric
Malic
Benzoic
Acetic
Boracic
Sulphurous
Nitrous
Carbonic
Prussic
V.
ALUMINA.
Sulphuric
Nitric
Muriatic
Oxalic
Arsenic
Fluonc
Tartaric
Succinic
Saclactic
Citric
Phosphoric
Benzoic
Acetic
Boracic
Sulphurous
Nitric
Carbonic
Prussic
VI.
OXIDE OF GOLD.
Muriatic acid
Nitric
Sulphuric
Arsenic
Fluoric
Tartaric
Phosphoric
Prussic
VII.
OXIDE OF SILVER.
Muriatic acid
Oxalic
Sulphuric
Saclactic
Phosphoric
Sulphurous
Nitric
Arsenic
Fluoric
Tartaric
Citric
Formic
Acetic
Succinic
Prussic
Carbonic
VIII.
OXIDE OF MERCURY.
Muriatic
Oxalic
Succinic
Arsenic
Phosphoric
Sulphatic
Saclactic
Tartaric
Citric
Sulphurous
Nitric
Fluoric
Acetic
Boracic
Prussic
Carbonic
IX
OXIDE OF COPPER
Oxalic acid
Tartaric
Muriatic
Sulphuric
Saclactic
Nitric
Arsenic
Phosphoric
Succinic
Fluoric
Citric
Formic
Acetic
Boracic
Prussic
Carbonic
X.
OXIDE OF IRON
Oxalic acid
Tartarous
Camphoric
Sulphuric
Saclactic
Muriatic
Nitric
Phosphoric
Arsenic
Fluoric
Succinic
Citric
Formic
Acetic
Boracic
Prussic
Carbonic
XI.
OXIDE OF NICKEL.
Oxalic acid
Muriatic
Sulphuric
Tartaric
Nitric
Phosphorie
Fluoric
Saclactic
Succinic
Citric
Formic
Acetic
Arsenic
Boracic
Prussic
Carbonic
XII.
OXIDE OF TIN.
Tartaric acid
Muriatic
Sulphuric
Oxalic
Arsenic
Phosphoric
Nitric
Succinic
Fluoric
Saclactic
Citric
Formic
Acetic
Boracic
Prussic
XIII.
OXIDE OF LEAD.
Sulphuric acid
Saclactic
Oxalic
TABLE OF DECOMPOSITIONS. 495
Arsenic
Tartaric
Muriatic
Phosphoric
Sulphurous
Suberic
Nitric
Fluoric
Citric
Formic
Acetic
Boracic
Prussic
Carbonic
XIV.
OXIDE OF ZINC.
Oxalic acid
Sulphuric
Muriatic
Saclactic
Nitric
Tartaric
Phosphoric
Citric
Succinic
Fluoric
Arsenic
Formic
Acetic
Boracic
Prussic
Carbonic
XV.
OXIDE OF BISMUTH
Oxalic acid
Arsenic
Tartaric
Phosphoric
Sulphuric
Muriatic
Benzoic
Nitric
Fluoric
Saclactic
Succinic
Citric
Formic
Acetic
Prussic
Carbonic
XVI.
OXIDE OF ANTIMONY.
Muriatic acid
Benzoic
Oxalic
Sulphuric
Nitric
Tartaric
Saclactic
Phosphoric
Citric
Succinic
Fluoric
Arsenic
Formic
Acetic
Boracic
Prussic
Carbonic
XVII. Spalte 3:
OXIDE OF ARSENIC.
Muriatic acid
Oxalic
Sulphuric
Nitric
Tartaric
Phosphoric
Fluoric
Saclactic
Succinic
Citric
Formic
Arsenic
Acetic
Prussic
XVIII.
OXIDE OF COBALT.
Oxalic acid
Muriatic
Sulphuric
Tartaric
Nitric
Phosphoric
Fluoric
Saclactic
Succinic
Citric
Formic
Acetic
Arsenic
Boracic
Prussic
Carbonic
XIX.
OXIDE OF MANGANESE
Oxalic acid
Citric
Phosphoric
Tartaric
Fluoric
Muriatic
Sulphuric
Nitric
Saclactic
Succinic
Tartaric
Formic
Acetic
Prussic
Carbonic
XX.
OXIDE OF TITANIUM.
Phosphor. acid
Arsenic
Oxalic
Sulphuric
Muriatic
Nitric
Acetic
XXI.
SULPHURIC ACID.
Barytes
Strontian
Potash
Soda
Lime
Magnesia
Ammonia
Glucina
Yttria
Alumina
Zirconia
XXII.
SULPHUROUS ACID.
Barytes
Lime
Potash
Soda
Strontian
Magnesia
Ammonia
Glucina
Alumina
Zirconia
XXIII.
PHOSPORIC ACID.
Barytes
Strontian
Lime
Potash
Soda
Ammonia
Magnesia
Glucina
Alumina
Zirconia
XXIV.
PHOSPHOROUS ACID.
Lime
Barytes
Strontian
Potash
Soda
Ammonia
Glucinia
Aluminia
Zirconia
XXV.
CARBONIC ACID.
Barytes
Strontian
Lime
Potash
Soda
Magnesia
Ammonia
Glucina
Zirconia
XXVI.
NITRIC ACID.
Barytes
Potash
Soda
Strontian
Lime
Magnesia
Ammonia
Glucina
Alumina
Zirconia
XXVII.
XXVIII.
MURIATIC & ACETIC ACIDS
Barytes
Potash
Soda
Strontian
Lime
Ammonia
Magnesia
Glucina
Alumina
Zirconia
XXIX.
OXYMURIATIC ACID.
Potash
SODA
Barytes
Strontian
Lime
496 TABLE OF DECOMPOSITIONS.
Ammonia
Magnesia
Aluminia
XXX. XXXI.
XXXII.
XXXIII.
FLUORIC, BORACIC, ARSE-
NIC, & TUNGSTIC ACIDS.
Lime
Barytes
Strontian
Magnesia
Potash
Soda
Ammonia
Glucina
Alumina
Zirconia
XXXIV.
OXALIC ACID
Lime
Barytes
Strontian
Magnesia
Potash
Soda
Ammonia
Alumina
XXXV.
CITRIC ACID.
Lime
Barytes
Strontian
Magnesia
Potash
Soda
Ammonia
Alumina
Zirconia
XXXVI.
BENZOIC ACID
Potash-
Soda
Ammonia
Barytes
Lime
Magnesia
Alumina
XXXVII.
SUCCINIC ACID.
Barytes
Lime
Potash
Soda
Ammonia
Magnesia
Alumina
XXXVIII.
CAMPHORIC ACID.
Lime
Potash
Soda
Barytes
Ammonia
Alumina
Magnesia
XXXIX.
SUBERIC ACID.
Barytes
Potash
Soda
Lime
Ammonia
Magnesia
Alumina
XL.
PRUSSIC ACID.
Barytes
Strontian
Potash
Soda
Lime
Magnesia
Ammonia
XLI.
FIXED OILS
Lime
Barytes
Fixed alkalies
Magnesia
Ammonia
Oxide of mercury
Other metallic oxides
Alumina
THE END.
Edinburgh, Printed by C. STEWART.