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1 2 3

" "^;t r

r:9'"

TEXT - BOOK OF CHEMISTRY

FOE

STUDENTS OF MEDICINE,

W. L. GOODWIN, D.Sc. (Edin.),

queen's UNIVBRSITV, KINGSTON.

TORONTO:
THE COPP, CLARK CO., LIMITED, PRINTEKS, COLBORNE STREET.

1887.

(x6

Entered according to Act of the Parliament of Canada, in the year one
thousand eifrht hundred and elgrhty-seven. by Thk Copp, C.AaK Co
LiMiTRD, in the Office of the Minister of .^griculture.

PREFACE.

This book was written to meet a want in my own teaching,
and is inten«le(l to give an outline of C/hemistry, from the medical
point of view, as far as possible. While no attempt has been
male to treat the theory of chemistry exhaustively, I have
tried to explain and apply the fundamental laws and princiides
of the subject in such a way as to render the mastering of the
facts an easier task. The writers of text-books of chemistry
have perhaps, in many cases, erred in arranging their matter too
logically, e.g., adopting an invariable order in describing the
compounds of the metals ; while, in other cases, the ei lor has
])eeu in the opposite direction. It has oeen my aim to steer a
course between these two. The principle adopted has been to
})roceed from the known to the unknown, as far as is consistent
with the limits of time and space imposed upon the teacher.
Thus, water is studied before oxyrien and hydrogen are introduced,
the study of air precedes that of nitrogen, &c., &c. I have
found it advantageous in teaching chemistry to medical students
to let them make for themselves such experiments as those de-
scribed in the text of this book. Nearly all the experiments de-
1 scribed are such as can be made by students easily and with

[very simple apparatus. Class experiments have a rather limited

lvalue, and can be advantageously replaced in most cases by

jimpler experiments made by the students themselves. The

jompounds 'f carbon have been described alo:ag with that ele-

lent, as there seems to be no longer any necessity for relegating

them to the end of the book, as is generally done. In the Ap-

jpendix is a Table of solubilities, which I have found very useful
for reference. Tests are given at the end of the description of

leach acid, metal, &c., and are collected into analytical tables in

[the concluding chapter.

I wish to express my gratitude to my colleagues, Professors
[Dupuis and Shortt, and to my friend Dr. John Waddell, for
I valuable assistance in revising proofs.

W. L. GOODWIN.

Queen's University, Kingston, Ontario.

March Ist, 1887

TABLE OF CONTENTS.

CHAPTER I.

Chemical Action. — States of Matter— Pure Substances — Elu-
triatioii — Filtration — Solution— Crystallisation — Distillation
— Sublimation — Fusion — Chemical Decomposition and Com-
bination — Elements and Compounds. — pp. 1-6.

CHAPTER II.

Weights and Measures.— Specilic Weight— Hydrometer or
Areometer. — pp. 6-12.

CHAPTER III.

Water. — Heat— Conduction — Radiation — Relation of Light and
Heat — Convection — Expansion by Heat — Temperature —
Thermometers — Maximum Density Point of Water — Freez-
ing and Melting — Change of Freezing Point by Pressure —
Change of Volume on Freezing — J^atent Heat of Water —
Specilic Heat — Evaporation and Ebullition — Ijatent Heat of
> Steam — Solution —Freezing Mixtures — Crystallisation — In-
fusion, &c. — Decomposition of Water — Composition of
; Water.— pp. 12-31.

•I

CHAPTER IV.

Oxygen. — Preparation, &c. — Combustion in Oxygen — Tempera-
ture of Ignition — Slow Combustion — Chemism — Metals and
Non- Metals —Table of the Elements.— pp. 32-40.

CHAPTER V.

Conservation of Matter — Definite Proportions — Combining
VVeights —Equivalents — Multiple Proportiois — The Atomic
Theory — Avogadro's Law— Combination by Volumes — Mole-
cules and Atoms — Molecular Weight of Gases — Chemical
Notation — Atomic Weights — Chemical Equations — Chemical
Calculations — Ozone. — pp. 41-54.

CHAPTER VI.

Hydrogen, — Hydroxides — Valence — Diffusion — Hydrogen Di-
oxide — pp. 55 66.

TABLE OF CONTENTS.

CHAPTER VII.

j^ir. — Boyle's Law — Charles' Law — Measurement of Volumes of
v'jases — Composition of Air — Combusticm in Air— Respira-
tion.— pp. 67-78.

CHAPTER VIII.

Nitrogen. — Ammonia -Nitric Acid— Nitrates — Basicity— Salts
~Oxide.-i of Nitrogen — Monoxide — Dioxide — Trioxide —
Nitrous Acid — Tetroxide — Pentoxide — pp. 79-97.

CHAPIER IX.

The Halogens. — Sea Water — Chlorine — Hydrochloric Acid —
Chlorides — Oxides of Chlorine — Monoxide — Trioxide — Te-
troxide — Oxygen Acids of Chlorine — Hypochlorous Acid —
Chlorous Acid — Chloric Acid — Chlorates — Perchloric Acid
— Bromine — Hydrobromic Acid —Bromine and Oxygen —
Iodine — Hydriodic Acid — Iodides — lodiile and Chlorine —
Iodine and Oxygen — Iodic Acid — Fluorine* — Hydrofluoric
Acid — Fluorides. — pp. 98-119.

CHAPTER X.

The Sulphur Group. — Sulphur — S-iilphur Dioxide — Sulphur
Trir./iide— Oxygen Acids of Sulphur — Hyposulphurous Acid
— Sulphurous Acid — Sulphites— Sulphuric Acid — Sulphstiea
— Normal and Acid Salts —Fuming Sulphuric Acid — Thio-
sulphuric Acid — Thiosulphates — Hydrogen Sulphide — Chlor-
ides, &c., of Sulphur — Selenium — Tellurium. — pp. 120-141.

CHAPTER XI.

Phosphorus- — Oxides of Phosphorus — Pentoxide — Trioxide —
Phosphoric Acid — Phosphates — P^hosphorous Acid — Hypo-
phosphorous Acid — Hypophosphites — Phosphoretted Hydro-
gen — Phosphorus and the Halogens. — pp. 142-154.

CHAPTER XII.

Arsenic. — Trioxide — Pentoxide — Arsenious Acid — Arsenites —
Arsenic Acid — Arsenates — Sulphides of Arsenic — Arseniu-
retted Hydrogen — Marsh's Test — Arsenic Chloride, &c. — ■
Tests for Arsenic. — pp. 155- 163.

* This element has been lately prepared by the (jlectrolysis of dry hydro-
fluoric acid. It is a gas having powerful cheniisuj.

VI TABLE OF CONTENTS.

CHAPTER XIIT.

Carbon. — Carbon Compounds— Sources of Carbon Compounds —
Dioxide — Carbonic Acid — ( ' irbonates — Monoxide — Bisul-
phide — Hydrocarbons — Marsli (ias — Chloroform— Ethylene
— Isomerism — Acetylene — Cyanogen Compounds — Potassic
Ferrocyanide — Hydrocyanic Acid-C'yanides — Cyanic Acid
— Sulphocyanates — Urea — Uric Acid — Urates — Alcohols —
Methyl Alcohol — I'^thyl Alcohol— Fermentation — Amyl Al-
cohol — Isomeric Alcohols — Amines — Etheis — Aldehydes —
Ketones — Chloral- - Fatty Acids — Formic Acid — Acetic Acid
— Acetates — Butyric Acid— Valerianic Acid — Acids of Fats
and Oils — Glycol — Oxalic Acid — Oxalates — Succinic Acid —
Glycerine — Hydroxy-acids — Lactic Acid — Tartaric Acid —
Tartrates — Citric Acid — Citrates — Carbohydrates — Sac-
charoses — Cane Sugar — Milk Sugar — Malt Sugar — Glucoses
— Dextrose — Levulose — Amyloses — Starch — Dextrin — Gly-
cogen — Gums — Cellulose. — pp. 164-!2v{l,

'^ CHAPTER XIV.

Aromatic Compounds. — Coal Tar — Benzene Series — Benzene
— Nitrobenzene — Aniline — Carbolic Acid — Creosote — Picric
Acid — Benzylic Alcohol — Benzoic Aldehyde — Benzoic Acid
--Saccharine — Salicylic Acid — Gallic Acid — Tannic Acid —
Terpenes — Camphor — Ciunamic Acid — Esfiential Oils —
Indigo — Naphthalene — Anthracene — Glucosides — Alkaloids
— Conine — Nicotine — Morphine — Quinine — Cinchonine —
Strychnine — C-ocaine — Atropine — Kairine, Antipyrine, Thai-
line — Albuminoids. — pp. *23'2-255.

CHAPTER XV. :

Silicon. — Silica — Silicic Acid and Silicates — Fluosilicic Acid-
Boron — Boric Acid — Borax, —pp. 250 -202.

CHAPTER XVi.

The Metals* — General Characters — Ores — Alloys — Compounds
— (Jxides — Sulphides — Chlorides, ^;c. — Oxygen Salts — Clas-
sification — Analysis. — pp. 203-271 .

CHAPTER XVII.

Metals of Group I. — Lead — Oxides — Salts — Acetate — Nitrate
— White Lead — Chloride — Iodide — Lead Plaster — Sulphate
— Commercial Preparations — Lead Poisoning. — Silver — Ox-
ides — Salts — N itrate — Mercuni — Amalgams — Mercurous
Compounds — Nitrate — Chloride — Iodide — Mercuric Com-
pounds — Nitrate — Sulphate — Chloride — Oxide — Iodide —
White Precipitate — Sulphide — Mercurial Poisoning. — pp.
271-292.

TABLE OF CONTNETS.

Vll

CHAPTER XVIIT.

Metals of Group II.— Co;>;jfr— Compomifls— Cupric Sulphate
— Oxide — Commercial Preparations — Cmfmium — N itrate —
Sulphate— Iodide— 7?J«mHM — Nitrate — Snbiiitrate — Trioxide
— Bismuthyl — Carbonate — A ututumi/ — Trisulphide — Tri-
chloride — Trioxide — Tartar Emetic — Thi— Stannic Oxide —
Stannous Chloride — Stannic Chloride— Oohl — Compounds —
Phitinum — Compounds — Palladium, &c. — pp. 293-315.

CHAPTER XIX.

Metals of Group III. — Iron —Ferrous Salts — Sulphate — Car-
bonate — Arsenate — Phosphate — Ferric Salts — Chloride —
Sulphate — Nitrate — Hydroxide — ' ' Scale " Compounds —
Chronihuii — Potassic Bichromate — ChroniicAcid- -Cnromates
— Chrome Alum — Chromic Hydroxide — Almninium — Alu-
mina — Alums — Aluminic Sulphate — Porcelain, &c. — Zitic —
Oxide — Chloride — Sulphate — Carbonate — Acetate — MaiKja-
nese — Dioxide — Manganous Salts — Manganic Salts — Man-
ganates — Permanganates — Cobalt — Oxides — Nitrate — Chlo-
ride — Nickel — Oxides — Sulphate — Cerium. — pp. 316-350.

CHAPTER XX.

Metals of Groups IV. and V.—<^'«^c''<"i— Oxide— Hydroxide
— Carbonate — (Jhloride — Sulphate — Bleaching Powder —
Phosphates — Mortars and Cements — Strontium— Barium —
Oxides — Chlorides — Nitrate — Majnesiiim — Sulphate — Car-
bonate — Magnesia — pp. 350-307.

CHAPTER XX r.

Metals of Group VI. — Sodium — Chloride — Sulphate— Carbon-
ate — Bicarbonate — Hydroxide — Nitrate — Sulphite — Phos-
phate — Bromide — Sulphide — Class — Potamium — Carbonate
— Bicarbonate — Hydroxide — Chlorate — N itrate — Bromide —
Iodide — Ammonium — Sulphate — Chhmde — Carbonate —
Phosphate- -Microcosmic Salt — Sulphiile — Lithium — Carbon-
ate — Euhidimn — Ccesium — Spectrum Analysis. — pp. 368-390.

CHAPTER XXII.

Electricity. — Electrolysis — Electro-chemical Series.
3^0-392.

CHAPTER XXIII.

Analysis. — Chemical Toxicol<»gy — Analytical Tables.
393-404. ^' ^

Appendix.— Table of Solubilities— pp. 405-408.
Index.— pp. 409-416.

— pp.

ADDENDA ET CORRIGENDA.

Page 7, table, for 0.064 read 0.0648.

" 7, table, for 28.3549 read 28.3495.

" 1 1, 1. 8, for 96 read 88,

** 26, 1. 18, for no read not much.

" 35, 1. 3, from bottom, for is read was called.

" 48, 1. 15, for always read generally.

" 48, 1. 15, for 6.6 read 6.3.

" 48, Is. 19 and 20, for specific read atomic.

" 53, last line, for BgO read ^HgO,

** 66, for Experiment 28 read Experiment 28 A.

" 57, 1. 3, for atomic read atom.

" 83, 1. 16, for red read blue.

" 122, 1. 4 from bottom, for that read tJie atom.

" 141, 1. 8, for KOH read NaOff.

" 145, 1. 7, for amphorcus read amorphous.

" 154, last line, for Ga^{PO^)^ read 3{Ca^{P0^)^).

" 163, first equation, for N&^CO read Na^GO^.
" 179, 1. 3 from bottom, for 151 read 159.'
" 193, 1. 6, after absent, insert, Fermentations are also caused
by certain nitrogenous organic compounds called un-
organised f€rm.ents, e.g. diastase, synaptase, &c.

** 201, 1. 4 from bottom, after chlorine read by a series of
reactions.

" 203, 1. 17, for C.H^Os read C^H^O^.

*' 209, 1. 2, for a solution of read sparingly soluble.

" 219, 1. 15, omit sparingly.

CHEMISTRY

FOB

STUDENTS OF MEDICINE.

CH APTE R I

INTRODUCTORY.

1. Chemical Action.— /ron rusts in air, and the
mat differs in pioperties from the iron. Iron heated in
-iftir becomes changed to a black substance (as in a black-
pmith's shop) unlike the iron in many respects. When
Placed in vinegar iron gradually disappears into the
vinegar, ^. e. dissolves, and a red liquid is formed, having
the properties of neither vinegar nor iron. Wood burns,
Heaving only a small portion of ash, unlike the wood in
Icolour, and other properties. The greater part of the
I wood has been changed into substances like air. A plant
Itakes food from the soil and from the air in the form of
[water, carbonic acid, ammonia, and various mineral sub-
stances. From these it elaborates sugars, starch, gums,
wood, &c., substances totally different from the original
[articles of food, and not to be found in the sources from
t which the plant gets its ^.od. An mivrnal brings about
[similar changes, forming out of its food substances quite

2 PURE SUBSTANCES.

unlike that food, converting starch into sugar, albumin
into fat, &c. In all these cases, substances undergo such
changes that they become converted into other and differ-
ent substances. Such processes are called chemical actions,
and Chemistry is, for the most part, the study of chemical
actions.

2. Three States of Matter. — All substances can

be grouped into three classes, viz. : solids, liquids, and
gases. Solids have a definite form and volume. Liquids
have no definite form, but their volume does not tend to
change. Gases are indefinite both in form and volume.
They tr.,ke the shape of the vessel in which they aj-e con-
fined, and readily undergo compression and expansion,

3. Pure Substances. — Simple inspection of granite
shows it to contain more than one substance. It is a
mixture or mixed substance. Soil, pudding stone, milk,
and, air, are other examples of mixtures. There are many
methods of separating mixtures into their ingredients,
ard thus obtaining pure substances, or chemical indivi'
duals. The commoner methods are given in the following
sections.

4. Elutriation, or " washing out," is a process used
by the gold miner who washes away the light earth, sand,
u/C, from the heavier gold. Winnowing is a similar
process.

5. Filtration is separating a liquid from a solid by
allowing the former to flow through some porous sub-
stance which retains the latter. Thus, muddy water can
be separated into mud and vater. Unsized paper, called
Jikcr paper, is very commonly used.

SEPARATION OF MIXTURES.

G. Solution. — In this process, a liquid called a solvent
is used to separate a soluhle substance, sugar for instance,
from an insoluble substance such as sand, > :

7. Crystallisation. — When all tho ingredients of

■ mixture are soluble in some one solvent, e. g. in water,
se[)aration can often be brought about by evaporating
the solvent. When there is not enough of the solvent
left to dissolve all the substances, that one whicli is most
difficult to dissolve (or the least soluble), separates from
the liquid, generally in regularly formed crystals. At
another stage of the evaporation, the substance next in
solubility cri/stallises, and thus a separation more or less
complete is effected. It is by this process that common
salt is separated from the other substances dissolved in
ijea water. -,. '^...v .^.^s /.v- ■.,. .,, - •^--, - ...• - ■'

8. Distillation. — If a dish of alcohol and one of
water be set side by side on a hot stove the alcohol begins
to boil much before the water. Alcohol boils at a lower
tejnpe7'ature than water, and a mixture of these two
liquids can be separated by distilling them. For, when

^eat is applied to the vessel (the boiler, or retort,) contain-
ing the mixture, the alcohol is first changed to vapour,
passes as vapour into the cold tube (or condenser), and is
there cooled and condensed (or made liquid). Thence it
runs into the receiver. Iiater, water begins to distil over
and may be collected in a different vessel. In a similar
way fresh water can be prepared from sea water, the pure
water distilling, and the salt remaining in the boiler.

9. Sublimation. —This is distillation applied to
solids which can be changed to gases by heat. Sulphur

4 CHEMICAL DECOMPOSITION.

is purified by heating it until it i& changed to a gas
which is then condensed in a clean vessel. The impuri-
ties rc^main, since they are non-volatile.

10. Fusion. — Some substances melt or fuse at lower
temperatures than others. Thus, butter fuses at the
temperature of the hand ; while salt can be fused only
by a strong, red heat. If a mixture of butter and salt
be gently heated, the butter melts, the salt sinks to the
bottom, and the liquid butter can be poured off. This is
the pharmaceutical process >! clarification. In some
cases the impurities are ligi.ter than the melted sub-
stance to be clarified. They, then, rise as a scum and
are removed by skimming.

11. Chemical Decomposition and Combina-
tion. — In the processes described above, no permanent
change is brought about in the pure substances which
are separated out of the mixtures. They preserve their
identity. In chemical actions substances lose their
identity.

lExperiment 1. — Heat a little red oxide of merctiry in a
tube of glass. The oxide disappears gradiially, and a silvery
liquid, quicksilver, gathers on the inside of the tube. Thrust a
splinter of wood with its end still glowing into the tube. Tho
splinter begins to burn very brightly.

Two substances have been formed from the oxide of
mercury, viz., the liquid metal quicksilver or mercury,
and the gas oxygen^ which causes a live coal to burst into
bright flame and therefore differs from ordinary air.
This is an example of chemical decomposition. Red oxide
of mercury has been decomposed by heat, and the pro-

ELEMENTS AND COMPOUNDS.

ducts of itft decomposition are mercury and oxygen. This
process differs from the separation of a mixture into its
ingredients, because the products of decomposition have
not the properties of the substance decomposed. The
chief agents which bring about chemical decomposition
ar(! heat, light, electricity, mechanical force (as in the
explosion of dynamite), and contact with certain sub-
stances. Chemical decompositions are also brought
about in some unknown way by living beings, as in
fermentation.

Experiment 2- — Mix well four parts, of flowers of sulphur
witli seven parts of very fine iron filings. A powder is obtained
in which the presence of both iron and sulphur can be easily
recognized. Shake up a little of the mixture with water in a
test-tube. The iron sinks to the bottom more quickly than the
sulphur and the two are separated. Move a magnet over
another small portion of the mixture. The iron sticks to the
magnet and the sulphur remains. The two substr.nces were
merely mixed. Now, heat the remainder of the mixture in a
a small, porcelain dish. It gets red hot, blackens, aud becomes
quite uniform in appearance. The closest examination does not
«how the precence of either sulphur or iron. Powder a little of
the black substance and shake it up with water as before, No
separation takes place. Move a magnet over another part. No
iron sticks to it. The iron and sulphur have disappeared and
this single black substance has taken their place.

This is an example of chemical combination. Iron and

sulphur have combined to form sulphide of iron (ferrous

sulphide), a substance differing altogether in properties

ftom iron or sulphur. Chemical combination must be

-distinguished from mixture.

12. Elements and Compounds. —The majority

of substances can be decomposed, but there are certain

b WEIGHTS AND MEASURES.

which cannot, so far as known. Thus, it has been found
impossible to obtain from a portion of pure mercury any-
thing else ; and the same is true of iron and sulphur.
These substances will combine with others to form new
substances, but from themsel ves, taken alone, nothing dif-
ferent has been obtained by any process yet tried. Such
substances are called Elements, or Simple Substances.
They unite to form compounds.

Definitions. — A chemical action or reaction is a change in
which from one or more substances there are formed other sub-
stances differing from the original in essential properties, e.g. in
colour, taste, smell, &c. In chemical combination simpler sub-
stances unite to form more^^ complicated. In chemical decomposition
complex substances are broken up into simpler. An element is a
pure substance which has never been decompoB<id into substances
differing from it in properties. A compound is a substance
formed of two or more elements elifmically combined.

There are at present six -seven elements known, and
all the known substances o:. nd in the earth consist of
these elements and their compounds with each other.
A list of the elements is given at page 39.

CHAPTER n.

WEIGHTS AND MEASURES— SPECIFIC WEIGHT.

13. Weights and Measures.— In order to study

chemical actions completely the quantities of substances
taking part in them must be known. The metrical sys-
tem of woights and measures has been adopted by chemists
everywhere. It involves very little calculation since its

WEIGHTS AND MEASURES.

I ^nits all increase in magnitude by tens^ so that the opera-
ions of reduction can be performed by merely moving
le decimal point. It is hence called the deci?nal system
if weiglits and measures. The unit of length in this
System is the metre intended to be equal to one ten-
;tnillionth part of a quarter of the earth's circumference
through the meridian of Paris.

Linear Measures.— 1000 millimetres (mm.) ^- lOO

Bntimetres (cm.) =10 decimetres (dcm.) = 1 metre (m.)
^ decametre = ^^n hectometre = xt^ kilometre =
).371 English inches.

M6wj,SUreS of Capacity.— 1000 cubic centimetres
(c.c.) = 1 cubic decimetre = 1 litre (1.) = 61.027 cubic
[inches ~ 1.761 pint.

Measures of Weight.— 1000 milligrams (mgms.)
= 100 centigrams (cgms.) =10 decigmms (dgmii.) = 1
I P^**^*- (g»Ti-) ^ 10 decagram = iwu hectogram = j^\^ kilo-
gram = 15.43 grains.

1 gram = the weight of 1 cubic centimetre of pure
water measured at 4° centigrade (its point of greatest
density).

delations of Pharmaceutical to Metrical Weights and Measures.

1 grain
1 ounce
1 pound

0.064 gram.
: 28.3549 "
:453.5'jJ5

((

CUBIC CENTIMRTRE.

1 minim = 0.059

1 fluid drachm rr- 3.549
1 " ounce = 28.396
1 pint = 567.936

1 gallon = 4543.487

or about 4^ litres.

8 SPECIFIC WEIGHT.

Exercises. — 1- In 17G4 millimetres how many metres ?

2. In .37 metres how many cms. ?

3. How many litres capacity has a tank 2 metres long, 1.5
metres broad and 1.5 metres deep ?

4. How many grams in a pound av:)irdupoi9 {=: 7000 "rains) ?

5. What weight of water will fill the tank in (3) ?

6. How many c. c. in a fluid ounce ? (Note. — The fluid ounce
is the volume of 1 ounce weight of water = 437.5 grains).

7. Reduce 38,674 cubic centimetres to litres.

8. In 1 kilogram how many pounds?

9. Find the number of kilometres in a mile.

10. How many inches in a kilometre ?

11. Find the capacity in litres of a tank 4 feet long, 2^ feet
wide and 3 feet deep.

12. What is the weight in grams of 8 fluid ounces of mercury ?
(mercury weighs 13.596 times as much as the same volume of
water).

14. Specific Weight. — When it is said that lead
is heavier than water it is meant that if equal volumes
of lead and of water be weighed, the lead will be found
to be heavier. Thus Specific Weights, or Specific Gravi-
ties, of substances are found by comparing the weights
of equal volumes of the substances with that of the same
volume of some substance chosen as a standard. For
liquids and solids water has been chosen as the standard ;
and for gases, air, or hydrogen. For example, 1 cubic
centimetre of water weighs one gram ; and the same
volume of mercury weighs 13.596 grams. Then, the
specific weight of mercury is 13.596.

SPECIFIC WEIGHT. 9

^Definition.— The Spedjic Weight of a substance is a number
jreasing how many times heavier the substance is than an
|ual volume of some substance chosen as a standard.

15. Spociflc Weights of Solids.— If the solid is

ivier than water it iis first weighed in the air, and
^en hanging in water. Its weight in v/ater (w) is
ss than its weight in air (W) by the weight of the
"^acer which it displaces, i.e., an equal volume of water.

Or, if S represents the specific weight, then S = vy^^— *

16. Specific Weights of Liquids.— (1) Fill a

W(iighed narrow-necked flask with water up to a mark
on its neck, and weigh the full flask to determine the
weight (W) of water. Fill the same flask with the

li<i[uid of which the specific weight is to be found and

find the weight (W) of the liquid. Then S = ;J^'

(2) The Hydrometer or Areometer is a glass tube with a
bulb blown on one end. In the bulb is a small quantity
of mercury which causes the tube to swim upright in
any liquid in which it is placed. The stem of the hydro-
meter is graduated and numbered. When placed in
water it sinks until the water reaches a certain mark on
the stem. When placed in a liquid heavier than water
it does not sink so far. In a liquid lighten than water
the instrument sinks farther than in water. Numbers
marked on the stem indicate the specific weights of the
li(|uids. This instrument in various forms is constantly
used in medical practice.

1 7. Specific Weights of Gases. — These are

found by methods the same in principle as the first

SPECIFIC WEIGHT.

method for liquids (§ IG). A large glass globe, whose
capacity is known, is madj as nearly an possible empty
of air by means of tlie air pump, and is then weighed.
The gas of which the specilic weight is to be determined
is then allowed to flow ii}, and tbe flask is re weighed,
i'he increase in weight is the weight of the flask full of
gas. This weight divided by that of an equal volume of
the standard gives the specific weight required. Ther(3
are many minute precautions and corrections which can-
not be described here.

18. In the following table are given the specific
weights of some of the commoner solids and liquids,
water at 4° centigrade being the standard : —

Platinum 22.069

Gold 19.362

Lead 11.352

Silver 10.474

Copper 8.788

Brass 8.383

Steel 7.820

Iron (wrought) 7. 788

Iron (cast) 7.207

Tm 7.291

Zinc 6.861

Diamond 3.531

Flmt Glass 3.329

Marble 2.840

Bottle Glass 2.600

Plate Glass. . : 2.370

Porcelain 2.300

Sulphur 2.030

Ivory 1.917

Graphite 1.8 to 2.400

Anthracite 1.800

Phosphorus 1.770

Magnesium 1.740

Amber 1.080

Water at 4° 1.000

White Wax 0.970

Sodium 0.970

IceatO°C 0.918

Potassium 0.860

Mahogany 1.060

English Oak 0.970

Beech 0.852

Ash 0.840

Yellow Pine 0.657

Cork 0.240

Mercury 13.596

Oil of Vitriol 1.840

Chloroform 1 .52r)

Nitric Acid 1.500

Hydrochloric Acid 1.220

Blood (human) 1.04.5

Milk 1.030

Sea Water 1.028

Port Wine 0.990

Castor Oil 0.970

Linseed 0.940

Proof Spirit 0.930

Oil of Turpentine 0. 870

Brandy 0.837

Absolute Alcohol 0.780

Ether 0.720

QUESTIONS AND EXKrClSES. 11

QUESTIONS ANi» EXEKOJSFS.

I. What is & imit of meafiure7ue ; Why anj thero maw?/ units
of length in use instead of only one ?

' 2. A fiaak filled with water was found to weigh 72 g'-aras, the
flask alone weighing 22 grams. The same flask filled with oil
of vitriol weighed 114 grams. Calculate the sp. wt. of oil of
titriol.

3. A piece of iron weighing 96 grams in air was found to
weigh 76.5 grams in water. Calculate the sp. wt. of iron.

4. A flask filled with water weighed 153 grams ; 25 [/. of cop-
per are dropped in. The flask and contents then weighed 175. 1&
^. What is the sp. wt. of copper ?

5. "'When a body is weighed in air its true weight is not
found." Why not? How must it be weighed in order to find
its real weight ?

0. A man of 160 lbs. weight immersed his body completely in
a bath 7 ft. long and 3 ft. wide. The water rose IJ in. What
w .3 thr sp. wt. of his body ?

7. A piece of cork weighing in air 15 grams is immersed in a
vessel of water 12 cm. long and 5 cm. wide. The water rises 1
cm. Calculate the sp. wt. of the cork.

8. What is the volume in cu. inches of a piece Ox lead weigh-
g 10 lbs. ?

9. Calculate the volume in cubic centimetres of 100 grams of
pper.

10. What is the weight in grams of a gallon of pure water
,t 4° C.

II. What is the sp. wt. of a body which floats with one third
)f its bulk out of water ?

12. When the lungs are inflated the specific weight of the
mman body is less than 1 ; but when the lungs are filled with
rater, it is greater than one. Explain this.

13. Write a short essay on the convenience of the metrical
system.

12 CONDUCTION.

CHAPTER III.

WATER— JIEAT-SOLUTION. |

1 9. "Water. — About two-thirtls of the weight of
animals and a large fraction of the weight of plants con
aist of water. As it occurs in nature water is not a pure
substance. This can be shown by distilling any sampK>
of sea, river, lake, spring or rain water. A solid residue
is left in each case. But if this distilled water {aqua
distillata) be redistilled again and again no residue is
left in the retort. Distilled water is a pure substance, a
chemical individual. It is generally a liquid, but if
sufficient heat be removed from it, it becomes solid (ice);
and when heat is added liquid water is changed to a gas
(water vapour, steam).

20. Heat - Conduction. — Heat and light were
once thought to be substances. They are now known to
be motion of some sort. When a body becomes hotter its
particles move {vibrate) faster, and the motion is com-
municated to any other body in contact with it. Simi-
larly, heat passes from a hot to a cooler part of a body
without any movement of the body as a whole. This
process is called conduction of heat.

Experiment 3. — Choose a piece of copper wire and anocher
of iron wire of about the same size and length. Hold the end of
each in the flame of a burner, and observe the time required for
the heat to become unpleasant at the other end held between
the fingers. The time is much longer for the iron than for the
copper. Copper is a belter conductor of heat than iron.

RADIATION. 13

A "Ihhs rod may be heated at one end until it melts
before the other end becomes warm. Glass is a poor
conductor of heat. The metals generally are the heat
luctora of heat. Wool, feathers, asbestos, fur, air
kd gases generally, and most liquids are bad conductors.
\e use bad conductora, as clothing, to keep the heat
)m leaving our bodies ; but we also use them as pack-
Ig for ice, &c., to keep the heat out.

Experiment 4 -Wrap a piece of copper wire round a
iall lump of ice and allow the ice to fall to the bottom of a
st-tube full of cold water. Holding the test-tube aslant, heat
water near the top until it begins to boil. The icf at the
bottom remains unmelted. Water is a bad conductor of heat.

.21. Radiation. — Heat reaches us from the sun by
ft j)roce8s different from conduction. It may warm the
•arth to 90° or 100° F., and still leave the air through
which it passes cool. In this way, too, heat and light
pass through space empty of everything as far as known,
Tliis movement of heat and light is called radiation. It
is extremely rapid — about 180,000 miles per second.

22. Relation of Light and Heat.— Light and

h(>at are related to each other just as the high notes of
music are related to the low. Light consists of short
waves, or I'apid vibrations, which produce in the eyes the
sensation ordinarily called light. Heat consists of the
longer, slower waves which are not capable of exciting
tliis sensation, — in our eyes at least. When light falls
upon a body which is not a good reflector, it is absorbed
and may be thus transformed into heat. It is in this
kway, principallj% that the earth is heated b/ the sun.

14 CONVECTION — EXPANSION.

23. Convection.

Experiment 5. —Fill a tall glass vessel (beaker) with wattr
containing tine sawdust, ami heat at the bottom. The movtv
ments of the sawdust show that the water as it is heated rises to
the top, while the couler water sinks.

Thus, heiut is conveyed from place to place by motion
en masse of the substance which is being heated, i. e., by
convection currents. Winds are convection currents on
a grand scale ; drafts are the same on a smaller scale.
From experiments 4 and 5 it is easily seen that a mass
of water can be much more quickly heated by applying;
the heat at the bottom, than by applying it at the top.

24. Expansion by Heat. — In Experiment 5 the
water rises as it becomes warm, because it is lighter than
the cold water. Its volume harj been increased. Meat
expands water.

Experiment 6. — Fill a glass tlask full with cold water, and
heat the water to boiling. A small quantity runs over as the
water becomes hot. Allow the water to cool. It sinks down
the neck of the ilask. Water expands when heated and con-
tracts when cooled.

Other liquids expand when heated and contract on
cooling, hut different liquids expand differently. For
example, mercury expands less than water for the same
increase in degree of heat. Solids also expand when
heated, but not so rapidly as liquids. It will be shown
later on that gases expand when heated much moie than
either liquids or solids, and that all gases expand almost
exactly at the same rate.

TRMPERATURE. 15

Ixperiment 7. — Fit a cork to a glass flask, boro a hole

through the cork, arnl through the hole put a glass tube fitting

tigh tly. Fill the flask with water, push in the cork tightly so

U^o cause the water to rise an inch or two in the tube. Pour

^■H water on the flask. The water in the tube at first sinks, but

'^mnediately afterwanls begins to rise steadily. When it has

■tQp])e(l rising it begins to fali, and finally remains at about the

le level as before the hot water was poured on the flask.

he flask expandt first when the hot water is poured
and the cont;unbU '.ater sinks down the tube. Then
the heat penetrates to the water which expands /aster
than the glass, and therefore rises in the tube. — Builders
of bridges allow for the expansion and contraction of iron
witli change of season, &c. In laying rails in cold
weather the ends are not put close together, but space is
allowed for the increased length in warm weather.

*o'

'25. Temperature — If an instrument such as that
desci-ibed in Experiment 7 were put into a body of water
which caused the water in the tube to rise, the conclu-
sion drawn from such an experiment would be that the
boi!\ of water was hotter than that in the flask. If, on
tihe other hand, the liquid should fall in the tube, it would
be concluded that the water under examination was cooler
^^an that in the flask ; if no change were produced, the
^[^nclusion would certainly be that it was neither hotter
abr colder. The sense of touch would confirm these con-
clusions in each case, if the hand were immersed succes-
"■'vely in the two quantities of water.

- Experiment 8.- -Lay a piece of iron and a block of wood

side by side on a table and after half an hour touch each of them

^th the hand. The iron feeU colder than the wood ; and yet,

".'S

16 TISRMOMETERS.

if an instrurnent such as that used in Experiment 7 be touched!
first to one and then to the other it shows them to be exactly inl
the same state.

The sense of touch does not always give the same ver-!
diet regarding heat as the effect on volume does. The^
iron feels colder because it conducts heat away from the
hand more rapidly, being a better conductor than wood.
For the same reason blankets feel warmer than sheets.
The words " hot " and " cold " do nob convey a correct
idea of tlie state of a body with regard to its sensible heat.
Generally, bodies which have been in contact for some
time are in the same state with regard to sensible heat,
for, if they are at first in different states, heat flows from
the hotter to the colder until they are, as it were, at the
same heat-level, or at the same temperature.

Definition. — Temperature is the state of a body with regard]
to sensible heat ; or temperature is heat-level.

26. Thermometers. — Teiuperatures are measured]
by thermometers, or heat-measures. In most thermo-
meters the temperature is indicated by the amount of!
ex[)ansion of a liquid enclosed in a graduated glass tube
with '\ bulb or resorvoir at the lower end. The most
convenient liquid for ordinary ranges of temperature is
mercury. It expands regv.larly, freezes only at a low,
and boils only at a high temperature. Alcohol is used
for very low temperatures as it does not freeze until the
temperature sinks much below any that oocui*s naturally.
The thermometer is graduated by placing it first in a
mixture of ice and water, then in steam at ordinary
pressure, and marking on the stem or scale the level at
which the mercury stands in each case. These are the

THERMOMETERS. 17

fa-ed lioints, and always whon the thermometer is placed
in melting ice the mercury stands at the lower fixed
point, and when it is placed in water boiling under
ordinary circumstances, the mercury remains stationary
at the higher fi^xed point. Under the same circumstances
water freezes always at the same temperttcure, and also
boils always at the same temperature. It only remains
to divide the interval between the fixed points into equal
parts called degrees, and to number these in re^^ular
ord(ir. The numbers chosen are diffi^rent in tliermo-
meters devised by different men. Any numbers may be
chosen, according to taste or convenience. On the Cen-
tigrade or Celsius thermometer, the one always used for
scientific purposes, the lower fixed point is marked 0°,
the upper 100°, and the space between is divided into
100 degrees. On the Fahrenlielt thermometer, generally
used in this country, the two points are marked 32° and
21 'J" respectively, so that the zero Fahrenheit is o2 de-
gi-c(is below the freezing point of water. On the Reau-
mur thermometer the space between the fixed points is
divided into 80 degrees numbered from 0^ to 80°. Thur:,
the degrees on the Reaumur scale are longer than on the
Qeutigrade, which in their turn are longer than those on
the Fahrenheit. The relations betw ien the degrees are
eicpressed as follows : — 1 degr^^e F. = \%% — % degree
Wm ^ tVo = ^ degree R. To change any temperature
Tfahrenheit to Centigrade (or Reaumur) subtract 32 and
multiply by f (or |). The 32 degrees between the
faluenheit zero and the freezing point must be sub-
'^:-A(^ted first, because the other thermometers reckon from
j|ie freezing point. To change any temperature Centi-
grade (or R^iumur) to Fahrenheit, multiply by | (or f )
^d add 32. Or, if t represent any temperature Fahren-

I 3

18 MAXIMUM DENSITY POINT. |

heit (t — 32) f represents the same temperature Centi |
grade, and {t — 32) f the same temperature Reaumur. |
Also let t be any temperature Centigrade, then § ^ + 32 1
represents that temperature Fahrenheit. Similarly for |
Reaumur. Ten^ peratures be^ow zero are indicated Ly |

the minus sign ( — ). 3

'■4

27. Maximum Density Point of Water. '^

'a
Experiment 9- — Bore a second hole in the cork in the appa |

ratus of Experiment 8, fit a centigrade thermometer in it, and |

arrange the apparatus as in Experiment 8. Surround the flask |

with snow or ice. The water in the tube falls until the ther |

mometer marks 4" 0. It then begins to rise, and continues to |

do so until the temperature sinks to 0°. , |

i
Water has the smallest volume at 4° C, and has,f|

therefore, the greatest specific weight at that tempera i

ture, which is for this reason called the maximum densUM

point of water. Most liquids are densest at their freezinjl

points. Water is exceptional in this respect. When if

body of water cools at the surface, as a lake in autumn

the cooled water sinks until the whole lake is at the teni

perature 4° C. When the water at the surface is cooled!

below thif? it remains at the surface, because it expands

and thus becomes specifically lighter than the warmer

water below. As water is a very poor conductor of henti

(see Experiment 4), the water below cools very slowlyj

even if the surface becomes changed into ice. Were it

not for this exceptional feature in the effect of cooling 011

water, our lakes would become masses of ice every winter.

28. Freezing and Melting.

Experiment 10- — Heat slowly a vessel containing snow or
ice, stirring constantly with a thermometer. The temperature

FREEZING AND MELTING. 19

of tlie whole mass remains at 0° C. until the last portion "f snow
or ice is melted. It then begins to rise.

Ice melts at 0° C. always, under ordinary circum-
stances. Other solids have different melting points, e. g.
Lead melts at 300° C. The word fuse is used instead of
melt, especially of solids which become liquid only at
high temperatures. If a portion ot water be cooled it
begins to freeze at 0° C, and the temperature does not
sink below that until the whole of the water is changed
to ice. The freezing point of water is the same as the
melting point of ice. This is true of most liquids, but
not of all.

21). Oiiange of Freezing Point by Pressure.

Experiment 11- — Support a slab of clear ice at either end
and lay over it a thin clean wire having a weight attached to
eacli end so as to cause the wire to press upon the ice. The wire
gradually passes through the ice, but does not cut it in two.

The ice is melted by the pressure of the wire upon it,

It solidities again as sooii as the pressure is removed by

onward movement of the wire. Ice at 0° C, can be

3lted by pressure, and cannot be frozen as long as the

jssure continues, without reducing the temperature

)?/? 0° C. In other words the freezing point of water

lowered by pressure. Water is exceptional in this

iipect also ; most liquids have their freezing points

liaised by pressure.

''"*(). Change of Volume on Freezing.— Since

I(^ floats on water it m ..o be specifically lighter than
j^tcr. Water expands on freezing. Most liquids con-

20 LATENT HEAT OF WA I'ER.

tract on solidifjing, e.g., solid lead sinks in liquid lead
Water expands about one-eleventh of its volume oi
freezing. Enormous force is exerted during this expan
sion ; hence the bursting of water-pipes, the splittin|
of rocks, the "heaving" of the foundations of build
ings, &c.

31. Latent Heat of Water. — From Experimen
10 we learn that when ice is melting heat goes into i
without I'aising its temperature. This heat become
latent or hidden. In order to freeze
latent heat must be removed from it.

latent or hidden. In order to freeze the water again tl

Experiment 12. — Mix 1,000 grams ice-cold water with l,()i
grams boiling water. The temperature of the mixture is 50° (
Now, mix 1,000 grams ice with 1,000 grams boiling water, st
well until the ice is melted. The temperature of the mixture
only 10.5° C.

From these experiments it is plain that the ho;
rendered latent by melting 1,000 grams ice would wan
2,000 grams water from 10.5° C to 50° C. If we tal ^
as the iinit of heat (or thermal unit) the quantity of lie;
required to raise the temperature of 1 gram of water
degree Centigrade, then 2,000 x 39.5 = 79,000 uni tj
of heat are rendered latent in melting 1 ,000 grams ic ii
or 79 for 1 gram. The Latent Heat of Water is 7 a
thermal units ; or, to change ice at 0° into water at n
as much heat is rendered latent as would warm the saii p
weight of water from 0° to 79°. The latent heat tU
water is much greater than that of most substance p
That of mercury is only 2.28; that of molten lead T).-^
Ice is thus an excellent cooling agent. ■ ^

-ftfe

SPECIFIC HEAT. 21

32. Specific Heat.

Experiment 13- — Take equal weights of iron and lead, about
1,00() grams ; cool them to 0° and immerse them in equal quan-
tities of water (500 c. c. ) at 50° C. After stirring for a moment
note the temperatures. That of the water in which the iron is
will be about 40° C. ; of that in which the lead is, about 47° C

The iron has taken more heat from the water than the
lead has, and yet its temperature has not been raised «o
high. Iron is harder to heat than an equal weight of
lead, i.e., requires more heat to raise its temperature, say,
one degree. Diflferent substances require different quan-
tities of heat to raise the temperature of equal weights
of til em one degree.

Definition. — The Specific Heat of a substance is the quantity
of h((it required to raise the temperatxire of unit weight (1 gram
or 1 Ih.J of the substance one degree (from 0° C. to 1° C.)

The specific heat of water is of course the thermal
unit. That of most other substances is much less. That
of l(;ad is only 0.031, of iron, 0.1137, and of copper,
0.095.

33. Evaporation and Ebullition.— Water in

the state of gas (water vapour) is constantly escaping
into the air from every exposed surface of water or ice ;
and, other things being equal, the hotter the water the
mor(! rapidly does it become changed to vapour. This
pro((5ss is called evaporation. Thus the air always con-
tains water-vapour. At any particular temj)erature a
pclHion of air is capable of containing only a certain
qt^iitity of water-vapour. When air contains as much
witer- vapor as it is capable of holding, it is saturated ;

EVAPORATION AND EBULLITION.

and if it be then cooled, some of the vapour is condensed ;
if it be heated, it becomes capable of containing more
vapour. The air coming from our lungs is warm and
saturated with water- vapour. When it comes in contact
with cold air in winter some of the vapour is condensed
and forms a " cloud." Dew, fogs, clouds, mists, (fee, are
explained similarly. Air is moist or dry according as it
is near to, or far away from, its point of saturation.
Thus, if moist air be heated it becomes dry, i.e., capable
of receiving more water- vapour. Evaporation is hastened
by heat, or by a current of dry air.

Experiment 14. — Heat some water in a glass flask until it
begins to boil, observing the temperature by a thermometer in
the water. The water begins to boil when the temperature rises
to 100° C. Observe the temperature of the steam. It is also
100°. Use a larger flame so as to make the water boil more
vigorously. The temperature does not rise. Now, close the
flask with a cork through which the thermometer passes. Heat
very carefully, and observe that the temperature rises above 100°
and yet the water scarcely boils. Remove the lamp when the
mercury has risen one or two degrees, otherwise the cork will be
driven out by the pressure of the steam. Take out the cork,
boil the water vigorously for a minute or two and while steam is
still coming out put in a cork firmly at the same time taking the
flask away from the lamp. Allow the water to cool a little, and
then pour cold water on the flask. The water in the flask begins
to boil.

Water in an open vessel boils at 100° C, and the tem-
perature cannot be raised above that, unless the vessel be
closed so as to increase the pressure on the surface of the
water. When the pressure on the surface is lowered, as
by condensing the steam — filling the closed flask in Ex-
periment 14, water boils at temperatures below 100° C.
The boiling 'point of water depends on the pressure on its

LATENT HEAT OF STEAM.

lurface, being higher the greater the pressure. On the
)p of a high mountain where the weight of air pressing
(n surfaces is less than it is lower down, water boils at
low a temperature that it can not cook.

Experiment 15- — Boil some alcohol in a flask, observing the

smperature of the boiUng liquid and of the vapour. If the

Icohol is pure, the temperature in each case is 78.4" C. Try

bie boiling point of ether, heating it by means of hot water.

Bther boils at 34,2°.

Every liquid boils at a particular temperature, just as
bvery solid fuses at a particular temperature.

BOILING

litrous oxide — 87.9

Carbon dioxide — 78.2

inimonia — 33.7

Sulphur dioxide — 10.5

Idehyde +19.8

ether 34.2

Jarbon Bisulphide .... 47.9

lethylic alcohol 55.1

Jhloroform 61 .0

Jromine 63.0

POINTS.

Ethyhc Alcohol 78.4

Benzene 80.4

Water 100.0

Acetic Acid 116.9

Naphthalene 216.8

Phosphorus 290.0

Mercury 350.0

Sulphur 440.0

Cadmium 860.0

Zinc 1040.0

34. Latent Heat of Steam. — From Experiment
[4 we learn that the heat which goes into boiling water
id changes it to steam does not cause any rise of tem-
)erature. This heat becomes latent, just as in the case
)f melting ice. The latent heat of steam is 536 thermal
mits ; i.e., to change any weight of water at 100° C. to
Jteam at the same temperature heat is required sufficient
raise the temperature of 536 times the weight of
ijrater one degree. The latent heat of steam is very
freat compared with that of other vapours. Water in
jvaporating from the earth's surface carries away a great

24 SOLUTION.

deal of heat. Wet clothes feel cold because of the heat
consumed by the evaporating water. Much heat is lost
to the body by thg evaporation of water through the
skin and lungs. The cooling effect of ether and other
rapidly evaporating liquids is explained in the same way.
Water can be frozen by rapidly evaporating ether. That
such an enormous amount of heat is required to evapo-
rate a liquid is accounted for by the great change of
volume. For example, I cubic inch of water forms 1,700
cubic inches of steam.

35. Solution.

Experiment 16. — Mix 100 grams finely-powdered saltpetre
with 100 grams distilled water in a beaker, stirring for some
time with a glass rod. Part of the saltpetre disappears ; the
water has now the taste of saltpetre, and is colder. Apply heat,
carefully stirring all the time. More of the saltpetre, and at
length all of it, disappears. Allow the liquid to cool ; some of
the saltpetre reappears in long crystals which grow as the liquid
cools. When quite cool, pour off some of the liquid into a small
porcelain basin, boil away some of the water, and allow the re-
maining liquid to cool again. More saltpetre crystallises out.
This process is called concentration. Hepeat this experiment,
using washing soda instead of saltpetre.

Experiment 17. — Carefully heat 300 grams saltpetre with
100 grams water. (Do not apply the flame to the beaker.)
Only part of the saltpetre disappears even when the water
begins to boil. Mix 10 grams of gypsum with 100 of water, and
heat to boiling. The gypsum does not disappear. Filter some
of the liquid into a porcelain basin and evaporate to dryness.
A small quantity of white substance, gypsum, is left. Repeat
this experiment, using clean white sand, and again with chalk.
In each case little or nothing remains when the water is evapo-
rated.

SOLUTION. 25

tltpetre and wasliing soda dissolve readily in water,
irting their taste and other jjroperties to the water.
They are soluble in water, and form solutions from wli?oh
they can be got again by evaporating the water.

Bxperiment 18- — Mix lO c c. hydrochloric acid with about
tour times as much water, pour it over three or four iron tacks
in ft porcelain basin, and warm gently. Bubbles rise from the
tacks, which gradually disappear, giving a greenish color to the
water. Evaporate the water. A solid remains, but it is not
iron ; it is ferrous chloride. Repeat the experiment, using
inarV)le instead of iron.

In Experiment 18 the process of solution is accom-
panied by chemical action. This kind may be called
ch§rnical solution. — Substances are generally more soluble
in hot than in cold water. — Gypsum is much less soluble
thiin saltpetre or washing soda. Sand and chalk are
vi^folable. A given quantity of water can dissolve only
a (Pertain maximum weight of each soluble substance at
a given temperature, forming in. each case a saturated
scmtion. For example, 100 grams of water will always
iiasolve 13^ grams of saltpetre at 0° C, and always 250
git-ms at 100° J. These weights may be taken to repre-
sent the solubility of saltpetre at the two temperatures.
(I^pr Table of Solabilitieii, see Appendix.) To make a
saturated solution of a substance at any temperature,
either stir it up with water at that temperature until no
m^e will dissolve (this requires much time and stirring),
of heat the water to a higher temperature, dissolve in it
as much as possible of the substance, cool, and decant or
filler. Water saturated with one substance will still
dissolve others. Solutions of solids in water are heavier

n pure water and boil at higher temperatures. Heat

26 SUPERSATURATED SOLUTIONS — FREEZING MIXTURES.

is rendered latent when solids dissolve in liquids, andl
reappeai*s when they become solids again (comparej
Art. 31).

Experiment 19. — Heat some sodic acetate in a flask withj
very little water until the salt is dissolved and steam issuesl
from the flask. Put a plug of cotton wool, or a cork, in thej
mouth of the flask, and let cool. The solution remains liquidl
Oi^en the flask and drop in a small grain of aodic acetate. CrysH
tals shoot out from the point where it falls, and soon the wholej
mass becomes solid. At the same time the flask becomes warm.!
(Why?) A solution of this sort is supersaturated. It containgl
more of the salt than can be dissolved at the lower temperature,!

Water dissolves a great many substances, solids, liquids,!
and gases. It is a good menstruum^ or solvent. Many
substances insoluble in water will dissolve in other!
liquids. Thus, mercury dissolves most of the metals
alcohol dissolves resins ; and ether dissolves fats ; all in!
soluble in water. No heat becomes latent when one liquid
dissolves another ; there is no change of state.* When a
liquid dissolves a gas the latent heat of the gas becomes
sensible, but becomes latent again when the gas resumes
its former state. This accounts for the coolness of effel'- 1
vescing drinks.

36. Freezing Mixtures.

Experiment 20. — Mix quickly and .loroughly 5 parts by
weight of snow with 2 parts of salt. Observe the intense cold.
Freeze some water in a test-tube. Note the melting of both
snow and salt. The temperature can be reduced in this way to |
—20° C. What becomes of the heat ? (See Art. 31 and Art. 35).
Salt water will not freeze until the temperature sinks much
below or 0.

' In some cases heat becomes sensible, as when alcohol and water ai'e mixed.

<<:

CRYSTALLISATION. 27

Another freezing mixture is IG parts water, 5 parts

si^tpetre, and 5 of sal-ammoniac.

'37. Crystallisation. — Crystals are beautiful geo-
metiic forms, e.g., cubes, pyramids, in which solids can bo
obtained. They may be produced in several ways, par-
ticularly by cooling or evaporating solutions, as in the
experiments with saltpetre (Art. 35). A substance is
known to be at least nearly pure, if it consists of distinct
and well-formed crystals. Tlus is the reason for the care
taken by manufacturers to prepare well-crystallised chemi-
cals in particular cases where adulterations are common.
Crystals are generally obtained by gradually cooling hot
saturated solutions, or by slowly evai)orating cold solu-
tions. The impurities remain dissolved in the mother-
Uquor. Substances are often purified by crystallisation.
Many substances combine with water as they crystallise.
Washing-soda crystals contain 63% of water of ci'ystallisa-
tion. The water is necessary to the form of the crystals.
It is chemically combined, and is solid. If it be driven
off by heat the crystals fall to powder. Many crystalline
Wibstances containing water of crystallisation lose this on
exposure to air, and become powdery. This phenomenon
ia called efflorescence. Other solid substances attract
moisture from the air and at last become liquid. This is
called deliquescence.

38. Infusion, &C. — Water and other solvents are
^ed to separate the soluble from the insoluble parts of

Medicinal plants, &c. Maceration, or cold infusion, is
CTirried on at the ordinary temperature of the atmos-
phere. The substance to be macerated is ground up, or

"in some other way intimately mixed with the solvent, is

28 INFUSION, ETC.

allowed to stand for some timo, and tlio liquid is then I
strained or filtered off. An in/usimi (hot infusion) is
made by pouring the boiling solvent on the substance,
and allowing it to cool gradually. Digestion (or simmer-
iny) is the process of making a solution with the solvent I
kept just below its boiling point. The differences in
these methods are mainly differences of temperature.
When it is required to extract a substance which is de-
composed at or below the boiling point of the solvent,
or a substance which is very volatile (easily evaporated),
the raetiiod of cold infusion or digestion is used. Tea
should be infused, or at most digested, and never boiled,
since boiling extracts a bitter and unwholesome principle,
which is not dissolved in so great quantity by infusion or
digestion. Tinctures are mostly macerations with alcohol
as the solvent. Percolation has now largely superseded
maceration in the preparation of tinctures. The sub-
stance is placed in a filter [percolator), and the solvent is
poured upon it and allowed to percolate (run through)
slowly. This method has the advantage of allowing a
fresh portion of the solvent to be poured on the partially
exhausted material ; so that the extraction can be com-
pleted more quickly and thoroughly. (Why 1) The same
principle is employed in filtrt\tion when it is wished to
wach away a soluble from an insoluble substance with as
little as possible of the solvent. Very little is poured on
at a time, and one portion is allowed to run through before
another is added.

39. Decomposition of Water.— In Experiment
1 heat was the kind of energy used to decompose a com-
pound. Very many chemical substances can be decom-
posed by heat, and under certain conditions water under

DECOMPOSITION OF WATER.

le action of her.t breaks u}) into two differbnt substances ;
hjit another kind of energy, electricity^ is more convenient
Ibr sliowing the compound nature of water. It must be
f^iiieuibered that electricity is no more a substance than
IjK'Ht is. It is classed along with light, heat, <kc., as a
ind of energy, power of doiwj work of some kind. One
nd of work for which electricity is specially suited is
separate compound into simpler substances. Chemical
jtion is generally accompanied by the development of
jat, and in the cfalvanic battery, a current of electricity
ikes the place of some of the heat which would be set
3e if the metal use . were allowed to dissolve ti?ely in
te acid of the battery. Good conductors of heat are
jnerally good conductors of electricity. Compounds
'liich will not conduct electricity, i. e., through which it
all not flow, are not decomposable by it. They may,
jowever, become conductors by mixing with other sub-
Itances, by melting, tfec, and then, they may be decom-
)osed. Water is a very bad conductor of electricity
rhen it is pure, but when slightly aciditied with sulphuric
icid it conducts well.

Experiment 21. — Fasten two pieces of platinum foil or wire

to the ends of the wires from a galvanic battery. Dip the foils

in a vessel of distilled water, keeping thetn about an inch apart.

\ nloss the battery is very powerful, there is no result. Add a

few drops of sulphur?'^ acid to the water. Bubbles of gas gather

jon the foil and rise. Collect the gases in two graduated tubes

filled with water and inverted over ttie pieces of platinum foil

\(('l('ctrodts). Observe that one tube fills faster than the oi her,

I and after some time the quantity in the one tube is seen to be

Mouble that in the other. Remove the tubes one at a time,

closing them with the thumb, and put a lighted match into each.

: Tlxe larger quantity of gases catches tire and burns, putting out

the match, but the smaller causes the match to burn more

COMPOSITION OF WATER.

brightly. With a very powerful battery a small portion of pure!
water could be completely decomposed into these two gasesj
differing in this and in other respects.

40. Composition of Water. — We thus provei

water to be a chemical compound of two gases, IlydrogenX
and Oxygen. These gases have never been further de-
composed and are therefore held to be elements. Water!
has been decomposed in a variety of ways, and always!
into these two gases ; further, the volumes of the gases!
have always been i'l the ratio of two of hydrogen and
one of oxygen. The next -ning to discover is the weights]
of oxygen and hydrogen which form a given weight of!
water. In Experiment 21 water is analysed — its com]
position by volume has been found by analysis, i.e., by I
decomposing it into elements. It will be seen later that!
the word analysis is used also in a broader sense. In
order to discover the composition by weight, the method
of building up, or synthesis, is used. A current of hydro!
gen gas (How dried? See Sulphuric Acid.) is allowed
to flow through a weighed tube containing black oxide
of copper (a v^ompound of oxygen and copper) heated to
redness. The hydrogen takes away oxygen from this
substance, forming water. This water is collected anuj
weighed, and the tube of cupric oxide is re-weighed.
The loss of weight in the latter case is the weight of I
oxygen consumed, and the difference between ^is and|
the weight of water collected gives the weight of hydro-
gen. (What law is assumed here*?) This experiment]
lias been made thousands of times and with the utmost
nicety, and always with the same result — for every 8 parts
by weight of oxygen taken away from the oxide of cojiper
9 parts of water are formed. Water is then composed

^ QUESTIONS AND EXERCISES. 31

of the two gaseous elements, hydrogen and oxygen,
uni(«^d in the proportion of 1 of hydrogen to 8 of oxygen.
(D<duce the relative weights of hydrogen and oxygen.)

QUESTIONS AND EXERCISES.

1. Is steam visible? .

2. It is observed that arctic animals are generally white. Of
what advantage is this to the animals ?

,S. Why does hot glass crack when a drop of water falls on it ?

4. (Jhange 10°, 32°, and — 40° Fahrenheit to centigrade.

45. At what temperature is the number on the Fahrenheit
swiale double that on the centigrade ? >

6. A Fahrenheit and a centigrade thermometer are placed side
Igr side in a vessel of water. The centigrade thermometer reads
80°. What does the Fahrenheit read ?

7. What is the latent heat of water if the Fahrenheit ther-
niometer is the standard ?

j: 8. Twenty grams of ice at 0° C. is melted with 1,000 grams
of water at 50°. What is the temperature afterwards ?

.• 9. W^hat weight of water at 100° C. is required to melt 10 lbs.
a| ice at 0° C. ?

?, 10. Why does snow fall powdery in very cold weather, and in
lirgt' Hakes in mild weather ?

I li. If 100 grains of steam at 100° be condensed in 1 lb. of water
at 0° C, what is then the temperature of the water ?

12. A piece of silver weighing 120 grams is heated in boiling
•flfater and then put into a vessel containing 500 grams of water
# 10° C. After stirring, the temperature of the water is found
%) be 11.2°. Calculate the specific heat of silver.

- IH. Why does stirring facilitate the solution of a substance ?

14. How much steam must be condensed to heat 10 kilograms
<J* water from 15" C. to 100° C. ?

32 DISCOVERY OF OXYGEN.

CHAPTER IV.

OXYGEN— COM BUSTION—CHEMISM— METALS AN H

NON-METALS.

41. Discovery of Oxygen. — Dr. Joseph Priesi
■ was the father of pneumatic chemistry, or the chem^istr.

of gases. He invented the pneu7natic trough and devisi
the method of collecting gases over liquids. Simple a;
this metliod seems to lis at this day, it required to 1>
invented. The pneumatic trough is a vessel provide
with a perforated shelf. The vessel is filled with wati
or other liquid until the shelf is covered ; jars or bottli
are filled with the liquid in the trough, inverted, and s*
upon the shelf. These jars or bottles can be filled with an
gas by allowing it to rise in bubbles through the liquid
which it displaces downward. In 1744 (August 1st)
Pri 3stly heated a compound of mercury known as rr
precipitate, or precipitate per se, and collected a colourles
gas which was driven off. (He called it an air, the nanv
gas not being used until later). He found that this ga
had the remarkable propert}'^ of causing a glowing coa
to burst into flame. For reasons to be presently explainei
it was afterwards called oxygen.

42. Preparation of Oxygen. — The most convon

lent way of preparing oxygen is by heating potam
chlorate mixed with a little black oxide of manganese.

Experimeni 22- — Grind about 10 grams of potassic chlorat
to powder in a mortar. Dry it by heating in a porcelain basin
taking care not to fuse it. It is best to stir constiintly with ;

PREPARATION AND PROPEKTIES OF OXYGEN. 33

glass rod while heating it. Dry in the same way about 1 gram
manganese dioxide. TTeat a small part of the potassic chlorate
in a small glass tube closed at one end, until the salt-like sub-
stance fuses (melts), and bubbles of gas rise through it. Insert
»Bmall glowing splinter, and observe its briglit flame. Mix the
remainder of the chlorate thoroughly with the manganese dioxide,
and put it in a larger hard-glass tube (test-tube size) provided
with a gas delivery tube leading from the test-tube and dipping
under the surface of water in the pneumatic trough. The tube
passes tightly through a cork in the mouth of the test-tube.
Arrange the test-tube, &c., conveniently, and heat at the bottom,
applying the heat gradually, but not removing the lamp when
once applied, unless the open end of the delivery tube is first
lifted out of the water. Otherwise, as the heated gas in the
retort (test-tube) cools, it will contract, and the cold water will
run back into the retort, breaking it. Collect the gas which
bul)bles off, until about as much as would fill the retort and
^eliv^ry tube is collected, then change the receiver (collecting
ssel), and fill 5 small bottles with the gas. (Why reject the
Jrst portion ?)

Oxygen can also be prepared by heating black oxide of

inganese or potassic bichromate, either alone or with

^11 of vitriol. The black oxide of manganese used in

Experiment 22 undergoes no change. It enables tlie

Oxygen to escape at a lower temperature. This is a case

if so-called contact-action. When oxygen is prepared

poni potassic chlorate it is generally contaminated by

le poisonous gas, chlorine, from which it should be

freed by bubbling it through water, in which chlorine

\b very soluble. It is very necessary to do this when

the oxygen is to be inhaled.

43. Properties of Oxygen.— Oxygen is an in-
risible gas, odourless, tasteless, and a little heavier than
^ir. Below — 130° C. it can be condensed to a liquid.
?here is a certain temperature for each gas, above which it
4

34 COMBUSTION IN OXYGEN.

cannot be condensed to a liquid by pressure, below wliicli
it can. This is the critical temperature, about — 130'^ (J,
for oxygen. Oxygen is a "supporter of combustion"—
many substances burn in it. It is necessary to anini;i]
and, generally, to vegetable life. It is obtained from tlic
air by animals when breathing, diffusing through tlic
thin walls of the lungs into the blood. In the air,
oxygen is diluted with four times its volume of anoi r
gas, nitrogen, so that its action is moderated. An at-
mosphere of pure oxygen would throw us into a state of
excitement and fever, and would cause a vast conflagra
tion over the surface of the earth. It was once oft(!ii
given as a stimulant. In cases of asphyxia and dyspnaa
it is valuable. The patient obtains tho necessary supply
of oxygen in a much smaller space, therefore with less
breathing. Oxygen is somewhat soluble in water, about
4 c. c. in 100 c. c. of pure water. When a glass vessel
filled with water is heated slowly, bubbles of gas collect
on the sides, and at length rise to the surface. These
have been collected and proved to be largely oxygen.
Fish ol>fcain their oxygen by diffusion from the water.
Hence, the necessity for a current of water, through the
mouth and out over the gills. When fish are drowned
they are in reality smothered. Water dissolves gases
according to a certain law. The quantity of any gas
which is dissolved by a given quantity of wafer is pro-
port: onal to the pressure and inversely as the temperature.
This law does not hold fo'* gases which unite chemically
with water, e.g., ammonia, carbon dioxide.

4t. Combustion in Oxygen. — When chemical
action is accompanied by light and much heat it is called
combustion. Flame also usually accompanies combus-

v*i,

ACIDS. " 35

tion. Ordinary combustion takes [)lace in an atmos-
phere which unites partially at least with tlie substance
burned. It is a supporter of the combustion. Oxygen
is tl'<j supporter of combustion in the case of wood and
coal fires, lamps, ka.

Experiment 23. — Fasten a small piece of charcoal to the end
of a copper wire ; heat the charcoal until it glows, and then
thrust it into a jar of oxygen. It glows more brightly and
bursts into flame. Pour a few drops of litmus solution into the jar,
dose it with the hand and shake it. The blue litmus turns red.

Litmus is colouring matter extracted from a lichen.
It turns red when acted on by sour substances (acids),
e.g., citric acid, hydrochloric acid, and vinegaj*. We can
conclude then that an acid is formed i.i this experiment.
it is called Carbonic Acid.

Experiment 24. — Set Are to a piece of sulphur in a small
^ng-handled iron cup, and then plunge it into a jar of oxygen.
The sulphur burns with a dazzling purplish light, and sutTocat-
ihg fumes are formed. Shake up with a little water, and note
iiie sourish taste. Add a few drops of litmus solution. It is
reddened. Sulphurous Acid has been formed.

Experiment 25. — Cut ofif a very small bit of phosphorus
under water, dry it carefully with blotting paper, put it in the
small cup used before {deflagrating spoon), hold it in a jar of
oxygen, and set fire to it with a hot wire. It burns with a
bright white light, and white fumes are formed. Shake up
with a little water, and note the sour taste. Test with litmus
§s before. Same result. Phosphoric Acid has been formed.

Certain substances burn in oxygen forming compounds

which give u, sour taste to water and turn blue litmus

jred. Oxygen is the add generator ; hence, its name,

from the Greek. To oxidise is to combine with oxygen,

as in the above three experiments. Oxides are com-

36 ^ .■-,*■;; V,' '■; BASKS. ,^.,/' -■ ■■■'■'■■'■'':■:'- ^y-'':

pounds of oxygen with other elements. Thus, in tho
above experiments, oxides of carbon, sulphur, and phos-
phorus are formed. The greater part of the earth's
crust is made up of oxides combined in various ways.
Oxygen forms compounds with all the elements except
Jluorine. To reduce an oxide is to deprive it of a part
or the whole of its oxygen, i.e., to lead it hack to the
original condition before oxidation.

Experiment 26, — Bum a small piece of the metal sodium in
a jar of oxygen containing a little water, using the deflagrating
spoon. It burns with a bright yellow flame forming white fumes
and a grey substance which remains in the spoon. Wash the
spoon in the water, and note the soapy feel and taste of the
water. Add some of the litmus turned red in Experiments 25
and 26. It is turned blue again. The same results can be
obtained by using the metal potos.smwi. . >r

The substances formed by burning these metals in :
oxygen in the presence of water have a character opposite \
to that of the acids. They are called bases. That formed |
from sodium is called caustic soda. Some other mc ;als I
form soluble bases, but most bases are insoluble and jan I
only be prepared indirectly from the metals.

Experiment 27. — Pour a few drops of litmus into a solution
of hydrochloric acid so as to produce a distinct red colour. ;
Then, add some solution of caustic soda, dropping it from a ;
pipette gradually, and stirring, until the red just begins to turn !
blue, i.e., becomes purplish. Observe that the solution now '
tastes neither sour nor soapy, but salt. Both acid and base have
disappeared ; the colour is neither blue nor red ; the solution is ;
neutral in its action on litmus. Evaporate it in a porcelain dish. ;
Crystals of common salt are obtained.

A similar result c\i\ be produced with sulphuric or T
nitric acid, and caustic potash. In eac'i case, by mixing i

TKMrEUATURK OF IGNITION. "S?

solutions of tlie acid and base in the right proportions a
point is reached whera the sohition turns litmus neitlier
blue nor red, both sour and soapy taste disappear, and a
|ttlt-like substance can be separated from the solution by
evaporation. Substances formed by the action of acids on
bases are called salts.

Experiment 28. — Make a bundle of thin strips of zinc foil,
idip the ends iu a little melted sulphur (Why?), set on fire and
plunge into a jar of oxygen. The zinc burns with a white light,
forming zinc oxide, or " philosopher's wool." Pour a little water
into the jar, and observe that the oxide does not dissolve. Add
A few drops of sulphuric acid ; the oxide dissolves ; evaporate in
a porcelain dish ; a salt, zinc sidphate, or white vitriol, remains.
Burn some fine iron wire in the same way.

The oxide of zinc is a base-foryiiing oxide, because it
acts on an acid to form a salt ; but it does not dissolve in
water forming a base, as the oxides of sodium and of
potassium do. But the corresponding base, known as
zinc hydroodde, can be prepared in another way. It is
insoluble in water, and does not turn red litmus blue, nor
feel soapy when rubbed between the fingers, as tlie char-
acteristic bases do. It is nevertheless called a base,
b(!cause it forms salts with acids. Iron and other metals
c;in be burned in oxygen. They all produce base-forming
oxides ; but it is to be noted that most bases have not the
8t rongly marked characteristics of ct.ustic soda. They are
mostly insoluble in water, and do not turn red litmus blue,
[but thei/ are all acted on by acids, and thereby form salts.

45. Temperature of Ignition.— It is necessary

[to heat combustible substances to a certain temperature

before they will catch fire. This is called the tempera-

Iture of ignition. It is very different for different sub-

3tl

SLOW COMBUSTION — CHEMISM.

stances. Thus, pliosphorus catches fire v\ air below
100° C, carbon bisulphide at 150^, sulphur at 400°,
while coal and wood begin to burn only at a red heat.

46. Slow Combustion. — Combustible substances
often combine slowly with oxygen at temperatures below
that of ignition. In such cases the more striking ap-
pearances of combustion are absent. Rusting of metals,
respiration, decay of animai and vegetable substances,
are processes of this kind, modified more or less by the
action of water. Heat is i)roduced in slow combustion.s
(as in the heating of grain, of damp hay, <fec.), but more
slowly than in ordinary combustions, so that it is con-
ducted away by surrounding objects and does not raise
the temperature so much. In some cases, however,
where the substance is finely divided, exposing a large
surface to the action of the air, oxidation goes on so
rapidly as to heat the mass up to the temperature of
ignition. Thus occur cases of spontaneous ignition and
combustion. Rags soaked with oil, and coal containing
much sulphur, have been known to catch fire in this way.

47. Chemisni. — That which causes oxygen to unite
with carbon, sulphur, &c., is called chemical ajffi7iity,
chemical attractio?i, or chemism. Oxygen may be com-
pressed with a pressure of several tons to the square
inch without liquefying it, and yet, when it combines
with iron it becomes solid. Chemical attraction must be
very powerful between oxygen and iron. Between some
of the elements the attraction seems to be very slight or
even wanting. Thus, oxygen forms no compound with
fluorine, and cannot be got to unite directly with
chlorine, bromine, iodine, or gold. As a rule elements

TIIK ELKMKNTS.

hich are unlike have the greate^i attraction for each
Other • for example, the metals and the non-metals.

48. Metals and Non- Metals. — All the suh-

atances described as burning in oxygen to form oxides
ai-e elements ; observe that some of them, as sulphur,
carbon and phosphorus, produce acid-forming oxides,
wliile othei-s, sodium, potassium, zinc, iron, produce base-
forming oxides. Elements which have base-forming
ou'ides are called metals ; those whose characteristic oxides
are acid-furming are called non-metals. Of the 07 elements
at present known,* 52 are metals and 15 non-metals ; but
some of the elements have the characters of both metals and
Di^n-metals, so that it is difficult to decide to which class
tlu^y belong. Thus, antimony is classed by some chemists
among the metals, by others with the non-metals.

TABLE OF THE ELEMENTS,
(Non-metals in heavy type, imperfect metals in italics.)

English
Names.

Latin Names.

tarbon ■ ■ ■ .
sriiim

ilorine ••

irominm. ,

Carbo

Cerium

Ciilorinum
Chromium.

obalt ICobaltum .

Aluminium. .. Aluminium..

bitinwny.. . . Stil)ium

[rsenic i Arsenicum ....

irium IJarium

Bryllium , , . .! Beryllium

Isiimth :Bismuthum . .

lor on iBorium

jromine — iBromum ....

|a<lniiiun iCadminm . . ,

Baeaium jCaesium

Balfium Calcium , . . .

Symbols.

Atomic
Weiffhts.

Al'v

27.3

Sb "i ▼

122.

A.= iii V

75 (74.9)

Ba'i

136.8

Beii

Bi iii V

210,

BiiJ

11,

Br!v

80 (79.75)

Co»

111.6

Csi

^32.56

Caii

40,

CiT

12 (11.97)

Ceiii

141.2

CI i iii T

35.37

Cr ii iv vi

52.4

Co •' iv

58.6

t Specific
Weijfhts,

2.6

6.71

5.73

3.75

2.07

9.8

2.5

3.19

8.6

1.88

6.7
2.45
6.5
8,5

Remarks,

Solid.

Gas.
Liquid,
Solid,
" (melts
at 32")

Gas.
Solid.

"*New elements are discovered fr(jm time to time,

t For the specific weights of solids and liquids water at 4° C. is the standard ;
i)r those of gases, air.

THE ELEMENTS.

TABLE OF THE ELEMKNTS-

-Continued.

English
Names.

Latin Names.

Symbols.

Atomic
Weights.

Specific
Weights.

Remark H.

Copper

Diayniium

Cunrum

Didymium. . . .

Cuii

63.

8.88

Solid.

Di iii

142.3

6.54

t'.

Erbium

Fluorum

Eriii
Fi

170.5
19.1

Gas prolVly
Solid (meltj

Fluorine . .

1.31

Gallium

GiT

69.80

5.95

at 30 s

Gold

Aurum

Ilydrogenum .

Au 1 ill

196.5
1.

19.32
0.0692

Gas.

Hydrogen ..

Indium

In iv

113.6

7.42

Solid.

Iodine

lodum

Ii iii T

126.5

4.948

Iridium

Ir ii iv vi

193.

22.42

Iron

Ferruni

Lanthanum...

Fe ii iv
Lain

56.
139.

7.86
6.1

Lanthanum. . .

Lead

Plumbum

Lithium

Pb ii iv
Li'

206.4

11.35
0.59

Lithium

Magnesium. ..

Magnesium . . .

Mgii

24.

1.74

<•

Manganese. ..

Manganesium.

Mn ii iv vi

54.8

8.03

Mercury

Hydrargyrum

Hgii

200 (199.8)

13.596

Liquid. ;

Molybdenum. .

Molybdenum .

Moii iv iv

96.

8.6

Solid.

Nickel

Niccolum ....

Ni ii iv

58.6

8.9

((

Niobium

Nbv

94.

7.06

Nitrogen.. ..

Nitrogenum . .

N iii ▼

14 (14.01)

0.971

Gas.

Osmium

Os ii iv vi

199.

22.48

Solid.

Oxygon

Oxygenum

Oii

16 (15.96)

1.105

Gas.

Palladium ....

Palladium. . . .

Pdii iv

106.2

11.4

Solid.

Phosphorus .

Phosphorus. . .

P iii V

31.

1.83-2.2

Platinum

Pt ii iv

196.7

21.5

Potassium.. ..

Kalium

39.

0.87

Rhodium

Rh ii IV vi

104.1

12.1

Rubidium ....

Rubidium.. ..

Rbi

85.47

1.52

Ruthenium. ..

Ruthenium ..

Ruii iv vi

103.5

12.26

Samarium. . . .

Samarium. .. .

Scandium

Selenium

Se '1 'V v-

150,
44.

79.

Scandium ....

Selenium.. ••

4.5

Silicon

Siliciiim

Si'v

28.

2.39

Silver

Argentum, . ..

Agi

107.06

10.47

Sodium

Natrium

NaJ

23.

0.978

Strontium

Srii

87.2

2.54

Suiphur

Sulphuium. ..

S ii iv Ti

32.

2.03

• <

Tantdluvi ....

Tantalum

Tav

182.

10.4

Tellurium ..

Tellurium . . , .

Te ii iv vi

125.?

6.4

Terbium

Thallium

Tb
Tl i iii

Thallium

203.6

11.85

Thorium

Th i»

231.5

11.

Tin

Stannum

Titanium

Wolframum ..

Sn ii iv
Ti li iv

WiTTi

117.S
48.
184.

7.29

If
It
<t

Titanium ....

Tungsten

19.12

Uranium

UlTYi

239.8

18.7

Vanadium

Vanadium ....

V ill V

51.5

5.5

Yttriujn

Yttrium

Zincum

Zirconium

Yiu
Znii
Zri»

89.5

05.

90.

Zino

7.
4.15

'«

Zirconium

CONSEUVATiON OF MATTKU.

CHAPTER V.

LAWS OF COMBINATION— ATOMIC THEORY.

49. Conservation of Matter. — In order to in-

tigate fully the chemical actions described in connec-
;on with oxygen it is necessary to weigh and measure
tile substances. This has been done with the greatest
accm-acy, and the experiments have been repeated in a
vui ioty of ways with materials from difierent sources.
TIki results which have been obtained are always the
8Rme for the same chemical action. Thus, 8 grams of
OS \ gen and 1 gram of hydrogen are always obtained by
tlic decomposition of 9 grams of water; 8 grams of
ygtn an . 100 grams of mercury, by the decomposition
108 grams of red oxide of mercury; and 8 grams of
ygen and 40.8 grams of potassic chloride from 48.8
ivms of j)otassic chlorate. We see that in chemical
[ecompositions the s^un of the weights of the products of
composition is always equal to the wei<jht of the substance
^pcomposed. Again, 8 grams of oxygen burn 3 grams
charcoal to form 1 1 gramj of carbon dioxide ; 8 grams
oxygen burn 8 grams cf sulphur to form 16 grams of
Iphur dioxide; 8 grams of oxygen burn 6.2 grams of
hosphorus to form 14.2 grams of phosphorus pent-
xide; 8 grams of oxygen burn 39. 1 grams of potassium
form 47. 1 grams of potassic oxide ; 8 grams of oxygen
t>urn 23 grams of sodium to form 31 grams of sodic
fxide ; 8 grams of oxygen burn 32.5 grams of zinc to
vm 40.5 grams of zinc oxide. From this statement it

42 DEFINITK PROPORTIONS — KQUIVALENTS.

is seen that in chomical combinations, also, the sum o?"
the weights of tlie substances combining is always equa The
to the weight of the substance formed. It may thus 1. in
stated generally that in chemical actions no matter i app
lost — put out of existence ; nor is there any gain <■ poii
matter. The weights of the elements entering into of \
chemical action remain the same at the end of tli wei)
action ; but the elements become differently arrang(;(i oxic
This law, founded on experiments, is the Law of the Cor B p<
servatlon of Matter. It is the fundamental law of tli den>
Science of Chemistry. pou^

50. Definite Proportions— Another law can l ^jj^

deduced from the facts stated in Art. 49. It is fouiic^^i.,
that water is always composed of hydrogen and oxyj
gen in the proportion of 1 to 8, that mercuric oxiilJ
is always composed of oxygen and mercury in the pro
portion of 8 to 100, and so with the others. Stated iri
general terms this is the Law of Dejinlte Proportions\
Each chemical compound is always composed of the sam^
elements and these are always in the same proportion in
this compound. In this respect chemical compounds diffei Bf ^
from mixtures, which may be made in any proportions^^"

51. Combining Weights -Equivalents. -ThfHy

weight ' '"vgen which combines with 1 part by weigha
of h''' - to form water is called the combining weiyhi

o ^L).. 17ie weight of any element which comhim?

Wvv.^ I 2)art of hydrogen is its combining weight; but, ;U|^e
many of the elements do not form compounds wittHrD
hydrogen, their combining weights must be ascertained]
as it were, at second hand. Thus, the weight of zina
which combines with 8 parts by weight of oxygen (itJ

MULTIPLE PROPORTIONS. 43

coni'iniiijL,' woij^ht) is the combining wciglit of zinc.
The expression eq^uvalent, or equivalent weight, is used
in Icxactly the same sense as comhining weight when
applied to the elements ; but it is also applied to com-
poui^'l^- Thus, the equivalent of water is the quantity
of water which will produce, when decomposed, 1 part by
weight of hydrogen, i e., 9. Again the equivalent of zinc
oxide is 40.5, since this weight of zinc oxide contains
8 parts (an equivalent) of oxygen. The equivalent of an
elem*'nt or a compound is the weight oj the element or cotn-
pound equal in value in chemical action to 1 part bi/
wieigJit of hydrogen. (Calculate the equivalents of all
the substances mentioned in Art. 40.) Hydrogen is
here, as in most cases, taken as the standard element.

2. Multiple Pre portions. — When charcoal (car-
boll) burns in a free supply of oxygon, 8 parts of oxygen
unite with 3 of carbon to form carbon dioxide ; but if
supply be scant, as in the centre of a fire, only 4
of oxygen unite with 3 of carbon, and carbon mon-
'e is formed. Thus, carbon combines with oxygen in
))roportions, and these are as 8 to 4, or as 2 to 1.
en phosphorus burns in oxygen it also forms two
coHpoiinds, the pentoxide when the oxygen is plentiiul,
anp the trioxide when it is scant. In the pentoxide 6.2
of phosphorus (Why use this particular number'?)
combined with 8 of oxygen; in the trioxide this
lit of phosphorus is combined with 4.8 of oxygen,
quantities of oxygen are as 5 to 3. Sulphur also
s two compounds with oxygen, the relative quanti-
of which are as 2 to 3. Many other exanq^les could
iven of an element combining with another in two
ore proportions ; and it is noticed that in every such

44 THE ATOMIC THKORY.

■

case these proportions have a siriiplc Mrithtuetical relati"

to each otlier, as in the above cases. This is stated ^

• t

the Lavb of Multiple Proportions : If tioo elements fur

several compounds with each other, then the divert

quantities oj the, first which combine with a fixed quanli!

of the second bear a sirnph ratio to each other, as 1 k

2 to 3, 3 to 5, (See. (Apply this law to the exani|ii

given.) I

53. The Atomic Theory.— To explain these r i
markable facts Dalton ( 1804 modified the atomic tlieo'
iw , ancient Greeks. According to this theory^
its modern form the elements are made up of indivisillfKi
extremely minute })articles — atoms. (What is a theory
The atoms of the same element are exactly alike,
those of different elements differ in weight, &c.
atoms of different elements unite to form molecu/cs
compounds, and this union always takes place 1 it
with 1 atom, 1 atom with 2, 2 wiJi 3, &c. For
ample, when zinc burns in oxygen, 1 atom of zinc coi
bines with 1 atom of oxygen, 1,000 atoms of zinc wi;
1.000 of oxygen and so on, until the whole of the ziiics
burned, when, of course, the oxide which is formed co2
tains equal numbers of atoms of zinc and of oxygen,
follows from this that if the ratio of the weights of tl
atoms of zinc and oxygen are as 65 to 16, the ratio!
the whole quantities combining must be in this prdiK
tion. As a matter of fact, zinc oxide is always coij
posed of the two elements isi this ratio. In this \vi
the atomic theoiy explains tl o lav) of definite propi
tions. The explanation o^ the law of multiple prop^
tions is equally simple. For example, sul}>hur uiiit|; '
with oxygen in two proportions. According to tf

AVOGADROS LAW.

lie theory the auvlition of oxygen to sulphur takes
place always by atoms, never parts of an atom ; in the
two 'ompounds different numbers of atoms of oxygen
unite with an atom of sulphur, in one case 2, and in the
oth<i 3. From this it follows that the weights of oxyi^en
unit i IK' with the atomic weight of sulphur are rc.^ec-
)ly twice and three times the atomic weigl.^t of oxygen.

f4. Avogadro's Law. — If equal volumes of hydro-

oxyj^.'n, marsh gas, and other gases generally are put

raduated tubes over mercury and heated equally, they

observed to expand equally, viz. : ^y^ of their volume

Y C. for every degree rise in temperature. Also, if the

le i!\crease of pressure be put on each gf;s, the volumes
diminished equally. These facts point to some close

lilarity in equal volumes of gases. The hypothesis

forward by Avogadro in 1811 is that equal volumes

\all gases under the same conditions of temperature

p7-cssure contain the same number of particles (mole-

s). This can also be deduced mathematically from

t^ molecular theory of gases.

>r). Combination by Volumes. — When water

decomposed by electricity (Art. 39) two volumes of

Idrogen are set free for one of oxygen. If the gases be

c(m1 and caused to unite again, water is formed, and

le of either gas is left over. It has been found that

|all cases where gases combine with each other, the

lines combining have a simple ratio to each other, as

2,2to3,<&c. . .-- : _ .--_ -

>(). Molecules and Atoms. — Two litres of hydro-
unite with one litre of oxygen to form water. If
union takes place at, say 200'' C, the water is in

46 MOLECULES AND ATOMS.

the gaseous state. It is then found that the vohinieiC di
steam formed is the same as the vohime of hydrogci
used, and according to Avogadro's law contains tl
same number of particles (Dalton's atoms). Let
suppose that the two litres of hydrogen contain t\fl v<
millions of particles ; then one litre of oxygen contaii* it
one million particles, and two millions particles of steawii]
are farmed. Each particle of steam contains oxygen, sf if
that the oxygen must be divided into two millions ilBa
parts when combination takes place. Therefore, tig of
particles of oxygen must be divisible. They are nttre
atoms, but 2)airs of atoms, which cannot be separat*^
excei)t by chemical action. They are called moleculm^
(little masses). The molecules of elements consist (wiiBB't
few exceptions) of two like atoms ; and those of cow'h
pounds, of two or more unlike atoms. The molecules ^^
substances are imagined as in constant motion of souftw'^
sort, the motion being different in solids, liquids, anP'J^
gases. In solids the motion is mostly vibration, tlfc?*
molecules moving about particular points ; in liquldME
there is a comparatively slow motion from place to place!
and in gases this motion from place to place goes Mpi
with great velocity, the molecules moving faster as m
gases become hotter. It is the battering of the moll
cules of an enclosed gas against the walls of the enck
ing vessel which produces pressure.

Deflnitions. — A molecule is the smallest portion of any m
stance which can exist by itself. Imagine a drop of water divida
and subdivided. A point is at last reached when no furtlwji
division is possible by mechanical means ; and if the division J|ie
forced by electricity or heat, it is no longer portions of wat«
which are obtained, but two different substances — oxygen aiij
hydrogen. At this point we have reached the molecule

MOLECULAR WEIGHTS OF GASES. 47

vn^^r. All atom is the smallest portion of an element tvhich can
exMt ill a molecule. The atom cannot be divided even by cliemi-
cal action ; it must enter into combination aa a whole.

7. Molecular Weights of Gases. — Since equal

niies of gases contain the same number of molecules,
it ft)llows that the weights of equal volumes of gases are
in proportion to the weights of single molecules. TJ us,
if a certain volume of hydrogen weighs 2 grams, if the
same volume of oxygen weighs 32, of nitrogen 28, and
o^arbon dioxide 44, these numbers may be taken to
esent the weif^l '^'^ of the molecules, or the molecular
his of the gases. In the case of the elementary
IS half the molecular weight gives the weight of the
, or the atomic weight (why halj ?). In estimating
specific weights of gases, the weights of equal volumes
compared, one gas being taken as standard, and its
ght taken as 1. Hydrogen is now usually taken as
standard gas, and it can readily be shown that the
ijic weight of a (/as is half its molecular weight.
(Miplain this. )

8. Chemical Notation— Atomic Weights. —

leal symbols are letters used to denote the atomic
hts of the elements. They are the initial letters of
tS| Latin names. Where two or more names begin with
til same letter, a second is added to distinguish. For
e:^nple H denotes 1 part by weight of hydrogen ; O, 1 6
by weight of oxygen ; C, 1 2 parts by weight of
n ; CI, 35.37 parts by weight of chlorine, &c. These
bers are obtained by experiments, by weighing and
uring. For example, it has been found that a litre
ygen weighs 16 times as much as a litre of hydrogen,
which it is concluded that a molecule of oxygen

48 CHKMICAL NOTATION.

weighs U> times as mucli as a molecule of liydrogen (An|
54), and that the atom of oxygen must also weigh IG tiiiid
as much as the atom of hydrogen i why 1). If, then, the!
atom of hydrogen be assumed to weigh I (1 what?), tJiJ
atom of oxygen will weigh 16. Again, 16 parts ofl
oxygen combine with 65 of zinc, and there is evidenal
that in this combination one atom of oxygen unites witlj
one of zinc. Hence it is concluded that the atomic weigli|
of zinc is 65. By similar methods the atomic weights o|
all the elements have been determined. There is a metlio
of determining the atomic weights which depends oi|
measuring the specific heats of the elements. It was dm
covered V>y Dulong and Petit that, if the atomic wel'jht J
each element is multijdied hy its sjiecijic heat, the iwodm
is always the same number {inearly), that is, 6.6. Froi
which it follows that 6.6 divided by the specific he
of any element gives its atomic weight. This number
called the specific heat of the elements, and Dulong an
Petit's law may be stated thus : The specific heat of l/|
elements is a constant quantity.

The symbols of the atoms are combined into formim
representing molecules. Thus (Art. 56), since the moll
cule of water contains 2 atoms of hydrogen and 1
oxygen, its formula is HjO. This formula is used
express the following : —

1. Water is a compound of the two elements, hydrogen a
oxygen, in the proportion by weight of 2 to 16. This is e^t
lished by experiment.

2. The molecule of water is made up of 3 atoms, viz. : 2 of 1
drogen and 1 of oxygen. This is deduced from the atoii
theory, which is now strongly supported by experimental t
dence.

CHEMICAL EQUATIONS. 49

Similarly, the molecule of oxide of sodium is repre-
sented by NajO ; of oxide of zinc, by ZnO ; of sulphuric
acid, by H0SO4, and so on. In these formulas the small
figure below the line multiplies the symbol immediately
before it. Thus, the molecule of sulphuric acid contains
2 atoms of hydrogen, 1 atom of sulphur, and 4 atoms of
oxygen. Very often the formulas are used loosely for
the names of compounds, but it must be always remem-
bered that they mean more than this. For example,
11.2^ means J.8 parts by weight of water, and not simply
ij^ter, or any quantity of water. The formulas of sub-
stances are used to express their molecular weights, and,
^ven the formula of a compound, its molecular weight is
found by adding together the weights of all the atoms in
the molecule. For example, the molecular weight of
sulphuric acid is (2 x 1) + 32 + (4 x 16) = 98. To
represent 2, 3, &c., molecules the number is prefixed to
tie formulas thus, 2ZnO, 3H2O, 4H2SO4, &c. Or, a
formula may be multiplied thus, (H20)3, (]S'aC])5.

rO. Chemical Equations. — These are short-hand

repi (!sentations of the quantities of the substances taking

Hprt in chemical actions. Before they can be written,

^eiiiical actions must be studied by weighing and

moiisuring. For example, the decomposition of water

electricity is represented as follows : — 2H2O = 2H2

Og,* a short-hand method of stating that 36 parts by

fit might be written tiiore aimply H^ O = H^ -\- 0, but since, accordiniar to

>ry, tiie molecule is the smallest portion capable of existing free, it is by

Sy considered advisable not to represent single atoms in equations. How-

\r, where weights alone are bein^ considered, this adherence to theory is

necessary and often cumbrous ; and, except when considering the volumes

iscs, 1 shall always write the equations in the simplest form.

CHEMICAL CALCULATIONS.

weight (or 2 molecules) of water decompose into 4 pait>
by weight (2 molecules) of hydrogen, and 32 parts by
weight (1 molecule) of oxygen.

(1) The equation should represent all the substances
taking part in the action, in the proportions in which thev
act on each other or are produced in the action. (2) Tin
sum of the weights on the left side of the sign (=) shoulii
be equal to the sum of those on the right. (3) The nuin
ber of atoms of each element represented on the left
should be the same as that on the right.

The decomposition of potassic chlorate into oxygen
and potassic chloride is represented by the folio wiiifff||
equation :—2KC103 = 3O2 + 2KC1. That is 2 x 12
gv3i.ms o^ potassic chlorate decomposes into 3 x 22 gramsl
of oxygen and 2 x 74.6 grams of potassic chloride. (Isj
it necessary then to use 245.2 grams of potassic chlorate!
in preparing oxygen V)

60. Ohemical Calculations— From a chemical!

equation we can calculate readily the proportions of tlie!
substances represented in the equation ; and equationsl
are useful as permanent records of chemical actions, tol
which we can refer when we wish to know in what prol
portions to use chemical substances in any reactionl
Thus, suppose it is desired to prepare 100 grams o|
phosphorus pentoxide by burning phosphorus in air]
The equation representing this action has been niada
out as follows : ~2P + 50 = P2O5. Referring to tli(
table, p. 40, we see that P represents 31 parts bj
weight of phosphorus. Also, P2O5 represents 62 + m
= 142 parts by weight of phosphorus pentoxide; aTil
62 grams of phosphorus burn to form 142 grams

VOLUMES OF GASES.

phosplionis peutoxide ; and 142 : 100 : : 02 : 43.62,
or 43.62 grams of phosphorus burn to form 100 grams
of j)entoxide.

Gases are usually measured instead of weighed. But,
since equal volumes of all gases (at the same temperature
and pressure) contain the same number of molecules,
weights of gases in the ratio of the molecular weights
are the weights of equal volumes of the gases. The
molecular weights of hydrogen and of oxygen are 2 and
%'l respectively; therefore, 2 grams of hydrogen will
Oieasure the same as 32 grams of oxygen ; and so for other
gases. The measurement has been made with the greatest
care many times, and it is found that 2 grams of hydro-
gen gJis measure (at 0° C. and 760 millimetres of mercury
pd'essure) 22.33 litres. The molecular weight in grama,
QSr gram-molecule, of any gas measures, at 0° G. and
760 mm., 22.33 litres.

Oab.

Hydrogen

t^ygen
itrogen

4tniinonia

tkrl)()n Dioxide
arsh Gas

' &c.

Formula.

NHg

CO 2

Molecular
Weight.

2
32

28
17
44
16
&c.

Volume of

Gratii-
Moleoule.

22.33

litres.

HpCalculate the volume of oxygen formed by heating 50
^a HI s potassic chlorate. The equation is :

2KCIO3 = 2KC1 + 30,

246.2 grams. 149.2 grams. .3 X 22.33 litres.

OZONE.

That is, 245.2 grams potassic chlorate givo 66.99 litres
of oxygen. Therefore, 50 grams give iff?.^ x 66.99 =
13.66 litres.

In making such a calculation we simply assume that
what is true for the molecules as represented in the
equation, is true for weights which are taken propor-
tionately to the weights of the molecules.

How much sulphur can be burned by 10 litres of
oxygen measured at 0° C. and 760 mm. pressure? The
equation is :

8 + 0^ =

32 grams— 22.33 litres.

SO,

That is, 32 grams of sulphur use up 22.33 litres of oxy-
gen. Then, 22.33 : 10 : : 32 : 14.33 ; i. e., 14.33 grams
of sulphur use up 10 litres of oxygen. What volume of]
sulphur dioxide is formed in this action ? On looking at
the equation we see that a molecule of sulphur dioxide is
formed from a molecule of oxygen ; therefore, the volume
of sulphur dioxide is the same as that of oxygen, viz., 10
litres.

61. Ozone. — This is a peculiar modification of oxy-
gen produced chiefly by the action of electricity. It is a
gas of a penetrating odour. It is one and a half times
as heavy as oxygen,,and its molecule must therefore con-
tain three atoms (O3), if that of oxygen contains two (0,).
Ozone has very powerful oxidizing properties, destroy-
ing paper, india-rubber, tfec, by rapid oxidation. It is I
slightly soluble in water, more so in turpentine. It is I
iioid to be a valuable means of disinfecting and deodoriz-
ing the atmosphere, and is supposed to exercise a bene-j

OZONE.

licial influence on the animal body. Of late, however,
some investigators associate the prevalence of certain
diseases of the respiratory passages with an excessive
(juiintity of ozone in the air.

Ozone is produced by the passage of electricity through
air (or oxygen) — for example, by flashes of lightning. It
is more abundant in pure than in impure air ; in the air of
the country than in that of the towns ; and in the higher
than in the lower strata of the atmosphere. Its quantity
is said to be smaller where cholera and other epidemics
are prevalent. Ozone is also produced in small quantity
during the electrolysis of water, and during the slow
oxidation of phosphorus in moist air. It is also formed
about an electrical machine when in motion. — If a strip
of filter paper soaked in starch and solution of potassic
iodide be brought into an atmosphere containing ozone,
the paper turns blue. Iodine is set free by the ozone, and
■unites with the starch forming the blue iodide of starch. —
When an element occurs in different modifications, these
Lare called allotropic modifications. Ozone is an allotropic
\form of oxygen.

QUESTIONS AND EXERCISES.

1. What percentages of sulphur and oxygen are there in sul-
Iphur dioxide (SO2), and in sulphur trioxide (SO3) ?

2. What are the molecular weights of the following : Chlorine,

I carbon monoxide (CO), ethylene C2H4), nitric acid (HNO3), and
cane sugar (CigHaaOu)?

3. What weight of mercuric oxide is required to give 20 litres
i of oxygen measured at 0° C. and 760 millimetres pressure ?
[K(iuation : HgO = 2Hg + O2.

54 QUESTIONS AND EXERCISES.

4. Calculate the weights of 1 litre of the following gasts
measiiretl at 0° C. and 760 millinietres of pressure : Oxygen,
nitrogen, carbon dioxide (COo), ammonia (NHg), acetylene
(CjHa), and sulphur dioxide (SO .^).

5. What volume (at standard temperature and pressure) will
60 grams of oxygen occupy ?

6. What weight of carbon dioxide will fill a vessel of 15 litres
capacity?

7. Point out the errors in the following eq^uation : — 2FeS04 =
Fe,0, +SO3.

8. The products of the combustion of a candle are collected,
and are found to weigh more than the weight of candle burned.
Is this contrary to the law of conservation of matter ? Explain.

9. In what respects does a chemical compound of iron and
sulphur differ from i , mixture of these two substances ?

10. 100 grams of oxygen combine with 39.*^. 75 grams of cop-
per. What is the equivalent of copper V

11. Iron forms two basic oxides. The percentage composition
of one is, — iron, 77.78% ; oxygen, 2'2.22y^ ; and of the other,—
iron, 70% ; oxygen, 30%. Apply the law of multiple proportions.

12. A litre of nitrogen unites with 3 litres of hydrogen. The
molecule of the compound formed contains 1 atom of nitrogen
and 3 of hydrogen. What is the change of volume when com-
bination takes place ?

13. What is the composition of the substances represented by
the following formulas :— NH3, H3PO4, S0^(0H)2, Fe^Ol,,,
CO(NH.2)2, and K4Fe(CN)6 ? How many atoms in the mole-
cules represented as follows :—Cili^(Oil)^, (NH.i)^f',0^, FeSO^.-
7H2O, and Fe.^(OH)e?

14. What weights of the following gases measure, at Stand^ftrd
temperature and pressure, 22.33 litres, viz. : — carbon monoxiib
(CO) ; ethylene (G^W^) ; hyilric sulphide {H ^S) ; phosphine (PH3),
and methylamine (CH^.N!!.^) ?

HYDROGEN.

CHAPTER VI.

HYDROGEN.

' ' ' ' ■ ■ ^ '

62. Hydrogen. — It was noticed by very early inves-
itif^ators that when metals dissolve in acids, an inflammable

gas is given off", but the properties of this gas (injlammable
\air) were not fully investigated till the advance of
pneumatic chemistry in the hands of Priestly and Caven-
dish towards the end of last century (1766 to 1781).
Cavendish showed that when it burns in air it forms
water; hence its name, which means, water-generator.
Hydrogen is found uncombined only in small quan-
tities, in volcanic gases, in the gas which occurs with
petroleum, and in meteoric iron. In combination, how-
ever, it occurs in vast quantities, forming ^th by weight
of water, |th of marsh gas, and a considerable part of
Bugar, wood, starch, and animal and vegetable substances
generally.

63. Preparation of Hydrogen.— Hydrogen can

[be prepared :

1. By the electrolysis of water :
H2O = H2 + O.

2. By the action of various acids on certain of the
[metals, particularly sulphuric acid (diluted) on zinc :

Zinc. Sulphuric Acid. Zinc Sulphate. Hydrogen.

Zn + K,80, = ZnSOi + H2 r:

65 98 IGl 2

HYDROGEN.

Hydrochloric acid may also be used :

Zinc. Hydrochloric Acid. Zinc Chloride.

Zn + 2HC1 = ZnCl, +
66 73 1 36

and iron may be used as the metal :

Iron. Hydrochloric Acid. Ferrous Chloride.

Fe + 2HC1 = Fed, + H2
66 73 127 ' 2

(If the weights of metals represented in these equations
be taken in grams, what volumes of hydrogen will be i)ro- 1
duced ?)

. 3. By decomposing water by metals. Sodium and
potassium decompose water at ordinary, and even at very I
low, temperatures ; magnesium begins to decompose it
only at 100°C.; und iron, copper, and silver, only at a red]
heat. > - ,

iSxperiment 28.— Put some small pieces of zinc in a tiiisk
provided with a gas delivery tube, and pour over the zinc some
sulphuric acid previously diluted with about five times its
volume of water and cooled. Collect the gas which comes off,
at first in an inverted test-tubo filled with water, and test it
from time to time with a match until it no longer explodes, but
burns quietly (Why does it explode ?) Then collect the gas in
jars for further experiments. When the gas ceases to come
off pour the liquid in the flask into a porcelain basin and set
it to evaporate. Crystallised zinc sulphate, or white vitrloll
(ZnSO^.THaO), is obtained. Repeat this experiment using iron
(in the form of tacks) instead of zinc. Hydrogen is obtained as
before, and on evaporating the liquid crystallised ferrous sul-
phate, or <j7'eeti vitriol (FeSO^.THjO), is left. (How do these
cases of solution differ from that of common salt in water ?)

HYDROGEN.

Oil consulting the equations representing these actions,
It is seen that one atom of zinc sets free a molecule of
lydrogen. In other words an atomic of zinc or of iron

f'niiivalent to two atoms of hydrogen. (What are the
\oinhinin(j weights of zinc and iron 1)

Experiment 29.— T)i8Sf>lve scraps of zinc, iron, and tin, in
Iniill ((uautities of hydrochloric acid (dihited with four times its
Wlk of water), in test tubes ; and observe that an inflammable
jas l>u])bles oflF. Evaporate the remaining liquids and examine
It' salts obtained (zinc chhride, ZnCla, ferrous chloride, B>Clj,
Iknd stannous chloride, SnClj). (Write the equations).

If the same weights of zinc and iron were used in this
jxperiment, as in Experiment 28, the same volume of
lydrcgen would be formed. The volume of hydrogen
lolved by dissolving any weight of a m,etal is not influ-
enced by the acid, if there are no secondary actions.

Experiment 30. — Stick a small piece of metallic sodium to
he end of an iron wire and push the sodium quickly under an
nverted test-tube tilled with water (a small jar may be used).
[ho sodium rises to the bottom of the tube disengaging a gas

hioh pushes the water down. Closing the tube with the thumb,

jmove it, and touch its mouth with a flame. The gas burns ; it

hydrogen. Pour a few drops of red litmus solution into the

Dst-tube and shake it up. The litmus turns blue, showing the

)resence of caustic soda

An atom of sodium displaces an atom of hydrogen from
Iwater :

H.,0 + Na = NaOH + H.
18 23 40 1

(( 'ompare with zinc and iron. What is the equivalent,
)r ( ombining weight, of sodium). The remaining atom

6^ :- - avDRoxrDEs.

of hydrogen can be driven out of the caustic soda by
heating it with a second equivalent of sodium, when aodic
oxide (NajO) is formed. (Write the equation for this
action). Similar actions may be brought about with
potassium (K) and water ; and it is found that 39.1 grains
of potassium decompose 18 grams of water, forming ?-2^^i
litres of hydrogen (1 gram), and 56.1 grams of caustic
potash. (Write the equation).

04. Hydroxides. — Caustic soda and caustic potash
are, in composition, midway between water and the
oxides of sodium and potassium. They are called hydrox-
ides. Other examples of hydroxides are quick lime,
or calcic hydroxide (CafOH).^), magnesic hydroxide
(Mg(OH)y), and hiitmuthic hydroxide (Bi(0H)3). (How
many atoms of bismuth, oxygen, and hydrogen in a mole-
cule of the last of these?) The two atoms OH constitute
a group, which, united with atoms of the metals, forms
hydroxides of the metals. Such a group of atoms, acting
together as a single atom, and being present in a series of
similar compounds, is called a compound radical The
name given to the compound radical OH is hydroxyl
(= hydrogen oxygen radical).

65. Properties of Hydrogen. -- (Symbol, H;

atomic weight, 1 ; molecule contains 2 atoms (H.>) ; 1 litre
vreighs 0.089G gram.) Hydrogen is an invisible gas, the
lightest substance known. Air is 14.43 times as heavy
as *.t.

Experiment 31. — Take a jar of hydrogen from the pneu-
matic trough, holding it upside and pour it carefully upward
into another jar filled with air. To show that the hydrogen has

PROPERTIES OF HYDROOKN. 09

risen into the second jar apply a flame to its mouth. (What
properties of hydrogen does this experiment illustrate ?)

Hydrogen is buoyant in air just as a cork is buoyant
in water. It was formerly used for inflating balloons,
but the cheaper coal gas has now largely taken its place.
If soap bubbles be blown with hydrogen they rise
rupiiUy, and can be set on fire while in the air.

Experiment 32. — Thrust up a burning pine splinter, or
small taper, into a jar of hydrogen held upside down. The
hydrogen catches tire and burns, but puts out the taper.

Hydrogen is not a supporter of ordinary combustion,
but is itself combustible. Still, a jet of oxygen will
burn in an atmosphere of hydrogen, just as a jet of hy-
drogen will burn in an atmosphere of oxygen. This
shows that the terms combustible and supporter of com-
bustion are only relative and would need to be reversed
in their application if we happened to be living in an
atmosphere of hydrogen. — When hydrogen burns in air
it unites vith the oxygen of the air to form water. It
is a constituent of most kinds of fuel, as wood, coal,
oils, &c., so that water is a constant product of fires and
lights. (Account for the gathering of water on the bot-
tom of a kettle of cold water set on the fire. )

Experiment 33. — Fill an inverted test-tube one-third with
oxygen (by pouring it upwards in the pneumatic trough) from a
jar of the gas, and the remaining two-thirds with hydrogen.
Close the tube with the thumb, remove it from the trough, turn
it several times to mix the gases, and apply a flame to its
mouth. The mixed gases explode with violence. Repeat the
experiment using air and hydrogen in the proportions of 5 to 2
liy vokuiie. The explosion is less violent.

PROPERTIES OF HYDROGEN.

The mixture of 2 volumes of liydr«^^en and 1 of I
oxygen is known as knall gas. The gases may remain
mixed for any length of time at the ordinary tempera-
ture without combining, but as soon as the temperature
is made high enough at any point, combination begins
at that point, water is formed, and enough heat is set
free to raise the temperature of the surrounding uncom-
bined gases to the point at which union takes place,
that the combination goes on spreading throughout the]
whole mass. This takes place with great rapidity, and]
an explosio7i results. (Why mix the gases in the pro-
portions given, rather than in any other 1) One gram I
of hydrogen in combining with oxygen liberates 34,462
heat units. (What is a heat unit ?) Thus, in Experi-
ment 33, the water formed by the combination of the]
gases is heated to a very high temperature; it expands
suddenly, and, losing heat, contracts suddenly, making a
disturbance in the air which reaches our ears as the|
sound of the explosion. — The flame of hyarogen is a very j
hot one. In the oxyhydrogen blowpipe a mixture of I
oxygen and hydrogen is used to give a flume of intense
heat. When directed upon a piece of lime, this flame,
although giving very little light it-elf, heats the lime to a {
bright white heat, producing the lime-light. Coal gas is
often used instead of hydrogen. — Hydrogen can be con-
densed to a liquid by pressure at a very low tempera-
ture. — Although hydrogen and oxygen do not usually
combine at the ordinary temperature of the air, yet in
contact with certain substances which have the power of
condensing gases on their surface, the two gases unite at
the ordinary temperature. Platinum has this power
very strongly, especially when in the finely divided con-

VALENCE. 61

litions of spongy platinum and platinum black. If a
boil of platinum wire is held in a flame of hydrogen
mtil it is red hot so as to drive the condenvsed gases oflf
its surface, it acquires the power of setting tire to a mix-
bure of hydrogen and air, even after it has cooled. This
)roperty of platinum is utilised in heating a kind of
Isurgical knife, which burns instead of cutting. — Hydro-
Igen is very slightly soluble in water. It can be
[breathed, and then gives a high squeaking tone to the
voice. It is not poisonous, but will not support animal
respiration. — Hydrogen is evolved during the growth of
fungi, and as it is being set free it has the power of con-
verting arsenic, antimony, and sulphur into poisonous
gaseous compounds. This accounts to some extent for
the poisonous effects of arsenical dyes in wall papei-s and
carpets.

66. Valence. — Two volumes of hydrogen unite with
one of oxygen. This indicates a difference between
hydrogen and oxygen atoms. "Wc shall hereafter study
ciises in which gases unite with hydrogen in equal
volumes, or, as is deducible, one atom with one atom.
One atom of nitrogen is united with three of hydrogen to
form ammonia ; and one atom of carbon is united with
four of hydrogen in the molecule of marsh gas. On refer-
ring to Art. 63 we find that while an atom of sodium dis-
places an atom of hydrogen, an atom of zinc displaces two.

The following formulas express some of these facts : —

Hydrochloric acid. Water. Ammonia. Marsh gas.

HCl, H,0, H3N, H,C.

The atoms of chlorine, oxygen, nitrogen, and carbon
tliffer in the number of atoms of hydrogen which they

DIFFUSION.

can take to form a molecule. The power, varying in tliis

way, is called atomicity, valence, or quantivalence. It is

measured for any element by the number of atoms oj

hydrogen with which an atom of the element will combine •

or by the n mber of atoms of hydrogen which an atom oj

the element will replace in a compound *Art. 63). The

woids bivalent, trivalent, quadrivalent, quinquevalent, &c.,

are used to denote the valence of atoms which combine

with or replace one, two, three, (fee, atoms of hydrogen.

The words monad, dyad, triad, tetrad, hexad, &c., are also

used. It will be seen later that the valence of an element

varies in different compounds, but it nearly always in

creases by twos. Thus, the valence of phosphorus is

sometimes 3 and sometimes 5, e. g., PClg and PCI-,

(Form a table of the elements mentioned in this article,

writing the valence of each opposite its symbol). The

valence of atoms is often indicated by Roman numerals

attached to the symbols, as H', Na', CI', O", Ca", Zn" ;

N"S Bi'", F" ; C'^ Si'^ ; N^, P^, Sb^, &c. In writing

the fonuulas of compounds the valence of the atoms is

often shown by lines joining the symbols. Formulas

thus written are used to picture the knowledge we have

of the way in which the atoms are groujyed in the molecide,

and are called Graphic, or Constitutional Form.ulas. For

II
example, H — O — H, water : ZnZzO, zinc oxide ; N^ "'

ammonia ; OazzS-il. calcic hydroxide.

67. Diffusion. — If a lump of sugar be placed at the
bottom of a glass of water, it dissolves ; but the water is
not at once sweetened, if it is kept still. After some
time the taste of the sugar can be detected at the top.
«,nd the sugar will at length become evenly mixed with

DIFFUSION.

jtlie v/hole quantity of water, without the sliglitest ap-
parent motion of the liquid. There must be some motion
of the particles of sugar; in fact, the motion of mole-
cules mentioned in Art. 56. It is supposed that the
molecules of sugar, after dissolving, move about continu-
ally until they are evenly (Hffused. This change of
place of substances by molecular movements is called
\di fusion. In one form or another it goes on in the
I most im})ortant processes of animal and vegetable life ;
e.g., digestion, assimilation, respiration, secretion, and
excretion. Various words, osmose, endosmone, dialysis,
kc, are used to describe diffusion under certain condi-
tions, but the process is essentially the same in each case.

Experiment 34. — Fill a tall glass cylinder nearly full of
water, and pour through a funnel with long capillary tube lead-
ing to the bottom a layer of saturated solution of potassic bi-
chromate. If the cylinder be kept undisturbed, the red liquid
will not be evenly diffused until several months have elapsed.

Diffusion of liquids is very slow. (Will solids diffuse?)

Experiment 35. — Fit with a bored cork a clean, dry, porous
earthenware vessel (inner cell of a galvanic battery); push a long
glass tube through the cork (it must fit tightly); and fix this
apparatus so that the free end of the tube may stand in a vessel
of some coloured liquid. Place over the cell a glass beaker or
other convenient vessel bottom up, and fill the space between
with Iiydrogen. The coloured liquid is at once forced down the
tube, and bubbles of gas are driven out. Remove the outer ves-
sel, and the liquid rises in the tube . (Coal gas answers in place
of hydrogen, )

In (he first part of the process, there is air inside and
hydrogen outside the porous cell. Both find their way
through the pores, but hydrogen diffuses faster than air,

HYDROGEN DIOXIDE.

the volumo of gases inside the tube is increased, and the
liquid is forced down to make room. (Explain tlie
second part of the experiment. ) Diffusion of gases is a
much more rapid process than that of liquids. (Why 1)
Law of Diffusion of Gases (Graham): — Gases diffuse at
rates {measured by volume) inversely proportional to the
square roots of their relative weights. For example, the
relative weights of hydrogen and oxygen are 1 and IG.
Their rates of diffusion are as \/\Q to yT, or as 4 to 1,
i.e., hydrogen diffuses four times as fast as oxygen.

68. Hydrogen Dioxide. — (H.^Oa). This substance
IS also called peroxide of hydrogen, and oxygenated water.
It is present in the air, and comes down with rain and
snow, but only in minute quantities. It is a compound
of hydrogen and oxygen in the proportion of 1 to 16 by
weight. The simplest formula representing this compo-
sition is HO, but if we try to write this graphicallij,
showing the atomicities, thus H — O, an anomaly ap-
pears ; the oxygen atom must be represented as monad,
and there is every reason to believe that it is dyad.
From this and other considerations the formula is
doubled,— HA , or H-0— 0-H.

Preparation. — Mix barium dioxide with dilute sulphuric
acid, allow to settle, and pour off the clear liquid. The sub-
stances formed in this reaction are hydrogen dioxide and baric
sulphate :

H3SO4 + BaO, ^ H2O2 4- BaSO^. 4 '

(Put this equation into words, giving weights and names.) — In
this action the hydrogen dioxide is obtained diluted with water,
while the heavy, white, insohible baric .sulphate falls to the

HYDROGEN I'EROXIDE. 05

bottom. As the dioxide is decomposed ])y heat it cannot be
separated from water by boiling away the latter ; but the water
can he removed by placing the solution under the receiver of an
air pump along with a vessel of oil of vitriol, which is very
hygruscojnc (attracts moisture strongly). When the air is pumped
out the water evaporates rapidly, and is absorbed by the oil of
vitriol.

Properties. — A colourless, oily liquid, heavier than water
(specific weight 1.452), soluble in water ; very unstable, decom-
posing slowly at low temperatures, rapidly when heated, into
water and oxygen. (Write the equation.) It easily parts with
half its oxygen to oxidisable substances ; i.e., it is an oxidismj
cKjeiU. For this reason it bleaches many colouring matters ;
e. g., that of the hair; and is commonly used for bleaching
dark hair, old paintings, &c. It forms a froth when taken
into the mouth, and excites the flow if saliva. It blisters when
undilute 1. Its principal use in medicine depends on its oxidis-
ing power.

Test. — Add a few drops of sulphuric acid to a solution of
hydrogen peroxide, then a little ether, and a few drops of pot-
assic bichromate solution. After being shaken the mixture turns
deep blue. The ether takes up the colouring matter, and formb
a layer at the top.

QUESTIONS AND EXERCISES. [

1. Would you expect to find hydrogen uncombined in the
air?

2. Calculate the percentage composition of water, i. e., the
quantities of hydrogen and oxygen in 100 parts. . - .

3. What volume of mixed gases, measured at 1000 mm. pres-
sure and 10° C, is produced by the electrolysis of 100 grams of
water ?

66 QUESTIONS AND EXKHCISES.

4. 50 grams of zinc are put into a closed vessel of 10 litres
capacity along with 1 litre of dilute sulphuric acid. What is
the pressure of gas when the action is completed ?

5. What weight of zinc must be dissolved in order to give SO
litres of hydrogen measured at 3 atmospheres pressure and
1G° C?

G. 20 grams of iron are dissolved in hydrochloric acid, and tbo
evolved gas is measured at 750 mm. pressure and 20° C. What
is its volume ? . m- , v :.

7. " One atom of zinc sets free a molecule of hydrogen."
What evidence can you bring in support of this statement ?

8. What is a hydroxide ? Are there hydroxides of the non-
metals ?

9. Define compound radical. What is the meaning of the
word radical as used here ? Should it not be spelled radicle ?

10. Calculate the weight of 20 litres of hydrogen measured at
25° 0. and 1000 mm. pressure. What volume of oxygen has the
same weight under the same conditions ?

11. How does it happen that the atomic weight of hydrogen
is 1?

12. Why does hydrogen explode less violently with air than
with oxygen ?

13. From the following formulas deduce the atomicity of bis-
muth (Bi), phosphorus (P), tin (Sn), and Sulphur (S) : HCl,
BiClg. PCI5, HaO, SnOa, SO3.

14. The specific weights of water vapour and oxygen are 9
and 16 (Hydrogen =1). If 100 c.c. of water vapour difi'use
into a vacuum in a certain time, what volume of oxygen will
diflfuse under the same conditions in the same time ?

15. Hydrogen dioxide is sometimes called %t/roa:y^. Explain.

TUB ATMOSIMIEUE.

CHAPTER VII.

AIR.

69. The Atmosphere. — This is the gas(50iis ocean,
supposed to be from 50 to 100 miles deep, at the bottom
of which we are living. Spaces said to bo empty are
generally full of air.

Experiment 36. — Pass the tube of a small glass funnel
through a bored cork having a short glass tube passing through a
seoontl hole (as in a xoash-hottle). Fit the cork into a flask, close
the glass tube with a finger and fill the funnel with water. A
little runs into the flask ; remove the finger from the tube, and
the whole of the water runs in freely. If the tube have only a
small opening, the water runs in slowly, and a flame held near
the opening will be blown by a stream of air coming out.

(What conclusions do you dra w from this experiment 1
Why is it necessary in filling a cask with water through
a funnel, to bore a second hole in the cask V)

Air has weight, as can be shown by weighing a glass
globe emptied by the air pump, then allowing the air to
flow in, and weighing it again ; a delicate balance shows
an increase in weight. One cubic foot of dry air at
standard temperature and pressure weighs 565^ grains
(calculate the weight, in grams, of 1 litre).

Since air has weight, the atmosphere presses upon the
surface of the earth, and upon every object on that sur-
face. This pressure can be shown by the barometer. Fill
a glass tube, closed at one end, and about 35 inches long,

68 ATMOSI'IIEUIC PRESSURE.

with mercury ; close it with the thumb, invert it, and
place the end beneath the surface in a dish of mercury.
Remove the thumb, and the mercury after a few oscilla-
tions comes to rest at about 30 inches above the level of
the surface in the dish (Torricelli, 1G43). Some pressure
on this surface balances the weight of the mercury in the
tube, otherwise the mercury would fall. This pressure is
the weight of the atmosphere. It is exerted in every
direction on the surface of any body placed in it. (What
is there inside the tube above the mercury 1)

Experiment 37. — Make an experiment such as that described
above, using water instead of mercury. Tlie water does not fall
at all when the inverted tube is opened under water. But if the
tube were, say, 40 feet long the water would fall and remain at
the height of about 34 feet.

An ocean of water 34 feet deep, or one of mercury 30
inches deep, would exert the same pressure upon the
earth as the atmosphere does. (Calculate the specific
weight of mercury). A column of mercury 30 inches
high and 1 inch square in section weighs 14.7 lbs.; and
the pressure of the atmosphere is generally taken as 15 lbs.
on the square inch. When a barometer is carried up a
tower (Blaise Pascal, 1648), or mountain, the mercury
falls ; if it is carried down a deep mine the mercury rises.
(Explain). At the top of Mont Blanc, it stands at 1 (5
inches only. When any great portion of the atmosphere
is heated, it expands and part of the air flows away over
to colder regions. This diminishes the weight of the air
in the heated region, and the barometer falls, until air
rushes in from surrounding regions to equalise the pres-
sure. (What natural phenomena does this explain ?)
Similarly, cooling causes rise of the barometer. These

royle's law. 09

iind other causes protluce variations in the hei<^ht of the
niorciiry in the bai'onieter, so tliat, in studying weatlier,
careful attention must be given to the readings of the
barometer. The average height at the see-level is 30
inches, or 7 GO millimetres. This is taken as the standard
pressure in calculating volumes of gases.

70. Boyle's Law (1662>. — If a quantity of air be
confined and the pressure upon it increased, its volume
is lessened ; if the pressure be decreased the volume be-
comes greater. This can be shown by a cylinder closed
at one end and provided with an air-tight piston. If
one presses the piston down, one feels a resistance^ but
the volume is diminished ; on the other hand, if the
piston is raised above a certain distance, one feels that a
weight is being lifted (\yhat is the weight"?) as the
volume increases. The law of change of pressure with
change of volume is as follows : — The volume of any
portion of air is inversely proportional to the pressure,
the temperature being constant. (Consult a work on
Physics for the experimental demonstration.) When
any j)ortion of air is closed ofi' from the rest of the at-
mosphere, the pressure upon it is that shown by the
barometer at that moment, say 30 inches of mercury.
If the pressure be doubled, the volume is reduced to |
the original ; if the pressure be tripled, to ^, &c. On the
other hand, if the pressure is reduced to ^, the volume
is increased to twice the original and so on. Stated in
general terms, V : V^ : : PM P, where V and V^ repre-
sent volumes at pressures P and P^ This law applies to
all gases far removed from their ])oini of condensation*
It does not, for example, apply to water at 105° C.

* At hif,'h pressures Boyle's Law is only approximately true.

70 Charles' law.

71. Expansion of Air by Heat — Oharles'
Law.

Experiment 38. — Place a narrow-necked flask with its .lock
downwards and dipping under water. Pour hot water on the
bottom of the llask ; the air inside expands and part of it is
driven out of the flask. Allov/ the ttaak to cool j the air con-
tracts, and the water rises in the neck of the flask.

The amount of tliis expansion and contraction has been
accurately measured for air and other gases. It u almost
exactly the same for all gases. If we begin with a i)ortion
of gas at 0° C and heat it to 1°, its volume increases by
^fjrd ; at 2° its volume is greater than at 0°, by ufjrds,
and so on. If the gas be cooled to — 1° its volume is
less by ^^I'd, at — 10° less by ^jVVtls, and at — 273°
(if we could reach such a temperature) the volume would
be 0. Hence — 273" C. is called the absolute zero of
temperature, and temperatures reckoned from this point
are called absolute temperatures. Evidently the absolute
temperature corresponding to 0° C. is 273°, and gener-
ally any temperature t of the centigrade scale is 273 + t
of the absolute scale. The Law of Expansion of Gases
ia as follows : — 17ie volume of any portion oj <jas is pro-
portional to the absolute temperature, the pressure being
constant.*

Example. — A quantity of air measuring 10 litres at 20° C
is heated to 50° C. What is its volume ?

273 4- 20 : 273 4- 50 :: 10 : a;

a; = Vrs** = 11.02 litres.

72. Measurement of Volumes of Gases.—

In measuring tlie volume of any portion of gas at dif-

* At hijfh pressures, and near the points of condensation, Charles' Law is
only approximately true. ""t r . . . ,

VOLUMES OF OASES. 71

forent times, it nearly always happens that both pressure
and temperature vary, so that it l[>ecomes necessary in
coni[)arin<j' volumes to apply both Boyle's and Charles'
laws.

Example. — 20 litres of hydrogen at pressure 755 mm. and
temperature 15° C. occupy what vohime at 740 nun, pressure
and20''C.?

740 : 755

273 4- 15 : 273 + 20 j • = 20

X = 20 X JS^ X ^1% = 20.7 litres.

A good chock on the correctness of the statement in
such calculations is to remeni))er the general effect of
change of pressure and temi)erature on volume, and see
if tlie fractional factors in the last equation increase or
decrease the number of litres. Thus,- in the above ex-
ample, the pressure is lessened, and therefore the volume
increased. I see that the factor lj%% is greater than 1,
and its effect is to increase 20. Similarily with tem-
})erature.

Volumes of gases are best compared at the standard
temperature and pressure (0° C. and 760 mm. of mer-
cury) ; and calculations of volumes of gases [)roduced
in chemical actions are always based on the experimental
facts that the gram-molecule of hydrogen (i. e., 2 grams of
hydrogen) measures, at 0° C and 700 mm. of mercury
})ressare, 22.33 litres, and that the gram-molecules of all
other gases occupy the same space, under the same con-
ditions. (Art. 60.)

Example 1. — What volume of oxygen measured at 15" C
and 740 mm. is formed by heating 100 grams manganese dioxide ?

Equation : 3MnO., = MusO^ + O2 '. :

—^ 3 X 86.8 22.33 ■■ .^

ffr.ams. litres.

'''J COMPOSITION OF AIR.

260.4 grains of the oxidtj; give 22.33 litres oxygon measured at

100

C" 0. aud 700 iiiiu. Thus, 100 grams give ^q~i x 22.33 litres at

100 273 + 15 7eO

0° and 760; a-nd ^^^ x 22.33 x ^^^ ^ ^ x ^j, = the volume n>.

} r C. and 74C mm.

example 2. — What weighb of potassic chlorate, when de-
composer, will give 10 litres of oxygen measured at 20° C. and
1000 mm. pressure ?

Equation : 2 KCIO, = 2 KCl + 3 O^

2 X 122.6 3 X 22.33

fjrams. litres.

i. e., 245.2 grams of the salt give 66.99 Ltres of oxygen measured
at 0" C. and 76t mm. In order tc coU'^are this volume with the
voliTme required, they must be reckoned at the same tomperature
and pressure. It is well, to avoid confusion, to compare
volun^ea of gases alicays at 0° and 760. In this case, then, we
first reduce the 10 litres to the vf»lume at 0° and 760 :

27 + C 1000

1<^ >< 2~93inio ^ ^3 = ^''^^- »* 0° and 760.

273 100

Then, 66.99 : 10 x ^ x yT — 245.2 : x

_ 10 X 273 X 100 X 2'i5.2
^ = 293 x"76~ X 66.99

73. Composition of Air.

Usperiment 39. — Put a bit of pbosphonis, dried on filter
paper, into a amall porcelain cup floated on a flat cork in a basin
of water. Touch the phosphorus with a hot wire and immediately
cover it with a beaker. It burns for some time, but at length
goes out. As the enclosed gas cools, water rises in the beaker,
showing a lessening of volume. Decant some of the gas ii\to ?.
tcbt-tube (Art. 41), close the test-tube with the thumb, remove
it, and thrust a burning match or splinter into the gas. The
flame is put out.

Fui-ther examina!,j.O'- of tliis gas has «hown it to be an
element, 7dtrogen, The combu.3r'o:. of phosphorus is driD

VOLUMETRIC ANALYSIS OF AIR. 1 3

to the oxi/i/en of the air. (What has become of thef«« in
the experiment 1} — Air is a mixture of tha two elementary
yoses, nitrogen and oxygen. That it is a mixture, and
not a chemical compound, is ^^een from the following
facts : —

1. If air be shaken up with water, oxygen dissolves
in greater relative quantity than does nitrogen.

2. Tiie two gases can l^e partially separated by dif-
fusion. (Which gas diffuses faster])

Ij. If nitrogen and oxygen be mixed in the ratio in
which they are present in air, no heat is given out, and
there is no other evidence of chemical action ; but the
mixture has the properties of pure dry air.

4. The volumes of the gases are not in any simple
ratio. (What law is here referred to?)

Volumetric Analysis of Air. — This analysis is made
in a graduated glass tube called a eudiometer. The
tube is closed at one end, at which two jdatinuin wires
are melted through the glass so as nearly to meet within
the tube. The endiometer is filled partly with mercury,
inverted in a trough of the same liquid, and the volume
of air thus closed off is noted, as well as the temperature
and pressure. To this air is added about half its volume
of pure hydrogen, find volume, temperature, and pressure
are once more noted. The eudioi! ^ter is now tightly
pressed d' wn on a sheet of India-rubber, and an electric
spark is passed between the platinum wires. An ex-
plosion takes [)lace within the tube, and the volume of
gas is seen to be much reduced. Volume, temperatui'e,

74 ANALYSIS OF AHl RY WEIGHT.

and pressure are once more read olf. The remaining gas
is a mixture of nitrogen and hydrogen. One-third of tlie
loss of volume after the explosion is due to the disap-
pearance of oxygen (What h:'s become of it?) ; and the
volume of oxygen being known, the remainder of tho
original volume of air is reckoned as nitrogen.

Sxample. — Volume of air enclosed, 20 c.c. ; temperature,
15° C. ; pressure, 750 mm. — Volume after addition of hydrogen,
32 c.c; t, 16* 0. ; j5, 718. Volume after explosion, 20 c.c;
t, 18° 0. ; p, 710 mm. Reduce these volumes to 0° C. and
760 mm., and find the decrease of volume after explosion to l)e
11.03 cc Calculate from this that 100 c.c. of air consist of
20.96 of oxygen and 79.04 of nitrogen,

COMPOSITION BY VOLUME,

Oxygen 20.90

Nitrogen 79.04

100.00

Analysis of air by Weight. — Air is dried and
purified, and then allowed to flow slowly tlirough a
weighed tube containing red hot copper filings. It loses
oxygen, cupric oxide (CuO) being formed ; and the nitro-
gen passes on into a weighed vacuous globe of glass,
he increase in weight of the tube gives the weight of
cxygen, and the increase in the globe the weight oi
Tiitrogen. The average of many careful experiments
gives as the percentage com[)Osition of air by weight :

Oxygen 22.77

Nitrogen 77.23

100.00

CARBON DIOXIDE, ETC". 75

Tlie composition of air is almost constant in all parts
of the world, and in all situations. In towns and in
fof^gy weather the percentaj];e of oxygen, by volume, may
sink to 20.8 ; and in crowded rooms it sometimes sinks
much lower. — The oxygen of the air is necessary to sup-
port life, fires, decaying processes, &c. (What is tho
use of nitrogen ])

74. Other Substances in the Atmosphere.—

The atmosphere contains several substances besides
oxygen and nitrogen, but in small and variable quantities.

Carbon Dioxide (CO^). — Constantly present in air,
from 4 to 6 volumes in 10,000. Its presence is of great
imi)ortance, as it forms an essenthil constituent of the
food of plants. The supply is kept up by the processes of
combustion, respiration, and the decay of organic matter.

Water (H^O). — This is present in the air, in the form
of vapour, in very variable quantities, depending on tem-
perature and degree of saturation. A cubic metre of air
at 25° C. contains when saturated 22.5 grams of water
vapour ; at 0° C, only 5.4 grams. Dew is formed by
the condensation of aqueous vapour from the air by con-
vCt with cooled surfaces. Leaves radiate heat much
fister ohan other objects, and therefore condense water
va[)oar much more rapidly. (Why does not dew form
on a cloudy or a windy night I) Aqueous vapour in the
air tempers the heat of the sun, thu rays of which would
be unbearably hot, if a large fraction of the heat were
not stopped on its passage through the atmosphere.
Water vapour has in a very high degree the power of
absorbing radiant heat.

76 co?.:bustion in air.

Compounds op Nitrogen. — Minute quantities of
oxides of nitroijen are formed in the atmosphere by tlie
action of electricity. (On what?) Ammonia (NH3) is
present in small proportions, generally as amnionic nitrite
or nitrate. These substances are brought down to earth
in rain and snow, and serve for plant food.

Dust, &c. — Under this head are included solid par-
ticles of all sorts, organic and inorganic. Com,mon salt
is always present in the air. If a little clean rain-wator
is evaporated on a microscope slide and the residue ex-
amined with the microscope, crystals of common salt
(NaCl) can always be seen. Spores, or eggs of minute
plants and animals, are constantly present. Many of
them are the eggs of ferments ; others are the cause, or
at least the concomitants, of diseases. The object of the
antiseptic spray in surgery is to kill such living dust ;
and it is important to note that disinfectants and anti-
septics which are to purify air must (unless the air is
drawn over them) be volatile. A\v can be purified from
dust by drawing it through ootton-wool, and other filters.

Ozone and hydrogen dioxide have been already men-
tioned.

75. Oombustion in Air. — Substances which burn
in oxygen usually burn in air, but not so rapidly.
(Why 1) The substances burned in la.mps, candles, and
fires are composed mostly of carbon and hydrogen, which
unite with oxygen to form carbon dioxide and water.
Thus, the oxygen of the air is used up, and in lamps and
stoves, (fee, provision must be made for a renewal of the
supply of air, — in other words, there must be a draught.

v.v : ,•/?•/!' f-fitr^i"^

RESPIRATION. 77

The consumption of oxygen must be taken into account
in considering questions of ventilation. An orcliiiary
lamp consumes as much oxygen in 1 hour as a man does
in 5. (How does a lamp or gas flame differ from a fire
in a stove or grate in their effect on the air 1)

76. Respiration. — In the air cells of the lungs the
air is separated from the blood by a very thin membrane
through which diffusion goes on readily and rapidly.
The blood comes into the lungs charged with carbon di-
oxide, a waste product which it has gathered from the fur-
naces of the body, — the muscles, glands, &c. These need
a continual supply of oxygen to feed the slow fires going
on in them. Carbon dioxide passes outwards by diffu-
sion, and is exhaled ; oxygen diffuses inward and is car-
ried away to the tissues. Thus, the air which returns
out of the lungs contains less oxygen and more carbon
dioxide than when it was inspired. In one hour an
adult man consumes about 29 grams (how many litres?)
of oxygen, and breathes out about 33 grams carbon di-
oxide. Besides carbon dioxide, water vapour and small
quantities of complex organic compounds are exhaled.
Botli the organic compounds and the carbon dioxide are
injurious to health ; and therefore the necessity for re-
newing the air which is breathed. It is estimated that
an average adult man requires 1500 cubic feet of fresh
air per hour.

QUESTIONS AND EXERCISES.

I. A flask billed with water and closec^ with a cork through
which passes a narrow tube open at both ends is held upside
ilowii. The water does not run out. Why ?

78 QUESTIONS AND EXERCISES.

2. Air is found to become less and less dense as we ascend.
Account for this.

3. Why do men need to breathe faster at great elevations than
lower down ?

4. Why does blood burst through any place where the skin is
thin, when a very great elevation is reached, as in balloons ?

5. What is the pressure of the atmosphere in grams on every
square centimetre ?

6. The specific weight of alcohol is 0. 784. What would be
the average height of an alcohol barometer ?

7. A quantity of air measures 2G4 c.c. at a pressure of 700 mm.
What will it measure when the pressure is increased to
1000 mm.?

8. Calculate the weight of hydrogen in a vessel of 10 litres
capacity, filled when the barometer reads 756 and the ther-
mometer 18° C

9. A quantity of air under a pressure of 32 inches of mercury
undergoes a change of pressure and increases from 10 cubic feet
to 12.4 cubic feet. Wliat is the new pressure? (Temperature
constant. )

10. What pressure must be used to compress 18 litres of
oxygen into a vessel of 6 litres capacity, the oxygen being origi-
nally under a pressure of 785 mm. ?

11. 150 c.c. of air at 50° 0. is cooled to 10° C. Calculate the
volume (pressure being constant).

12. A quantity of air measures 24 litres at 15°. ; the tempera-
ture is reduced to — 16° C. What is now the volume ? (Pres-
sure constant.)

13. What volume of gas at 200° C. will measure 320 c.c. at
0° C? (Pressure constant.)

14. What volume of oxygen measured at 2000 mm. and 12° C.
is formed by the decomposition of 600 grams potassic chlorate ?

NITROGEN. 79

CHAPTER VIII.

NITROGEN AND ITS COMPOUNDS.
Nitrogen— (N'" = 1^).

11. Occurrence. — Forms about fo'U'-fifths by
volume of the atmosphere ; in combination, it forms part
of all living matter, and is tlioreforo an essential consti-
tuent of plant and animal food. Other compounds oc-
curring in nature are nitre (KNOa^, Chili nitre (NaNOg),
and ammonia (NHg).

78. Preparation. — Nitrogen is most readily pre-
j)ared from air (Exp't 39) ; see Art 73, " Analysis of Air
by Weight." It can also be prepared from nitre (salt-
petre).

Experiment 40- — Heat 10 grams iron filings in a hard-glass
test-tube with ^ gram saltpetre. Collect the evolved gas in
the usual way. It is nitrogen, the ^^nitre-generator,"

79. Properties. — An invisible gas, without smell or
taste. It is 14 times as heavy as hydrogen and a little
lighter than air. (Calculate its specific weight, air being
standard.) It is incombustible and not a supporter of
combustion (Make experiments to show this). It is re-
markable for chemical inactivity, not entering readily
into combination with other elements. Under the in-
fluence of electric sparks or flashes it unites with oxygen,
and, in very small quantities, wit)i hydrogen. It is

80 AMMONIA.

slightly soluhlo in vvjiter, about 1^ vols, in 100 of water.
It })as boeii liquefied at — 146° C. by a pressure of 33
atmospheres.

Coinpouruls of Nitrogen.

80. Ammonia.— (NH3 = 17.)

Experiment 41. — Heat apiece of dried meat in a glass tube
closed at one entl. It chars, and moisture collects. Wet a small
strip of filter paper with red litmus and bring it in contact with
this moisture. The litums is turned blue. Same result, if a hit
of coal, bread, or horn be heated.

The alkaline reaction of the moisture is due to the
presence of a volatile alkali, ammonia. (What alkalis
have already been noticed 1) It is always formed when
animal or vegetable bodies are destructively distilled.
Coal, wood, bones, and other animal and vegetable sub-
stances are distilled on a large scale in the manufacture
of gas, charcoal, bone-black, &c.; and the watery liquid
(a by-product) contains much ammonia. From gas
liquor ammonia is prepared by heating with lime and
condensing the ammonia in cooled water. Formerly, it
was prepared by distilling scraps of the horns of the
hiirt ; hence the popular name, " spirits of hart's horn."
— Ammonia is always one product of the decay of ani-
mals and vegetables, excrement, guano, &c.

Preparation. — Ammonia is most conveniently pre-
pared from one of its salts, sal ammoniac (NH^Cl).

Experiment 42. — Mix thoroughly about 2 parts of dry
powdered sal ammoniac with 1 of powdered quick-lime. Note
the smell of ammonia. Put the mixture into a hard glass test-

AMMONIA. 81

tube or flask, ar.d arrange a gas delivery tube so as to collect the
evolved gas in inverted bottles, to the tops of v hich the delivery
tube mu8t reach. ( Why not over water ?)

Equation :

Ammonic Calcic

I-ime. Cliloriile. Cliloriiic.

CaO + 2Nir,01 = CuCJ, + 2Nlf., + lf,().
56 1()G.8 110.8 44.()6

grams. grams. grams. litres.

Aininonia is generally used in water. To pioprue the
solution slaked lime is employed instead of quick lime,
and the gas is passed into water, which must be kept well
cooled. (Why I)

Properties. — Ammonia is an invisible gas, with a
pungent smell, and a sharp alkaline taste. It is lighter
than air. (How does Exp't 42 show this "?) (Calculate its
specific weight, air being standard ; also when hydrogen is
standard.) It is liquid at 15.5° C. under a pressure of
7 atmospheres (What is an atmosphere of pressure ?), and
at — 70° C. is solid. It is ,very soluble in water, 1148
vols, dissolving in 1 of water at 0° C. Much heat is
given out during the process. (Account for this.) When
a solution of ammonia is warmed the gas is driven off
ra})idly.

Experiment 43. — Fill a test-tube with ammonia gas (Experi-
ment 42), close with the thnmb, place the mouth under water,
and remove the thumb. The water rises to the top, if there is
no air in the tube. Close again with the thumb, remove the
tube and examine the water in it, as to its smell, taste, feel,
and action on red litmus.

The solution of ammonia in water {liquor ammoniae)
has a strong alkaline reaction and probably contains
cuiimonic hydroxide (NH4OH). It neutralises acids, and

7 --

82 LIQUOll AMMONIiE.

thereby forms salts. The dry gas, also, combines with
acids, and it is to be observed that no WHter is pro-
duced when ammonia unites with acids to form salts,
e.g., NH3 + HCl = NH4CI. These salts are called
ammonium salts, since they contain the compound radical
ammonium (NH4) acting as a monad metal. Ammonia
is not a supporter of combustion, and is incombustible in
air ; but a mixture of the gas and oxygen burns with a
pale bluish flame, and forms water, nitrogen, and a little
nitric acid.

Experiment 44. — Try the combustibility of anunoiiia gas l)y
thrusting a burning match into a jar of it.

Composition of Ammonia. — Tiie gas is decomposed
by electric s{)arks. Two volumes of ammonia give one
of nitrogen and three of hydrogen. That is, two mole-
cules of ammonia decompose into one molecule of nitrogen
and three of hydrogen. From this it is concluded that
the molecule of ammonia contains an atom of nitrogen
and three of hydrogen.

Liquor ammonlce fortior is a nearly saturated solution of am-
monia in water, prepared by distilling in an iron retort 3 lbs.
ammonic chloride (NH^Cl), with 4 lbs. slaked lime (Ca(OHj._,),
and receiving the gas in water. It is lighter than water
(sp. wt. 0.892), and contains 32.5 per cent, of ammonia. It
must be kept well stoppered, otherwise the ammonia escapes.
As ammonia is less soluble at high than at low temperatures this
solution should not be allowed to get very warm, (What
would happen ?)

Liquor ammonioi or aqua ammonioe is a weaker solution, made
by mixing 1 pint of the stronger solution with 2 pints distilled
water. It contains 10 per cent, of ammonia.

Ammonia has a stiong inflammatory action on the respi-
ratory and other mucous membranes. When breathed

NITRIC ACID. 83

diluted with air, it stinuilatos ; but its constant uso may
at length produce serious indumination. Since it unites
with acids to form mild salts, it is an antidote to acid
gases. (What are antidotes for ammonia ?).

Hydroxylamine (NH3O) ia a substance nearly related to am-
monia. Its molecule contains hydro xyl (OH) instead of one of
the atoms of hydrogen. If the molecule of ammonia is repre-

eeuted by N-^h> that of hydroxylamine is N^u • It is pre-

pared by the action of nascent (just being set free) hydrogen on
nitrogen dioxide (NO) :— NO + 3H = NH;,0.

81. Nitric Acid (HNO3 = 63).

Experiment 45. — Put a little saltpetre in a test-tube, and
drop on it from a pipette a small (quantity of oil of vitriol. Heat
very gently, and observe the drops of fuming liquid wliich gather
on the sides of the tube. Gather them on a glass rod and try
their action on red litmus.

The acid liquid is nitric add, or aquafortis. Saltpetre
is a salt of the base, potassic hydroxide, and nitric acid.
When it is acted upon by the stronger acid, the weaker
is displaced, and a new salt, potassic sulphate, is formed.

2KNO3 + H2SO, = 2HNO3 + K2SO4.

Nitric acid occurs naturally only in small quantities ;
but its salts are found in large quantities. Chili salt-
petre, or sodic nitrate (NaNOg), is most plentiful, and is •
now used in preparing the acid.

Preparation. — Distil at a gentle heat, from a glass
retort, equal weights of Chili* saltpetre and oil of vitriol,
keeping the receiver well cooled. Nitric acid distils,
and a white salt remains in the retort. This salt has

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84 NITRIC ACID.

acid properties. In fact it is still half acid, and is called
acid sulphate of sodium, or sodic hydrio sulphate :

NaNOa + H^SO^ = HISTOa + NaHSO,.

Why not use double the quantity of sodic nitrate, as
represented in the preceding equation? Because, in
this case, the action would go on only at such a high
temperature that the nitric acid would be partially
decomposed.

Properties. — Pure nitric acid is a colourless fuming
liquid of sp. wt 1.52. It has a strong attraction for
water, and it is hard to prepare it free from water. The
strong acid of commejce a,] ways contains about 10% of
water, and is generally reddish or yellowish from im-
purities. Red fuming nitric acid is strong nitric acid
coloured by nitrogen trioxide and tetroxide. When
strong nitric acid is boiled it loses acid faster than it
does water, until a liquid containing 70% of acid distils
at 121° C. unchanged. If a weaker acid be boiled it
loses water faster than acid until it contains 70°/^ of
acid.

Experiment 46. — Put a few cubic centimetres of strong nitric
acid in a test-tube, and add an equal volume of water. Note the
rise of temperature. ( Account for it. ) Pour the contents of the
tube into about one litre of water, stir well, and taste.

Nitric acid is a powerful oxidising agent. (Calculate
the percentage of oxygen which it contains).

Experiment 47. — Drop a little strong nitric acid on some
powdered charcoal heated to redness in a deflagrating spoon.
N. B. — The acid must contain very little water.

KITRIC ACID. 85

Experiment 48— Very carefully drop a small piece of phos-
phorus into a little nitric acid in a small porcelain dish. It dis-
solves with the evolution of reddinh fumes. If the acid is very
strong, the phosphorus catches fire.

K the solution from Experiment 48 be evaporated,
phosphoric acid is left. (How has this acid been before
obtained 1) Similarly, sulphur can be oxidised to sul-
phuric acid by boHing with nitric acid. Turpentine can
be set on fire by . lixture of nitric and sulphuric acids.

Experiment 49- — Dilute a few cubic centimetres of nitric acid
with about 4 times its volume of water, and pour it over a small
bit of lead in an evaporating dish. The lead begins to dissolve,
and red, strongly-smelling fumes come off. Apply heat to hasten
the action, and when the lead is completely dissolved evaporate
the solution on the water bath. Crystals of colourless plumbic
vitrate (i'b(N03).^) ^-re left. Eepeat the experiment, using cop-
per instead of lead. Fine blue crystals of cupric nitrate are
formed :

3Pb + 8HNO3 = 3Pb(N03)2 + 2N0 + 4H2O.
30u + 8HNO3 = 3Cu(N03)2 -f 2N0 + 4U^0.
(Write down the names and weights.)

Nitric acid dissolves most metals, forming nitrates of
the metals, oxides of nitrogen, and water. It dissolves
silver, but not gold, and can thus be used to separate
silver from gold. If the strong acid be used in dissolv-
ing metpis, the gaseous product is nitrogen trioxide
(N2O3); dioxide (NO), monoxide (NoO), nitrogen, and
even ammonia, are obtained at successive stages of dilu-
tion. As a rule, the more violent (rapid) the action of
tlie acid, the less oxygen does it lose. Thus, the higher
oxides of nitrogen are formed when the acid is strong^

86 NITRATES.

the temperature high, or the metal ea^sily oxidised. —
Nitric aciJ is a strong corrosive poison. It 'eats up' or-
ganic tissues when it is strong, and partially destroys them
even when it is weak. The antidotes are mild alkaline
substances, as magnesia. A drop of the weak acid left on
the skin for a few moments colors it bright yellow {Picric
acid is formed).

Nitro-glycerine and gun-cotton are chemical compounds
of glycerine and cotton with nitric acid, in which the
oxygen of the acid is ready to combine with the carbon
and hydrogen of the glycerii>e and cotton. (Explain
their explosiveness.) Dynamite is a commercial prepara-
tion of nitro-glycerine.

Tests. — 1 . Heat with some bits of copper. Red fumes are
given oflF.

2. Colour light blue with a drop of sulphate of indigo, and
heat. The colour disappears, because the indigo is oxidised.

3. Mix in a teat-tuba about equal volumes of strong sulphuric
acid and solution of ^errous sulphate (FeS04), cool, and., holding
the test-tube aslant, carefully pour down the side so as to form
a layer on the top a dilute solution of nitric acid. Either at
once or after a few moments a brown ring appears between the
two layers. This is due to the formation of a brown compound
of ferrous sulphate and nitrogen dioxide : SHjSO^ -f- 2HN0g
+ 10 FeSO^ = 3Fea(SOj3 + 2(FcSOj2NO -f 4H2O.

82. Nitrates.— Basicity.

Experiment 50. — Put a pipette ful of caustic potash solution
in a porcelain basin, colour with litmus, and add dilute nitric
acid (1 of strong acid to 4 of watei) slowly with a pipette, stir-
ring constantly, until the blue litmus turns purple. Taste the
solution. Evaporate on the water bath. Long prismatic crys-
tals of saltpetre are obtained.

BASICITY. 87

If this experiment be made quantitatively it will be
found that to get the neutral point, pure potash and pure
acid must be mixed in the ratio by weight of 56.1 to 63.
If any other ratio be used, some of the acid or of the base
is left over :

KOH 4- HNO3 = KNO3 + H2O.

66.1 63

Base and add give salt and water.

If a similar experiment be made with caustic soda,
sodic nitrate, in cubical crystals, is formed ; and it
is found that in this case also the base and acid unite
in only one proportion^ viz., 40 to 63.

NaOH + HNO3 = NaNO., + H.O.
40 63

40 g. of caustic soda are equivalent to 63 g. nitric acid
(and to what weight of caustic potash 1) Since nitric
acid acts on these two bases in only one proportion for
each, and forms only one salt for each, it is called a
monobasic acid. The bases are monacid bases.

Experiment 51.— Put some dilute nitric acid in a porcelain
dish, colour with litmus, and add dilute solution of ammonis.
until the litmus just turns blue. Then evaporate to dryness on
the water bath, and preserve the crystals of ammonic nitrate for
a later experiment : —

NH3 + HNO3 = NH4NO3.

Experiment 52. — Warm a little plumbic oxide (litharge) in a
porcelain basin with dilute nitric acid. The oxide dissolves to a
colourless solution. Evaporate on the water-bath. Colourless
crystals of plumbic idtrate (PbfJsOg),) are left : —

PbO 4- 2HNO3 = PMNOs)^ 4- H^O.

Keep this salt for a later experiment.

88 SALTS.

The molecule of plumbic oxide is equivalent to two
molecules of nitric acid. There is a corresponding base,
plumbic hydroxide, Pb(0H)2 , the molecule of which is
also equivalent to two of nitric acid. It is therefore
called a di-acif base. We shall see later that there are
also di-basic acids.

(We have observed three ways in which nitric acid
forms salt. What are they ?)

The nitrates are, almost without exception, soluble in
water. They can all be decomposed by heat. The nitrates
of the heavy metals ^copper, iron, lead, <fec.,) give off a
mixture of oxygen and oxides of nitrogen, when strongly
heated. The nitrates of the alkali metals (sodium, potas-
sium, &c,,) decompose slowly only at a bright red heat,
giving off one-third of their oxygen and leaving nitrites :

KNO3 = KNO2 + O.

The nitrates are used in many operations as oxidising
agents. Gunpowder is a mixture of potassic nitrate,
charcoal, and sulphur (AVhat becomes of the charcoal and
sulphur during the explosion?) Nitrates of barium, cal-
cium, and strontium, are used to prepare coloured fires.

Tests. — Same as in Art. 81, but add sulphuric acid in (1) and
(2). (Why ?) Try these tests with solution of saltpetre.

83. Salts. — The general nature of acids and bases can
now be seen. They are opposite in properties, and, when
brought together, tend to neutralise each other, i.e.,
destroy each other's distinctive properties. But only the
stronger acids and bases do this completely. The sub-
stances formed when acids and bases act on eacli other

NOMENCLATURE OF SALTS. 89

are mostly like coininon salt in their properties, and are
thence called salts. Their relation in composition to the
acids and bases from which they are formed can be best
shown as follows : —

H.NO3, nitric acid.
K.NO3, potassic nitrate.
Na-NOg, sodic "

Pb(N03)2, phmibic "
Bi(N03)3, bismnthic
NHfNOg, ammonic

((

K.OH \ potassic hydroxide.
K.NO3 / " nitrate.

Na.OH \ sodic hydroxide.
Na.NOg J "■ nitrate.

Pb(0H)2'\plmiibic hydroxide.
Pb(N03)2/ " nitrate.

Bi(0H)3 \bismuth hydroxide.
Bi(N03)3/ '■ nitrate.

An inspection of these two lists shows that the nitrates
differ from nitric acid by having metal ivjtead of hydro-
gen, and from the bases by having NO3 instead of OH
(hydroxyl). Salts may be regarded as made up of
two parts, metal, and salt-radical. The salt radical of
the liviates is then — N0;<, and we write the formula of
any nitrate by adding to the symbol of the metal n times
NO3, n being the valence of the metal. Thus, for monad
metals put NO3 once ; for dyads, NO3 twice, and so on.

Names 0/ salts are formed from the names of the metals
(as adjectives), and tlioso of the acids (as nouns). The
syllabic -ic is generally added to the root of the name of
the metal. In case the metal forms two bases, the salt
of that containing the greater relative quantity of metal is
distinguished by the ending -ous.^ Thus, ferrous nitrate,
Fe(N03)2; Q-nd /e7'riG nitrate, Fe2(N03)6. The names of
acids generally end in -ic, and (with the exception of the
haloid acids and a few others) this ending is changed to

* Latin osum, abounding in.

90 OXIDES OP NITROGEN.

-ate for the name of the salt. When the name of the acid
ends in -ous, the name of the salt ends in -ite. Thus,

Nitric acid Nitrate.

Sulphuric ** Sulphafe.

Nitrons *' Nitride.

PhosphoroMS * * Phosphide.

T'lere is a class of acids containing no oxygen, e.g.,
hydrochloric acid (HCl), hydrohromic acid (HBr), <fec.
The salts of these acids are called chlorides, bromic?e«^<fec.
They are named in the same way as oxides and sulphides.

84. Oxides of Nitrogen.- -Nitrogen and oxygen
do not readily combine ; but by muii 3ct methods 5 com-
pounds can be obtained. If electric sparks be passed
through dry air, a red gas, nitrogen tetroxide (NOj),
appears, and this in presence of water and oxygen forms
nitric acid. It is probable that considerable quantities
of nitric and nitrous acids are formed in the atmo^here
by lightning. The five oxides are as follows : —

Nitrogen monoxide NjO

'' dioxide NO.

" trioxide NgOg.

** tetroxide NOg or NgO^.

" pentoxide NjOg.

If the formula of the second be doubled it will be easily
seen that the proportion of oxygen increases regularly
from 1 to 5. This is a good illustration of the Law of
Multiple Proportions. (Apply it.)

85. Nitrogen Monoxide (N.2O) — Also called laugh-
in<j (jas, and nitrous oxide.

Pii PARATiotf. — Experiment 53. — Dry some ammonic nitrate
(Exp't 51) by fusing it in a porcelain dish. Break the dried
salt into small lumps and heat some of it in a test-tube provided

NITROORN MONOXIDE. 91

with a gas-deli verv tube. The salt melts easily to a clear liquid,
and a continuous stream of gas comes off. Collect G jars of the
gas over loarm water, and try its action on a glowing match and
on burning phosphorus.

Properties. — Colourless gas, of ethereal smell and
sweetish taste. ^^Try it.) (Calculate its specific weight.)
At 0° C. it becomes liquid under a pressure of about 30
atmospheres. It is soluble in water to the extent of
about IJ vols, in 1 of water (at 0° C). (Try solubility
in cold water.) It supports ordinary combustion better
than air does. (Compare the percentages of oxygen in
air and nitrogen monoxide). The whole of the oxygen is
easily sejmrated from the nitrogen by carbon, phos-
phoru.^, <fec. :

C 4- 2N2O = 2N2 + CO.,
2P + 5N2O = 5N2 + PA-

(Translate these equations into ordinary language).

Experiment 54. — Set fire to a little sulphur in a deflagrating
spoon, and at once plunge into a jar of nitrogen monoxide. The
tlame is extinguished. Light it again, and let it burn vigorously
before putting it into the gas.

Nitrogen monoxide extinguishes a weak flame of sul-
phur, because the temperature is not high enough to
start the action. Sulphur burning well in air, burns
more brightly in nitrogen monoxide. The substances
formed are nitrogen and sulphur dioxide (SO2). (Write
the equation.)

When breathed, nitrogen monoxide causes at first a
peculiar intoxication with insensibility to pain. If
mixed with about one-fifth of its volume of air it can be

92 NITROGEN DIOXIDE.

breathed for some time ; but, as it diffuses into the blood,
and cannot supply oxygen to the blood, symptoms of suf-
focation at length appear. When prepared for inhala-
tion, it should be freed from acid fumes and nitrogen
dioxide by bubbling it through solutions of caustic soda
and ferrous sulphate. — Salts of an acid, hyponitrous, cor-
responding to this oxide, are known ; e.g., KNO, pot,
hyponitrite.

86. Nitrogen Dioxide. — NO. (Nitric Oxide).

Preparation — Experiment 55. — Mix 1 part strong nitric
acid with 3 of water in a t. t. or fiask, and add some scraps of
copper. Heat gently and collect six jars of the gas over watc

Other metals, as mercury, silver, iron, lead, &c., may
be used. Nitrogen and the monoxide are always present
as impurities.

Properties. — An invisible gas, a little heavier than
air. (Calculate specific weight.) Smell and taste not
known. (Why?) It can be condensed to a liquid at
— 11° 0. by a pressure of 104 atmospheres. It is the
most stable of all the oxides of nitrogen. It is very
sparingly soluble in water.

Experiment 56. — Set fire to a bit of phosphorus and plunge it
quickly into a jar of the gas. It is extinguished. Try again,
allowing the phosphorus to burn brightly before putting it in the
gas. Try a lighted match, and sulphur burning strongly. They
are both put out.

Experiment 57-— Pass up a little oxygen into a jar of the
gas over water ; red fumes appear and then disappear, the
volume of gas being lessened :

NO + O = NOa

3 NO. + HaO = 2HNO3 + NO.

NITKOUEN TRIOXIDK. 93

Nitrogen dioxido supports only very vigorous coinbus-
Uon. It combines with oxygen to form nitrogen tct-
roxide (NO^). (What takes place on contact with air 1)

Experiment 58. — Pour some solution of green vitriol into a
jar of the gas, close, and shake up. The gas dissolves, giving
a dark brown colour to the nolution. A weak compound
('iFeSO^.NO) is formed. This can be decomposed by heat, giv-
ing pure nitrogen dioxide. (In what former experiment was
this compound obtained ?)

Tn writing the graphic formula of nitrogen dioxide,
eitlier the nitrogen must be represented as dyad, NmO,
or one atomic bond must be left, unemployed, — NziO.
In either case the compound seems anomalous. Other
cases of this kind warn us that the idea of valence is one
to be used caut! jusly, however convenient ordinarily.

87. Nitrogen Trioxide. — N2O3. It is also called

anhydrous nitrous acid.

Preparaton. — Late experiments seem to show that
this substance docs not exist at ordinary temperatures,
but decomposes above — 18° C. It can be prepared by
mixing nitrogen dioxide with one-fourth its volume of
oxygen, and cooling to — 20° C.

Experiment 59. — Heat a little starch with some nitric acid
dihited with about one volume of water. Red vapours are
evolved, said to be nitrogen trioxide. If these are cooled below
— 18° C. they form a deep blue liquid.

Properties. — Nitrogen trioxide is a blue liquid which
decomposes at — 18° C. into the dioxide and tetroxide :

JS.Oa = NO + NO.,.

94 NITROUS ACID.

Experiment 60.- Uepeat Experiment 59 on a larger scJile
and lead the red gas ini'^^o a t. t. containing water and surrounded
by ice and salt. A blue solution is formed, having acid proper-
ties. Add some caustic soda solution to this. The colour dis-
appears. Evaporate on the water bath, and keep the remaining
salt, sodic nitrite.

88. Nitrous Acid. - HNO.^ This is the blue solu-
tion of Experiment 60. It has not been obtained pure,
and is easily decomposed. Its relation to nitrogen tri-
oxide is seen thus :

N2O3 -I- H,0 = 2HNO2.

It is a monobasic acid, and forms salts called nitrites.
The " nitrous acid " of pharmacy is impure nitric acid.

Nitrites. — The nitrites are nearly all soluble in water,
and quickly absorb oxygen to form nitrates : — KNO.^ -f
= KNO3. Nitrites are produced by the decomposition
of animal matter, and their presence in water is an
indication of pollution.

Tests. — 1. Put a few drops of dilute sulphuric acid on a little
of the salt from Expt. CO. Red fumes are evolved :

2NaN02 + H.,SO, = Na^SO^ -f N2O3 (?) + H^O.

2. Add a little potassic iodide and starch paste to a solution of
sodic nitrite ; to this add a few drops of dilute sulphuric acid.
The deep blue of iodide of starch appears.

3. Add a little potassic permanganate (KMnO^) to solution of
any nitrite ; then some acetic acid. The colour of the perman-
ganate dissappears. It is reduced by the nitrous acid. Try the
acetic acid without the nitrite. •

TETROXIDE AND PENTOXIDE OF HYDROGEN. U5

89. Nitrogen Tetroxide, NO, or N^O^.-^This is

also called peroxide of nitrogen.

I'liEPARATioN. — Experiment 61. — Dry some plumbic nitrate
(Expt. 52) by gently heating in a porcelain dish ; transfer to a
hard-glass t. t. anil heat gradually. Receive the red gas in a 1. 1.
surrounded by a freezing mixture of snow and salt :

PbCNOa)^ ^ PbO + N^O^ + O.

(What is the substance left in the t. 1. 1 How can it be
again converted into lead nitrate ?) Nitrogen tetroxide
can also be prepared by cooling a mixture of nitrogen
dioxide and half its volume of oxygen : NO -{- O = NO,.

Properties. — A colourless liquid at low temperatures,
a reddish brown gas above 22° C, its boiling point.
With cold water it forms nitric and nitrous acids :
N,04 + H.,0 = HNO3 -f HNO2. Similarly, with caus-
tic sodf^ or caustic potash it forms nitrate and nitrite
(and water). ("Write equations). It is irritating when
breathed, and injures the mucous membranes of the
respiratory passages.

90. Nitrogen Pentoxide. — N2O5. Also called

onhydrous nitric acid.

Preparation. — By passing dry chlorine gas through
a tube containing dry silver nitrate heated to 50° C; or
by distilling pure nitric acid with phosphorus pentoxide:

2HNO3 + PA = 2HPO3 + NA-

Properties. — A white crystalline solid, beginning to
decompose at 40° C. into tetroxide and oxygen. (Write

9G QUKSTIONS AND KXKIUMSKS.

the LMiuation.) It is Vijry hygroscopic, aiul rapidly doli-
(pioscoa in moist air. It unites witlj water forniiiig
nitric acid :

N,()r. + up --= 2HNO3.

QUESTIONS ANJ) K\KKC1SI<]S.

1. Calculuto tlie weights of 1 htro of nitrogon and of ammonia,
meaamed at 0° and 7(50.

2. Calculato tJ:o vohime of air to give 20 Htres of nitrogen.

3. What weight of amnionic chhiride is retiuired to give 5
Utres of anunonia gas measured at 17*"' C. and 700 mm. pressure?

4. Calculate the volume of ammonia gas at 20° C. and
700 nun. formed by heating 100 grams amnionic cliloride with
lime.

5. Hold the moist stoppers of the ammonia and hydrochloric
acid bottles near each other. Explain what you observe.

6. Warm some amnionic chloride solution with sodic hyd-
roxide solution. Observe the smell. What substancew have
been formed ? Write the equation.

7. In determining the composition of ammonia (Art. 80), how
can the hydrogen be got rid of in order to measure the volume
of nitrogen ?

8. What weight of sodic nitrate (NaNOg) is required to pre-
pare 200 ^rams of nitric acid? How much sulphuric acid is
used ?

9. How much nitric acid can be o})tained by the decomposi-
tion of 10 lbs. of saltpetre?

(^(TEHTiONS AND EXKRCISES. 97

10. Linu! wi'tor is an antidote to poisoning by nitric acid.
Explain its action.

11. Calculate the weights of nitric acid required to neutralise
10 grams each of the following bases and oxi<le8 :-Sodic hyd-
roxide (NaOH), i)ota8Hic hydroxide (KOH), calcic hydroxide
(Ca(OK)a), magnesia (MgO), and litharge (PbO).

12. Write the formulas for nitrates of the following metals,
referring to the table of elements f(<r the valences: — Calcium,
silver, iron, n. jrcury, copper, cobalt, barium, magnesium, and
aluminium.

13. What experiments already made illustrate the direct re-
placement of hydrogen by metals ?

14. How many litres of nitrogen monoxide, measured at 15° C.
and 730 mm. pressure, can be prepared from 10() grams ammonic
nitrate ? What weight of water is formed ? What volume will
it occupy at 200° C. and 700 mm. pressure ?

15. How much ammonic nitrate must be used to fill a 10 gal-
lon receiver with citrous oxide under a pressure of 60 lbs. to the
square inch when the thermometer reads 10° C. ?

16. What volume of nitrogen monoxide at 16° C. and 750 mm.
will completely burn 1 gram carbon ?

C 4- 2N2O -= 2N2 -f COa.

17. What volume of air will convert 10 cubic inches of nitro-
gen dioxide into the tetroxide ?

98 SEA WATER.

CHAPTER IX.

THE HALOGENS.

91. Sea Water. — Sea water is a dilute solution o
salts, some in much larger proportions than others. Thi
total quantity in 100 parts is about 3.5. The specifi(
weight of sea water at 0° C. is 1.03. Common sal
(NaCl) is present in the greatest pr ^^;ortion ; next comi
magnesia chloride (MgClj), magnesfj sulphate (MgSO^)
calcic sulphate (CaSO^), potassic chloride (KCl), an(
magnesic bromide (MgBrj). The bitter taste is due t(
the magnesic salts. Magjiesic iodvie (Mglg) is presen
in sea water in very minute quantity.

When sea water is evaporated, the sparingly solubli
gypsum (CaS04.2H20) first crystallises out, and later
sodic chloride. This latter salt is a compound of tin
motal sodium with a non-metal, chlorine, which i
therefore called a halogen, or " salt generator." Th(
" mother liquor," an intensely bitter liquid {bittern)
contains compounds of two elements very similar t(
chlorine, viz., bromine and iodine] and these three
with a fourth, form the group of halogens, whicl
are peculiar among the elements, as forming wit)
the metals salts which contain no third element, e.g.
NaCl, KBr, Mgl2, CaFj, <fec. (Compare with KNO3
Na2S04, (fee.) Sea water is the principal source of th(
first three of the halogens. — (In the following sectioni
note resemblances and difierences among the halogens.

CHLORINE. 99

CHLORINE AND ITS COMPOUNDS.

92. Chlorine.— (Cr = 35.37). Very widely diffused
in water and on land ; never free, but in combination as
chlorides.

Preparation. — Experiment 62.*— Put a little sodic chlo-
ride mixed with manganese dioxide (MnOg) in a t.t,, pour
some sulphuric acid in, and heat gently. Chlorine gas is set
free. Note colour and smell (cautioualy) .

This chemical action is most clearly represented in
three steps :

(1) HjSO, + NaCl = NaHSO, -f HCl.

(2) MnOj + H2SO4 = MnSO^ + H2O -\- O.

(3) 2HC1 4- = HjO -h CI2.

The substances ultimately formed are sodic hydric sul.
pkate (NaHSO^), manganous sulphate (MnSO^), chlorine,
and water. (Write a single equation representing the
action. You know the formulas of all the substances.
Remember that the equation must balance.)

Experiment 6«^.^ — Heat gently a little manganese dioxide
and hydrochloric acid in a test-tube. Chlorine is given oflf :

4HC1 + MnOa = MnCla + Clj, + 2HaO.

This is the method by which chlorine is generally pre-
pared on the large scale.

Experiment 64.* — Warm a little hydrochloric acid with a
small crystal of potassic chlorate (KClOa), and note the evolu-
tion of chlorine : KCIO3 -f 6HC1 = KCl + SClg -f 3Hj,0.

All these and similar methods may be considered as so
many ways of oxidising hydrochloric acid :

* Fill the test-tube with dilute caustic soda when the experiment is finished.

100 CHLORINE.

2HC1 -h O = HjO + CI,,

and, indeed, chlorine is prepared on the large scale by
passing a mixture of air and hydrochloric acid over hot
bricks.

Prcfbrties. — A heavy, greenish yellow gas ; i? liquid
at f>° under a pressure of six atmospheres ; causes suffoca-
tion when breathed ; has violent irritating action on
mucous membranes, and may cause catarrh or ulceration;
soluble in water, 3 v^ols. in I at 10° C; the aqueous solu-
tion acts as a powerful irritant both externally and inter-
nally ; antidotes are white of egg, milk, ammonia, lime
water, soap, and other alkaline substances. Chlorine, both
as gas and solution, is a powerful antiseptic and deodoriser;
it is an antidote to poisoning by prussic acid (HON),
sulphuretted hydrogen (HgS), and ammor,i< sulphide
((NH4)2S). The action on prussic acid has not been ex-
plained ; that on sulphuretted hy'rogen and ammonic
sulphide is explained by the follow; ^ equations :

HjS + CI2 = 2HC1 -t S

(NHJ^S -h 4CI2 = 8HC1 + N, 4- S.

The substances formed are not poisonous.

Experiment 65. — Prepare a little chlorine as in Experiment
63, and hang a narrow strip of moist turkey-red cloth in the t.t.
It is bleached whit'^. Try other vegetable colours, e.g., a small
flower. Try a mineral colour, e.g., red lead.

Chlorine and water bleach organic colouring matters,
but not mineral. The presence of water is necessary.
If dry chlorine be used, it does not bleach. A solution
of chlorine in water griidnally decomposes :
H2O -f CL, = 2HC1 -f- O.

HYDROCHLORIC ACID. 101

This shows the nature of the bleaching action of chlo-
rine. It is really an oxidation by means of the oxygen
of water, the hydrogen combining with chlorine to form
hydrochloric acid. The colouring matter is destroyed, —
geiit^rally oxidised to carbon dioxide and water.

Experiment 66. — Prepare some chlorine water, by leading the
gas prepared as in Experiment 63 into a bottle of water, using a
gas-iJelivery tube bent twice at right angles and reaching to
the bottom of the bottle. (This should be done under a hood or
in ,1 draught crpboard. ) Note the colour of the solution. Try
its effect on litmus. Explain.

Chlorine combines directly with most elements and
thereby forms chlorides.

Experiment 67- -Prepare a little chli>rine (Experiment 63)
and drop some powdered antimony into the tube. It catches
tire as soon as it falls into the gas : 8b -|- 5C1 = SbClg. Try a
bit of ph 'sphorus in the deflagrating spoon ; and a lighted taper.

Chlorine supports the combustion of tallow, wax, tur-
pentine, and other organic substances containing a large
percentage of hj'^drogen. It combines with the hydrogen
to form hydrochloric acid, setting the carbon free.

Test. — Add some starch paste to a dilute solution of potas-
sic iodide (Kl), and then a few^ drops of chlorine water. The
deep blue iodide of starch is formed : KI -|- CI = KC) -f- I.

Compounds of Chlorine.

93. Hydrochloric Acid (HCl = 36.37.)-Alao

called muriatic acid, and spirit of salt. If equal volumes
of hydrogen and chlorine 1 • mixed in the dark and then
exposed to diffused daylight they combine without any

102 HYDROCHLORIC ACID.

change of volume, forming a colourless gas, hydrochloric
acid. If exposed to direct sunlight they combine with a
violent explosion. '

Preparation. — Experiment 68. — Put some dry sodic chlo-
ride in a t.t., pour strong sulphuric acid over it, fit the gas-delivery
tube used in Experiment 66, warm gently, and collect a t. t. of
the gas by displacting the air. (You can see when the t. fc. is
full by the fuming of the gas at the top ; and by its overflowing on
Ihe fingers and making them feel warm.) Close with the thumb
and open under water. Test, by taste and litmus, the water
which rises in the tube.

Solution of hydrochloric acid is prepared in this way
on the large scale as a by-product of the alkali manufac-
ture :

2NaCl + H2SO4 = 2HC1 -f- Na^SO,.

(Write the names and weights. What remains in the
t. t. in Experiment 68])

Properties. — A colourless gas, soluble in water, 500
vols, in 1 at O'* C; the solution is heavier than water.
The saturated solution becomes weaker on boiling until
it contains 20;^ p. c. of the acid, then distils unchanged
at 110° C. The specii^c weight of this solution is 1.11.
(What similar case has been studied already 'i) The
specific weight of the gas is 1.269 (air = 1 ). At — 4° C.
and with a pressure of 25 atmospheres it condenses to a
colourless liquid.

iExperiment 69. — Colour some solution of hydrochloric acid
with litmus, and add to it a solution of caustic soda until the
litmus begins to turn blue. Taste the solution. (What does it
taste of?) Evaporate to dryness on the water bath. Crystals of
common salt remain: NaOH + HCl = NaCl -f H2O. Try
the same with potassic hydroxide.

CHLORIDES. 103

Hydrochloric acid is a monobasic acid, as can be seen
from xi/8 formula. Its molecule contains only one atom
of liydrogen, which cannot be partially replaced by atoms
of metals. It is called a haloid acid Its aquecub solu-
tion dissolves tin, iron, zinc, alumii.ium, and other metals.

Chlorides. — These are formed by replacing the
hydrogen of the acid by metals, a monad replacing H, a
dyad 211. a triad 3H, <fec. (Write the formulas for
chlorides of silver, mercury, lead, copper, nickel, anti-
mony, and tin.)

Experiment 70- — Drop a little hydrochloric acid sohition
into solutions of argentic nitrate (AgNOg), mercurous nitrate
(Hg2(N03)2), and plumbic acetate (Pb(C2H30.^):i). Precipitates
are formed. Note any differences in their appearance.

Mercurous chloride, and the chlorides of silver and
lead are insoluble in water (plumbic chloride, sparingly
soluble) ; the chlorides of the other metals are soluble
(but a few are decomposed on contact with water).

AgNOg + HCl = AgCl + HNO3.

The silver and hydrogen atoms exchange places. (Write
equations for the other two.)

Hydrochloric acid is irritating when breathed as a gas. The
strong solution is a corrosive poison. (Alkaline substances are
antidotes ; magnesia, lime water, or soap may be used,) A
very dilute solution is a tonic. Hydrochloric acid is secreted
into the stomach during digestion, in which it plays an impor-
tant part.

Tests. — Add a few drops of argentic nitrate (AgNO,). A
curdy white precipitate (AgCl) is formed, insoluble in nitric acid,
sohible in ammonia solution. (Try with solution of hydrochloric
acid, and also with a chloride. )

104 OXIDKS OF CHLORINE.

94. Oxides of Chlorine. — Chlorine and oxygen
do not unite directly, but by indii'^ct methods three
compounds can be obtained, viz., chlorine monoxide,
CljO ; trioxide, CI2O3 ; and tetroxide Cl.^O^. They are
dangeiously explosive compounds of little ir'iportancc.

95. Chlorine Monoxide.— Cl^O. A yellow gas

prepared by the action of dry chlorine on dry mercuric
oxide :

2HgO + 2CI2 = HgCl.,.HgO + Cl.p.

It dissolves in water forming hypocJdorous acid :
C1,0 + H2O = 2HC10.

96. Chlorine Trioxide. — Cl.pa. A greenish yel-
low gas, of irritating action when breathed, dangerously
explosive. Prepared by warming a mixture of nitric
acid, potassic chlorate, and sugar : 2HCIO3 -f- ^'S^s =
CI2O3 -f- 2HNO3. It dissolves in water forming chlorous
acid :

CIA 4- H2O = 2HCIO2.

97. Chlorine Tetroxide.— CI2O4. Also called per-
oxide of chlorine. It is a yellow gas of not unpleasant
odour. Very explosive when heated.

Experiment 71. — Put a small crystal of potassic chlorate iu
a t.t., held by the t.t. holder or a pair of forceps. Add a few
drops of strong sulphuric acid, and heat gently, taking care that
the mouth of the t.t. is directed away from everybody. The gas
is evolved and quickly explodes with violence :

3KC10, + 2H.,S0^ = KCIO4 + 2KHS0^ -f G\^0^ + H,0.

HYPOCHLOKOITR ACID. 105

It dissoh 31, in a caustic potash solu ion forming chlorite and
chlorate. ( Wh>>* substance already stu 'ed is similar ?) :

01,0, -f ?KOH = KCIO, 4- KCIO3 4- H,0.

98. Oxygen Acids of Chlorine. — Like nitrogen

chlorine combines with hydrogen and oxygen in several
proportions, forming a series of oxygen acids :

Hypochlorous acid HCIO

Chlorous acid HCIO.^

Chloric acid HCIO3

Perchloric acid HCIO^

The names of these acids illustrate very well the use of
the terminations -ic and -ous ; and of the prefixes hi/po-
und per-. Hypoc\i\oronH acid is below chlorous acid in
proportion of oxygen, /^erchloric contains more oxygen
than chloric- -These acids are all monobasic, and mostly
unstable.

99. Hypochlorous Acid.— HCIO.

Prepakation. — By the action of chlorine watei on
freshly precipitated mercuric oxide :

HgO -f H,0 4- 2CI2 = HgCl, + 2HC10.

Properties. — It has never been obtained except as
a dilute aqueous solution. It has a pleasant, somewhat
chlorous, smell (that of bleaching powder), and bleaches
powerfully.

Hypochlorites. — The salts of hypochlorous acid are
important, particularly bleaching powder :

(CaCl, . Ca(OCl),).

106 CHLOROUS ACID.

Erperiment 72. — (Generate some chlorine as in Experiment
62, and pass it for a short time into a beaker containing a very
dilute solution of sodic hydroxide :

2NaOH -h CI, = NaCl -|- NaClO + H,0.

Sodic chloride, sodic hypochlorite, and water are
lorraed. Keep tlie solution for furtlier experiments.

Experiment 73. — Moisten a small piece of turkey-red cloth
with acetic acid, and put it into a portion of the solution from
Experiment 72. The colour is bleached.

Experiment 74. — Heat another portion of the solution nearly
to boiling, and then try Experiment 73 with it. The colour is
not bleached.

Hy})oclilorites are readily decomposed by heat into

chlorides and chlorates, one portion giving up its oxygen

to the other :

3KCI0 = KCIO3 + 2KC1.

Experiment 75. — Warm a third portion gently with a little
hydrochloric acid and note the smell of chlorine :

KCIO + HCl = HCIO + KCl
HCIO 4- HCl = CI, + H,0.

Hypochlorous acid is a very weak acid, its salts being
decomposed even by carbonic acid. Hence the chlorous
smell of bleaching powder. (Explain).

100. Chlorous Acid. — HCIO2. Cannot be obtained
except as a solution in water (Art. 96). Its salts, the
chlorites, are unstable and unimportant.

101. Chloric Acid. — HCIO3. There is no corres-
ponding oxide known. (What would its formula be 1
Compare with nitric acid.)

CHLORIC ACID. 107

Preparatiox, — By action ofjluosilicicacid on solution
of potassic cljlorate. An insoluble salt of potassium is
formed {jyrecipitated)^ and chloric acid remains in solu-
tion :

2KCIO3 -\- HjSiF^ = K,SiF8 + 2HCIO3.

Properties, — It forms a colourless, acid solution, of
strong oxidising properties. It readily decomposes into
chlorine, oxygen, and perchloric acid, and cannot be ob-
tained free from water.

Uhlorates. — Chloric acid is monobasic, and its salts
are all soluble in water. They can be prepared by dis-
solving the corresponding bases in chloric acid ; but
those of the stronger bases can be formed directly by the
action of chlorine. Thus, when chlorine gas is passed
into a Jiot solution of pocassic hydroxide, chloride and
chlorate are formed (Exp't 74) :

6K0H -f 3CI2 = KCIO3 -f- 5KC1 -f 3H2O.

Similarly with sodic, calcic, baric, and other hydrox-
ides. The weaker bases, however, do not react in this
way. Potassic chlorate is only sparingly soluble, and
can thus be separated from the more soluble chloride.
(How 1)

Experiment 76. — Pass chlorine gas through a strong solution
of caustic potash until it begins to smeil of chlorine. Evaporate
on the watei- bath until crystals begin to form, then set aside
to cool. Pour off the liquor, dry the crystals on filter paper and
keep them.

Tests. — 1. Dry chlorates are known by the formation of
chlorine tetroxide when acted on by strong sulphuric acid.

2. Colour with indigo sulphate, add a few drops of sulphuric
acid, and boil. The colour disappears. (What other acid an-
swers to this test ? How would you distinguish ?)

108 PERCIILOKH' A('II>.

102. Perchloric Acid— H CI 04. This is the most
stable of all the oxygen acids of rllorine.

PuEPARATioN. — By 'Hstilliiig chloric acid :

3HCIO3 -= HCIO, -h 01, + 20, -f- H,0.

AIho, by the action of fiuosilicic acid on solution of potas-
sic perchloratfi :

2KC10, -I- H,SiF8 = KaSiFfl + 2HC10,.

(How are tlie two substances separated?)

pHOPEUTiKs. — It is a strong acid, of very great oxid-
ising power, exploding violently when dropped on char-
coal. It sets fire to wood, paper, tfec. Tlie acid and its
salts are uniniportaut practically.

Perchlorates. — Potassic perchlorate is prepared by
heating potassic chlorate until it fuses and at length be-
comes nearly solid again :

2KCIO3 = KCIO4 + Oo + KCl.
(How can the two salts formed be separated i)

BROMINE AND ITS COMPOUNDS.

i03. Bromine. — (Br' = 79.75.) Found as bromides
in sea water, salt springs, and crude Chili saltpetre ; also
as silver bromide (AgBr) in some silver mines. Certain
sea-weeds extract bromine and iodine from sea water and
store it up in their tissues. These two elements are pre-
pared generally in one operation from the " mother
liquor " of common salt, kelp (ashes of sea-weed), or
Chili saltpetre.

Prepa RATON. — A jmall sample of the liquor is first
analysed and the quantities of iodine and bromine de-

BROMINE. 109

tenuiiied. Then enough niangaueso dioxide and sul-
phuric acid to set free the whole of the iodine is added
to a large quantity of liquor : 2K[ -\- 3H.^S04 -f MnO.^
= 2KHSO4 + MnSO^ + J, + 2H2O. The iodine is
distilled off, more manganese dioxide and sulphuric
acid are added to set free the bromine, which is then
distilled and condensed in separate receivers : 2KBr -j-
3H2SO4 -f MnOj = 2KHSO4 + MnSO^ + Bra +
2H,0.

Experiment 77. — Mix about equal (juantities of well pow-
dered manganese dioxide and potassic bromide, put in a t.t.,
add a little sulphuric acid, and heat gently. Bromine is evolved,
condensing on the sides of the t.t. as a dark reddish -brown
liquid. Take care not to breathe the vapour. Pour some of the
heavy vapour into a second t.t. containing a little water, and
shake it up. The water dissolves the bromine.

Properties. — A heavy liquid (specific weight = 3. 18),
almost black when in ma.ss ; dark red, in thin layers.
It is the only liquid element at ordinary temperature,
excepting mercury. It freezes at — 22° C, and boils at
63° C, forming a reddish-brown vapour, which has a very
unpleasant smell and an irritating action on the mucous
membranes. On account of its low boiling point and
corrosive action bromine should be handled very care-
fully. Its vapour should never be inhaled unless diluted
with much air.

Experiment 78. — Try to bleach with bromine water made in
Experiment 77.

Bromine is soluble in water to about 3%. It bleaches
in the same manner as chlorine, but not so powerfully.

Experiment 79- — Dissolve a small crystal of potassic bro-
mide (KBr) in a test-tube one-third full of water, and add a few

110 HYDROBROMIC ACID.

drops of chlorine water. Bromine is set free. Add a few drops
of carbon bisulphide, close with the thumb and shake the t.t.
violently. Allow to stand a moment and observe. (What
property of bromine is illustrated ?)

Chlorine displaces bromine from combination with
metals ; in other words chlorine has greater chemical
affinity (chemism) for the metals.

COMPOUNDS OF BROMINE.

104. Hydrobromic Acid.— HBr.

Preparation.— Experiment 80.— Add a few drops of
strong sulphuric acid to a crystal of potassic bromide and warm.
(What action would you expect ? What do you observe ?)
Hydrobromic acid cannot be prepared in this way because of its
decomposition by strong sulphuric acid ;

H^SO^ 4- 2HBr = Br^ + SO, -f 2H,,0.
Compare hydrochloric acid.

Hydrobromic acid is prepared by the action of phos-
phorus and bromine on water. A bromide of phos-
phorus is first formed and this is then decomposed by
the water :

P. tribroniide. Phosphorous acid. .

PBrg -f 3H2O = 3HBr + P(OH)

To prepare it on the small scale, put a little bromine in the
bottom of a t.t , then a layer of pieces of glass on which a few
small bits of phosphorus are laid, cover this with an inch or
two of small bits of glass, moisten with a drop or two of water,
and distil with a gentle heat, receiving in a t.t. of water. A
solution of hydrobromic acid is obtained.

Properties. — A heavy^ fuming gas, very soluble in
water, forming a solution similar to that of hydrochloric

BROMINE AND OXYGEN. Ill

a.iu. It is a monobasic acid, and acts on bases to form
salts called bromides.

Bromides. — These are very like the chlorides in ap-
pearance and properties. Bromine unites directly with
nearly all metals. The bromides can all be decomposed
by chlorine. The potassium salt (KBr) is the most im-
portant. It is much used in medicine. Argentic bromide
(AgBr) is used in photography. Ammonic bromide
(NH^Br) is used as a medicine. Most of the bromides
are soluble in water. A few are insoluble.

Experiment 81. — To a few drops of solution of potassic
bromide add a drop of argentic nitrate. Argentic bromide is
precipitated :

AgNOj 4- KBr = KNO , + AgBr.

Note its colour and try the action of ammonia solution and of
nitric acid on it (dividing it into two portions). Make the same
experiment with solutions of mercurous nitrate (Hga(N03)a),
and plumbic acetate (Pb(C2H302)5), instead of argentic nitrate.
Write the equations.

Tests for Bromides. — Experiments 79 and 81. In the
test with chlorine care must be taken not to use too much, as
there is a colourless chloride of bromine. Except in weak solu-
tions the bromine can be liberated by strong sulphuric acid.
(Try it. ) Free bromine colours starch-paste orange-yellow.

105. Bromine and Oxygen. — No compounds of

bromine and oxygen are known, but two oxygen acids,
hypobromous (HBrO), and bromic (HBrOg), have been
prepared. They and their salts (the hypobromites and
bromates) are prepared by methods similar to those for
the hypochlorites and chlorates. Potassic hypobromite
(KBrO) is used in estimating urea. (Write equations

112 IODINE.

for the action of bromine on moist mercuric oxide, and
on dilute and strong solutions of potassic hydroxide).

IODINE AND ITS COMPOUNDS.
106. Iodine.— (I' = 126.5). Never f und free in
nature, but always as iodides, in small relative quanti-
ties, but widely ditfused. Minute traces of iodides are
present in sea-»7ater. Certain plants (kelp and sponges)
extract these and store them in their tissues. Some
sea animals do the same, e.g., the cod. The ashes of
kelp contain from 0.1 per cent, to 0.3 per cent, of
iodine, and are the principal source of this element.
The weed is washed up on the coasts of Ireland and
Scotland in great quantities. It is gathered, dried,
burned in shallow pits at a temperature not hisfh enough
to volatilise the iodides and bromides, and then lixivi-
ated. The solution contains sodic carbonate (NajCOg),
chloride (NaCl), sulphate (Na2S04), bromide (NaBr),
iodide (Nal), &c. It is evaporated to crystallise the
carbonate, chloride, and sulphate ; and the iodine and
bromine are prepared as described in Art. 103.

Preparation. — Experiment 82. — Mix well about equal
quantities of potassic iodide (KI) and manganese dioxide, put in
a t.t., add a little strong sulphuric acid, and heat very slightly
for a few minutes. Violet vapour of iodine appears and con-
denses on the cooler parts of the tube, as a steely looking solid.

2KI + 3H2SO4 -f MnOa = MnSO.^ + 2KHSO4 + Ig + 2HaO.

Properties. — Blackish grey solid, somewhat metallic
in appearance (compare sulphur, selenium, and tel-
lurium), opaque and crystalline. Its odour suggests that
of rotting sea-weed. The specific weight of the solid is
4.948 (calculate that of the gas). It melts at 11 4** C,

IODINE. 113

and boils at 200° C, forming a splendid deep-blue vapour,
which is purple when mixed with air. It volatilises
slowly at ordinary temperatures and must therefore be
kept in well stoppered bottles. Both iodine and bromine
(as well as chlorine) corrode cork.

Experiment 83. — Put a few crystals of iodine in a t.t., fill
half-full of water, shake for some time, and note that a little of
the iodine dissolves. Add a small quantity of potassic iodide,
and shake up. The whole of the iodine dissolves. A tri-iodide
(KI3) is formed.

Iodine is sparingly soluble in water, but freely so in
solutions of certain salts, particularly potassic iodide.

Experiment 84- -To f ion of potas&ic iodid, in two test-
tubes add respectively chlorine water and bromine water, then
a few drops of carbon bisulphide (CSg) ; shake well and allow to
stand a moment. tWhat conclusions do you draw with regard
to the relative chemism of the three halogens ?)

Experiment 85- — Try the solubility of iodine in a mixture
of equal volumes of alcohol and water, and in chloroform, using
small quantities of each of the substances mentioned.

Iodine has an irritating action on the skin and mucous
membranes, but not so violent as chlorine and bromine.
It stains the skin yellow, but the stain disappears very
soon, unless the iodine is applied often. It promotes
absorption and thus reduces swellings, and is much used
as an external application.

Tincture of Iodine is a solu+ion of iodine and potassic
iodide in rectified spirit (alcohol a'ld water) — I pint of
spirit to ^ oz. iodine and ^ oz. potassic iodide.

Solution of Iodine. — Twenty grains of iodine, thirty

grains of potassic iodide, dissc' ed in 1 oz. of distilled

water.

114 HYDKIOlJlO ACID.

Tests. — 1. With chloriEe water and carbon bisulphide as in
Experiment 84.

2. Free iodine colours starch paste deep blue. (Try with
iodine water).

COMPOUNDS OF IODINE.

107. Hydriodic Acid, HI.—

Preparation. — In the same way as hydrobromic acid
(Art. 104). (Write the equation.) Hydrogen and iodine
do not unite directly under ordinary circumstances.

It can also be prepared in solution by the action of
iodine on sulphuretted hydrogen iHoS) in presence of
water.

Ezperimeilt 86. — Put a few small pieces of ferrous sulphide
in a t.t. fitted with the gas-delivery tube of Experiment 66, add
some sulphuric acid diluted with about five times its volume of
water, and pass the evolved gas into a test-tube of water in
which is some finely divided iodine. The iodine disappears and
sulphur is precipitated :

HaS + la = 2HI -f- S.

Test a portion of the solution with litmus, add a little iodine
water, shake up, and set aside for further experiments.

Properties. — A heavy gas (specific weiglit 4.41G),
colourless, fuming in moist air owing to its strong attrac-
tion for water, with which it forms minute droi)s of solu-
tion. It dissolves readily in water, forming a strongly
acid solution similar to those of hydrochloric and hydro-
bromic acids. The gas is easily decomposed by heat, and
the solution in water is decomposed by the oxygen of

the air :

2HI 4- O .= H,0 + I,.

IODIDES. 115

(Compare with the stability of hydrochloric acid.) It is
a monobasic acid and unites with bases to form iodides,

e &f< •

KOH + HI = KI + HjO.

Iodides. — Of these the most impoT-tnant is potassic
iodide (KI), of which very large quantities are used in
medicine. The following iodides are insoluble in water
and are bright in colour : Argentic (Agl), merairous
(Hg2l2), mercuric (Hgl2), cuprous (Cu^IaS and plumbic
(Pblj), the latter very sparingly soluble.

Experiment 87. — Put a little of the solution of hydriodic
acid in four test tubes, and add a drop or two of argentic nitrate
to one, of mercurous nitrate to a second, of mercuric chlo'ide
(HgClj) to a third, and of plumbic acetate to a fourth, xsote
the color, &c., of the precipitates formed :

AgNO, + HI =- Agl + HNO,.

Write equations for the other three. Try the same experiments
with a dilute solution of potassic iodide (KI).

Tests. — These apply to both free acid and iodides.

1 . Add to the solution a few drops of argentic nitrate solution.
A yellow precipitate of argentic iodide is formed. Divide this
into two portions. Test one part with ammonia solution ; it is
whitened, but not dissolved. Test the other with nitric acid ;
it is not dissolved.

2. Add some starch paste and a few drops of chlorine water
to any solution containing an iodide. A blue colour appears.
(Explain).

To test for chlorides, bromides, and iodides in a mixture — Distil
a small portion of the carefully dried mixture with dry powered
potassic bichromate (K^CrjOy), and strong sulphuric acid. (The
apparatus must be dry.) Receive the distillate in a t. t. contain-
ing a little water, add caustic soda to it, until the colour of the

116 IODINE AND OXYGEN.

bromine and iodine disappears. A yellow colour remains, that
of sodic chromate. This proves the presence of a chloride in
the mixture. — Explanation : A volatile compound, chromic
oxychloride (CrOjCl.^), is formed, distils, and forms chromic
acid with the water :

CrOaCl, + 2H2O = H^CrO^ + 2HC1.

Dissolve a small quantity of the mixture in water in at. t.,
add a few drops of carbon bisulphide, and then chlorine water
drop by drop, shaking up after each addition and observing the
colour of the carbon bisulphide. The violet of iodine appears
first, but disappears on the addition of more chlorine owing to
the formation of an almost colourless compound (ICl); after-
wards, on the addition of more chlorine, the orange colour of
bromine appears.

108. Iodine and Chlorine. — Two compounds are
known, the monochloride (ICl), and the trichloride
(ICI3), formed by direct union of the elements. (What,
then, is the valence of iodine 1)

109. Iodine and Oxygen. — ^Only one compound

of these two elements is known, viz., iodine pentoxide
(I.2O5), prepared by carefully heating the corresponding
acid, iodic acid (HIO3) •

2HIO3 = H.,0 + I.A-

When heated more strongly it decomposes into its ele-
ments. It is a deliquescent white solid, and unites with
water to form iodic acid.

Iodic Acid, HIO3. — Can be prepared by oxidising
iodine with strong nitric acid, and evaporating the solu-
tion to dryness. It is a white crystalline solid, freely
soluble in water, forming a strongly acid solution. It

FLUORINE. 117

is a powerful oxidising cagent. When mixed with hydri-
odic acid, it oxidises the latter, setting free iodine :

HIO3 + 5HI = 31, + 3H,0.

loDATES. — Besides the normal iodates (KIO3, ifec),
there are peculiar acid iodates, e.g., KIO3.HIO3, and
KIO3.2HIO3.

Tests — Add chlorine water and starch paste to a solution of
an iodate. No blue colour appears. (What conclusion do you
draw with regani to chemisra of iodine and chlorine in oxygen
salts?) Now add a little sodic sulphite or sulphurous acid.
Blue colour appears : KIO3 + SNa^SO, = KI + SNa^SO^.

KI + CI = KCl + I.

FLUORINE AND ITS COMPOUNDS.

110. Fluorine (F' = 19.1).— Is not known free,
but only through its compounds, the fluorides. Many
attempts have been made to prepare it, but with no suc-
cess. It invariably attacks the vessels in which its
preparation is attempted. It seems to have even stronger
chemical affinities than chlorine. — The chief compounds
of fluorine occurring in nature are fluor spar or calcic
fluoride (CaF,), and cryolite (3NaF.AlF3). — Fluorine
forms no compound with oxygen, and is the only element
of which this is true.

111. Hydrofluoric Acid.— HF.

Preparation. — By distilling fluor spar with sulphuric
acid in lead or platinum vessels and receiving in water :

CaF2 + H2SO, = 2HF 4- CaSO^,

Glass or porcelain vessels cannot be used, as they are
corroded by hydrofluoric acid. The pure acid is very

IIH HYDROFLUORIC ACID.

dangerous, and is not often prepared. The aqueous
solution is kept in leaden or gutta percha bottles.

Properties. — A colourleay, fuming, acid liquid, boiling
at 19.4'^ C. It is soluble in water, forming a strongly
acid solution.

Experiment 88- — Put a little calcic fluoride in a small leaden
dish, add some sulphuric acid and cover the dish with a piece
of glass which has been coated with paraffin wax through which
some word has been scratched with a knife or a pin . Set aside
for a while, then warm the wax, and rub it oflF. The word has
been etched into the glass.

Glass contains silica (SiO.^). This is acted on by the
hydrofluoric acid with the formation of volatile com-
pounds :

SiO, + 4HF = SiF^ -I- 2H2O.

Hydrofluoric acid is monobasic. It forms salts called
fluorides, analogous to chlorides, bromides, and iodides.

Fluorides. — These are mostly colourless salts, soluble
in water ; but calcic Jluoride (CaFj), baric Jluoride (BaFj),
and strontic jluoride (SrFj) are insoluble. The fluorides
have a tendency to unite with each other and with hydro-
fluoric acid forming double Jluorides, e.g., SNaF.AlFaand
HF.KF.

Test.— See Expt. 88.

QUESTIONS AND EXERCISES.

1. Compare the halogens (1) as to their chemism for metals,
and (2) as to their chemism for oxygen.

QUKSTIONS AND EXERCISES. 119

2. What wtiight of manganese dioxide (MnOa) must be used to
prepare chlorine for tlie conversion of 10 lbs. of potassic hydrox-
ide (KOH) into chlorate and chloride ?

3. Calculate the specific weight of chlorine (air = 1). Calcit-
late the weight of I litre at 0° and 760 mm.

4. Why cannot chlorine be collected over mercury or water ?

5. What weight of pure hydrochloric acid is there in 1 litre of
the solution of sp, wt. 1.11?

6. Compare the bleaching power of chlorine (and water), and
hypochlorous acid .

CI2 + HjO = 2HC1 + 0.
HCIO - HCl -j- 0.

What weight of chlorine is equivalent to 100 grams of hypochlor-
ous acid ?

7. Compare the oxygen compounds of chlorine and of nitrogen.

8. What weight of sodium chloride must be used to prepare
chlorine enough to set free the bromine from 100 oz. of potassic
bromide (KBr) ?

9. What weight of potassic chlorate (KCIO3) contains one
equiv-^lent (in grams) of oxygen ?

10. Write the formulas of magnesic, amnionic, ferric, cobaltie,
and wercMrojis chlorides ; of mercuric, argentic, and ftaric iodides ;
and of ferric bromide.

11. Fluorine has never been prepared. How then has its
atomic weight been determined ?

12. Write the formulas of the chlorine acids and calculate the
percentage of oxygen in each. Apply the Law of Multiple Pro-
portions.

13. What weight of hydrochloric acid is equivalent to 100
grams sodic hydroxide (NaOH) ? To 100 grams potassic hydrox-
ide (KOH) ? To 100 grams calcic hydroxide (Ca(OH) J ?

120 THE SULPHUR (JROUP.

CHAPTER X.

SULPHUR, SELENIUM, AND TELLURIUM.

112. The Sulphur Group.— The three elements
mentioned hero form a group closely related in their
chemical and physical properties. Each unites witJi
hydrogen to form a gas analagons to water in formula
(HjS, H.^Se, HjTe). They unite with oxygen in two
proportions (SOj, SO3 ; SeOj, — ; TeOj, TeOg) ; and eacli
has tw ) acids corresponding to the oxides. As in the
case of the halogens, there are gradations in the proper-
ties in passing from one element to the next of this
group of elements. Thus, while sulphur is a distinct
non-metal, selenium is slightly metallic, and tellurium
more so, in its appearance. The attraction for oxygeii
is stronger in sulphur, weaker in selenium and tellu-
rium.

SULPHUR AND ITS COMPOUNDS.

113. Sulphur (S"'*^'^^ = 31.98).

Occurrence. — Found uncombined, in grea^ isses in
volcanic districts, particularly in Italy, Iceiand, and
Sicily. The compounds of sulphur found in nature are
very numerous and abundant. There are two principal
classes : (1) sulphides, including a great many ores of
metals, e.g., galena (PbS), zinc blende (ZnS), cinnabar
(HgS), and iron and copper pyrites; and (2) sulphates,
e.g., gypsum (CaS04.2H20), heavy spar (BaSO^), Epsom

SULPHUR. 121

salts (MgS0,.7H,0), and green vitriol (FeSO^.TH.O).
Sulphur also forms an essential constituent of animal and
vegetable bodies.

Preparation. — (1) Crude sulphur is heated in shallow
pits, and the melted sulphur is run ofl' from the earthy
impurities. It is further purified by distillation, the
vapour being led into cool chambers where it solidi-
fies and falls down as " flowers r>f sulphur." When the
walls of the chamber become hot the sulphur remains
li(piid and is run off into moulds roll brimstone).

(2) Iron pyrites (FeSo) when distilled gives off one-
third of the sulphur :

3FeS, = Fe^S^ + Sj.

This can be condensed, <fec., as above. (Try with
j)owdered pyrites in a narrow glass tube sealed at one
end.)

(3) Sulphur is also obtained as a by product in the
process of purifying coal gas.

(4) The waste liquor from the alkali manufacture con-
tains sulphur, and has been used as a source.

Properties. — Sulphur has three allotropic modifica-
tions, two crystalline, and one amorphous (formless).
These differ in specific weight and other [)hysical pro-
perties.

Experiment 89. — Heat carefully until completely fused
some pieces of roll sulphur in a porcelain dish. Then take the
burner away, and hold a cork in the liquid until a crust forms
over the surface. Break two small holes in this crust on op-
posite sides, and pour out the liquid part into another dish.

122 SULPHUR.

(Why /wo holes?). Thcu cut out the crust with a knife, and,
lifting it carefully by the cork, observe the beautiful crystals of
sulphur. Lay aside for a day, and observe that the translucent
amber solid becomes opaque and yellow.

Su]i)hur melts at 114.5° C. to a clear amber liquid;
if allowed to cool at tlie ordinary temperature of the air
it crystallises in needle shaped crystals (monoclinic).
These are unstable and gradually change to another
crystalline form (rhombic prisma). Sulpliur is therefore
dimorphous. Each monoclinic crystal becomes trans-
formed into a great number of minute rhombic crystals,
and hence the opacity. This change goes on gradually,
and its progress can be watched.

Experiment 90. — Melt some sulphur in a dry t. t. (using the
holder), and continue heating it. The mobile amber liquid be-
comes (at 200° C. ) dark and viscid (will not pour). Continue
the heat. It becomes mobile again, and at length begins to rise
as a heavy vapour. Now pour it in a thin stream into a beaker
of cold water. Plastic sulphur is obtained. Keep and observe
it.

Plastic sulphur is amorphous — has no particular form,
as crystals have. It can be drawn out into threads, but
slowly hardens and changes into rhombic sulphur. This
latter is t)ie permanent form of sulphur. Large crystals
can be obtained by evaporating solutions of sulphur in
carbon bisulphide. — Sulphur boils at 450° C, forming a
dark red vapour. The specific weight of this vapour is
peculiar. If determined at a temperature near its boil-
ing point, it is 96 (hydrogen =1). The molecule must
then weigh 192 times that of hydrogen, and must con-
tain 6 atoms, since the atomic weight of sulphur is 32.
The formula for sulphur at temperatures not much above
450° C. is then Sg. The specific weight at 1040° C.

MILK OP SULPHUR. 123

(boiling [)oiiit of zinc) is, hovvevor, only 32. (How many
atoms in the molecnlo at tluH tern* oiature 1)

Experiment 91- — Try the solubility of flowers of sulphur in
water, alcohol, carbon bisulphide, and paraftiu oil, by shaking
in test tubes with a very large proportion of the solvent Use a
little heat also before deciding in the negative.

Sulplinr burns in air with a pale blue flame forming
sulphur dioxide (8(^2)- I^ oxidises very slowly in moist
air to sulphuric acid H.^SO^).

Milk of Sulphur {Lac sulphuria). — This is b'.ilphur
in a very finely divided state suspended in water. Wi»<^n
dried it is called precipitated sulphur.

Experiment 92. — Boil for some time in a t. t. a little of the
flowers of sulphur (5 parts) with slaked lime (10 parts) and
water (20 parts), filter, and divide the filtrate (the clear liquid
which runs through) into two parts. To one part add dilute
liydrochloric acid until the liquid is acid. Sulphur is precipi-
tated as a -whiufc powder. Allow it to settle, collect it on a
filter, wash (by pouring hot water on the filter), and allow it to
dry. To the second portion add dilute sulphuric acid, until the
liquid is faintly acid, and proceed as before. Compare the two
specimens in appearance. Burn a small portion of each on a
piece of mica. That prepared with sulphuric acid leaves a white
residue ; the other leaves little or none. Test a few specimens
obtained from druggists.

When sulphur and lime water are heated together a
persulphide and thiosulphate of calcium are formed :

3Ca(OH)2 + 12S = 2CaS6 + CaSjOj + 3HjO.

The action of the acids is shown in the folio winsr
equations :

2CaS5 -f CaS.Oa + 6HC1 -= 3CaCl, + 12S + 3H3O.
2CaS6 -f CaSijOs + SH^SO^ = 30aS0, -f 12S + aHjO.

124 SULPHUR DIOXIDE.

Prepared with sulplmric acid, precipitated sulphur is
very impure. Calcic chloride (CaClo) is freely soluble in
water and is washed away from the sulphur; while
calcic sulphate (CaS04) being spai'ingly soluble, remains
mixed with the sulphur. The impure })recipitated sul-
phur has a glistening look, and feels slightly gritty.

SULPHUR AND OXYGEN.

114. Oxides of Sulphur. — Four oxides of sulphur
are known. Their composition is represented as follows:
S0.2, SO3, S2O3, and S2O7. Of thesv. only the first two
are of importance.

115. Sulphur Dioxide. — SO.^. — Also called SM/^^/mr-
ous anhydride. As has been seen, sulphur burns in
oxygen forming an oxide which, dissolving in water, gives
an acid substance. This oxide is sulphur dioxide.

Preparation. — Sulphur dioxide can be prepared (I)
by burning sulphur in air (Is it obtained pure 1) ; (2) by
burning iron pyrites in ,ir : 4FeS2 + IIO2 - 2Fe203 +
8SO.2; (3) by heating strong sulphuric acid with char-
coal : 2H2SO, + C = CO2 + 2SO2 + 2H2O ; and (4)
by heating strong sulphuric acid with certain metals,
e.g., copper, mercury, silver.

Experiment 93. — Heat a littk iron pyrites on mica. Notice
that it burns with a blue flame and the smell of " burning sul-
phur." (What action has taken place ? What substance is left ?)

Experiment 94. — Put a considerable quantity of scraps of
copper in a small flask, or a large t. t. and pour in enough con-
centrated sulphuric acid to cover the metal. Fit with the deliv-
ery tube of Expt. 66, and heat carefully until a gas begins to bubble

SULPHUR DIOXIDE. 125

oflF. Collect three jars of it by displacement of air (downward or
upward? Calculate the sp. wt.) Then, still heating very little,
allow the gas to bubble through a bottle of distilled water cOv^led
to 0° C. by snow or ico. After some time a white crystalline
solid .H2SO3. 14H,0) is formed.

(Try preparation on a small scale with charcoal.)

Properties. — An invisible gas of suffocating smell
("burning sulphur"), about 2| times as henvy as air;
soluble in water (at 0° C, 8) vols, in 1 ; at 20°, 40 in 1);
condenses to a liquid at — 8° and with ordinary atmos-
pheric preshure.

Experiment 95. — Put a burning taper or match in a jar of
the gas, and observe.

Experiment 96-— Hang a strip of moist turkey-red cotton in
another jar, close it, and allow it to stand. The colour is
bleached.

Sulphur dioxide bleaclies only in presence of water ;
and its bleaching action is the reverse of that of chlorine.
It is due to the action of hydrogen from water :

SO2 + 2H,0 = H,S04 4- H2.

The hydrogen unites with the colouring matter forming a
colourless compound. In many cases the colour may be
gradually restored by the oxidizing action of the air.
The action of sulphur dioxide is not so destructive aa
that of chlorine, and it is therefore ased for bleaching
delicate materials, such as silk, wool, &c. Sulphur diox-
ide is a reducing agent, but most of the reducing actions
take place in presence of water, which is decomposed
under the double influence of sulphur dioxide attracting
the oxygen, and some other substance attracting the
hydrogen.

126 SULPHUR TRIOXIDE.

Experiment 97- — Test the action on litmus of the solution
prepared in Experiment 94. It contains an acid, sulphurous acid
(HjSO,). Note the smell and taste of the solution.

Sulphur dioxide forms a weak compound with water,
which cannot be obtained free from water, except at low
temperatures.

Experiment 98. — Mix some sulphurous acid with iodine
solution until the colour is just discharged. Note that the odour
of both is now absent. Test with litmus,. The solution Js still
acid : SO., + I., + 2H,0 = H.^SO^ -f 2HI. Do similarly with
chlorine water.

Experiment 99. — Colour some sulphurous acid in a porcelain
dish with litmus, add solution of caustic soda until the colour
becomes blue, and evaporate to dryness on the water bath. A
white crystalline salt, sodic sulphite, remains :

HaSO„ + 2NaOH = Na^SOj -f 2H,0.
Sulphur dioxide is a good disinfectant and antiseptic.

Teste. — 1. Wet a piece of filter paper with a mixture of
ferric chloride (Fe,Cla) and potassic ferricyanide (KaFeCgNe) in
solution, and b *ld it in an atmosphere containing sulphur
dioxide. It turns blue. The ferric yanide is reduced to fer-
rous cyanide, and this forms Prussian blue with ferric chloride.

2. Mix a few drops of solution of sulphur dioxide with starch
paste and solution of iodic acid (HlOg). Blue iodide of starch
is formed : 2HI0, + 580, -f 4H2O = SHjSO, + I3. If more
sulphu dioxide be added the colour disappears. (Explain.)

116. Sulphur Trioxide SO;^. — Also called sul-
phuric anhydride, or anhydrous sulphuric acid.

Preparation. — (1) By passing a mixture of sulphur

dioxide and oxygen over heated spongy platinum, or

platinised asbestos :

SO., -f O SO3.

OXYGEN ACIDS OF SULPHUR.

127

(In what proportions by volume do the gases combine 1)
(2) By distilling pure sulphuric acid with phosphorus
pentoxide (PoOg) :

H2SO, + P2O5 = 2H?03 + SO3.

Properties. — A transparent 'white crystalline solid,
melting at 16° C, boiling at 46° C. It readily combines
.vith water, forming sulphuric acid (HjSO^). It hisses
like red hot iron when thrown into water, and when
exposed to the air it deliquesces. Its relation to sul-
phuric acid is seen thus :

H.p 4- SO3 = H2SO4.
117. Oxygen Acids of Sulphur. — These are

very numerous, but only two are of any importance as
acids, viz., sulphurous and sulphuric. The others will
be studied mostly through their salts.

fli/po8ulphurou« acid H2SO2
Sulphurous acid .... H2SO3

Sulphuric acid H2SO4

T/iiosulphuric acid . . H 2 S 2 O <

HjSgOg

Dithionic acid. . .
Trithionic acid. .
Tefrathionic acid. H2S4O
Pen^athionic acid

HaSgOe

HjSgOe

118. HypOSUlphurOUS Acid, H2SO2.— Also called
hydrosulphurous acid. Prepared by the action of zinc
on sulphurous acid solution in closed vessels :

H2SO3 -h H2 =^ H2SO2 + H.O.

(What is the source of the hydrogen represented in the
equation 1) It is a strong reducing agent, and readily
absorbs oxygen from the air. (What is formed 1) It is
a monobasic acid, and forms salts, the * yposulphites, in
which half the hydrogen of the acid still re.Tiains. The

128 SULPHUROUS ACID.

second atom of hydrogen in the molecule cannot be re
placed by metal.

SoDic HYPOSULPHITE (NaHSOa^ prepared by dissolv-
ing zinc in a solution of sodic hydric sid2)hite (NaHSO,),
is used to reduce indigo in calico printing.

119. Sulphurous Acid, H-^SOg. — Has been already
mentioned (Art. 115). The pure acid exists as a solid
at low temperatures, and the solution of the dioxide in
water has acid properties.

Preparation. — By heating in a glass flask 1 part of
charcoal, broken in small pieces, with 7| parts concen-
trated sulphuric acid. The sulphur dioxide is washed by
passing tliiough a small quantity of water, and is then
dissolved in cold water to saturation. The solution
must be kept well stoppered. It contains about 1 2 ^ j^
of sulphurous acid, and its specitic weight is 1.04. For
proi)erties see Art. 115.

Sulphites. — Sulphurous acid neutralises strong bases
(Exp't 99) and forms salts, the sulphites. There are two
classes of sulphites : (1) normal sulphites, cont lining no
hydrogen, e.g., sodic sulphite (NajSOg) ; and (2) acid
sulphites, containing hydrogen, e.g., sodic hydric sulphite
(NaHSOg \ Sulphurous acid is dibasic; it unites with
bases in two proportions. This subject will be more fully
discussed in treating of sulphuric aoid. — The sulphites are
generally colourless salts, not very stable, readily absorb-
ing oxygen from the air to form sulphates. They are
strong reduci \g agents, and are used as such in the arts.
In medicine, sodic sulphites are administered to introduce?
sulphurous acid into the stomach. (What is the action ?)

SULPHURIC ACID.
Testa—See Art II5 o , ,., ^^^

Experiment inn t^ , .

.men of the g^ ,voW t, \ hylrochloric acid. Note V:

Maokena. By the reducing aotioL „/ ^r"" °' '"« '• '• K
Mno sulphide, H.S) is for^d so "i'^ ■"««»' Mrogen
Ihis acts on the lead salt t„ f„ , ' + ^^' = H,S + ow o

substance. "" '° '°™ P'"»Wo .»W.* (PbS) a blac^

. !f ^- Sulphuric Acid, H so V
"■^'ly as " oil of vitriol " or ^ , ~ "'"'" <"'°"°«'--
formerl^ prepared by dt'tilliL '"^ " "*™'" ^^ --
■ng ^--^Iphuric acid " i,;« T ^T "'"'"• ^""l "f-n-
tle most important f aj aS . " '"'' ^'''- ^* «
P-a«on of „.ost other a id? ;r V: "'^' '" ">« P-
-n„factu.d a„„,.a„, inteat BHttir'"'" '""' "^

Manufacture Tn f

it « necessary only to ^,1^''^:'' "' "•'P''""« -W

yh>-a and a molecule of water :

SO,

+ O + H,0 = H,SO,.

J>ut this union does n^^f + i

"■e influence of pTa inl": l^:? tf ^"^ --P' -der
'"bstance. In practice r^ . " "°"*^'^' ='««<»> "

o'.en.ical action. ' ^:Z^^'f"-: "^ --"-
femes with the oxygen of tL Jr A^^ '""""^ '="^'"''i"e«

"; (NO,). Thisifrers;" s .; tTrr^ ''" *«"--

Phur dioxide and water and T, Z^ ^^ '*^^«<'" *° «"1-
•"sygen from the air Th,„ !•. '° "'''''' "S^*'" "-itt

"carrier of oxygen "froLtheT" '''""''^ "^'^ «» a
j^ yg from the air to sulphur dioxide and

130 SULPHURIC ACID.

water. (Of course, this carrying goes on between mole-
cules, and not between vessels or rooms ! ) Thus :

NO + O = NOj.

NO2 + H2O + SO2 = H2SO, + NO.,
<fec., (fee.

Sulphur dioxide (from iron pyrites by burning), water,
air, and nitric acid (from sodic nitrate and sulphuric
acid), are brought together in large leaden chambers.
The nitric acid immediately suffers reduction to nitrogen
dioxide, and the actions described above go on continu-
ously. Theoretically, one molecule of nitrogen dioxide
would in time convert any quantity of the materials into
sulphuric acid. In practice there is waste, so that a fresh
supply of nitric acid is needed from time to time. (What
is left in the chambers after the sulphuric acid is formed V)
The sulphuric acid, as fast as it forms, falls in a fine
shower to the floor of the chamber into a layer of water.
It is drawn off and concentrated in leaden pans to 78%
(sp. wt. 1.71), at which strength it is sold as " brown oil of
vitriol " (B.O.V.) For special purposes it is further con-
centrated in glass or platinum vessels to 96% (sp. wt.
1.84).

Properties. — The pure acid free from water is a
crystalline white solid below 10° C, a colourless oily
liquid above this. It has such a strong attraction for
water thii it is impossible to keep it pure unless it is
sealed up. Thus in practice we have to deal with an acid
containing more or less water. The sp. wt. of the pure
liquid acid is 1.85. With many of the properties of sul-
phuric acid the student has already become acquainted.
It is the strongest of acids, and its powerful attraction for

SULPUHRIC ACID.

Experiment loi J:" ''"''"'"'"'"' *° ''°™' '^«*«'--

» a porcelain diah ThnurVlf """'"='•' ™ •««'« »ug„
I-"* « .Irop of acid „„ a pte o^t I """ ^ '^'^ "-■"-

Paper and su;,a,. , ' '"'"' "' '=°""» "'"*•■■

S"<ph..no acid Js%Lri: ZXTal '° 'T ^'''-•
gen and oxygen aa water The dil ^ "^ *''' ''^<'™-
eloth reddish. If '„■ \'^ ''''"'« ««<! turns dyed

restored.' *""'"""'* '"' "Pl'Jied the colour is

Experiment in9 w« i.

Sulphuric acid boils at SSRo n T
hal dissociation (tempomrv d« ""dergoes par-

«o«de and watlXoSrtT"' '""' ^"'p'"
a-r. Hence, the anpeamnl nf. "« ^^'^ '" the

"»» of ,01,1, ^toilC and : f r '^'"' *« «™P-
di^^olves all the me"l 7 • '' ''*'''''^' ^"'Ph^ric acfd

eonce„t„.ted acidTs nsLdT'"? """''""■ '^'"'" ''^^
(Exp't 94), and sulphur dioxidTis" T ""''''"'"^ "^-'
-"etals, as copper, sLer C ^ ^ t'^-P^doct. S„„e

»ly by the stVong hltla ' "''■''"'■^' "« ""^^'^"^

2Ag + 2H.S0,=Ag,S0, + S0, + 2H0
Others, as «««, iron and ./ •

the strong acid witT'n "'""'"'"'"' ^■'^ '"^^o'ved by

^- can aL be d^v! ^^Stlu:; T"^ '"''''-
oase hydrogen is the gas evoied . ' "'"' '" "-"

— _____*M^SO. := Peso. + H,.

132 SULPHATES.

Impnritiea in Sulphuric Acid.

Plumbic Sulphate (PbSOi) is very commonly pre«ient
in the commercial acid. It comes from the leaden evapo-
rating pans, which are attacked when the concentration
is pushed too far. This salt is soluble in the concen-
trated acid, but is precipitated on diluting with water.

Experiment 103. — Pour a little commercial oil of vitriol into
about four times its volume of distilled water. A white preci-
pitate indicates the i>re8ence of plumbic sulphate.

Arsenic, derived from the pyrites, is often present;
and, as it forms many volatile compounds, it is a danger-
ous impurity. For example, when arsenical sulphuric
acid is used in the preparation of hydrochloric acid, the
arsenic distils over as trichloride (AsClg), and thus
renders the hydrochloric acid highly poisonous. It can be
tested for by diluting the sulphuric acid with water and
adding hydric sulphide (HjS), when the yellow arsenic
trisulphide (AsjSg) is thrown down. — The colour of
B. O. V. is due to organic matter. — Sulphur dioxide, and
oxides of nitrogen occasionally occur as impurities.

Sulphates. — Sulphuric acid is a dibasic acid. Its
molecule contains 2 atoms of hydrogen, and both of these,
or one of them only, can be replaced by metal. Thus,
there are two series of sulphates, nor^nal and acid', e. g.,
K2SO4, normal potassic sulphate, and KHSO4, acid
potassic sulphate. The acid sulphates are often called
bisulphates {Art. 121). — The following normal sulphates
are insoluble or very sparingly soluble in water : Plum-
bic (PbSOi), baric (BaSO^), and strontic (SrS04). Calcic
(CaS04), argentic (Ag2S04), and mercurous (Hg2S04) are

"OKMA,, .K„ ^^,^ .^^^^

si«n»g/;, soluble. TI,e.-esfnfM ,

"'0«ly easily or^stallisable 1°L "''*"""" "^ «"•""«.

''-Trot J'^"' ^"*-^"'' * '- --pa of ,„,„f .
" 0' "'"IP'esic sulphate (MgSO,) '""" *'"' »»'"-

I2h Normal and Acid Salts
-txpenment 105 ~Pnf ^
;» -^ poreaiain ba.! o„r"jr rf" "' "■''"*-"'P"-Tic acid

"^th- Repeat this operation I . . «*'»Po™te o„ the water
l-*»d<'a.econdpip'ett:;X;,:;":;;^7 '^^""'"^ '"^ -"-'

."■f ; -'I ti.at obtain dt,:*r ^ ^^-'" l-perties
- taste, Ac. In fe^j^ ;, is "t IJ h!,r ■ ?'''''"'' '^ -"
^3' referring to the equatills '"'' "' "^^ '- --en

2NaOH + H,SO. = Na ^n , „
NaOH+HSO ,, ^*'^' + 2H,0.

f no:« : :«. ~ 7;;;- ^wo p™,ortion,
' '« '>ase a neutral salt is fol , T"' P^Po^ion of

""aiier proportion an Jrf 1 *^ f "^"^- With the

term "„eut„,l salt" applies a" f ' "''"''• ^«-. *he
ba^e are well n^arked but f A, ^^ "^ '""'' ^^id and

134 FUMING SULPHUHK? ACID.

litmus to red, or red to blue. It has been agreed to
restrict the use of the term ** neutral " to the action
of substances on litmus ; and to use the word normal
instead.

Deflnitions. — A normal nail is one in which all the replace-
able hydrogen is replaced by metal.

An acid salt is one containing replaceable hydrogen (i.e., re-
placeable by metal).

(Can monobasic acids form acid salts?)

122. Fuming Sulphuric Acid, or Nor dhausen sul-
phuric acid. — This is of somewhat variable composition.
It is sulphuric acid combined with the trioxide ; gener-
ally H.2SO4 -f SO3. It is prepared from green vitriol
(FeSO4.7H.2O) by roasting in air to drive off the water
of crystallisation and oxidise the salt :

2(FeS04.7H20) + O = Yq,0,.{^0,\ + UHA

and then distilling. Enough moisture is obtained from
the air and the apparatus to form a certain proportion of
sulphuric acid :

FeA.(S03), + H^O = FeA -f H,S04.S03.

It is used to dissolve indigo, and in the manufacture of
alizarine.

123. Thiosulphuric Acid, HaSjOa.—Formerly called
hyposulphurous acid. The name now in use means suU
pho-sulphuric acid, and refers to the composition, the
acid containing an atom of sulphur in place of one of the
four atoms of oxygen. The acid itself cannot be isolated,
as it decomposes quickly on being set free from its salts :

HoS-Pa = H.,0 H" S -h SO,.

THIOSULPHATES.

Experiment lOfi a.h

( Wnte the equation.) '^^^- ^^"^ note the odour.

Thiosulphates TJi*

.™l»'t-t -It is soclic S ; :^ "^ ■"■"«'• Tl.e .noat
"'« «0''io sulphite with sulphur ' ^''''""'''' ''^ '■""''i°-

Experiment m? p i

^'™e -^ » i'"-,ai,fi;.7,r::tr;::r;i:t """"-•'^ ""• «-

'"," ''"'•'"<' to small bulk »„.|! "'P''"''' «"". evaporate
^'ourfes, crystals (xVaAO 4 1, """' *" "'•^'*»"-- Ftae
''■■ythemonfiit paper^^ =•'''""' "^ 'ormed. Collect and

-</'•»« render,, it verv , fu," ""'f'^'" ^'» "^t'on „„

.V useful ,„ analytical chemist, y
Experiment 108 — j\h,i . '^'

-'-tion to a solution oliodL J "''\ "' '""'= "-iosulphate
wears: """"o- ^i' colour of the iodine d"

I^ + 2Na,8,03 = 2ifU + Na S O

determined. (flow could" " •" "''""°" "^ ^

-..red indirectly hytSsrLrr '^ ^""^"^ "«
Experiment 109 —Pr,^

136 HYDRIC SULPHIDK.

timefl. (This is wanhing hy decanUttion.) Now, add some sodic
thiosulphate solution to the argentic chloride. The latter is dis-
solved, forming a very sweet solution of the double thiotulphate,
NaAgSaOg :

AgCl + NaaSaOg - NaAgSaOg + NaCl.

If any of the argentic chloride has become darkened, it remains
undissolved.

Sodic thiosulphate is used in photography to dissolve
out the undarkened chloride, bromide, or iodide of silver,
so as to Jix the negative or print. — It is used in medicine
to destroy certain organisms in tlie stomach (sarcina;
ventriculi). (What is the action of the gastric juice on it ])

SULPHUR AND HYDROGEN.

124. Hydric Sulphide, H2S.— Commonly called
sulphuretted hydrogen. It occurs in volcanic gases and
in " sulphur springs." It is a product of the decay of
animal and vegetable bodies, and is one cause of tlie at-
tendant bad smell and poisoning of the air.

Preparation.— Experiment 110.— Pour a few drops of
dilute sulphuric acid upon a little /errows sulphide (FeS) in a watch
glass. Note the odour of the gas given oflf. Repeat, with dilute
hydrochloric acid and ferrous sulphide. Try also with antimony
trisulphide (SbaSs) and rather strong hydrochloric acid solution
(1 vol. of the strong so) '^ion to 1 of water), warming them in a 1. 1.

The gas, knc .cs unpleasant smell, is hydric sul-

phide (H.,S) :

Ferrous sulphate.

(1) FeS + HaSO^ = H^S + FeSO^.

Ferrous chloride.

(2) FeS -f 2HC1 - HjS + FeCla-

Antimony trichloride.

(3) SbgSa + 6HC1 = SHgS + 2SbCl3.

IIYDKIC SIJLPIIIDK 137

Experiment 111. -H«at a little pumffin wax and flowers of
Bulphur together in a small porcelain dish. Hytlrie sulphide is
evolved.

Paraffin wax is a mixture of hydrocarbons, or com-
pounds of carbon and liydrogon. Hydric sulpliide is
prepared on the large scale in this way. — When hydric
sulphide is prepared from ferrous sulphide it contains
hydrogen, owing to the presence of uncombined iron in
the ferrous sulphide of commerce. (Wliat is the action 1)
The method with antimony trisulphide gives the pure
gas.

Properties. — An invisible gas, of very unpleasant
odour (that of rotten eg^'s), and of sweetish taste.

Experiment 112- — Prepare sulphuretted hydrogen with fer-
rous sulphide and dilute sulphuric acid, evolving it in a small
flask or bottle, and bubbling it through a small (quantity of water
in a wash bottle (to wash it free from small drops of sulphuric acid
carried up by the gas), and then through water in the reagent
bottle provided. Gases are washed by passing them through a
liquid in a bottle provided with a twice-bored cork. The tube
from the generating flask passes through one hole and nearly to
the bottom of the water. A second tube passes just through
the other hole to lead the washed gas away. Note that after the
air is driven out, most of the gas dissolves in the water. Some,
however, escapes solution, and this experiment should be made
in a draught cupboard or under a hood. After the gas has been
running for a few minutes, bubble a little of it through test
tubes containing solutions of cupric sulphate (CuSO^), tartar
emetic, and stannous chloride (SnCl2). Then set fire to the gas
and note its inflammability. Evaporate the solution remaining
in the flask, and obtain crystals of green vitriol (FeS04.7H20).

Hydric sulphide is soluble in water, about 3 volumes
in 1 of water. The solution has the smell, &c., of the
gas. It slowly decomposes, absorbing oxyger from the

138 HYDRIC SULPHIDE.

air (H.^S -\- O ^=: H^O -j- S), and sulphur is deposited
as a white powder. The gas burns in the air with a
bluish flame and the formation of water and sulphur
dioxide : H2S -f 30 = H.^0 + SOo.— It can be lique-
fied at — 70° C. under the ordinary pressure of the
atmosphere. — Hydric sulphide is a valuable reagent {te:}t
substance) in analytical chemistr3^ Either as gas or in
solution, it preci[)itates the sulphides of certain metals
from solutions of their salts, while it does not precipitate
others. It precipitates the sulphides of some metals in
presence of a free acid, others only in the presence of a
free alkali. 1\. ^o, all metals can be divided into three
groups :

1. Those precipitated as sulphides in presence of a free
min'3i*al acid (Hg, A.g, Pb, Cu, Bi, (M, Sb, Sn, As, Pt,
Au, (fee.)

2. Those precipitated only in presence of a free alkali
(Fe, Ni, Co, Zn, Mn, Al, Cr, the last two as hydroxides),

3. Those not precipitated at all V)y hydric sulphide
(Mg, Ca, Sr, Ba, K, Na, Li, kc.)

Hydric sulphide is very poisonous, even when largely
diluted with air. It produces lassitude, headache, giddi-
ness, fainting, and at last death. The best antidote is
chlorine gas largely diluted with air. It can be adminis-
tered by inhalation as evolved from a mixture of " chloride
of lime " (bleaching powder) and vinegar.

Experiment 113 — Mix some chlorine water with solution of
hydric sulphide in u t. t. Note that sulphur is p'-ecipitated. If
the right proportions are used, the smell ' f both chlorine and
hydric sulphide is destroyed :

H2S -H Cla = 2HC1 + S.

SULPHIDES OF METALS. 139

When hydric sulphide is taken as a medicine it is par-
tially given off through the skin. Hence, its eflScacy in
skin diseases.

Sulphides of Metals. — Sulphur combines d' ctly
with most of the metals, forming sulphides. In these
compounds the sulphur is dyad, as in hydric sulphide.
TliC sulphides of the heavy metals can be formed by pre-
cipitation with hydric sulphide (see above) ; the sulphides
of potassium, sodium, calcium, <fec., can not be formed in
this way, but are best prepared by reduction of the sul-
phates by heating with charcoal ;

K.^O, + 4C = K,S + 4C0.

The sulphides run parallel with the oxides in composi-
tion, as the following formulas show :

H2S, FeS, Fe.^S3, FcgS^, Ag,,S, Na..S, AS2S3, &c.
H.,0, FeO, FeA, FeA, Ag.O, Na,0, AsA, &o.

Tests. — Free hydric sulphide blackens lead jiaper.
Pb(C,H,0,), '\- H^S = PbS + 2C2H^O,.
Most sulphides when treated with hydrochloric acid give the
sniell of hydric sulphide. Insoluble sulphides when fused on
charcoal before the mouth blow-pipe with sodic carbonate, give
a bead which stains silver black, when placed upon it and moist-
ened with dilute hydrochloric acid.

Hydrogen Persulphide. — The exact composition is
unknown ; perhaps H^S.j, analogous to H.^Oo. It is pre-
pared by pouring a strong solution of an alkaline peraul-
phide (e. g., K-jSr^, into dilute hydrochloric acid. It is
an oily liquid, readily decomposing into sulphur and
hydric sulphide.

125. Sulphur and the Halogens. — Sulphur

unites directly with chlorine in several proportions
(SoClo, S2OI4, and SCit). The chlorides are all decoin-

140 SELENIUM — TELLURIUM.

posable by water. — Sulphur cotnbines with bromine in only
one proportion (S.^Br^) ; with iodine it forms two com-
pounds (Sjl.j and SJg). The moniodide (S2I2) is prepared
by heating together four parts of iodine with one of
flowers of sulphur. It is a crystalline greyish-black solid,
insoluble in water, bub decomposed by boiling with it.
It is soluble in glycerine. It is used in medicine in the
form of an ointment.

126. Selenium (Se"-'^-^' = 79).— Rather rare, and
found only in small quantities, in sulphur ores, &c. It was
discovered by Berzelius (1817), in the deposit found in cer-
tain sulphuric acid chambers. Selenium has two allotropic
forms, one of which is somewhat metallic in appearance.

Compounds. — These are similar in composition to those
of sulphur; seleniuretted hydrogen, or hydric selenide
(H.^Se); selenium dioxide (SeOa); selenious acid (H^SeO^);
and selenic acid (HySe04), are similar in properties to the
corres[)onding compounds of sulphur ; but no trioxide is
known with certainty. Selenic acid differs from sulphuric
acid in being easily reduced to selenious acid. Metallic
selenium conducts electricity, and its conductivity is in-
creased by exposure to light. Ifc is so sensitive to the
influence of light, that an electrical instrument has been
constructed which shows the slightest variations in the
intensity of the light falling on the surface of the selenium
which is placed in the electric circuit.

127. Tellurium (TV- ^"' "' = 128).— This is also a rare
element, being generally found combined with silver,
gold, or bismuth. It forms compounds with hydrogen
and oxygen, parallel with those of sulphur and selenium,
but tellurium dioxide (TeO-J has weak basic properties.

QUESTIONS AND EXERCISEEu 141

QUESTIONS AND EXERCISES.

1. Show how the oxider of sulphur ilhistrate the law of mul-
tiple proportions.

2. How much oxygen is there to 1 part by weight of hydrogen
in each of the oxygen acids of sulphur ? How much sulphur to
1 of hydrogen ?

3. What weight of sulphuric acid is equivalent to 100 g. sodic
hydroxide (KOH) ? To 100 g. calcic hydroxide (Ca(0H)2) ?

4. 196 g. sulphuric acid in solution is mixed with 150 g. sodi^
hydroxide. Is the solu*"i neutral, acid, or alkaline?

5. What is the valence of sulphur in sulphur dioxide ? In
sulphur trioxide ? In hydric sulphide ? In sulphur hexiodido
(Sle)? In Sulphuric acid (SO 2 Zl^g)?

6. What volume of chlorine is nece-.sary to decompose 1 cubic
foot of hydric sulphide gas ?

7. Define normal and acid salts with regard to the equivalence
of the acids and bases forming them.

8. Write the formulas for the following normal sulphates :
Sodic, argentic, ammonic, ferric, cuprir, zincic, bismuth, chromic,
and mercuric.

9. Write the formulas for the following compounds : potassic
hydric sulphite, calcic thiosnlphate, sodic argentic thiosulphate,
zincic hyposulphite, mercuric sulphide, and argentic sxdphide.

10. Moisten a strip of filter paper with plumbic acetate and
hold it in the mouth of the bottle of hydric sulphide solution.
It is blackened. Explain.

11. What weight of ferrous sulphide (FeS) must be used to
saturate 2 litres of water with hydric sulphide ?

12. Balance the following equations : '

(1) SbClg 4- HjS = SbgSg + HCl. : ^"

(2) H2SO, + FeaOg ^ Fe^ (804)3 f H^O.

(3) SOa + I + H2O = H2SO4 H- HI.

(4) FeSO^ = FegOg + SO2 + SO3.

142 PHOSPHORUS.

CHAPTER XI.

PHOSPHORUS AND ITS COMPOUNDS.

128. Phosphorus (P'"'' = 31).— The name phos-
phorus (light-bearer) was at first given to substances
which shone in the dark, particularly to Bononian phos-
phorus (barium sulphide). The substance at present
called phosphorus was discovered about 1678 by an al-
chemist, Brandt, while distilling the residue left by
evaporating urine. It created a great deal of interest
on account of its luminosity and inflammability ; and,
besides, it was held to be a very valuable medicine. A
few years after Brandt's discovery, Boyle discovered the
secret of its preparation from urine, having had only the
vague information that it was prepared from the human
body. At present the phosphorus of commerce is pre-
pared from bones and from mineral phosphates.

Occurrence. — Phosphorus is never found in nature
uncombined. (Why?) It occurs in phosphates^ e. g.,
phosphorite (Ca3(P04)2), apatite (3Ca3(P04)2 -|- CaClg),
and coprolites, or fossil dung of serpents. It is present in
all fertile soils and is an essential constituent of the food
of plants. Animals take it into their bodies along with
their food and build it up especially into bones, which
consist very largely of calcic phosphate (Ca3(P04)2). It
is also found in sea-water, and in all parts of the earth's
crust.

PHOSPHORUS. 143

Preparation. — Bones are either distilled, bone-black
and bone-oil being the products ; or they are heated
under pressure with water to extract the animal matter
as gelatine. In the former case, the bone-black is used
in sugar-refining and then burned to bone-ash, which is
impure calcic phosphate. In the latter case the calcic
pliosphate is left from the extraction process. In either
of these ways, then, or from some mineral source, calcic
phosphate is obtained. This is treated with dilute sul-
phuric acid, when two-thirds of the calcium is precipi-
tated as calcic sulphate, while an acid phosphate goes
into solution :

Ca3(?0,)2 4- 2HoSO, = 2CaS0, + CaH4(PO,)2.

The solution is drawn off, evaporated to dryness, and
strongly heated. It loses water, and calcic metaphos-
phate remains :

CaH,(P04)2 = Ca(P03)2 + 211,0.

This is mixed with charcoal and sand (SiOs), and
strongly heated in earthenware retorts. The object of
the charcoal is to remove oxygen from the phosphate ;
the sand forms a silicate of calcium, and thus aids in
setting free the phosphorus, which distils, and is collected
under water :

Ca(P03)2 + 5C + SiOa = CaSiOg + 5C0 -f 2P.

It is purified by melting under water and pressing through
chamois leather, or by oxidising the impurities by means
of a mixture of potassic bichromate (KjCrjO;) and sul-
phuric acid.

Properties. — Phosphorus has several allotropic modi-
fications, of which two only will be described.

144 YELLOW PHOSPHORUS.

(1) Common or Yellow Phosphorus is a translucent,
waxy solid, of sp. wt. 1.8. It melts at 44*^' C.

Experiment 114 —Put a small piece of phosphorus in a por-
celain dish half-tilled with water and heat the water. Notice
that the phosphorus melts before the water becomes uncomfort-
ably hot. Note the smell, Sec, of the phosphorus. Is it
heavier or lighter than water ? Does it dissolve in wator ?

If heated in an atmosphere of some inactive gas (nitro
gen) it boils at 290° C. The specific weight of its
vapour is 4.3 (air =1). (How many atoms in the
molecule ?) If heated in the air it catches fire at GO'^ C.
It catches fire at lower temperatures if ex})0sed to ti\e
oxidising action of the air for some time. Very slighi
friction often sets it on fire ; and as it burns very vigor-
ously, and causes frightful wounds if it comes in contact
with the skin while burning, it should always be
handled under water. It should be kept in well stop-
pered bottles of water in a cool, dark place. — Yellow
phosphorus is soluble in carbon bisulphide (CS2), in
fats, oils, and slightly in ether and oil of turpentine.
If the solution in carbon bisulphide be evaporated, crys-
tals of phosphorus are obtained. — Yellow phosphorus
is very poisonous, and as it is often used in making
matches, phosphorus-poisoning cases are not rare. The
fatal dose is as low as 1| grains. The symptoms are
pain in the stomach, nausea, vomit with garlic odour.
The antidote is blue vitriol in 3-grain doses (dilute solu-
tion) every 5 minutes until vomiting ensues.

Experiment 115. — Put a bit of clear phosphorus in a small
quantity of cupric sulphate solution. It is blackened.

When a poisonous substance is taken into tho
stomach it begins at once to pass into the circulation.

RED PHOSPHORUS.

The object of an antidote i» t«

decomposing the poisolaf U r^"'"' ''''' ''''^^ ^^

rendering it insoh.ble and th f * .'=<""P»"n<l), or by

P«0" into the eireXn'r:;:'"''''^"^''^'"'-
phosphorus is combined witi, '"«?'«««"' ca«e, the

-oinble black compound "''" *'""^^''' ^°'™"'g «»

coifnTh:;t:rbrh:atwrr ™ " '-'--' '--

" «mall quantity of IdTnl ? """ ''"^ =" 240«C.,

>-'""'g«- It is an al nt T^ '""^'' '° ^''^'^n *«
^.2 ; insouble in carbon bi,, T /'"' "' 'P<«"^« --ght
250«, catches fire onl/a? o''''l'%*'^-^ "^ -' f"- at
i« prepared on the large scaieln V' ''"''°"""'- ^*
--es, to repiace the p^oison^ ^7:;::: "

aJhf<:3,aSt;™rretrT:vr"^--

eg-, m ca,e3 of pois„„i„g, the sub.t»„ ";' ™''" l-^tities,

" ^ ^-^ --. When t J' u;c:r :;;'-« -"^ -«

PHOSPHORUS AND OXYGEN
wHh' IS?' °' ^^-PJ^O-a-Two are W„

Phosphorus pentoride. . p n

Phosphorus trioxide .' p '""

»d the existence of a third is probable." ' '

Phosphorus monoxide p^q

i>e-ved from these are three acids :

Phosphoric acid. ... „

Phosphorous acid H p *

^^ Hypophosphorous acid .' ." ." .' ." .' ;h3Po'

146 OXIDES OF PHOSPHORUS.

130. Phosphorus Pentoxide.— PA— Already

noticed. Prepared by burning phosphorus in air. It is a
snow-like solid, very hygroscopic, and hence used to dry
gases, and in separating water from acids. In moist air
it quickly deliquesces forming metaphosphoric acid :

H2O + PA = 2HPO3.

If put into water it hisses and dissolves, forming at first
metaphosphoric acid ; but, gradually at ordinary tempera-
tures, and quickly if heated, it combines with more water
to form orthophosphoric q,cid :

HPO3 + H.,0 = H3PO4.

131. Phosphorus Trioxide. — PA— Prepared by

burning phosphorus skwly with a scant supply of air.
If heated in air it combines with oxygen and forms the
pentoxide :

P.A + 0, = P2O5.

It combines with water to form phosphorous acid :
P2O3 + 3HoO = 2H3PO3.

132. Phosphoric Acid. — Phosphorus pentoxide
unites with water in three proportions, forming three
different acids, each of which is called phosphoric acid,
but prefixes are used to distinguish them. The ordinary
acid is that formed with the greatest proportion of water,
and is called or^/iophosphoric acid :

3H,0 + P.Og = 2H3PO4.

(1) Orthophosphoric Acid, H3PO4. — This is gener-
ally called simply phosphoric acid.

PHOSPHORIC ACi;,.

Pkeparation.— Bone n^h •

solved in nitric acid : "'"'^'''"^ P^^^«I^^^-*e is dis-

Plumbic acetate /PbA \ I'o ^ 1 .

- J^Osli'OJj 4. CaA^ -f 4Ha.
Tlie object of the first ,■»..„*• •

-J impurities i„ soluti^ Z ''rf^' '''' ''''"^'^''''^
'■«"ove tlie phosphoric aci,I V " '^''»"'' "« to

"-" »m« tinfe obtain a p 1^. ? '""""•'"-' -" -'
«• be easily obtained in 2 f T "'""'' *'"' «''»
Pi-^phate is washed, suspenid ' "^ '''"' P'-"""""

h ^.Iphuretted hyd;oger ""^''' """ ^''^''"'Posed

Phosphoric acid dissolves and r.1 u-

""dissolved. (How is he 0.0 ^ """ ' '"^^^^^^^ ^'^"^-i-«
V IS tlie process completed ?)

Experiment lie — Pnf ^

J'- phoaph„r„3 melts aid „'r' """° ''°"'- ^-^ g^nu;
»">es. (What are the"?, ^"7 . '"," '™"'«™ «' -d
d'"P» concentrated nitric acid I?, *" '''■*'""'»• ''dd a few

-^P-'^o acid regain.; ^I^^rir^nTC ""^^'

^e'sre7t°:r:r::^7''t-p-me„t,asitea„

«P'osivel,on,eliow;ro!;tl"''™ ^''"'' "'''"" -»'
Properties A thi V

' »'ou.-less orystais ; solubieTn" water '"'' """'P"-"'.

water, giving a strongly

148 PHOSPHATES.

acid solution, (Try it by taste and litmus.) It is a
tribasie acid, and forms three series of salts, e. g. :

(1) NagPO^, trisodic phosphate.

(2) Na2HP04, disodic hydric phosphate.

(3) NaHjPOi, sodic dihydric phosphate.

(To which of these classes do the phos[)hates mentioned
in Preparation belong 1)

Phosphoric acid is used in medicine in dilute solution
as a tonic, &c.

Phosphates (orthophosphates). — Of the normal and the
mon-acid phosphates, only those of the alkali metals
(Na, K, NH.4, tfec), are soluble in water. The di-acid
phosphates are all soluble.

Tests. — 1. Add a drop or two of argentic nitrate to a solu-
tion of sodic phosphate (Na.^HPOJ. A yellow precipitate is
formed. Divide into 3 parts, and add to one part ammonia ; to
the second, dilute nitric acid ; and to the third, acetic acid. The
precipitate is soluble in each. (Could this test be used in a solu-
tion containing hydrochloric aoid?).

2. Add ammonic chloride, magnesic sulphate, and ammonia to
a solution of sodic phosphate, and stir with a glass rod. A
granular white precipitate of magnesic ammonic phosphate
(Mg.NH^.POJ is formed :

Na.HPO^ + NH3 + MgSO^ = MgNH^PO, + Na,SO,.

3. Baric chloride (BaCl2) gives a white precipitate, soluble in
nitric acid.

Phosphates are present dissolved in urine, and when
the urine becomes alkaline by decomposition (Explain.)
crystals of microcosmic salt, or sodic amnionic hydric
phosphate (Na.NH^.H.PO^) are formed.

META PHOSPHORIC ACID. 149

(2) Metaphosphoric Acid. — HPO3. — Formed when

phosphorus pentoxivlc is dissolved in cold water ; but is

generally prepared by heating orthophosphoric acid to a

red heat :

H3PO4 = HPO3 -i- H2O.

Properties. — It is a hard glassy colourless solid
{glacial phosphoric acid) — the common phosphoric acid
of commerce. It dissolves in water, but gradually com-
bines with the water to form ortho-phosphoric acid. — It
is a monobasic acid (To what acid is it similar in compo-
sition "J), and forms salts called metaphosphates, e.g.,
NaPOa, Mg{P03)2, kc.

Tests.— 1. Add argentic nitrate to a solution of the acid or
a salt. A gelatinous white precijntate is formed . It is soluble
in nitric acid.

2. Add some white of egg to a solution of metaphosphoric
acid, or to a metaphosphate acidified with acetic acid. The
white of egg is coagulated. Try with orthophosphate.

(3) Pyrophosphoric Acid. — K^Pfi^ ( = PoOg -|-
2H,0).

Preparation. — Heat orthophosphoric acid till the
temperature rises to 215° C. :

2H3PO, = H,P.,0; + H.,0.

Properties. — A sott glassy liquid ; when heated with
water, forms orthophosphoric acid. It is a tetrabasic
acid. Its salts can be formed by heating acid orthophos-
phates of the class M2HPO4. (Write the equation.)
The pyrophosphates are changed to acid ortho-salts when
they are boiled with water.

150 PHOSPHOROUS acid.

Tests. — I. White precipitato with argentic nitrate, soluble
in nitric acid.

2. Pyrophosphoric acid does not coagulate white of egg.

133. Phosphorous Acid — H3PO,.

Preparation. — This acid is formed when phosphorus
oxidises slowly in moist air j but it is best prepared by
the action of phosphorus trichloride (POI3) on water :

PCI3 + 3H2O =-- P(0H)3 + 3HC1.

This action of water on a chloride is a very frequent one.
Observe that hydroxyl ( — OH) replaces chlorine ( — CI).

Properties. — A white solid with garlic odour. Oxi-
dises readily to phosphoric acid. When heated it de-
composes into phosphoric acid and gaseous phosphorettcd
hydrogen (PHg) :

4H3PO3 = 3H3PO, + PH3.

There are many decompositions of compounds containing
oxygen, such that one part gains oxygen at the expense
of another part. (Mention ono already described.) —
The phosphites are unimportant. Only two of the three
atoms of hydrogen seem to be readily replaceable by
metal.

Tests. — 1. Add argentic nitrate to a solution of a phosphite.
Metallic silver is precipitated.

2. Add solution of 6anc chloride. It gives a white precipitate
soluble in nitric acid. *

3. Heat a little of the substance on mica and smell. The
odour of phosphorettcd hydrogen is observed.

4. Add lime water to solution of phosphorous acid or a phos-
phite. A white precipitate is thrown down (CaHPOs).

HYPOPHOSPHOROUa ACID. 151

134. Hypophosphorous Acid. — HgPOj. — The

acid itself is of little importance. It can be prepared from
its barium salt by treating with sulphuric acid, (Why
use the barium salt in particular 1) It is a monobasic
acid, of very strong redu(;ing power, and quickly absorbs
oxygen from the air.

HYPOPHOSPHITES.--Experiment 117.— Heat a small piece
of phosphorus in a t. t. with milk of lime. Connect the t. t.
with a gas-delivery tube dipping under water. A gas having
the smell of decaying fish is evolved, and catches fire as soon as
it comes in contact with the air. Continue the heating until
the phosphorus is dissolved, and no more gas appears. The
solution contains calcic hypopho$phiie (Ca(H2PO,)2). Filter,
pass into the clear solution a current of carbon dioxide to preci-
pitate the uncombined calcic hydroxide as calcic carbonate
(CaCOg), then filter again.

The actions which take place are represented thus ;

3Ca(OH)2 + 8P -f GHoO = 3Ca(H,PO.,)2 + SPH,.
Ca(OH)., -;- CO., = CaCOg + H.,0.

The hypophosphites of sodium, potassium, barium, and
strontium, may be prc:>ared in the same way. The
hypophosphites are powerful reducing agents. They
must be kept out of oontact with air, otherwise they
become oxidised to phosphites and finally to phosphates.
They are used in medicine, and are supposed to produce
the same specific effects as free phosphorus ; but this is
very doubtful.

Tests. — 1. Argentic nitrate gives a white precipitate which
quickly turns brown and then black :

iAgNOg + H3PO2 + 2H2O = 4HNO3 -f H3PO4 + 4Ag.
2. Baric chloride gives no precipitate,

152 PHOSPHINE.

3. Zinc and hydrochloric acid (nascent hydrogen) give the
amell of piiosphoretted hydrogen.

4. Evaporate to dryness, heat residue on mica ; odour of phoa-
phoretted hydrogen :

2H3POa = PH3 + H3PO4.

Note. — Try these tests with the solution of calcic hypophos-
pliite (Experiment 117); also with a sample of " hypophosphites "
from the druggist's.

The " hypophosphites " of medicine is a preparation of
calcic hypophosphite.

135. Phosphorus and Hydrogen. — There are

three compounds known :

Gaseous phosphoretted hydrogen, or phosphine . .PH3

Liquid '* " ..P2H4

Solid " " ..P4H2

Only the first will be described.

136. Phosphine (gaseous phosphoretted hydrogen).
PHg. — Prepared as in Experiment 117, but better with
a strong solution of potassic or sodic hydroxide :

3K0H + 4P + 3H2O = 3KH.,P02 + PH3.

It is formed by the decay of fish and other animal and
vegetable bodies. It is supposed to be the cause of that
dancing phosphorescent light which, under the name of
ignis fatuus, or will 0' the wisp, wanders over marsh}
and swampy places.

Properties. — An invisible gas, of strong smell (that
of rotting fish), very poisonous, even when largely diluted
with air. It readily burns in air (spontaneously inflam-
mable when containing vapour of the liquid compound,
as in Experiment 117) :

PH3 + 2O2 = H3PO4.

CHLORIDES OP PHOSPHOKUS. jgj

In Chemical characters it resemhlp,

w.th acids to form salts e. . """''''' """"onia, uniting

pxT ,^^ Phosphonium iodide.

^^3 + HI == pjjj.
PHOSPHORUS XNO THK HALOOBNS.

pounds a^\Ti°™' """^ OWorine.-Two corn-
Phosphorus trichloride pp.

pentachloride . p!^,'

Phosphorus Tk.chlor.de rPCl , ;' '

"'gdry chlorine gas over hJ,A P'"^P*™d bypa^s-

It is a colourless Tiquid fumi! '""<"i^''°"« Phosphorus.
^>y water ,A... .^ 'VS!;™-' ^i^- "composed

Phosphohus P™tac„lor,„. /PC, ,' ;
reatmg amorphous phosphorus with d T'""'"' ''^
low temperature until n„ '*'■•'' "^loi-ine at a

-"d. of pungent r:;''"r'-''--''ed. Iti^awhite

posed b, warer in Z^'J:;^. "" """"' "''•' '"'"^ ''--

n ^ Pni . TT oxychloride.

/S-cl^X^^-Ao^n'sHOl

Pi>on.s oxyohlorfde; and hv7 tf '''''^•'* (» P'--
TMs is the action with a ,2 "" •"'" '"'^ ^<'™«<'-
'i.e second stage the three rl" '^™^°''' "" °^ *«'-- I"
^placed by three hydroxv 7 ^"^ ''°"^ "' ^'"»"— e
'^ formed, alor.g with a forth '"'' '"' "'"^"''""^ -"<»
«««• Prom thfs it 1 se^r',:rt""T "' ''^'^™«'"<'-
VdroxideofatrivalentTri '/'r'T" '"'"'^ '^ '"«
«- acids generally can be Xl:^^^^ ^^^

-^^2 -OH, SO,(OH),. ^"

154 QUESTIONS AND EXERCISES.

138. Phosphorus and Bromine, &c. — With the

other halogens phosphorus combines forming compounds
the formulas of which are :

PBr^ PBrs ; P2I4, PI3 ; and PF,.

These compounds, excepting the last, are prepared by
direct union of the elements ; and all are of great value
in preparing halogen derivatives of carbon compounds.
By means of these (as well as the chlorides), the oxygen
and hydroxyl of carbon compounds can be replaced by
the halogens. (Compare the action of phosphorus penta-
chloride on water. ^

QUESTIONS AND EXERCISES.

1. Compare nitrogen and phosphorus, as to their compounds.

2. In what dehydrating processes is phosphorus pentoxide
used ?

3. When an orthophosphate of the class MH2PO4 is heated,
water is driven off. What is left ? Write the equation.

4. Mix a solution of sodic phosphate (NaaHPO^) with one of
plumbic acetate. What result ? Try with phosphite and hypo-
phosphite.

5. When an orthophosphate of the class M2HPO4 is heated,
water is driven off. What is left ? Write the equation.

6. What is the basicity of phosphorous acid ?

7. By what tests can the acids hypophosphorous, phosphorous,
and phosphoric be distinguished from each other ?

8. "The atomicity of phosphorus is 3 in some compounds and
6 in others." Apply this statement.

9. Calculate the wt. of 1 litre of phosphorus vapour at 400° C,
and 760 mm. pressure.

10. Calculate the wt. of 1 litre of phosphorus vapour at 1040°
C, and 760 mm. pressure.

11. What is the percentage of phosphorus in pure apatite
(Ca3(P0jo.0aCl,,)V

ARSENIC. 155

CHAPTER XII.

ARSENIC AND ITS COMPOUNDS.

139. Arsenic (As'"''= 75). — Arsenic is found free
in nature in crystalline masses. The ores from which
the elementary substance is principally derived are mis-
pickel (FcgAsoS.,), arsenical iron (FeAso), and arsenical
ores of cobalt, nickel, and copper. Iron pyrites often
contain arsenic.

Preparation. — Chiefly by sublimation from mispickel.
The ore is 'leated in earthenware retorts, and the metal
condensed m sheet iron and earthen cylinders :

FesAs^Sa = 2FeS + 2 As.

It can be prepared on the small scale by heating* the tri-
oxide (As.^O,) with charcoal.

Experiment 118- — Mix a small quantity of white arsenic
(AsgOg) with powdered charcoal, put in a narrow hard-glass +.ube
closed at one end (matrass), drop in a small splinter of charcoal,
and heat the tube slowly in the Bunsen flame, applying the flame
first to the part of the tube in which the charcoal splinter is. A
mirror of arsenic forms as a ring around the inside of the tube.
The charcoal has reduced the oxide of arsenic :

A82O3 + 3C = 2As + SCO.

Properties. — A steel grey solid, of somewhat metallic
appearance. Sp. wt. = 5.727. It sublimes at 356^ C.
It can be melted by heating under pressure. Sp. wt.

156 ARSENIC TRIOXIDE.

of vapour =10,2 (air =1). (Calculate the number of
atoms in the molecule.) It oxidiseb in moist air ; and
burns brightly when heated in air or oxygen, forming the
trioxide (AS2O3). Can also be oxidised by heating with
nitric or sulphuric acid. It is not soluble in hydrochloric
acid. ^rsenic and all its volatile compounds are very
poisonoas. Lead is hardened in the manufacture of shot
and bullets by alloying it with a small proportion of
arsenic.

UO. Arsenic and Oxygen. — Two oxides are

known, viz. :

Arsenic trioxide A82O3

Arsenic pentoxide AsgO^

They are both acid-forming oxides, and this marks arsenic
a3 a non-metal, although it has some metallic characters.

141. Arsenic Trioxide (AsoOg). — Also called (in-
correctly) arsenious acid. This is the *' white arsenic "
of the shops.

Preparation. — By roasting arsenical pyrites and other
ores of arsenic in a good current of air and receiving the
fumes in cool chambers to condense them. These crude
^' flowers of arsenic " are purified by resublimation.

Properties. — A white solid, either a crystalline po"/-
der, or a porcelain-like cake ; of sweetish, metallic taste ;
sparingly soluble in water. (Carefully study the appear-
ance of specimens.) It is volatile, and sublimes readily.
(Try a little in a 1. 1.)

Experiment 119, — Boil a little arsenic trioxide with distilletl
water in a t, t. It dissolves only to a small extent. Prove this
by evaporating a little of the clear lic^uid in a watch glass. Add

ARSENIC PENTOXIDE. 157

about I of its volume of hydrochloric acid to the water, and heat
again. The arsenic trioxide dissolves readily. Keep the solution.

Experiment 120- — Try the solubility of arsenic trioxide in
solutions of Bodic hydroxide, ammonia, nitric acid, and sulphuric
acid.

Arsenic trioxide has very weak basic j)roperties. It
forms with acids no salts which are not decomposed by
water. Its acid forming properties are distinct. (What
proof of this have you had 1) It is used in the manufac-
ture of pigments, glass, &c., and in calico printing. —
One grain (0.06 gram) of arsenic trioxide is a dangerous
dose. Doses of 2 to 4 grains are nearly always fatal ; but
by use the system becomes able to withstand its action.
In one case more than five grains were eaten without ill
effect.

142. Arsenic PentOXide—AsaOg.— Is unimportant.
Can be prepared by heating arsenic acid (H3ASO4) nearly
to a red heat : 2H3ASO4 = 3H2O -|- AsjOg. (Compare
with phosphoric acid). At a red heat it begins to de-
compose into oxygen and arsenic trioxide. — It is a deli-
quescent white solid, uniting with water to form arsenic
acid.

143. Arsenious Acid— HgAsOg (hypothetical). —
This acid is known only in solution and through its
salts. Its relation to arsenic trioxide is the same as that
of phosphorous acid to phosphorus trioxide. It is a
tribasic acid ; but arsenites are known corresponding to
a monobasic acid, HAsOo. (Compare HMO.^).

Arsenites. — Experiment 121. — Heat powdered arsenic tri-
oxide with solution of sodic hydroxide until no more will dis-
solve, filter, dilute the filtrate, and preserve it for the following
experiments.

158 ARSENIOUS ACID AND AKSENITES.

This solution contains an arsenite of sodium; say

NagAsOg.

Experiment 122- — To a little of the solution add a few drops
of solution of ferric chloride (Fe.^Cle), A reddish brown precipi-
tate appears :

FejCle + 2Na3As03 = Fe2(As03)2 + GNaCl.
Test its solubility in dilute hydrochloric acid, and in ammonia.

This precipitate o^ ferric arsenite is harmless when taken
into ^' e stomach, provided the contents of the stomach
are i ,o acid. Hence^ freshly precipitated ferric hydroxide
(Fe2(OH)8) is the best antidote to poisoning by arsenic.
It unites with the acid of the stomach to form ferric
chloride and precipitates the arsenic as arsenite. The
ferric hydroxide can be prepared by the action of am-
monia on ferric chloride, but must then be carefully
washed, since ferric arsenite is somewhat soluble in am-
monia. It is better prepared by the action of calcined
magnesia on solution of ferric chloride ; or a mixture of
sodic carbonate and ferric chloride may be given.

Experiment 123. — Add some cupric sulphate solution to
sodic arsenite in a t. t. A green precipitate (Scheele's green) is
thrown down :

CuSO^ -f NaaHAsOs = CuHAsOg + NajSO^.

This green is often used for colouring wall papers, <fec.,
and has been the cause of many cases of poisoning.
Schweinfurth green is prepared from Schesle's green by
boiling it with acetic acid. (Try it). Paris green is a
variable mixture of these substances with others used
merely as make-weights, or diluents.

Experiment 124. — Add a few drops of argentic nitrate solu-
tion to sodic arsenite. A yellow precipitate of argentic arsenite
is formed. Test its solubility in nitric acid and in ammonia.

ARSENIC ACID AND ARSENATES. 159

144. Arsenic Acid. — HjAsOi. — Prepared by action
of oxidising agents and water on arsenic trioxide.

Experiment 125. — Put a little arsenic trioxide in a small
porcelain basin, add a small quantity of strong nitric acid, and
heat on the water bath. Red fumes are evolved (N2O;,) ; evapo-
Fcate to a syrup, and keep. This is arsenic acid containing a little
water :

2Hm)3 + AS2O3 + 2H2O = 2H3ASO4 -\- N2O3.

Orthoarsenic acid (H.5ASO4) is a strong tribasic acid.
Ft/roarsenic (H^As-.O;), and metarsenie (HAsOg) acids
can be prepared by heating the ortho-acid.

Arsenates are very like the corresponding phosphates,
being generally exactly the same in crystalline form (iso-
morphous). Uisodic liydric arsenate (Na2HAs04.7HoO)
is used in medicine. It is a white, crystalline, soluble
salt, prepared by fusing together arsenic trioxide (10
parts), sodic nitrate (8| parts), and dry sodic carbonate
(5^ parts) ; dissolving in 35 parts of distilled water,
filtering, and evaporating. ^''

Experiment 126. — Dissolve the acid from Experiment 125 in
a little water, colour with litmus, and add solution of caustic
soda until neutral. With this solution make the tests for
orthophosphoric acid (Art. 122). ' .

Arsenates respond to the same tests as phosphates,
but argentic nitrate gives a chocolate coloured precipi-
tate (AgyAsO^).

Experiment 127. — To solution of sodic arsenate add a little
sodic acetate (NaCaHgOa) and then ferrous sulphate (FeS04).
A white precipitate of ferrous arsenate (Fe3(AsO^)2) is thrown
down. It quickly turns greenish owing to absorption of oxygen
from the air :

2Na2HA804 -f 2NaC2H302 + SFeSO^ =

Acetic acid.

Fe3(As04)2 + SNagSO^ + 2HC2H3O2.

160 SULPHIDES OF ARSENIC.

Ferrous arsenate is used in medicine. Ferrous phos-
phate (Fe;,(P04).j) can be prepared in the same way
from sodic phospliate. (Try.)

145. Arsenic and Sulphur.— Three sulphides are
known :

Arsenic disulphide, or realgar AsgSa

Arsenic trisiilphide, or orpiment AsgSg

Arsenic pentasulphide AsjSg

Experiment 128. — Treat some solution of arsenic trioxide in
dilute hydrochloric acid with hydric sulphide. A yellow preci-
pitate (AsgSg) is formed :

A82O3 4- 3H2S = AS2S3 + 3H2O.

Teat its solubility in sodic hydroxide, in amnionic sulphide
((NH4)2S), and in strong hydrochloric acid.

Experiment 129. — Dissolve a litt/e arsenic trioxide in sodic
hydroxide and treat the solution with hydric sulphide. No pre-
cipitate is formed. (Why is arsenic trisulphide not formed, as
in Experiment 128 ?)

Experiment 130. — ^Test some solution of sodic arsenate with
hydric sulphide. No precipitate is formed. Acidify with
hydrochloric acid and repeat the test. A yellow precipitate
(AS2S3 + S2) is formed. Try its solulnlity as in Experiment
128.

Two of the sulphides of arsenic (A S2S3 ana AsjSg) com-
bine with the sulphides of the alkali metals to form
soluble sulphur salts, in which sulphur plays the part of
the oxygen of ordinary salts. This explains the solu-
bility of these sulphides in alkaline sulphide solutions ;
for example, in Experiment 128, when arsenic tri-
sulphide dissolves in ammonic sulphide, ammonic sulph-
ur aenite ((N 114)3 AsSs) is formed.

maksh's test. 161

146. Arsenic and Hydrogen. — Arsine, or arseni-
uretted hydrogen (AsH.,) is the only compound of impor-
tance.

Experiment 131. — Fit a 4-oimce wide mouthed bottle with
a cork twice bored and provided with a thistle fuuiiel passing
nearly to the bottom, and a hard glass tube passing just through
tlie cork, })oth tul)es fitting tightly. The hard glass tube must
be bent at right angles and drawn out at the point. Cover the
hottom of the bottle with granij^lated zinc, push in the stopper
tightly, pour in through the funnel enough dilute sulphuric acid
to fill the bottle about one-fourth. Be sure that the funnel dips
below the surface of the acid. Hydrogen is evolved and issues
from the glass jet. After two or three minutes wrap a towel
around the bottle and light the hydrogen. (Why not at once?)
Hold a piece of cold porcelain in the tlame for a second or two and
see if it is blackened. If it is, there is probably arsenic in the
zinc. If not, pour through the funnel a few drops of aqueous
solution of arsenic trioxide. The liame of hydrogen very soon
becomes livid bluish. Try with the cool porcelain. A metallic
spot is formed. Make several of these, and then set the apparatus
in a draught or out of doors. Try the effect on the spots, of (1)
amnionic sulphide, (2) hydrochloric acid, (3) bleaching powder
solution. Results: »

(1) (2) . ^. . .

(3)

This is Marsh's test for arsenic. For very delicate

cases, the hydrogen should be dried by a soda-lime tube.
Explanation : Nascent hydrogen reduces arsenic trioxide,
forming arsine and water :

AsA + 6Ho = 2ASH3 + 3H.,0. .

Arsine (an invisible gas) is decomposed by the lieat of
the hydrogen flame, and the metallic arsenic is con-
densed on the porcelain.

Arsiiie is formed in vegetable matters containing
arseuic when certain minute fungi are growing in them,
i2

162 ARSENIC AND HALOGENS,

e.g., ill ai'senical wall jiapera. The air of a room may
thus become coiitamiiiated by this intensely poisonous
gas. One small bubble of the pure gas has been known
to kill a man.

147. Arsenic and Halogens.

Aksenic Trichlokidk (AsCly) is a colourh^ss volatile
liquid, formed by the action of sulphuric acid on a mix-
ture of arsenic trioxide and sodic chloride. This explains
its presence in hydrochloric acid prej^ared by means of
arsenical sulphuric acid. It dissolves in water, at the
same time decomposing :

2A8CI3 + SHjO = A82O3 4- <>HC1,

Arsenic Trt-iodide (Asia) is used in medicine It
is pi'epared by carefully heating arsenic and iodine to-
gether. (In what proportion'/). In Donovan's solution,
it is combined with mercuric iodide (Asia -}- Hgl.,), and
forms a clear colourless solution. The other halogen
compounds are of little importance (AsBi'y, ASF3, and
AsFj). — Clemen's " bromide of arsenic " (so-called) is a
solution of arsenic acid and hydrobromic acid, prepared
by the action of bromine on arsenic trioxide.

148. Tests for Arsenic. — (See Experiments 118,
128, 130, and 131.)

1. To a solution of arsenic trioxide in dilute hydrochloric acid
add a drop of ammonio-rupric sulphate (prepared by adding
ammonia to cupric sulphate solution gradually, until the preci-
pitate at first formed is just redissolved). A green precipitate
(Scheele's green) appears.

2. Beinfich's Test. — Put a thin strip of bright copper in some
hydrochloric acid sohition of arsenic trioxide, and boil (in a
t. t.). Arsenic is deposited on the copper. Remove the copper,
wash it well (without rubbing), dry it by holding it over a flame

QUESTIONS AND EXKHOISES. Ifi3

(not too near), put it in a narrow dry t. t. and heat it. Arsenic
and the triox'de are sublimed upon the tube. Try this test
with some grt jn wall papers, by digesting them with strong
hydrochloric acid, diluting with water, and then using the solu-
tion as directed above.

QUESTIONS AND I<]XEKCISES.

I. (Compare arsenic and phosphorus (a) as to physical proper-
tits, and (h) as to their compounds.

'_'. Show the analogy between oxygen and sulphur, as seen in
till- compounds of arsenic.

3. In what proportion should ferric chloride and sodic car-
hdiiate he mixed so as to produce ferric hydroxide :

FesCli, + SNaaCO + 3U^0 = Fe2(0H)e + GNaCl + aCOj.

4. What data have you for concluding that arsenic is triad
and pentad ?

f). How much mispickel will (theoretically) give 10 lbs. of
arsenic.

0. In what respect does the molecule of arsenic deviate from the
general rule ? What other element shows the same deviation ?

7. Is arsenic a metal or a non-metal ?

8. What is the meaning of "isomorphous " ?

9. In testing for arsenic with hydric sulphide the solution is
made acid. Why ?

10. In Marsh's test oxidising agents must be absent. Why ?

II. Balance the following ec^uations :

(1) As + HNOg - n3A8()4 + NO2 + H2O.

(2) A82O3 + HNaO = NagAsOg -f HgO.

(3) NH4OH -f Fo2Cle = NH4CI -f Fe2(0H)«.

(4) NaaHAsO^ + AgNOg = Ag3As()4 + NaNOa + HNO3.

12. Write the formulas for the following compounds : Sodic
(Ithi/ib'lc arsenate, ciq»ric hi/dric arsenite, sod'tc thioarstnite, and
(( tn monk orthoamenate.

164 CARBON.

CHAPTER XIII.

CARBON AND ITS COMPOUNDS.

149. Carbon (C^ = 12).— This element has three
allotroi)ie modifications : (1) diainond, (2) grapJdte, (3)
charcoal (lamp black, tfec.) Diamond and graphite are
crystalline ; charcoal is amorphous.

1. Diamonds are f'^-nd in pebbly deposits of ancient
rivers, in South Africa, Australia, South America, Ac.
It is the purest form of carbon, and its nature remained
long unknown, until it was proved to be carbon by burn-
ing it in oxygen, — An impure black variety, carbonado^
is used for polishing the diamonds. — Diamond is one of
the hardest substances known. When ])ure it is colour-
less. Specific weight =3.5 to 3.6. Its crystals are
modifications of the cube. Its great lustre is due to its
strong refractive power on light. At a high temperature
it burns in air or oxygen forming carbon dioxide (CO.,).
It has never been prepared artificially, although many
attempts have been made.

2. Graphite is found in lumps in granite, ifec, well
crystallised ; or in obscurely crystalline masses of plum-
bago, or black lead. The best black lead is found in
Cumberland, England. Graphite can be artificially pre-
pared by crystallising carbon from molten iron. It often
occurs in pig iron. It is not pure carbon, but leaMs
considerable ash on burning. — It is a black metallic-

r'AKiJON. 105

loi>king substiuicc, groasy to tli« touch ; Hpecific weight
rr: 2 to 2.6. It hiiriiH with groat difficulty at a higli
toiiiperature to form carbon dioxide. It is used for lead
pencils, crucihles, for [>olishing gunpowder grains, ifec,
and as a lubricant.

3. Amorphous Carbon. — Jjamp-black, gas-carbon,
coke, charcoal, and animal black are impure amorphous
ciubon. Lamp-black is prepared by burning turpentine,
tkc, with a scant supply of air and collecting the soot
on woollen cloths. It consists of particles of carbon
covered with tar. It is used in the prei)aration of Indian
ink, black paint, and printers' ink, and to give a grey
shade to calico. — Gas carbon gathers in the upper part
of the retorts in which coal is distilled in the manufac-
ture of coal gas. It is very hard and resonant, and con-
ducts electricity. It is used as the negative element in
electric batteries, and in the manufacture of micro-
ph(jnes. — Coke remains in the bottom of the gas retorts
when the process of distilling is complete. It is hard and
dense, and burns (at a high temperature) without smoke
and giving an intense heat. It is used in smelting opera-
tions and as fuel in engines. — Charcoal is prepared by the
destructive distillation of wood or bones. In the latter
case it iaacalled ayiimal charcoal, or bone black.

Experiment 132.— Heat a small bit of dry wood in a mat-
trass, applying a match to the open end. A combustible (jas is
evolved, tar and water gather on the sides, and charcoal re-
mains as the skeleton of the wood. Try the same experiment
with a bit of l)one, horn, or dried meat. Similar results are ob-
tained.

Charcoal bus the power of absorbing gases and causing
tlieir oxidation when they are oxidisable, A piece of

lOf) CllAllCOAL.

charcoal made from tlic sliell of IIh^ cocoa nut will aWjil,
171 times its volume of ahin>oiiia gas ami 100 times its
volume of liydric sulphide. It must first be heated to
expel the gases already condensed in its j)ore.s. On ac-
count of this pronertv it is used as a filter foi* air, oeii)*'
.nade into so-called " res[)irators." Evidently the char-
coal in these respirators should be often renewed, or
taken out and heaied red-hot, in order to expel the con-
densed irases.

Experiment 133. -Fill a filter paper (placed in a funnel)
about two-thirds full of bone-black. Colour some water with
indigo, heat it, and pour it on the filter.

Charcoal has the property of extracting colouring mat-
ters from solution. Bone-black is used for this purpose
in sugar refining.

Experiment 134- — Fill a filter with fresh ground charcoal,
.•ind pour some hydric suljjhide water on it. If thf" smell has
not been uostroyed when the water runs through pour it on again.

Charcoal has vhe power of extracting offensive animal
and vegetable matters from water. It is used for filter-
ing water. Filtei-s should be renewed very often. The
charcoal should either be replaced or be taken out and
heated red-hot to destroy the substances extrac|jfd from
the water, — Charcoal poultices are usod foi purifying
foul wounds. They are very efficacious. — Coed is impure
amorphous carbon. It is the remains of primeval forests
which have undergv>r'^ a slow proces:^ of decay. Thi.s
process is now going on in peat l)og^. A^Uhradte is very
pure, containing as high us 94 '°/^ carbon. Bitunmioux,
or soft coal ccntair mud', hydrogen, oxygen, and nitro-
gen, and only uj) to 75 °i^ car'^on. fAi/nitf is coal in

COM l»OUNt)S OF CARBON. ICT

the })rocess of formation. It ooDtaiiis up to 70 °/^ carbon.
Jet is a hard variety of coal wliich takes a good polish.

150. Compounds of Carbon. — Carbon occurs in
Tiature combined as well as free. As shown in Experi-
ment 1-^'i, it forms an essential constituent of anirnal
and vegetable bodies. In fact, it is the element of organic
tissues. — It is found in vast quantities, as carbonates,
e. g., calcic carbonate (limestone, marble, chalk, &c.),
magnesic carbonate (in mountain limestone) ; also in t}»e
air as carbon dioxide (COo) ; in marsh gas (CH^), petro-
leum, shale, ikc. — The number of the compounds of
carbon is so vast tliat a special branch of chemistry.
Organic Chemistry, is devoted to their considera-
tion. Many of them exist already formed in the
bod.es of plant's and animals, and in the crust of
the earth ; but many are the product of the labora-
tory. The great number of the carbon compounds is
due to the property which ( irbon atoms have of unit-
ing ivith each other so as to form groups of carbon
atoiiis capable of acting as the nuclei of molecules.
Thus, carbon and hydrogen can unite in a great
number of different proportions, the simplef-t com-
pound being that having one carbon atom in the mole-

H H H

' . . II

cule, H — C — H, the next containing two, h — C — C — h,
I II

H H H

I I I

the next th^-ee, h — C — C — — h, and so on. The

i I i

H H H

hydrogen atoms can be replaced oy other atoms

108 CARKON niOXTDE.

Hid loiiiK'd. Tims.

aiul groups,

and tlius derioatiiiCH

H C CI, H-

C OH, etc.

1
H

!
H

151. Sources of Carbon Compounds— P/an<.s

and animals supply compounds of carbon ready formed,
and the most fruitful natural sources are the remains of
organised bodies. In fact, if we exclude some of the
naturally occnring carbonates, it may be stated that all
carbon compounds not of aitificial origin are the products
of vegetable or animal organisms.

Petroleum supplies a great number of compounds of
carbon and hydrogen, mostly belonging to the class of
parajfins (C,iH2,i + 2)- — By the distillation of coal, coal
tar is obtained. This once waste product has developetl
during the last 30 years into an almost inexhaustible
source of new and valuable compounds. From it ai-e
manufactured the aniline and other beautiful colours,
artificial essences and perfumes, and substances which in
some degree serve as substitutes foi' quinine, tfec.
La^^dly, saccharine, said to be 220 times as sweet as
sug.\r, has been made from coal-tar products. — Bone-oil
and ivood-tar are sources of organic compounds.

CAP BON AND OXYGEN.

152. Carbon Dioxide, CO,. — Commonly called

carbonic acid.

Ojoukrence. — Free in the air and in the crust of the
earth, issuing from fissures, as in the celebrated Grotto
del Cane. It is found combined in the carbonates. If

CARhON DIOXIDK. 161)

is !i product of the coiuliustion, ilecay, and fermentation
of organic substances. It is also given out l>y animals
ill respiration.

Preparation. — Experiment 135. — Put some lumps of mar-
ble or limestoue in an S-ouuce bottle provided with a gas-delivery
tube bent twice at right angles so as to collect a heavy gas by
displacement of air. Fill the bottle al)out one-third with dilute
liy<lrochloric acui, and collect several bottles of the gas by dig-
{ilacement of air, covering them with pieces of glass. Try to
light the gas as it issues from the tube. Bubble some of it
through blue litmus. Allow it to bubble through lime water.
Evaporate the solution left in the botM.:; and get crystals of
calcic chloride (CaCl.j.OH.jO).

CaCO,, + 2HC1 - CaCla + H./) + CO2.

Carbon dioxide can also he prej)ared by heating lime-
stone to a red lieat :

CaCO;, = CaO -h CO^.

Properties. — A heavy, invisible gas, of slightly pun-
gent smell, and sharp, sour taste. Specific weight =
(Calculate.) It is not a strong poison, but has
a »rcotic action, and does not support animal life. It can
be Uque'ied at — 78.2° C. under the atmospheric pressure.
At hif^lier temi^eratures it can be liquefied by increased
pressure ; and when the pressure is removed the liquid
boils, jxirt of it becoinimj frozen into a snow-Like solid.
(Explain this?!^) It is somewliat soluble in water; at
0° C, 1.8 vols, in I of water; at 15° C, 1 vol in 1.
The solution is slightly acid, and probably contains car-
honic acid {ll.,CO.^). ' _ _ ^

Experiment 136. — Put a lighted match into a bottle of car-
hou dioxide. Put another bottle, mouth downwards, in recently
l»oiled cold water, and let it stand a few minutes with occasional

170 ("AKBONIC A(.'iD.

shaking. Try the same experiment with sohition of caustic
soda. Pour a l)ottle of gas into a bottle (illed with air, testing
with a lighted match.

Experiment 137. — Bubble air from the lungs through clear
lime water by means of a glass tube. .

Caibon dioxide is absorV)ed by strong bases, with
which it forms salts, the c.irhonates. It is being con-
stantly given off into the ai]; from the bodies of animals,
but the (|iiantity in tlie air does not increase. Vege-
tables use it as fast as animals excrete it. Carbon diox-
ide is present in the air to the extent of about 4 volumes
in 10,000. In poorly ventilated rooms the proi)ortion
much exceeds this, and the relacive quantity of gas is
a good measure of the purity of the air. The danger,
however, is not so much from carbon dioxide as from
other waste products of thw body expired with the air
and exhaled from ttie ger.oral surface of the body. It is
these which give the state smell to a poorly ventilated
room. — On account of its high specific weight carbon
dioxide collects in depressions such as wells and cellars.
Accidents often occur from workmen descending into
wells and brewery vats filled with the gas. A good pre-
caution is to lower a light before descending, although
air which will support combustion often contains enough
carbon dioxide to produce death.

153. Carbonic Acid and Carbonates. — The

acid is not known except in solution. It is dibasic, ard
very weak, not forming salts with the weaker bases,
such as ferric hydroxide, aluminic liydroxide, &c. — There
are two series of carbmiates, (I) normal^ e.g., Na.>CO,,
and (2) acid, e.g., NaH0O;{. The carbonates of the
alkali metals (K._,(JO;,.Na._,CO;i, ka.) are soluble in water;

CAHP.ON M(>N<)XII>K. 1^1

ill! other normal carhoiiatas are insoluUlt.'. lUit many of
tlie insoluble normal carbonates combine with carbonic
acid to form unstable, sparingly soluble acid salts. Thus,
calcic carbonate (CaCO.,), magnesic carbonate (MgCO^),
ferrous carbonate (Fe(yO;.), tfec, dissolve in water con-
taining carbonic acid. The solulnlity is increased by
pressure of the gas.

Tests. — 1. Carbon dioxide renders lime water turbid :

Ca(OH)., -f- CO2 = CaCO.^ + H2O.

2. Carbonates effervesce with hydrochloric acid. (Try with
several of the carbonates. ) If the evolved gas be poured into a
t. t. containing clear lime water, it renders it turlnd on shaking
up«

154. Carbon Monoxide, CO. — Also called cariomc
oxide.

Preparation.— Experiment 138.— Carefully heat a little

dry powdered potasnic ferrocjianUle (K^F^eCoN^) with about 10
times its weight of conceuti ated sulphuric acid, and apply a light
to the mouth of the tube. A gas is evolved which burns with a
lambent blue flame :

K4FeC,.N„ 4- OHaSOj + GH.,(3 - 2X280^ +

3(NHJ2S0^ 4- FeSO^ + GCO.

Carbon monoxide is also formed when oxalic acid
(CH-.O^) is heated with sulphuric acid :

C2H2O4 = CO + CO2 + H2O.

Ft is formed 'dien carbon burns in a scanty sup[)ly of
air, as in the inner parts of a tire. • - --

Properties. — A colourless gas, of very faint odour;
s[). wt. - I). !)(>('). It burns with ii j»ale bluo tlame

172 f'ARIJON HIS rT.PIllDK.

(CO + O ^ COo), as soon on tlio top of a coal fire. It
can be con«lenso(l to a li({ui(l at — 139,5'^ by a pressure
of 35.5 atinos[)heres. It is sj)aring]y soluble in water
(3 in 100); easily in ammoniacal solution of cuprous
chloride (Cu.^Cl.,). It is u deadly poison, combining with
the ha3molglobin of the blood and thus preventing its
aeration. As it often escapes combustion in coal and
charcoal fires, it contributes greatly to the poisonous
condition of ill-ventilated rooms. Open charcoal fires
(braziers) are es[)ecially dangerous.

155. Carbon Bisulphide, C8.,.—

Preparation. — By i)assing sulj)hur vapour through
long tubes filled with red hot charcoal.

Properties. — A mobile colourless liquid, of pleasant
ethereal smell when pure, but generally having a disgust-
ing odour due to impurities. Sp. wt. = 1.29. It does
not mix with water.

Experiment 139. — Pour a little carbon bisulphide into a t. t.
of water. Note the smell. Shake up with the water. Heat a
few drops of carbon bisulphide gently in another t. t. It boils
readily. Put a light to the mouth of the t. t.

Carbon bisulphide boils at 46° C, forming a heavy
vapour, very explosive when mixed with air :

CSa + 30a = CO2 + 2S()a.

It evaporates quickly when exposed to the air and lowers
the temperature. (Try a drop on the hand.) It mixes
in all proportions with ether and alcohol ; and dissolves
fats, oils, india-rubber, phosphorus, iodine, bromine, itc.

"YDROCARBONS.

A solution of india-uibber in > i . ^^^

fo; ce.entia, n.bbe; ,o ^ iL"^ ''''''^''^'^ - "-,
nit'-ogen dioxide fXor h. ' '"^"''"* ^^^^^^^ with

'^^.^^ -d in J^^^'r^' -^'\ ^ dazzling .Mte

i— us. It is antis: S,W TZ '""^^'^^^'^^ -
meat, &c. • ^ ''^' ^"^' ^« "«ed for preserving

^'^"fphomrbonic add H r*i

carbonates. . ^'^ '"^^^^>g-"« to carbonic acid and tht

Potasmc sulphocarbonate K OS
-■"on bi.„,pHMe in .„,„«;, ^fp^il^r^^ "^V ^i-,.,„

K.OS, + 2HC1 . 2KC1 + H.cs';

H.CS3 = H,S + CS,.
CARBON AND HYBEoOEN.

156. Hydrocarbons —Thp „, .

S>eat that onlv a very Zl] 7 "'''''" "'' «'««« i« bo

«- - "-toontainLg lLT„^'';'™•••'°"-dhyd..o-
= carbon atom and 4 hydrogen

^"""'« i" the molecule, „_(]__„ , ,

"' * '""'"». --""I J of these is

174 PARAFFINS.

employed in holding the carliou atoms tlicinselvcs together.

H H

.11
The graphic formula for this molecule is li — C — (J — ii.

I I

H II
II II II

III • ■■ •

The next would be n — (J — C — C — ii, and so on, tlic

I ' I

II II H

molecules increasing regularly by CH.^ ; so that a general
formula, Cf,U'>^ + 2, ean be written. Very many mem-
bers of this series are known. Most of them are found
in petrcleum oil and in the gas accompanying it. It is
called the Paraffin Series :

„ Marsh gas, or methane. . . . CH4

Ethane OgHf.

Propane C.^Hj,

Butane ^4Hi

Pentane C5H12

Hexane - . . C,.Hi ^

&c. &c.

The different members of this series resemble each
other in chemical properties. Paraffin oil (kerosene) is
a mixture of the liquid members. Paraffin wax, used in
making candles, is a mixture of solid paraffins, the higher
members. These substances are obtained by the frac-
tional distillation of petroleum, which is a product of the
decomposition of primeval forests.

Besides the paraffin series there are several other series
of hydrocarbons containing a less proportion of hydro-
gen, the Olpjines having the general formula Cj^H.jm,
— (C0H4, C^jHq, tkc.) ; the Acetyleme Series, UnH.jn-

. . Gas

. Gas

.. Gas

Boila at V C.

*' 38° C.

" 70° C.

'^fAKsir GAS.

'liff-;encrCtirLrjc!;tivi",'''1 "^ ""-^ '"■'<^ tho.

'"• Marsh Gas, or Methane Cr

"■•"t pools, Hsi,., ,„ ,:v;;';^' °'' ---i., .„„ ou.,,. „

;;™t of wato, ,„.,, ,„, ,,;"'» => bottle L^ d;,,,,,,^.

'['- -,..,, an.\:i t::'::'i ■■" -- -.-ntii:

A«H g,.e „«■ „,,,., <,„„„^ i-'yi;"'S» Of America „„,

''■f --■bon. I„ .;„:..,:""; ->"-''«- of othe":
-'•-) gas i. ,„,d fo.. ,•„.,;;,.:' ^--y'vHnia, this

f"-- ages. Jlarsh gas i, tL . , ' '"'™ ''^'^n bu™i„„

"'■"ora- It is ,1 ''*""'<'<' " fi'-e .lam,> " .f ?

" i!- also present in „„ •, '"'"P ofcoai

««/<?««. '"'°"'"''^'*l''e quantity in

Pheparation — Pv„» •
w& acela/e W»l ■ 'j.'^f ''^"ment 140.— Mix w^ll „

N«C.H303 . NaOH = Na.CO, ^ CH

'- -hen breathed. "ftT-!! 'r,""''""^' ''-' '-".,-
;■* a pale blue flame aid d^^e!' ' '' "^"'^ '" -'■
»mb,,stion. ..'''"' "°'«"PPo.-t ordinary.

Experiment W -_ti.. , .

S» Lew upside ,!„„, ' I '';' ^ ''gl,t„,, „,,t„^ j^^,^

'■"" " i- «ioc. with »i, " '"" «^^ '■■'»" -"i- ja/:;"jj.'i:

170 MARSH OAS.

Methane is very explosive when mixed with air or

oxygen :

CH^ + 20a = COg + 2H2O.

Frightful explosions occur in coal mines. For the pro-
tection of miners Sir Humphrey Davy invented the
" Davy Lamp," in which the flame is surrounded by wire
gauze. The metal conducts away the heat of the flanu!
rapidly, and thus keeps the explosive mixture next to it
below its point of ignition. The flame cannot pass
through the gauze.

Experiment 142. — Hold a piece of wire gauze above a jet of
gas, apply a light above the gauze and observe that the flame
does not pass below.

Methane is sparingly soluble in water. It is very
stable, like all the paraflSns {parum ajfinis = having
little afiinity), resisting the action of nitric, sulphuric, and
hydrochloric acids, and of other vigorous chemical sub-
stances. It cannot be got to unite with any element or
compound, except by losing one or more of its atoms of
hydrogen. The hydrogen can be replaced in fourths by
the action of chlorine :

Monoehlorinethane.

CH, +

CI2

= CH3CI + HCh

Dichloniietliane.

CH3CI +

CI,

= CH2CI2 + HCl.

Trichlonuethane.

CH2CI2 +

CI2

- CHCI3 + HCl.

Tetracliloriiietlmne.

CHCI3 +

CL,

= CCI4 + HCl.

The molecule of marsh gas is incapable of taking up
atoms except by replacement. It is a saturated coni-
j)Ound, i.e., the carbon is saturated with hydrogen. T/ie
parajfins are the saturated hydrocarboris.

f'HLOROFOHM.

'58. Chloroform CHvi ^ ^^^

fr'MoTmethano. ' '^'■'•— t^or.nerly inentioiied as

(^L'H«()). ^^ith coimnon alcohol

Experiment 14<i p i ^

•■""' burni,,,, tote "l ""'"^ ■"'""•'' "^ P'^a^ant s„,el,
Experiment 144 -Put, •Vwt. = ,.525.

'■ '• »f water aml^hak? ,?,"'' ^'"''"' '^'"^ "< cWorofo™ ,•„

-^ a.„h„, ,,3.., „, .. jr::xr xr '"'""™ "■ ^'^

It IS now used in s„rm™l "^""'"s Simpson, 1848 )

;";■""=' point renc'e.: '1 ^ "^"^-.'-geons. Its lo'^

, --.-:^ .. CW„o.o. !IT ^ ^ """"^•
'aten ,„ selecting chloroform fo, ""''" '''»"''' ^e

'«nons s„b.tance.,, e.g. 1 " in "'.'' "'*^" -"'ains dele-
'■'''"■■i-'e« of other or: „','"" '""'■ ^'''°""«. and

'3 ""^ °' S"« a (precipitate with

IMAGE EVALUATION
TEST TARGET (MT-3)

C/j

1.0

I.I

If IM IIM

«■ ■- 12.2

t:&

12.0

1.8

1.25

1.4

1.6

-m 6" —

►

sir jj^

W
^

Photographic

Sciences
Corporation

23 WEST MAIM STREET

WEBSTER, N.. 14580

(716) 872-450.}

^^-.-^^

178 ETHYLENE.

argentic nitrate (impurities, HCl and CI); it does not
colour a mixture of potassic bichromate and dilute sul-
phuric acid green (alcohol, &c.) ; it is not coloured brown
by potassic hydroxide or sulphuric acid ; it does not cause
bright sodium to tarnish, even when heated (O2H4CI2. &c.).
If, when allowed to evaporate on a clean watch glass,
chloroform leaves a strongly smelling residue, the alcohol
from which it was prepared contained fusel oil.

Experiment 145- — I'ry these tests with samples from the
druggists.

Iodoform (CHI^) is a yellow crystalline solid prepared by
adding iodine to a mixture of common alcohol and solution of
sodic carbonate heated to 60°. It is insoluble in water, but
soluble in alcohol and ether.

159, Ethylene, CH^. — Also called "olefiant gas.'
Is a constituent of coal gas.

Preparation. — By the action of potassic hydroxide on
monochlorethane (CoH^Cl) :

C2H5CI + KOH - C2H4 + KCl + H2O.
Or, by heating alcohol with strong sulphuric acid :
CgHeO = C2H4 + HgO.

Properties. — It is the first member of the olejine series.
It is a colourless gas, distinguished from the paraffins by
the facility with which it unites directly with other sub-
stances, ivithout losing hydrogen. Thus, it unites with
an equal volume of chlorine to form chloride of ethylene
(C^HiCl^^ an oily liquid ;

, C2H4 + CI2 = C2H4CI2.

Its molecule is unsaturated, and we express this fact by

H H

the graphic formula, n — C = C — H, in which the carbon

ISOMKRISM. 179

H*^.oins tire represented as united by two bonds. One of
tlies'^ can be divided so as to receive 2 atoms of chlorine,

H H

II — C - C — H. The olejines are all wisaturatcd compounds.

I I

Cl Cl

160. T'^omerisni. — Ae has been mentioned', methane
is capabiv entering into tliose chemical actions only in
wliich its hydrogen atoms are rej)laced by other atoms or
compound radicals. Thus, an atom of chlorine replaces
One of hydrogen to form monochlormethane. This re-
placement has been made in a great many different ways,
;ind the same substance is always obtained. It has been
concluded that the fc-r hydrogen atoms are exactly alike
ill relative position, so that it does not matter which is
replaced. It is very important to get this idea clearly
at the outset. It has been found also that only one sub-
stitution product of ethane having the formula, C-.H^Cl,
can be obtained ; and it is therefore concluded that

H H

I I

the six hydrogen atoms in ethane, ii — C — — n, are alike

I I

H H

ill position. But, when a second atom of hydrogen is
replaced by chlorine, two substances are obtained, identi-
cal in chemical composition (C\,H4Cl.j), but differing in
p i-operties. One of these is the substance mentioned in
in Art. 151 as ethylene chloride. The only other differ-
ent arrangement of the atoms is represented as follows :
H H

i L
n — C — C — Cl, both chlorine atoms being attached to

I I

II Cl

180 ACETYLENE.

the same carbon atom. This second compound can be

' I

prepared from aldehyde (h — C — C = O), by replacing

I I

H H

oxygen by chlorine ; and it is distinguished from the first
by the name ethylidene chloride. These two substances
are alike in composition, hut different in properties. This
is a case of isomerism..

161. Acetyleno, C.^H.^. — This compound is a
colourless gas formed by the incomplete combustion
of gases containing hydrocarbons. It has a strong dis-
agreeable smell, which is easily observed in the smoke
of a candle just blown out. It is produced in consider-
able quantity in a Bunsen burner " burning below."
(Try it.) It can also be prepared by the action of alco-
holic solution of caustic potash on ethylene chloride or
bromide :

C2H4CI., -f- 2K0H = C2H2 + 2KC1 + 2H2O.

It is poisonous when breathed, uniting with the haemo-
globin of the blood as carbon monoxide does. As it is
formed by lamps when the flame is turned low, this
practice should be discountenanced, especially in sick
rooms.

Acetylene can be formed from the elements by passing
a powerfid current of electricity between carbon poles
in an atmosphere of hydrogen. This is an important
synthesis.

POTASSIC KKHKOCYANIItK. 181

CAHHON AND NITKOCKN.

1G2. Cyanogen Compounds. — Nitrogen is pre-
sent in all organised bodies. If nitrogenous matters such
as horn, flesh, &c., be heated with sodium, a compound is
o'ntained composed of sodium, carbon, and nitrogen
(NaCN), and called sodivm cymiide. When nitrogenous
substances are heated with 2)otassic carbonate (KoCO;.),
and iron scraps, a fused mass is obtained which yields on
lixiviation a yellow crystalline salt, potassic ferrocyanide
(K4Fe(CN),.). This fealt gives a fine blue colour (Prus-
sian blue) with ferric salts, and is the starting point in
the preparation of the cyanogen {blue-generating) com-
pounds. All these compounds contain the monad radical
— CN, cyinogen, which can be set free, but, like an atom,
unites immediately with another to form a molecule
(CN)2. The substance cyanogen (CoNo) can be prepared
by heating mercuric cyanide (Hg(CN)._,). It is a very
poisonous gas, having chemical properties like those of
clilorine ; and its compounds with metals are called cyan-
ides, e.g. :

KCN, Fe CN)2, Ca(CN)2, &c.

163. Potassic Ferrocyanide— K,Fe(CN)c.3H.,0.

Commercially known as yellow prussiate of potash .

Preparation. — Fuse refuse animal substances with
i)otassic carbonate, and lixiviate the fused mass. A solu-
tion containing potassic cyanide (KCN) is obtained. To
this add freshly precipitated ye^rmts carbotiate (FeCOo).
It dissolves :

6KCN 4- FeCOa =-- K4Fe(CN)„ + KgCOg.
The solution is eva[)orated and the two salts separated by

1<*^2 UVDHOCVANIC ACID.

cystallisation, the potassir carUoiiato Itoing much tlic
more soluble of the two.

Pkopertiks. — A salt crystal lisiiig in large yellow pi-is-
matic crystals. (Examine a crystal, noting its " feel,"
taste, the ease with which a splinter can be split off, and
the flexibility of the s})linter.) It is soluble in about 4
times its weight of water. (Dissolve a small quantity and
taste the solution.) It is not poisonous, and in large
(loses acts as a mild [)urgative.

Experiment 146. — Heat slightlj^ a small crystal of potassic
ferrocyauide in a t. t. It falls to a powder and water is con-
densed ?n the side of the tube. (From what source does the
water come '!) Heat more strongly, and the salt turns brown.
It has been decomposed into potassic cyanide (KCN), carbide of
iron (FeCa), and nitrogen. (Write the equation.) Keep the
residue. »

Potassic ferrocyauide belongs to the class of double
cyanides^ and is composed of potassic and ferrous cyan-
ides, 4KCN.Fe(CN)._,. But these are so united that no
ordinary test shows the presence of iron ; and the salt
does not possess the characters of a simple cyanide. It
is a salt o{ ferrocyanic acid (H4Fe(CN)g). All soluble
simple cyanides are deadly poisons.

161. Hydrocyanic Acid, HCN. — Originally

called prussic acid. This is one of the most deadlj^
and sudden poisons known. The vapour of the pure acid
causes almost instant death, and even when largely
diluted with air it causes headache and giddiness for
some hours if inhaled for a few seconds. Unfortunately
some persons are not able to detect its subtle odour — tha'
of crushed cherry stones. Experiments with it must b*

t-'VAXlOES.

183

mude very cautio.isJv __,/,,,; 7 .

rine water. ^' ^'"'^''^''^''^-^^nmonia and e/do-

-l-d i„ ,0 o^. ^.te'lii iT^'fl '■-■°»y»"icle dis.
»ith ;) oz. distilled water p •."'''''"'"""oiJ diluted
0^. distilled water until tl^ere TlTi, , ''"""*"' '" «
yo o. with distilled water TM^l 7. ^'^'^^ «"
2 / hydrocyanic acid; it is tt,„ , '"" <=0M>iinn

'«'*'« of the British Phalacojraf '^*'"'^«-«-
2K,Pe{CiV)„ + cH.Soi =

6KHS0, + FrrFifp't.

•Experimeat 147 —4^,1 . ,x„
'^^peri.ent ,46. »d mtr T 't ^f'T *» «» -»>ue f™„
ph„„o »ei.,, and carefully 3m j,'';!'' "'" ^°»^ ^-^ dilute
™a,eac,d can be noticed. [wC" • ^l"' , l'^^""'"- odonr of
« nte an equation showi„„ til , <'«»<>l™d in the water '
»luti„„ of potassic ferr: Z, a ;*»;' -'P^uHc acid., "t^
Hydrocyanic acid i. „„t Jj f^^ """■ *•"= 'Wuted sulphuric acid

-t ROPERTIES Th

"^"'O- The dilute sltl^i « " ""'T^'^^^ ™'''«'''
"nd is feebly acid in reac on t T"" °^ '''^ -"^H
'he acid uniting with t: I" J,' ^'-''^ '-°»I'oses:
mate (NH,.CHO,) .- "'■"""S «'«momo for.

HON + 2H,0 = HCO, NH
p "' '""""^««''^« (C.N,) is formed

"e»- The cyanides of the a/1 f """'^' P'°f«'-

184 DOURLK CYANIDES.

(II^(CN)..) fii'o solu)>l«; in water. Tlio oilier siiin)l(!
cyanides are insoluble in water, but ilissolve in solutions
of the alkaline cyanides to form double cyanides.

Experiment 148. — To a solution of argentic nitrate add a
drop of solution of potassic cyanide. A. white precipitate of
argentic cyanide (AgCN) is thrown down :

AgNOg + KCN = KNO3 + AgCN.

Add more potassic cyanide, and the precipitate is dissolved,
owing to the formation of a soluble double cyanide (AgCN. KCN).

There are two classes of double cyanides : ( I ) those
easily decomposed by dilute acids, and from which hydro-
cyanic acid is set free, and (2) those from which hydrocy-
anic acid is not set free by dilute acids. To (1) belong the
double cyanides of potassium with silver, mercury, &c.
To (2) belong the ferrocyanides, &c. All the soluble simple
cyanides and the double cyanides 0/ class (1) are deadly
poisons. The double cyanides of class (2) are not poison-
ous.

Tests. — 1. To a solution of hydrocyanic acid, or of a cyanide,
add argentic nitrate. A white precipitate of argentic cyanide is
formed. This is insoluble in nitric acid, and sparingly soluble in
ammonia. (Compare AgCl. ) ( Why must a considerable quantity
of argentic nitrate be added before a permanent precipitate is
obtained with potassic cyanide ?)

2. To a solution of the acid or of a cyanide add a few drops of
ferrous sulphate solution, a drop or two of ferric chloride solution,
and caustic soda (caustic potash, potassic carbonate, lime water,
&c., will answer) : warm gently, and acidify with hydrochloric
acid. A blue colour or precipitate is formed (Prussian blue).

(1) 2KCN 4- FeSO^ = Fe(CN), + K^SO^.

(2) 4KCN + Fe(CN), == K^Fe(CN)o.

(3) 3K,Fe(CN)o + 2Fe2Clc = 12KC1 4- Fe^(FeCeNe)3.

CYANIC ACID. 185

According to equations (l) an<l (2) potassic cyanide is converted
into potassic ferrocyanidc. Tliis takes place best in presence of
an alkali. When the alkali is neutralised by an acid, insoluble
Prussian blue is formed. Both potassic ferrocyanide and Prus-
sian blue are hannless.

3. To a drop or two of solution of potassic cyanide add a little
amnionic sulphide (yellow), and evaporate to dryness in a porce-
lain dish on the water bath. Add a small (juantity of ferric
chloride solution. A blood red colour appears.

Explanation. — The sulphur in the yellow ammonic sulphide
unites with potassic cyanide to form potassic sulphocyanate
(KCNS). This, when treated with ferric chloride, forms ferric
tnlphocyanate (Feo(CNS)g). The object of evaporating is to get
rid of the excess of ammonic sulphide. (Add a drop of ammonic
sulphide to solution of ferric chloride.)

165. Cyanic Acid. — HCNO. The potassium salt of
this acid is formed along with potassic cyanide by the
action of cyanogen gas oh a solution of caustic potash :

(CN), + 2K0H = K(ON) + K(CN;0 + H.,0.

(Compare with chlorine.) It can also be prepared by
oxidising potassic cyanide by fusing it with manganese
dioxide (MnO,) : KCN + O = KCNO. '

The auid itself is of little importance, but its ammonium
salt (NH4.CNO) possesses for us a great interest. It
was from this salt that Wohler, in 1828, first prepared
urea artificially, and thus broke down the barrier between
organic and inorganic cliemistry. Previously to this, it
was supposed that the chemical compounds associated
with animal and vegetable life could not be made in the
laboratory, and thus organic chemistry was a separate
branch of the science.

18() uki:a.

Sii/})fiori/anati't<. —^Thcsc tiro salts of .an acid (HCNS) wliicb is
related to cyanic in the same way aa sulphocaiLonic is to carbonic
acid. The potassium salt (KC^ S) is prepared by fusing potassic
cyanide with sulphur. The ferric salt (Fey(CNS)n) is of a blood
red colour, seen when solutions of ferric chloride and potassic
sulphocyanate are mixed. These salts are also called thiocyanates,

16G. Urea. — CO(NH.^).^. This substance is isomeric
with amnionic cytmate ; and it* an aqueous solution of
the latter be heated it is transformed into urea.

Occurrence. — Urea is a waste product of the human
and other animal bodies. It is the vehicle by which the
waste nitrogen is carried out of the body in the urine.

Preparation.- Experiment 149. — Evaporate a small
quantity of urine on the water bath to about one-third its bulk.
Add to it about twice its volume of concentrated nitric acid.
Pearly white scales of nitrate of urea are precipitated. Evapo-
rate anotlier small portion of urea ta dryness, warm the residue
with alcohol, filter, and evaporate the filtrate carefully to a
small volume. On cooling, it deposits colourless needle-shaped
crystals of urea.

Urea can be prepared artificially from i)otassic cyanide
by oxidising it to cyanate (KCNO), from wliich amnionic
cyanate is prepared by double decoinposition with ammonic
sulphate ((NH4)2S04) :

2KCN0 + (NHJ^SO^ = K.^SO^ + 2NH4 CNO.

Strong solutions of the salts are mixed, and the sparingly
soluble potassic sul})hate is precipitated. The solution
at first contains ammonic cyanate, but this soon under-
goes a change, especially if heated, by which the atoms in
the molecule are rearranged, and urea results :

NH4.CN0 = co^^2^

AMIMKS. 1S7

PuopiiiiTiKS. — Uroji is a colourloss cryKtRlHne solid,
soluble in its own weight of cold water, and in five parts
of alcohol, Imt neaiJy insoluble in ether. It has a cooiin({
taste like that of saltpetre. It unites with acids just as
ammonia do(!S, forming crystalline salts.

Experiment 150- — Heat a little pure urea with solution of
caustic soda and note the sniull, &c. , of annnonia.

Urea is closely related to ammonia. It can be prepared
by the action of ammonia on chloride ofcarho7iyl (COCl.j),
a substance formed by the direct union of chlorine and
carbon monoxide :

COCl, + 2NH, = CO(NHA, + 2HC1.

In thi'- action CI is re[)lacod by the monad radical — NH.^,
called amidoyen. Chloride of carbonyl is related to
carbonic acid (CO(OH )._,), which may be looked upon as
the hydroxide of carbonyl. Oxygen acids generally are
the hydroxides of acid radicals ; and most acid radicals
can be got combined with amidogen, thus foiming a class
of bodies called «??ddes from their relation to a7>imonia.
Urea is carbamide. Amides readily combine with water
to form ammonium salts. Thus, when u-ea is heated
above 100° C, with water, anmionic carbonate is formed :

CO(NH,l, + 2H„0 = C0(0NHJ2.

This decom})osition can be brought about more easily
by heating with alkalis or acids. (Explain Experiment
150.) It goes on at the ordinary temperature during
the fermentation of urine.

Tests. — 1. Evaporate the liquid to small bulk, and treat with
concentrated nitric acid as in Experiment 149. The crystals of
urea nitrate (C0(NH,)2.HN08) are tpute easily recognized.

188 URIC! ACID.

2. FiVaporatc, ami add a strong solution of oxalic acid
(CatljO^). Crystals of oxalate of urea are formed (iiCUi^l^N).,.
Cj HqO^).

Estimation of Urea. — The <|uantity of urea in urine
can be readily determined by tlio Davy-Knop method,
whicli de[)ends on tlie fact that urea is decomi)Osed by
sodic liypobromite, and all its nitrogen set free :

CO(NH2)2 -f SNaOBr = CO2 + N2 + 3NaBr -|- 2H2O.

This decomj)Osition is brought about in an apparatus
provided with a graduated tube in which the nitrogen is
collected and measured. From the volume of nitrogen
obtained from a given quantity of urine, the quantity of
urea can be calculated.

167. Uric Acid. — CSH4N4O3. This substance is
found in small quantities in human urine, but forms the
principal part of the nitrogenous excrement of birds and
reptiles. It occurs also in the hum-in body as " chalk
stones " in gout, and urinary calculi. Guano is the ex-
crement of sea-fowl. It contains much hydric ammonic
urate (NH4H.C5H.2N4O3), and from it large quantities of
uric acid were formerly prepared for the manufacture of
TKiurexide, a red colouring matter, now superseded by
aniline red. — If human urine be strongly acidified with
hydrochloric acid and set aside for 24 hours small crys-
tals of uric acid collect on the sides of the vessel. The
buff-coloured sediment of urine is generally uric acid or
the acid ammonium salt. As these compounds are about
ten times as soluble in hot as in cold water, they dis-
appear when the urine is heated.

URATES.

189

--'"MOO,,.,. xu:i:r:!:it:--t

*-^RATPS TT * •

-« the acid Jtri::^":; /'•'"' '"^-'--.-.t.

f"""'! m the ,„.i„e andi'''' """' (^'^^^■} «
soluble at I5» ift ),,oo to ^onT^ "'"'o'-eHons. It fe

'00° in 123 to 125 partslT," '""''' "' ^''*''' ""^ ««
''■ssolves at 20" i„ 700 *„ Son ^''""*'"'« »«'< (KHUr)
'o «0 ,,a,.ts of wate... I ;, T* Pf "' ""'' «' 100" i„ 70

than e.the,- of the above dilu ^ '' °'°'-'' ^"'"hle
P'-Tte, and at 100° in 39 7, ! T' 20» i„ about 370
-'te a,-e fi-eely ,„,„ye -/Cl T^''' ^''"' "-™"'
I'-'Po.it ,u,c acid when aeidrfied ^^f"'""""-^ "^ "■'"^^
"nportance in the treatment If • '*"' '^ <"■ g^eat

Both the.e d.ea.ses are "L to elT "" ^"'"^' ''"'' ^""t-
''<"''. and the treatment adontedr"' ''""'■^"°" "' "'•'«
-id or acid salts into n^^'t'r ,/""'°™' "'<" "™
''« "--e is decreased bratnLi ^ ' ^''<' -''''t, of

donates. As can be easil/see^] I ""^ ''"^'"'"'' <">•-
''^st. "y '<'^". i'thium carbonate is the

Experiment ^^^ t.,, ^ ,.

Ac-d.,y the sol„ti„„ With hydroXic al"" ''"°'™ «-%•

- ^--'«e^t:re— ^^ -» -<■ aaa a few drop,
evaporated to dryness.) The rejdt f""" " ""»* «"« b"

190 ALCOHOLS.

CAKBON, HYDROGKN, AND OXYGEN.

168. Alcohols. — A.llied to the paraffins is a series
of compounds which differ in composition from the
paraffins by containinfi; an atom of oxygen in the mole-
cule.

Paraffins. A Icohols.

Methane CH4 Methyl alcohol.. . . CH4O

Ethane CgH,, | Ethyl " .... CgHoO

Propane C^Hf, [ Propyl " .... CgHgO

Butane O^H^o j Butyl " . . C4H10O

Pentane CflHia Aniyl " .. . . C5H12O

<.V5C.

&C.

These alcohols can be prepared from the monochlor-
paraffins (CH3CI, tfec.) by the action of water :

CH3.CI + H.,0 = CH3.OH + HCl.

Further, when they are acted on by phosphorus penta-
chloride (PCI-), they lose an atom of oxygen and one of
hydrogen, and gain one atom of chlorine :

CH,0 + PCI, = CH3.CI + POCI3 + HCl.

From these facts it is concluded that the molecules of
the alcohols contain the radical Jiydroxyl ( — OH ). They
are thus hydroxides of the radicals, CH3, C2H5, &c.

Methyl alcohol CH3.OH

Ethyl " C2H5.OH

Propyl *' C3H7.OH

&C. &G.

169. Methyl Alcohol. CH3. OH.— Occurs in na-
ture combined with acids, as in oil of umitergrecii or

METHYL ALCOHOL. 191

meJliyl mlicijlate. When wood is destnictively distilled
in the preprAiation of wood -charcoal, three other ]>roducts
are obtained : (1) A mixture of combustible gases (CH^,
«fec.), (2) a watery liquid, and (3) a tarry liquid. From
wood tar, creosote and other substances are obtained.
The watery liquid (jxijroligneous acid) is strongly acid,
an('i from it is obtained v)ood vinegar, or impure acetic
acid, and wood spirit, or methyl alcohol. The acid liquor
is neutralized with lime, and the methyl alcohol is then
distilled off and purified by fractional distillation, &c. It
is also prepared in considerable quantities by distilling
the waste (" vinasse ") from the beet sugar indu.stry.

Propertiks. — Pure methyl alcohol is a colourless
liquid, similar to common alcohol in smell, and boiling at
55°. 1. Specific weight = 0.8142. It mixes with water
in all proportions, with contraction of volume and evolu-
tion of heat. It burns in air with a pale blue flame. It
is a good solvent for fats, oils, resins, &c.

Experiment 152. — Mix a little methylic alcohol with an
ec^ual volume of water, and note the evolution of heat.

Experiment 153- — Set fire to a little methyl alcohol in a
porcelain diah.

CH^O + 80 = CO2 + 2HoO.

Commercial methyl alcohol is always impure, and has
an unpleasant odoui*. It is used as a solvent, in the
manufacture of aniline dyes, and in the preparation of
methylated spirit, a mixture of common alcohol with a
small percentage of crude methyl alcohol. This is unfit
for use as a beverage, and is imported and manufactured
free of duty in Gieat Biitain. It is, however, often

192 ETHYL ALCOHOL.

purified and used to adulterate liquors. It is probable
that many of the cheaper sorts of strong liquors sold in
this country are preparations of methylated spirit.

Methylic alcohol acts towards acids like a weak base,
forming salts, wliich jtre unstable in presence of water.
Thus, with hydrochloric acid it forms methyl chloride :

CH3.OH + HCl = CH3.CI + B.,0.
Compare K.OH + HCl = K.Cl + H,0.

The reaction is not f 'nplete unless the water be re-
moved as fast as it is ic . ned. The radical methyl CH..)
thus plays the part of a monad metal. The salts of
alcohol radicals are called ethereal salts. Many of them
are volatile and have a pleasant ethereal smell. — When
methyl alcohol is oxidised by a mixture of sulphuric acid
and potassic bichromate (K.jCroOj) formic acid is pro-
duced :

CH4O + O, = CHA '+ H,0.

170. Ethyl Alcohol. — CoHgO. This is common
alcohol, the intoxicating principle of all spirituous bever-
ages. It is also known as spirits of wine. It is pre-
pared by the fermentation of sugar.

Fermentation. — This is a chemical action brought
about by minute plants and animals, called ferments.,
which grow and multiply in the fermenting liquid. Cer-
tain conditions are necessary to the life of tiie ferments,
and fermentation ceases when these conditions are
absent. (1) The fermenting liquid must contain the
elements of food for the fei'ment ; a solution of imre
sugar will not fcM'uiont. (2) The tomj)orature must not

FERMENTATION. 193

be much above 40® C. nor much below 20° C. (3)
There must be a proper proportion of water present.
(4) The products of fermentation must not accumulate
too much ; and (5) certain substances called antiseptics,
which are fatal to the life of the ferment, must be
absent. — There are several kinds of fermentation :

1. Alcoholic. — Caused by yeast (saccharomyces), the*
products being alcohol and carbon dioxide :

CgHiaOe = 2C2H6O + 2CO2.

2. Acetous. — Due to the vinegar plant (mycoderma
aceti), which transforms alcohol by oxidation into acetic
acid.

3. Lactic. — The lactic acid ferment has the power of
transforming sugar into lactic acid. The ferment is pre-
sent in sour milk.

4. Butyric. — Sugar is fermented into butyric add by
a ferment present in rotten cheese.

The germs, or sporules, of these ferments are present
everywhere in the air, and wherever they find a suitable
liquid they at once cause fermentation to begin.

Experiment 154. — Make a solution of commercial grape
sugar in 40 or 50 times its weight of water. Put some yeast in
the solution and fill three convenient dishes with it, also three
test tubes. Invert the latter in the dishes. Keep No. 1 in a
warm room. To No. 2 add a little carbolic acid and set it in
the same room with No. 1, but not too near it. Set No. 3 in a
cold place and surround it with snow or ice. Fermentation
soon begins in No. 1, and bubbles of gas rise into the test tube.
After a considerable quantity has collected, test it for carbon
dioxide. Fermentation does not begin in Nob. 2 and 3. — Distil
14

194 ALCOHOLIC LIQUORS.

a few drops of alcohol from ale, receiving it in a cool test tube.
Try taste and inflammability.

Alcohol is separated from fermented liquors by dis-
tillation. Common alcohol contains water, and often

fusd oil, which consists principally of amy I alcohol.
This is removed by fractional distillation and by filter-

,ing through charcoal. As it is poisonous it is important
to Lave it absent from spirits of wine used in medicinal
preparations. — Absolute alcohol is alcohol containing not
more than 5 % of water. It is prepared by distilling
the commercial article from quicklime, which holds the
water. The last traces of water are very difficult to re-
move. — Much alcohol is now prepared from glucose, a
sugar made from starch. When the glucose is made
from potato-starch, the alcohol contains a large percen-
tage of fusel oil and is highly poisonous.

Properties. — A colou. ^«s liquid of pleasant smell,
boils at 78°. 3, freezes at — 130°. 5. When evaporated on
the hand it leaves no unpleasant smell (if fusel oil is ab-
sent). It burns with a pale blue flame, forming carbon di-
, oxide and water. (Write the equation.) It is a good solvent
for organic substances, especially those insoluble in water ;
and is used extensively in the preparation of tinctures, <fec.

Experiment 155. — Dissolve a litttle powdered resin in warm
alcohol, and add water.

Beers contain from 2 % to 10 % of alcohol ; wines,
from 8 % to 30 % ; distilled liquors (whiskey, brandy,
(fee), up to 76 %. The different flavours are due to
small quantities of substances present in the saccharine
juice, formed during fermentation, dissolved out of the

ETHVL SALTS. 195

wood of the cask, or added by the manufacturer. Proof
spirit contains 49 % by weight of alcohol.

In its chemical characters ethylic alcohol is like
methylic. It is the hydroxide of ethyl (C.Hg), and forms
salts, e.g., ethylic nitrate (C2H5.NO3), chloride (C.,H-.C1),
sulphate ((00115)2804), (fee. (Write equations showing
the action of nitric, hydrochloric, sulphuric, and phos-
phoric acids on ethylic alcohol). Sweet spirit of nitre is
a solution in alcohol of ethijl nitrite (C2H5.NO2).

Experiment 156- — Mix some alcohol in a t. t. with one-tenth
its volume of concentrated sulphuric acid, a little more of nitric
icid, and some scraps of copper. Warm gentb/^ and note the
smell. It is that of ethyl nitrite (" nitrous ether"). Attach a
bent tube and distil a drop or two into a cool t. t.

Acetic ether in ethyl acetate (C2H5.C2H3O2).

Experiment 157— Pouv a little rectified spirit (alcohol) on
some dried sodic acetate in a t. t. Add a small quantity of
concentrated sulphuric acid and distil into another t. t. kept
cool. Note the smell, &c. of the acetic ether obtained.

Teste for Alcohol.— 1. Heat a little alcohol (diluted with
water) with a few drops of "bichromate mixture" (4H3SO4 -\-
KaCrijOy). It is turned green, and the pungent odour of acetic
aldehyde (C2H4O) can be observed:

SC^H^O + 4H2SO, + KaCr^Or =

Chromic sulphate.

3C2H4O + K2SO4 + Cr2(SO,)3 + 7H2O.

2. Mix a little alcohol with solution of sodic carbonate, add
iodine, and warm somewhat. Yellow crystals of iodoform
(CHI 3) appear. This is a very delicate test.

196 AMYLIC ALCOHOL.

171. Higher Alcohols.— Pro^^yZic (0,H;.OH), 6m-

tylic (C4H9.OH), and amylic (C^Hn.OH) alcohols are
formed in small quantities during the fermentation of
sugars. They boil at higher temperatures than does
ethylic alcohol, and are partially separated from if: in
the process of distillation.

Amylic Alcohol (CgHn.OH) forms the greater part
of "fusel oil." It is formed in large proportion by the
fermentation of glucose prepared from starch {amylum).
Hence its name. The quantity is especially large when
the glucose has been manufactured from potato-starch ;
and amylic alcohol is sometimes called " potato-oil."

It is a colourless oily liquid of penetrating oppressive
odour. It boils at 132° G. Specific weight = 0.818.
When oxidised by bichromate mixture it forms first an
aldehyde (CgHioO), and then valerianic acid (Ct,HioO.,).
It io used to prepare sodic valerianate (NaCgHoOa). It
is highly poisonous, and its presence in cheap spirits is
the cause of the furious intoxication often resulting from
their use.

Amyl nitrite (CgHn.NOa) is prepared by passing nitrogen
tricxide (from nitric acid and starch) into amyl alcohol. It is a
light yellow liquid, boiling at 99°. Specific weight = 0.902.
It is insoluble in water, but soluble in alcohol. It has a peculiar
action when inhaled, increasing the rate of the pulse and caus-
ing flushing of the face. If inhaled too long it causes suffocation
by preventing the oxygen of the air from combining with haemo-
globin .

Experiment 158. — Dissolve a little amyl alcohol (or fusel oil)
in an equal volume of concentrated sidpliuric acid and cool.
Add to this some solution of potassic or sodic nitrite in half its
weight of water. Heat, and observe odour of amyl nitrite.

ISOMERIC ALCOHOLS. 197

Several artificial essences are prepared from amyl alcohol, e.g.,
essence of jargonelle pear ia amyl acetate (C^\iii.O.,li^O.^).

Test. — To detect aniyl alcohol in spirits add a few drops of
dilute acetic acid and votasdc permanganate (KMn04) solution.
The per-manganate is (quickly decolourised if amyl alcohol be
present. Or, shake with small crystals of potausic iodide. They
are coloured yellow by amyl alcohol.

172. Isomeric Alcohols. — There is only one
alcohol having the formula CH4O, and one, C.^jHgO ; but
there are two propylic alcohols. One of them, when
oxidised, gives first an aldehyde and then an acid — pro-
]>ionic acid — having the same number of carbon atoms in
the molecule ; the other gives a ketone and then breaks
up into two acids having fewer carbon atoms in the
molecule. For this and other reasons, it is believed that
the hydroxy 1 is differently situated in the molecules of
the two acids.

H H H

Primary propylic alcohol H — C — C — C — oh

! I I

H H H
H H H

Secondary propylic alcohol . . h — C — C — C — H

I I I

H OH H

A third kind of alcohols is known which, when oxidised,
break up at once into acids having fewer carbon atoms
in the molecule. These are tertiary alcohols ; e.g. :

CHa

I
Tertiary hutylic alcohol CH3 — C — ch,

I
o

198 AMINES — ETIIKR.

1. Primary alcohols are iliose fn which tho hydroxy!
is attached to a carbon utorn which is joined to only one,
other cj rbon atom.

2. Secowl ar 1/ '^Aco\io\H *»ave tlie hydroxy! attached to a
carbon atom which is joined to ino other carbon atoms.

3. Tertidrji alcohols lu^ve the hydroxyl attached to a
carbon atom wliich is joined to three other carbon atoms.

173. Amines, or Substituted Ammonias —

These are compounds related to the alcohols in the same
way as urea is to carbonic acid (Art, 10(5); and they
can be prepared by similar methods, viz., by the action
of dry ammonia on the chlorides, bromides, or iodides of
the alcohol radicals. Thus,

Methyl chloride. Methylainine.

CH3CI + NH3 = CH3.NH2 + HCl.

They can also be regarded as derivatives of ammonia,
formed by replacing a hydrogen atom by an alcohol radi-
cal. But a second, and a third hydrogen atom may be
replaced, so that there are three classes oj amines, pri-
mary, secondary, and tertiary, e.g., Tnono-methyl-amine
(CH3.NH.2), di-methyl-amine ((CH3).2NH), and tri-
methyl-amine ((0113)3^). Many of these compounds are
found in nature. They resemble ammonia in their pro-
perties, uniting with acids to form salts, e.g , C2H5.NH3CI,
ethyl-ammonium chloride, and dissolving freely in water to
a strongly alkaline solution. They generally smell like
ammonia.

174. Ether. — (C2H5).20. Also known as sulphuric
ether. Ethers are oxides of alcohol radicals, and bear
the same relation to alcohols as the oxides of the metals
da to their hydroxides.

ETHER. 199

Preparation.— Ej )eriment 155).— Mix 4 parts of alcohol
with 9 of sulphuric aci and heat the mixture until it begins
to boil (at 140° (J.). Ether distils over. Note its odour.

On the large scale, as soon as the mixture begins to
boil, a small stream of alcohol is allowed to ilow into tl)e
still, and the temperature is kept at 140° C. Ether and
water then distil over together continuously.

Explanation. — Alcohol forms with sulphuric acid^
ethyl sulphuric acid, or ethylic hydric sulphate

aMg.OH -f H.,S04 = C.,H,,H.SO, + HA

Tlie water distils as fast as it is formed. Alcohol decom-
poses ethyl sulphuric acid, forming ethyl ether and sul-
phuric acid :

C,H5.0H + C.H^HSO^ = (C2H5),0 + H.SO^.

The process is continuous, the alcohol being run in as
fast as the ether and water distil. As far as the ulti-
mate result goes, the action can be represented thus :

2C2H5OH = (C,H5)20 + H2O,

as a simple dehydration of alcohol. — It is purified by dis-
tilling from calcic chloride and lime to remove water and
acids.

Properties. — A colourless liquid, bright and mobile.
It boils at 3 4°. 9, and the vapour forms aa explosive mix-
ture with air. Ether should never be boiled over a
naked flame, but always in a hot water bath. Specific
weight, 0.736.

Experiment 160. — Set fire to a little ether in a porcelain dish
tilled half -full of water.

200 ALDEHTDES.

Put lome ether in » t. t. »nd immerse iu water as hot at the
hand can bear it. The ether boils.

Ether is sparingly soluble in water, but mixes in all
proportions with alcohol. It is a good solvent for fats
and oils, resins, alkaloids, <kc. Water is very slightly
soluble in ether, and commercial ether generally leaves a
wet stain when evaporated. — Ether is a good anaesthetic,
but not so rapid in its action as chloroform. Its latent
heat is high, and, as it evaporates so readily, an eiiier
spray can be used to deaden by cold the sensibility of
any part. Water can be frozen by the rapid evaporation
of ether. (Try a drop or two of ether on the hand.)

Commercial ether generally contains considerable
alcohol, which can be removed by washing with water.
The presence of alcohol can be detected by finding the
specific weight.

175. Aldehydes. — When primary alcohols are oxid-
ised slowly, the first substances formed contain two
atoms of hydrogen less than the alcohols. They are
ilfcohols dehydrogenated, or aldehydes.

Alcohols. Aldehydes.

Methyl CH^O

Ethyl CaHeO

Propyl CgHgO

«ftc.

Formic CH2O

Acetic C2H4O

Propionic CgHgO

&c.

The atom of oxygen can be replaced by two atoms of
chlorine ; and from acetic aldehyde chloride of ethylidene
(CaH^Cla) is thus formed. It is concluded that the atom
of oxygen is not united with any of the hydrogen atoms.

KETONES — CHLORAL. 201

and the formulas of the aldehydes are written graphically
thus :

I
H — C=0, H — C — C=0, (fee.

I I I

H H H

The group — C=o is characteristic of the aldehydes. —

(In what test already made was acetic aldehyde formed 1}

Ketones are compounds analogous to the aldehydes, and
are formed by the oxidation of secondary alcohols. Thus,
secondary propyl alcohol (CHg.CHOH.CHg), yields on
oxidation, di-methyl ketone, or acetone (CH3.CO.CH3).
By further oxidation the ketones are broken up into
acids having fewer carbon atoms in the molecule. In
this they differ from the aldehydes.

176. OLloral. — CCI3 — C=0. As can be seen by

the formula, choral is derived from acetic aldehyde by
the replacement of three atoms of hydrogen by chlorine ;
it is trichloraldehyde.

Preparation. — By the action of chlorine upon alco-
hol. Aldehyde is first formed :

CH3.CH2OH + CI2 = CH3.COH + 2HC1.

Then, chlorine replaces hydrogen :

CH3.COH + 3CI2 = CCI3.COH + 3HC1.

Properties. — A colourless, somewhat oily liquid of
pungent irritating odour. It boils at 94°. Specific weight

202 (;il LORAL HVnilATE — FATTY ACIDS.

= 1.502. When mixed wifch jj itH volumo of water it
unites with it, forming chloral hydrate (CC1;,.CH(0H)..),
a white crystalline solid.

Experiment lf\. - Mix a drop or two of chloral on a wat<)h
glass with a drop of water. (Jrystallisation takes place. Dis-
solve these crystals in water, and note taste, &c.

Chloral hydrate is soluble in alcohol, water, and
ether. By the action of strong bases it (as w^U as chloral)
is converted into chloroform and formic acid ;

Chloral. Pctasslc; formate.

CCI3.CHO 4- KOH = CHCI3 4- HCO2K.

This explains tlie formation of chloroform by the action
of bleaching powder on alcohol. Bleaching powder
yields chlorine, and it always contains calcic hydroxide.
— The substance generally sold as chloral is really the
hydrate or its aqueous solution. It should give no pre-
cipitate with argentic nitrate, and should have an agree-
able, somewhat aromatic, smell. Its taste is bitter and
astringent.

When chloral hydrate is injected under the skin it is
decomposed by the alkali of the blood into chloroform
and a formate, as shown in the above equation. Its
effects are thus the same as those of chloroform. It is
much used in cases of sleeplessness.

177. Fatty Acids. — By further oxidising the alde-
hydes a series of acids is obtained. They are called
fatty acids, because the higher members are found com-
bined in fats. They differ from the aldehydes by having
one atom of oxygen more in the molecule.

FORM 10 ACID.

203

Ah'ohoh Aldehifdes.

Mothyl. . . . CH4O Formic .... OHaO

Acetic CaH40

Propionic... C^HrtO

C.HeO

Ethyl....

Pn.pyl C.,H80

&0.

Ac ids.

Formic CHaOa

Acetic CaH^Oj

Propionic. CgHgOa
&c.

Tlicse iicid^ are tlioiight to contain hydroxyl, for, when
they are treated with phospliorns trichh)ride (PCI3), they
yield s'lbst.ii^ces in which CI takes the place of OH, e.g.:

.•iCall^Oj •- 2PCI3 = 3C3H3O.CI + P^Og 4- 3HC1.

The expanded formulas of the acids are H — C=o,

(JH.,.C=:0, &c., and the group — C=o is characteristic.

H H

It is called carhoxyl^ and the number of carhoxyls in the
molecule of an organic acid marks the basicity of the acid.

178. Formic Acid.— HCO.OH. First prepared by
distilling the bodies of red ants ; hence the name
[formica, an ant). It can be prepared by careful oxida-
tion of methyl alcohol ; but more conveniently by dis-
tilling oxalic acid (C0H2O4) with glycerine (CaHgOg).
The glycerine undergoes no change, aiid the oxalic acid
is split into carbon dioxide and formic acid :

C^HoO^ = CO, + CH2O.,.

Properties. — A colourless liquid, strongly acid, boil-
ing at 99°. 9. Specific weight = 1.22. When heated with
concentrated sulphuric acid it breaks up into carbon
monoxide and water. (Write the equation). It is a
strong reducing agent, and when heated with argentic
nitrate is oxidised to carbon dioxide, silver being set

204 ACETIC ACID.

free. — It is a monobasic acid, an J forms salts, the for-
mates, all soluble in water, and all having the reduc-
ing properties of the acid.

Tasts. — 1. Neutral formates give a red colour with solution
of ferric chloride.

2. Forniates or formic acid, when boiled with solution of argen-
tic nitrate, precipitate silver.

179. Acetic Acid. — CH3.C=o. Acetic acid is

I
o

formed when acetic aldehyde (C.^H^O) is oxidised ; but
its usual method of preparation is by the direct oxidisa-
tion of ethyl alcohol in the vinegar process.

Preparation. — 1. By acetous fermentation of wines,
beers, &c. In many cases sugar is the raw material,
and it undergoes first alcoholic and then acetous fermen-
tation :

C^HeO + O2 = C^H.O, + H,0.

This gives a dilute solution.

2. By the destructive distillation of wood, a mixture
of aoetic acid, methyl alcohol, &c., is obtained. The
watery acid liquid is neutralised with slaked lime
(Ca(0H)2), with which the acetic acid forms calcic
acetate (Ca(Q,H302)2) :

2(H.C2H302) + Ca(0H)2 = (JAiC^B.O^)^ + 2H2O.

The volatile liquids are distilled ofi*, and the calcic acetate
is purified by recrystallisation and then decomposed by
sulphuric acid :

Ca(C2H802)a + HaSO^ = CaSO^ -f 2C2H4O2.

ACETATES. 205

Sodic carbonate (NR.2CO3) is often used instead of lime.
(Write the equation for this.) (How can the acid be
separated from the sodium salt 1)

Properties. — A colourless liquid, of pungent, vine-
gary odour, and sharp acid taste. When free from water
it boils at 119°. When pure, it acts upon the skin
powerfully, causing blistering. It is solid below IG°.7,
but may be cooled below 0° in closed vepsels without
causing it to solidify, being then in a state analogous to
mpersaturation. Glacial acetic acid is the solid acid. Of
course, in warm weather it is not solid. The specific
weight of the liquid is 1.08. Acetic acid dissolves in
water in all proportions. Vinegar is an impure dilute
solution (5 % to 10 %). Sulphuric acid is a frequent
adulterant of vinegar, and can be detected by its giving a
white precipitate with baric chloride. It sometimes con-
tains sulphurous acid. (How test for this ?). — The acidum
aceticum of the B. P. contains only 33 % of the pure
acid. A dilute solution (44 %) is also used.

Acetates. — Acetic acid, like all the acids of this
series, is monobasic. Only one of the 4 atoms of hydro-
gen is replaceable by metal. The normal acetates are all
soluble in water. (Of what other salts is this state-
ment true]) Sodic acetcde (Na.C.HgOj), zinc acetate
(Zn( 03^302)2), and plumbic acetate (Pb.(C2H302)2) are
the most important.

Experiment 162. — To a solution of sodic carbonate in water
coloured with a drop of litmus, add acetic acid (dilute) until the
reaction is acid. Evaporate and obtain crystals of sodic acetate.
This salt readily forms a supersaturated solution.

Experiment 163. - I^issolve a littlo litharge (PbO) in acetic
aciil, and evaporate to crystallisation. Examine the crystals as

206 . BUTYRIC ACID.

to taste, &c. Redissolve in water, and boil with some more
litharge. It dissolves forming a basic acetate (FhZ^\ q ).

Commercial acetate of lead (sugar of lead) often contains
this basic salt. — Verdigris is basic cupric acetate. It
forma as a green rust on copper or brass kitchen utensils
when these are allowed to stand in contact with vinegary
articles of food, (fee. As it is very poisonous, cases of
poisoning sometimes occur in this way. — Acetic acid dis-
solves many of the heavy metals, e.g., iron, zinc, lead,
copper, (fee, either unaided or aided by the oxidising
action of the air. When it is formed in badly sealed
cans of fruit, &^ , it often dissolves the solder and thus
renders the fruit highly poisonous.

Tests. — 1. Warm some sodic acetate with sulphuric acid and
observe the vinegary smell.

2. Heat a solution of an acetate with strong sulphuric acid
and a little alcohol, and note the smell of acetic ether (ethyl
acetate).

3. Add a few drops of neutral ferric chloride solution to
neutral solution of an acetate. The blood-icd colour of ferric
acetate appears :

eNaCjHaO., + Fe,01e = Ye^[G^B.^O^)a + 6NaCl.

Add a few drops hydrochloric acid to a part of the solution ;
the colour disappears. Boil the remainder for some time ; basic
ferric acetate is precipitated :"

FeatC^HgOa), + H,0 = Fe.,(0H),(C,H30,)^ + 2C.,H^03.

180. Butyric Acid. — €3117.0=0. This acid is

combined with glycerine in butter, — wlience its name.
When butter turns rancid, the characteristic odour is
that of free butyric acid. It is prepared by the fernien-

VALERIANIC ACID. 207

tation of sugar by the butyric acid Jerinent of putrid
cheese. It is an oily liquid with chemical characters
similar to those of acetic acid. Butyrate of sodium
(Na.C4H702) is often present as an impurity in valerian-
ate of sodium, being formed by the oxidation of the
butylic alcohol of fusel oil. — Ethylhutyrate (CoHg.C^H^Oj)
is the artificial essence of pineapple.

181. Valerianic Acid.— C^Hg.C^o. It is the

acid of valerian root. It is now prepared from amy lie
alcohol (1 oil) by oxidising "'ith bichromate mixture :

3C5H11OH + 2K2Cr207 + 8H2SO4 =
3C5H10O2 + 2K2SO4 + 2Cr2(SOj3 + IIH2O.

SoDic Valerianate (Na.CgHgOj) is prepared by neu-
tralising the acid with sodic hydroxide. From this,
valerianate of zinc is prepared by double decomposition
with solution of zinc sulphate (ZnSOi). The valerianate
is sparingly soluble and separates out in pearly white
scales :

ZnSO^ + 2NaC6H902 = Zn(C5H802)2 + Na2S0^.

182. Higher Fatty Acids. — Fats and oils are
ethereal salts of glycerine (an alcohol) and the higher
members of the faitv acid series. The acids of common
fats and oils are :

Palmitic acid CigHgj.CO.OH

Stearic acid C17H35.CO.OH

In this connection may be mentioned oleic acid (CiyHjj.
CO. OH) derived from the olefine series. — These acids

208 GLYCOL — OXALIC ACID.

are oily liquids or soft buttery solids Their metallic
salts are called soaps. Hard soaps are the sodium, and
soft soaps the potassium salts. These are soluble in pure
water. Other salts ire mostly insoluble, e.g., the cal-
cium, magnesium, and lead salts. (See Glycerine.)

183. Glycol. — 02X14(011)2. Prepared by the action
of water on ethylene bromide (C2H4Br2).

C2H4CI2 + 2H2O = C2H4(0H), + 2HBr.

(Are the hydroxy Is attached to the same or to different
carbon atoms '?) — Glycol is a colourless liquid, of burning,
sweet taste. It has the properties of an alcohol, forms
ethereal salts, and when oxidised gives first an aldehyde,
and then an acid [oxalic acid.) It unites with acids in
two proportions, forming two series of ethereal salts : ( 1 )
Those in which one hydroxyl is replaced by salt radicals,
e.g., O2H4.OH.CI, C2H4.OH.NO3, &c.; and (2) those in
which both hydroxyls are replaced, e.g., C2H4CI2,
C2H4(N03)2, &c. It is thus analogous to diacid bases,
such as calcic hydroxide (Ca(0H)2) ; and is therefore
called a diacid alcohol.

184. Oxalic Acid.— C2H2O4.2H2O.

Occurrence. — In juices of wood sorrel, rhubarb, sour
dock, &c., as hydric potassic oxalate (HKC2O4) ; in
some plants and in urinary calculi, as calcic oxalate
(CaCjOt); and in guano as ariimonic oxalate ((NH4)2C204).

(What is the basicity of oxalic acid ?)
Preparation. — Oxalic acid is formed when sugar,
starch, <fec., are oxidised with concentrated nitric acid ;
but is now made from pine sawdust by roasting at about

OXALIC ACID. 209

200'* with a mixture of potassic and sodic hydroxides.
The fused mass yields a solution of sodic oxalate
(Na2C204), which is decomposed by boiling with milk
of lime (calcic hydroxide stirred up with water). In-
soluble calcic oxalate is precipitated and sodic hydroxide
remains in solution :

NaaCaO^ + Ca(0H)2 = CaCaO^ + 2NaOH.

The calcic oxalate is then drained, washed and decom-
posed by dilute sulphuric acid :

CaCaO^ + H2SO4 = CaSO^ -f HaCaO^.

Calcic sulphate is only sparingly soluble, so that most
of it remains undissolved. The solution of oxalic acid is
drawn off, and evaporated to crystallisation. It is puri-
fied by re-crystallisation, and, if this is not done, it is
contaminated by a small quantity of calcic sulphate. —
The method of preparing organic acids by precipitating
the calcium salt and then decomposing with sulphuric
acid is very common. The o eject of the precipitation is
twofold : (1) To separate the acid from the other sub-
stances dissolved along with it, and (2) to get it com-
bined with a metal whose sulphate is insoluble. (Why
is this advantageous ?)

Properties. — Oxalic acid is a white crystalline solid,
of sharp acid taste. The crystals are long and pointed
(prismatic), and somewhat resemble those of Epsom salts.
The acid is soluble in 10 parts of water. It is a strong
acid, and decomposes carbonates with effervescence. The
pure acid is entirely decomposed and dissipated by heat.
If any residue remains, it is impurity.

HaCaO^ = HaO + CO + COj.
IS

210 OXALATES.

Experiment 164. — Examine carefully some crystals of oxalic
acid, noting shape, taste, &c., and comparing with Epsom salts.
Heat a small quantity on mica. Dissolve a little in water, taste
the solution, and try its action on sodic carbonate and on lime
water.

Oxalic acid in large doses (60 grains and upwards) is,
like all strong acids, a corrosive poison. In smaller
doses it is a cumulative poison. The oxalates of the
alkalis are also poisonous. The antidotes are chalk and
water, magnesia, and lime water; tUeii' object being to
form insoluble oxalates.

Oxalates. — Oxalic acid is dibasic. Its molecule is

CO. OH
made up of two carboxyls, i . — There are two classes

^ ' ■" ' CO.OH

of oxalates, nm'mal (K0C2O4, CaCgOi, <fec.), and acid

(KHC2O4, (fee). Besides these there are salts composed
of ordinary acid oxalates, combined with a further quan-
tity of acid, e.g., salt of sorrel (KHC2O4.H2C2O4.2H2O).
Of the normal oxalates only those of alkalis are soluble
in water :

Experiment 165- — Prepare some ammonlc oxalate by neutral-
ising solution of oxalic acid with ammonia, filtering if necessary,
and evaporating to crystallisation. Make a solution of this salt
for the following experiments. (Write the equation.)

Experiment 166. — Add solution of calcic chloride (CaCla) to
solution of ammonic oxalate. Calcic oxalate (CaCaO^) is pre-
cipitated. Test its solubility in acetic and in hydrochloric acids.
Repeat with baric chloride (BaClg).

Experiment 167- — Add solution of ammonic oxalate to solu-
tion of ferrous sulphate (FeSO^). Ferrous oxalate is precipi-
tated. Note its colour, &c., and write its formula.

Tests. — 1. (Experiment 166.)

GLYCERINE. 211

2. Dry oxalic acid or an oxalate heated with concentrated sul-
phuric acid gives oflf a mixture of carbon monoxide and dioxide ;
the monoxide can be lighted, and burns with the characteristic
bluish flame.

3. Argentic nitrate gives a white precipitate of argentic oxa-
late (Ag2C204). This is soluble in nitric acid. (Can this pre-
cipitate be obtained with free oxalic acid ?)

4. " With a solution of sulphate of lime, oxalic acid gives a
white precipitate which is soluble in nitiic acid, but insoluble in
the vegetable acids." (B. P.)

5. Heat a little calcic oxalate in a small t. t. , applying a light
to the mouth. The flame of carbon monoxide is seen. Add a
little hydrochloric acid to the cold, white residue. It efl^ervesces.

CaC^O, = CaCOg + CO.

CaCOa -f 2HC1 = CaCla + CO., + H,0.

In this way insoluble oxalates can be tested for.

185. Higher Dibasic Acids. — Oxalic acid is the

first member of a series :

Oxalic acid (C00H)2

Malonic acid CH2(COOH)2

Succinic acid G2B.^{COf^B.)2

&c. &c.

Succinic acid is formed in small quantities during
the alcoholic fermentation of sugar. It is found in the
urine of the horse, and in the fluids of hydroccele and
hydatid cysts. It is prepared by distilling amber.

186. Glycerine. — 03115(011)3. Glycerine forms the
alcoholic (basic) part of the ethereal salts called fats and
oils, and is prepared from them in the process of soap-
making.

Soaps are made by boiling fats and oils with aqueous
solutions of sodic hydroxide for hard soaps, and potassic

212 SOAPS.

hydroxide for soft soaps. The principal fats used are mix-
tures in various proportions of stearin (C;,Hr,(Ci,oH350,_,)3),
palmitin (Q.^^{Q^^^^O.^r^, and olein (CgllgfCigHg^Oo);,).
Stearin is the chief constituent of tallow. It is solid.
Palmitin (a solid) is the chief constituent of palm oil,
and olein (a liquid) of olive oil. Human fat consists
mostly of palmitin. In the process of saponification y the
glycerine is separated as indicated in the following equa-
tion, in which, for the sake of simplicity, F is put as a
symbol for the salt radicals of the fatty acidi> :

Fat. Soap. Glycerine.

CgHsFa + 3NaOH = 3NaF + CaHgCOHJa.

The soap is separated as a curd by the addition of com-
mon salt to the solution, and the glycerine is recovered
from the mother liquor. In many factories the fata and
oils are decomposed by heating under pressure with
water and 2 to 3 per cent, of sulphuric acid. Aqueous
solution of glycerine and fatty acids are obtained in
separate layers. The glycerine is drawn off and purified
by distilling with steam at 180° C. The acids are neu-
tralised with caustic soda to form soap :

CgH^F" + 3H2O = C3H5(OH)3 + 3HF.
HF -f NaOH = NaF + HgO.

Sodium and potassium soaps are soluble in water and in
alcohol. Most soaps are insoluble in salt water, but
soap made from cocoanut oil and resin (" marine soap ")
is soluble in salt water. Lime and magnesium salts de-
compose ordinary soaps forming insoluble lime and mag-
nesium soaps. Thus, in washing with hard water, there
is always a waste of soap. — Lead plaster is a lead soap,
made by heating litharge with olive oil (or lard) and a

GLTCERFNE. 213

little water. It consists of plumbic oleate and palmitate
principally, with some glycerine.

Properties of Glycerine. — A thick, sticky, colour-
less liquid, of sweet and burning taste. Specific weight
= 1.28. It dissolves in water in all proportions, and is
hygroscopic. It mixes with alcohol in all proportions.
It is a very good solvent for metallic oxides, salts, ifcc;
and is used in medicine in preparing glyceritum acidi
carbolici, &,c., which are solutions in 4 fluid ounces of
glycerine, of 1 ounce of carbolic, gallic, and tannic acids.
Glycerine has antiseptic properties, and borate of glyce-
rine has been successfully employed in surgery. — Gly-
cerine cannot be distilled alone, but decomposes at 280°,
giving oflf pungent choking fumes of acrolein (C3H4O).
If water be present part of the glycerine distils along
with the water. — Glycerine is a triacid alcohol, and is
analogous to triacid metallic bases, such as bismuth hy-
droxide (Bi(0H)3). It forms three series of ethereal
salts, in which one, two, and three hydroxyls respectively
are replaced by acid radicals ; e.g., C3H5(OH)2.N03,
03H5(OH).(]SrO3)2, and C3H6(N03)3, the three nitrates of
glyv^erine. The latter, trinitrate of glycerine^ is com-
monly called nitro-glycerine, and is prepared by the ac-
tion of a mixture of concentrated nitric and sulphuric
acids on cooled glycerine. When the resulting liquid is
poured into water, nitro-glycerine separates out as a
heavy oil :

C3H5(0H), -f 3HNO3 = C3H5(N03)3 + 3H2O.

Dynamite is made by absorbing glycerine in a porous
siliceous sand. It is less dangerously explosive than
nitro-glycerine, — On account of its attraction fc-r mois-
ture, glycerine is valuable in surgery as an emollient.

214 LACTIC ACID.

It is also used for preserving fruits, for making copying
ink, and as a lubricator.

Impurities, — Glycerine is often adulterated with cane
sugar and glucose. To detect cane sugar, dissolve iii
water, add a few drops of sulphuric acid, and evaporate
on the water bath. If cane sugar is present it is black-
ened. To detect glucose, heat with solution of caustic
soda. If glucose is present the solution turns brown.
(Try with samples of glycerine.) Glycerine should be
neutral to litmus. Owing to imperfect purification it
sometimes contains acids.

Test. — 1. If a liquid containing glycerine be made slightly
alkaline with caustic soda, a borax bead dipped in it will give
a green colour to the Bunsen flame.

2. Heat a little glycerine with concentrated sulphuric acid,
and note the smell of acrolein.

178. Hydroxy- Acids. — There are organic acids,
the molecules of which have alcoholic hydroxyl. They
partake of the nature of both alcohols and acids, but the
acid properties predominate. They are called hydroxy-
acids. Thus, hydroxy-acetic acid has the formula
CHjOH.COOH. There may be two hydroxy Is in the
molecule, as in the case of tartaric acid, which is dihy-
droxy-succinic acid.

188. Lactic Acid, C2H4OH-COOH.— This is hy-
droxy-propionic acid. Ordinary lactic is formed by fer-
mentation of milk, which contains a fermentable sugar
(galactose). It is present in the gastric juice, and in
pickled cabbage and cucumber. It is generally prepared
by the lactic fermentation of cane sugar, by means of
putrid cheese. Zinc carbonate is added to neutralise the

TARTARIC ACID. 216

acid as fast as it is formed. — It is a monobasic acid.
Ferrous lactate (Fe( 031X503)2) is prepared by dissolving
iron filings in warm dilute lactic acid. It is used in
medicine.

189. Tartaric Acid, QJ^^O^. — This is dihydroxy-

... . ^ , ^ , . CH.OH— COOH

succinic acid, and its expanded formula is I

CH.OH— COOil

It is at the same time a diabasic acid and a diacid
alcohol. There are three isomeric tartaric acids, and our
chemical theory is inadequate to explain their isomerism.
Ordinary tartaric acid is found in the juice of grapes,
berries of the mountain ash, cucumbers, potatoes, &c.

Ppeparation. — From tartar or argol, which is impure
potassic hydric tartrate deposited in wine casks and vats
during fermentation. (It is less soluble in alcohol than
in water.) From this salt, purified by crystallisation,
the acid is prepared as follows : " Boil 45 oz. cream of
tartar (potassic hydric tartrate) with two gals, water;
add 12| oz. prepared chalk gradually, stirring constantly:

2KHT + CaCOs = KgT + CaT + H2O + COj.

(T = C4H4O6.) Then add 13J oz. calcic chloride in
2 pints of water :

K2T + CaCla = Caf + 2KC1.

Allow the calcic tartrate to subside, pour off the liquid
(What does it contain?), wash the precipitate with dis-
tilled water until tasteless, and pour on it 1 3 fluid ounces
sulphuric acid diluted with 3 pints of water. Boil for
half an hour and filter :

CaT + HaSO^ = OaSO^ + HaT.

J16 8EIDLITK POWDEH.

£yapor>>/^e the filtrate at a gentle heat to specific weight
1.21, allc to cool, and Bepa''ate the deposited gypsum
(CaS04,2H.jO). Again evaporate till a film forms ou
the surface, cool, and drain the crystals of tartaric acid
which form." (B.P.) (Potassic hydric tartrate is spar-
ingly soluble, the normal tartrate quite soluble, calcic
tartrate insoluble in water. Explain the steps of the
above process).

Properties. — Large colourless crystals or a white
granular powder, of acid taste, soluble in water (2 parts
in 1 of water), and in alcohol, but not in ether.

Experiment 168. — Examine the appearance and tawte of a
crystal of the acid, then heat on mica. It browns and chars
with the smell of burning sugar ; with a stronger heat it burns
away completely.

Experiment 169. — Carefully add solution of tartaric acid
to some solution of potassic carbonate (coloured with litmus)
until the solution is neutral. (What salt is present ?) Then add
more tartaric acid, stirring all the time with a glass rod. A
white granular precipitate of the acid tartrate forms. (Write
equations. )

Experiment 170. — To a strong solution of hot sodic car-
bonate in a porcelain basin add, a little at a time, cream of
tartar (7 .HT) until it causes no eflfervescence. Evaporate to
crystalhsation. Sodie potassic tartrate, or Hochelle salt (KNaT),
is formed :

Na.CO, 4- 2KHf = 2KNaT + HaO + CO,

Rochelle salt is one ingredient of seidlitz powder. The
blue paper contains usually 3 parts Rochelle salt and 1
part sodic hydric carbonate; and the white, 1 part tar-
taric acid. When ihe solutions are mixed the tartaric

TARTAR EMETIC. 217

acid decomposes the carbonate, while the Kochelle salt
takes no part in the action :

2NaHC0, + Haf - NajT + 2H3O + 2C0a.

(From this equation calculate the proportions of car-
bonate and acid which must be used in order that there
may be excess of neither.)

Tartar Emetic is antimonyl potasaic tartrate
(SbO.K.T), prepared by boiling cream of tartar with
antimony trioxide :

feoaOg + 2KHT = 2SbOKf + BjO.

The radical antimonyl (SbO) acts the part of a monad
metal.

Tests. — 1 . To neutral solution of a tartrate add calcic chlo-
ride or to a solution of tartaric acid add lime water ; calcic tar-
trate (CaT) is precipitated. Wash the precipitate on a filter,
break the filter, wash the precipitate into at. t., and add sodic
hydroxide ; the precipitate dissolves.

2. To tartaric acid or solution of a tartrate add acetic acid
and potasaic acetate and stir. Fotassic hydric tartrate ib pre-
cipitated as a white granular powder.

3. Tartaric acid or tartrates in solution, when heated with a
considerable proportion of concentrated sulphuric acid, turn
brown or black at once.

4. To neutral or alkaline solution of a tartrate add a few
drops of potassic permanganate solution, and heat, The colour
disappears.

Note. — Solution of tartaric acid in water undergoes
slow decomposition owing to the growth of a fungus.
Spirits of wine prevent this.

218 CITRIC ACID.

190. Citric Acid, CgHgO^.Hp. This is a tribasic

( COOH

acid and monacid alcohol, C3H4.OH \ cooH. It is found

in the juices of limes, lemons, currants, raspberries,
gooseberries, <kc.

Preparation. — From the evaporated juice of unripe
limes and lemons by almost the same inethod as that for
tartaric acid. One hundred parts of lemon yield 5^
parts of acid.

Experiment 171- — Squeeze the juice of a lemon upon a filter
and allow it to run iato a porcelain basin. Heat to boiling and
add prepared chalk by degrees until it does not cause effer-
vescence :• -

2H3Cr+ SCaCOs = OaaCi^ + 3H,0 + 300^.

Filter, wash the precipitate with hot water four or five times,
break the paper and wash the precipitate through into a porce-
lain basin. Add a small quantity (2 or 3 c.c.) of sulphuric acid,
boil gently for a little while, filter and concentrate the filtrate
to crystallisation. Crystals of citric acid are obtained mixed
with gypsum. The acid can be purified bj' recrystallisation
from a small quantity of hot water.

Properties. — Usually sold as large, colourless, sharp-
pointed crystals. These are soluble in ^ their v.' eight of
cold water, in | of boiling water ; less soluble in alcohol ;
still less in ether. Citrie acid melts at 100° ; above this
it loses water of crystallisation^ then c?ia.-' with the smell
of burning sugar.

El^periment 172.— Heat a little sohd citric acid in a t. t.
by placing the t. t. in boiling water. The acid melts. Wipe
the t. t. and heat it gently in the Bunsen flame. Note the
water condensing. Heat more strongly. Note smell and char-
ring. Heat a small crystal strongly on mica.

MAONESIC CITRATE. 219

Experiment 173 — Put a pipetteful of citric acid solntion in
each of three porcelain dishes, and carefully neutralise with so-
lution of potassic carbonate. To one add a second pipetteful of
the acid, and to another two pipettefuls. Number and evapo-
rate the three solutions on a water bath to a syrupy consistence,
and then set aside to crystallise. Three salts are obtained, dif-
ferent in appearance. What are they ? Taste them.

Experiment 174. — Dilute a little of the normal potassic
citrate prepared in Experiment 172 and add to it about an equal
volume of the reagent solution of calcic chloride. If no precipi-
tate appears, boil. If a precipitate appears, gradually add
distilled water and shake up until it is dissolved, and then
boil. Calcic citrate (Ca3Ci2.4H20) is less soluble in hot than in
cold water. (Try with citric acid and lime water. )

Magnesic citrate (Mg3Ci2.4H20) is a white sparingly
soluble salt which can be prepared by the action of the
acid on magnesium carbonate :

SMgCOa + 2H3Cr = MgaCTa + aHgO -f- 3CO2.

Effervescing powders are made by mixing the substances
in the solid state. Solids act on each other very slowly
or not at all ; but as soon as tliey are brought together
in solution action begins. The moi\. coarsely granular
the solid ingredients are, the slower is the action between
them. (Why 1) " Granular effervescing citrate of mag-
nesia " is a mixture of coarse granules of Epsom salts
(MgS04.7H20), citric acid, tartaric acid, and hyd.io
sodic carbonate (HNaCOa). (What substances are
formed when it is dissolved 1)

Tests. — 1. (Exp't 174.) The precipitate of calcic citrate is
insoluble in sodic hydroxide.

2, Citric acid and citrates give no precipitate with acid solu-
tions of potassium salts. (See tartaric acid).

220 CARBOHYDRATES.

3. Heat with concentrated sulphuric acid. The solution
darkens only after some time.

4. To neutral or alkaline solution add a few drops of potaasie
permanganate solution and heat slowly. The permanganate is
reduced to the green mangQnate (KjMnO^.)

5. All solid citrates are charred by heat.

Note.' -Citric acid is sometimes adulterated with tartaric acid.
This can be detected by the test with potassium salts. The
addition of alcohol increases the delicacy of the test.

191. Oarbohydrates. — Under this head are in-
cluded three groups of isomeric compounds, containing
either 6 or 12 atoms of carbon in the molecule, to-
gether with hydrogen or oxygen in the proportions to

Jorm water. They are all naturally occurring sub-
stances, many of them being quite familiar vegetable pro-
ducts, e.g., sugar, starch, and cotton. (What compounds
already discussed contain h3^drogen and oxygen in the
proportion to form water 1), — The carbohydrates are in
all probability poly-acid alcohols, and at the same time
aldehydes or ketones. There are three groups :

• 1. Saccharoses (C12H22O11). — Comprising cane sugar
(saccharose), milk sugar, malt sugar (maltose), &c.

2. Glucoses (CgHisOft). — Grape sugar (dextrose), fruit
sugar (levulose), galactose, inosite, (fee.

3. Amyloses (CgHioOg). — Starch, dextrin, cellulose,
glycogen, gums, inulin, (fee.

192. Saccharoses, — Ox^l.>.f>^y The saccharoses
seem to be analogous to ethers — they all unite with
water to form, glucoses ;

CANE SUGAR. 221

(Compare this with the relation of ethyl ether to ethyl
alcohol.) This takes place under the influence of fer-
ments, and by boiling with dilute acids or alkalis.

1. Cane Sugar (Gi<JBLr,20^{). — Cane sugar is so called
because of its manufacture from the juice of the sugar-
cane. It is also now largely made from the sugar-beet.
It is found also in the sugar-maple, sorghum, turnips,
carrots, coffee, walnuts, hazelnuts, almonds, and in tht
blossoms of many plants along with more or less fruit-
sugar.

Preparation. — The juice is expressed from sugar-
cane or beet-root-pulp, and the solution of sugar is
evaporated in '' vacuum pans." It is necessary to evapo-
rate at moderate temperatures in order to avoid the change
into uncrystallisable members of the glucose group.
The evaporated solution is allowed to crystallise, and
the crystals are drained on " centrifugals," which are
large revolving sieves. Molasses is the mother liquor
drained from the raw cane-sugar. It is much used in
the manufacture of rum, and lately a process has been
devised to obtain more sugar from it. It contains
cane-sugar, together with inverted sugar, or glucoses pro-
duced by the action of water on cane-sugar, — inverted,
because the action on polarised light is the exact op-
posite. It must be remembered t-iat beet-sugar and
cane sugar, when pure, are the same substance. Vinas-
ses, the mother liquor of beet-sugar, is evaporated to
dryness, and distilled. A variety of useful products is
obtained, viz., potassic carbonate, ammonia, methylic
alcohol, trimethylamine, <kc.

222 CANE SUGAR.

Properties. — A hard, colourless, crystalline solid of
specific weight 1.593. It dissolves in about one-third of
its weight, of cold water, and in all proportions in boil-
ing water. It is insoluble in absolute alcohol, and in
alcoholic liquors is soluble in proportion to the water
present. It melts at 160° C, and at 190* gradually
loses water and darkens, forming a substance called
caramel {saccharum ustum), much used foi colouring
wines and liquors. When heated more strongly it chars,
giving off fumes having a characteristic odour.

Experiment 175. — Make a solution in water of pure cane-
sugar, add to part of it a few drops of cupric sulphate solu-
tion, and then solution of caustic soda. A blue solution is
formed. Heat this. If the sugar is pure no change takes place.
Add a few drops of sulphuric acid to a little of the sugar solu-
tion and boil for some time in a porcelain dish ; add wa^ 3r as it
evaporates. Then repeat the test with cupric sulphate and
caustic soda. A precipitate is formed on heating, at first yellow
and then red. This precipitate is cuprous oxide (CuaO). (Feh-
ling's test.)

As we shall see later this reduction of cupric sulphate
solution is brought about by glucoses, but not generally
by saccharoses. The cane-sugar has been inverted by
boiling with an acid :

Dextrose. Levulose.

C12H22O11 + H2O = CgHigOs + CeHiaOfl.

This process goes on slowly in moist impure sugars
(brown sugars). Cane-sugar does not at once undergo
alcoholic formentat'm when its solution is mixed with
yeast. It must first be inverted by the action of the
ferment.

Experiment 176. — To a dilute solution of pure sugar add
some brewer's yeast, and set in a warm place for half an hour.

MILK SUGAR. 223

Then test the solution as in Experiment 175. It will be found
to contain inverted sugar.

Thore are many ferments which cause the inversion of
cane-sugar. The saliva has this power owing to the
presence of a ferment, ptyalin, which however loses its
power when the solution becomes acid, and, hence, as
soon as it reaches the stomach. Oxidising agents con-
vert cane-sugar into oxalic and other acids. Formerly
oxalic acid was made by the action of nitric acid on cane-
oi'gar. — Cane-sugar forms soluble compounds with many
substances which are insoluble or sparingly soluble in
water. It is thus useful for keeping in solution certain
metallic compounds employed in medicine, e.g., slaked
lime, calcic hypophosphite, <fec. — Oxymel is a mixture of
honey (80 %), acetic acid (10 %), and water 10%). The
name means acid-honey.

Tests. — 1. Fehling's test as in Experiment 175. Fehling'a
solution is made by dissolving 34.64 grains cupric sulphate (blue
vitriol) in water, adding 200 g. Rochelle salt (KNaT), 600 g. to
700 g. solution of caustic soda of specific weight 1.12, and mak-
ing up to 1 litre with water. It must be kept well stoppered,
and put in a cool, dark place.

2. Evaporate on the water bath with a few drops of sulphuric
acid. Blackening shows the probable presence of cane-sugar.
Grape sugar does not blacken.

3. Heat with solution of caustic soda, caustic potash, or po-
tassic carbonate. Does not turn brown.

2. Milk Sugar (Lactose) (C12H.22Ou.H2O). — Milk
suga.' is found in the milk of all mammalia. Human
milk contains 4 °/^ to 5 °/^, cow's milk 3 7o-

Preparation. — From whey, by evaporating and crys-
tallising on threads or sticks.

224 MALT SUGAR.

Properties. — A hard, colourless crystalline solid,
with one molecule of water of crystallisation. It is
not so soluble in water as cane-sugar, dissolving in 6
parts of cold, or 3 of hot water. It is almost insoluble
in alcohol. Its taste is less sweet than that of cane-
sugar. Specific weight 1.534. — Milk-sugar does not
ferment with yeast ; but it undergoes another fermenta-
tion with the formation of alcohol and lactic acid, as in
the preparation of the fermented liquor called koumiss.
— Milk sugar is used to a considerable extent to increase
the percentage of sugar in cow's milk for feeding infants.
It is also used in the powdered state as a diluent of solid
medicines, e.g., iodoform.

Experiment 177. — Try Fehling's test with milk-sugar. It
differs from the other members of this group in that it reduces
cupric to cuprous oxide.

Experiment 178- — Heat some solution of milk-sugar with an
alkah. What result ?

Experiment 179. — Add a few drops of argentic nitrate solu-
tion to a solution of milk-sugar, then some ammon %, and warm
gradually. Silver is deposited as a mirror on the ^ . t.

Tests. — Distinguished from cane-sugar by Experiments 177
and 178 ; from glucose by not fermenting with yeast.

3. Malt Sugar (Maltose) (C12H22O11). — This is also
sometimes called starch-sugar.

Preparation. — By fermenting potato-starch with air-
dried malt, and extracting the sugar with alcohol.

Properties. — A crystalline solid freely soluble in

water, and to a considerable degree in alcohol. It can

be transformed into grape-sugar by boiling with dilute

ulphuric acid. It is used in the preparation of caramel.

DEXTROSE. 225

193. Glucoses. — CgHioOe. Glucoses are widely dis-
tributed in nature, occurring in both plants and animals.
Fruits contain cane-sugar in the early stages of their
ripening, but this gradually combines with water to form
ghicoses, generally equal quantities of dextrose and levu-
lose. This mixture is called invert-avgar.

1. Dextrose (Q^-^^O^. — Also called glucose and
grape-sugar.

Occurrence. — In sweet fruits, almost always accom-
panied by an equal quantity of levulose, thus showing
the origin of these sugars from cane-sugar. The latter
is also generally present, until the fruit becomes fully
ripe. Dextrose is also present in honey, and in the blood,
liver, and urine of man. In cases of diabetes mellitus
the quantity in the urine may reach 10 °/q.

Preparation. — Dextrose can be prepared artificially
from starch, dextrin, cellulose, <kc., by the action of
acids. It is manufactured on the large scale from corn
and potato starch, by heating with dilute sulphuric acid,
generally under pressure. Dextrin, isomeric with starch,
is first formed, and this combines with water :

Experiment 180. — Boil eome starch paste for half an hour
with about one-fifth its volume of dilute sulphuric acid, re-
placing the water as it evaporates, and then test the solution
for dextrose by Fehling's teat. Try Fehling's test with starch.

The sulphuric acid is neutralised with chalk or lime-
stone (CaCOa), and the solution of dextrose is drawn off
and evaporated to crystallisation. It is difficult to crys-
tallise, as it tends to form supersaturated solutions.
16

226 GLUCOSE.

Properties. — The glucose of commerce is either a
thick syrup (" mixing syrup ") or a hard, white solid
(" grape sugar "). Specific weight = 1.825. It always
contains dextrin, and other substances of unknown
composition. The dextrin is harmless, but the unknown
substances have an effect on the human system similar
to that produced by fusel oil. Dextrose is not so sweet
as cane-sugar, the sweetness being as 1 to 1.66 (or as 3
to 5). At 15° C. it dissolves in 1.2 parts of water. It
is more soluble in alcohol than cane-sugar. It ferments
to alcohol and carbon dioxide under the influence of
yeast :

CeHiaOg = 2CO2 + 2C2HeO.

It also undergoes the lactic and butyric acid fermenta-
tions. — "Granulated grape sugar" looks very like cane-
sugar, and is used to adulterate it. Many of the cheap
sugars contain 10 °/q to 20 °/q of grape-sugar. It is
used in the preparation of alcohol, artificial wines, &c.
Wines and liquors made froi i such materials are poison-
ous. — Dextrose has the power of keeping in aolutiou
some substances which are insoluble in pure water.

Experiment 181, — A.dd a solution of sodic hydroxide to solu-
tion of cupric sulphate. Cupric hydroxide (Cu(0H)2) is precipi-
tated, and is not redissolved by excess of the precipitant. Re-
peat the experiment, with a solution of cupric sulphate contain-
ing grape-sugar. A blue solution is obtained. Heat the solu-
tion , and red cuproMS oxide is precipitated, the sugar undergoing
oxidation. This explains Fehling's test.

Experiment 182. — Add a few drops of argentic nitrate solu-
tion to dilute solution of grape-sugar in a 1. 1. and warm gently.
The inside of the t. t. is silvered.

Experiment 183. — Heat a solution of grape-sugar with sodic

LEVULOSE. 227

hydroxide. Try also wi^h potassic hydroxide, and with aodio
carbonate. The solution of sugar turns brown.

Tests. — Experiments 181 and 183 serve to distinguish from
cane-sugar.

Note. — Olncoaides are peculiar ethereal salts of glucose, which
break up under the action of a ferment (or of dilute acids) into
ghicose and other substances, an aldehyde being very commonly
among the number.

2. Levulose, (fee, CgHj.^Og. Levulose is nearly as
sweet as cane-sugar. It was at one time thouglit to be
iincrystallisable, but it can be crystallised, althoiigli with
difficulty. As has been previously observed, it occurs in
ripe fruits accompanied by an equal quantity of dextrose.
It is fruit-sugar. — Galactose is formed together with
dextrose by the inversion of milk-sugar. It does not
ferment with yeast, but reduces Fehling's solution. —
Inosite (C6H12O6.2H.2O) is found in the heart, lungs,
(kc, of the ox, and sometimes in the urine of man. It
does not reduce Fehling's solution. It is soluble in 6
parts of water, and insoluble in alcohol.

AMYLOSES.

194, Starch {amylum'). — CgHioOj. Found in grain,
potatoes, arrowroot, nuts, and very generally distributed
throughout vegetable tissues. It is the form in which
plants store up a reserve of food, just as animals store
up fat. — Starch is manufactured from wheat, Indian
corn, rice, and potatoes. The materials are ground up
vnth water, strained through sieves, and treated with
dilute caustic soda, or fermented. The starch is allowed

228 STARCH.

to settle, washed, tfeo. Sago is a starch made from the
pith of the sago palm of the East Indies. Arrowroot m
starch prepared from the roots of Maranta arundinacea,
a West Indian plant. Tapioca is a similar preparation
from Jatropha manihot.

Properties. — Starch is a white substance, forming
granules of peculiar structure. Under the microscope
these granules show concentric layers around a spot or
hilum. The granules are different for different plants,
and an examination by the microscope at once reveals
the source from which any specimen of starch has come.
— Starch is insoluble in water, but, when heated with it,
swells up and forms a paste. Continued boiling, or the
action of acids or alkalis, renders the starch soluble.

Experiment 184. — Scrape a piece of potato and place the
pulp on a muslin filter. Pour a thin stream of cold water on it,
catching the filtrate in a t. t. Allow the starch to settle, pour
off some of the water, and then heat to boiling. Starch paste is
formed.

Experiment 185. — To a little cold starch paste (mucilago
amyli) add a few drops of iodine solution. A deep blue colour
is produced. Heat, and the colour disappears. Allow to cool
again.

Starch paste (or mucilage of starch, as it is called in
medicine), changes gradually into a solution of dextrin.
This change is hastened by boiling with dilute acids, or
by the action of ferments (malt, <fec.). — Starch is used in
medicine as a vehicle for enemata, <fec. The blue starch
of the shops is coloured with indigo or smalt, and should
not be used for medicinal purposes.

Test. — Experiment 185 is a very delicate test. The sub-
stance should be as cold as possible.

DEXTRIN — GLYCOGEN. 229

Iiinlin is a compound (CnHioOj) which partially replaces
starch in elecampane, the roots of dahlia, &c.

195. Dextrin. — CgHioOj. Dextrin is prepared by
heating starch to about 250° C. It is formed from starch
at lower temperatures (up to 95° C.) by the action of
tlie ferment (diastase) of malt, and also by boiling with
dilute acids.

Experiment 186. — Boil in a t. t. for several minutes a little
starch with water and a few drops of sulphuric acid. A clear
solution is obtained. Cool this and test it with iodine.

Dextrin is soluble in water, but insoluble in alcohol.
By the further action of malt or dilute acids it is changed
first into maltose (CigHo-^Ou), and then into dextrose
(CgHiaOg). — It is made on the large scale, and sold as
calcined farina, or British gum, a cheap substitute for
'^nm arabic. — Considerable quantities of dextrin are
tormed in the baking of bread. Toast is more easily
digested, therefore, than bread. The first stage in the
digestion of the insoluble starch is its transformation
into soluble dextrin.

196. Glycogen. — CgHiuOg. This name means sw</ar-
generator. Glycoger is found in the livers of most animals ;
it is also present m the blood and in muscles. Oysters
contain a large percentage. It can be extracted from
fresh liver by boiling with water or with alkalis. It is
precipitated from its aqueous solution by the addition of
alcohol, in which it is insoluble.

Properties. — A white amorphous powder, somewhat
soluble in water. Under the action of malt, &c., it com-
bbes with water to form maltose and dextrose. It is

230 GUMS — CELLULOSE.

generally supposed that the liver stores up the surplus
sugar of the food in the form of glycogen. The liver
contains a ferment which has the j)Ower of transforming
glycogen into maltose or dextrose.

197. Gums. — CjHioO.,;. These must be distinguished
from resins, often called gums in this country. Gum.
arahic, guin tragacanth, and bassorin are examples of
true gums. They are non-crystalline, soluble in water,
but insoluble in alcohol. The}' are converted into glii-
coses by boiling with dilute acids. Vegetable mucilages,
e.g., that of linseed, are of a similar character.

198. Cellulose. — CoHioOg. This is the groundwork
of vegetable tissues, forming the walls of vegetable cells.
Cotton, hemp, and flax are nearly pure cellulose. Paper
is also very pure, especially when prepared from cotton.
Woods consist in large part of cellulose.

Properties. — A white amorphous solid, insoluble in
water, and in most chemical substances. It is, however,
soluble in ammoniacal solution of cupric hydroxide
(Schweizer's reagent), in strong, hot solution of caustic
soda or potash, and in strong acids. These facts must
be remembered in filtering processes. It can be con-
verted into dextrose by dissolving in strong sulphuric
acid, diluting, and boiling for some time.

>;rilI16Ilt 187. — Dissolve a piece of filter paper in a little
>ig sulphuric acid, dilute, boil for some time, and test with
. ehling's solution.

Gun-cotton, pyroxylin, or nitro-cellulost, is the trinitrate of
cellulote, CoHyOaCNOaJj, prepared by the action of a mixture of
concentrated sulphuric and nitric acids on cotton or wood. It
is very explosive, containing as it does an oxidisable and ai)

QUESTIONS AND EXERCISES. 231

oxidising part. (Explain). — Celluloid is a preparation of nitrates
of cellulose and camphor, prepared by a method similar to that
for gun-cotton. It softens when heated and can l)e moulded
into any shape. — Collodion is a solution in alcohol and ether of
nitrates of cellulose. It is used in photography.

QUESTIONS AND EXERCISES.

1. Compare carbon dioxide and carbon bisulphide, as to their
compounds.

2. What causes the eflfervescence of soda water ?

3. How would you prove by an experiment that carbon di-
oxide is formed by the burning of a candle ?

4. Show that most of our materials for fires and lights are
from a vegetable source. '

5. Write graphic formula for acetylene (C2H2). \\^ith how
many atoms of chlorine would you expect its molecule to com-
bine ?

6. Show how green vitriol, ferric chloride, and sodic carbonate
may be usei as an antidote to poisonous cyanides.

7. Accou nt for the smell of ammonia about stables and water
closets.

8. A quantity of urine (70 c. c.) is decomposed by sodic hypo-
bromite, and yields 8 c. c. of nitrogen. How riany grains of
urea per gallon ?

9. Write formulas for methyl nitrate, sulphate, and ortho-
phosphate ; and for ethyl bromide, acid suipJiafe, and sulphite.

10. What is the practical distinction between primary,
secondary, and tertiary alcohols ?

11. Calculate the specific weight of ether vapour (air = 1).

12. Given zincic carbonate and acetic acid, prepare zincic acetate.
Try it practically.

13. What chemical actions accompany the souring of milk ?

14. What is " invert sugar " ? Why so called ?

15. Why is toast more easily digested than bread ?

232 COAL TAR.

CHAPTER XIV.

CARBON AND ITS COMPOUNDS (Coxcluded).

199. Ooal Tar. — About thirty years ago coal tar
was an offensive waste product of gas manufacture, and
the problem was how to get rid of it. To-day it is the
pubstance for which the coal is distilled in many fac-
oories ; and the gas manufacturers regard it as one of
the chief sources of their revenue. This change is due
to the discovery of the aniline dyes, the raw materials
for their manufacture being obtained from coal tar. —
The tarry liquid which collects in the condensers of the gas-
works is redistilled fractionally. There distils over fii-st
a light oil which floats on water ; this contains benzene
(CgHg), toluene (CyHg), carbolic acid (CgH^O), &c. Later
there distils a heavy oil containing xylene (CgHio),
mesitylene (C9H12), cymene (CiqHi^), naphthalene, anthra-
cene, &c.

200. The Benzene, or Aromatic, Series.— We

have already studied unsaturated hydrocarbons, such as
ethylene and acetylene, the marked characteristic of
which is the readiness with which they combine with
such substances as chlorine to form saturated compounds.
The benzene compounds are unsaturated as far as their
composition goes, but they are characterised by the
difficulty with which anything is added to their mole-
qules. They yield substitution^ rather than addition,

BENZENE. 233

products, and in this respect resemble saturated hydro-
carbons. The chiof members of the series are ab follows :

Boiling

■ ' points.

Benzene, CqH^ 81°

Toluene, CyHg Ill

Xylenes (3 isomers), C 8 Hi about 140

TMesitylene ] 163

^ Pseudocumene VC9H12 151

I^Cumene J 166

201. Benzene (Benzol). — CgHfi.

Preparation. — From the light oil of coal tar. This is
washed first with caustic soda solution to dissolve out
carbolic acid and other acid impurities, and afterwards
with dilute sulphuric acid to remove basic substances.
It is then distilled fractionally, and the part coming
over between 80° and 90° is used for the preparation
of benzene. — It can also be prepared by heating benzols
acid with lime : .

CeHs.COOH + CaO = C^B.^ + CaCO

This method is analogous to that for the preparation of
methane.

Properties. — A colourless liquid of specific weight
0.89. It boils at 80".5, and has a pleasant aromatic
odour. It burns with a brightly luminous flame.

Experiment 188. — Pour a little benzene into a basin of
water and set fire to it.

Ezperimont 189. — Pour a few drops of benzene into a t. t.
of water heated nearly tc the boiling point. Observe that the
benzene boils.

Benzene is solid at 0°C. — It is a good solvent for fats,

234 BENZOL BINO.

oils, and resins. — When benzene is acted on by chlorine,
substitution products are formed. There is only one
monochlor-benzene (CgHgCl). If the atoms of carbon in
the molecule were connected as they are supposed to
be in the hydrocarbons already studied, we should
expect the hydrogen atoms to be diflferently situated and
thus to permit the formation of isomeric derivatives
by the replacement of the hydrogen atoms. Now mono-
chlor-benzene has been prepared in a variety of ways,
some of which lead to the conclusion that different
hydrogen atoms have been replaced by chlorine ; but
the products are identical. It is plain, then that the
six hydrogen atoms are similarly situated in the mole-
cule. Kekul^, of Bonn, has devised a structural for-
mula showing this. It is called the benzol ring, and
although it only pictures an hypothesis, yet it has
proved a powerful lever in the hands of experimenters.

(6)H h(1)

I I

c c

/ \

(5) H— C C— H (2)

c c

(4)H H(3)

The molecule is represented as being symmetrical, each
carbon atom being united to a hydrogen atom, to another
carbon atom by a single bond, and to a third by a double
bond. (Study this formula, and observe that the hydro-
gen atoms are represented as similarly situated.)

When two hydrogen atoms of the benzene molecule

SUBSTITUTION PRODUCTS. 235

are replaced, three isomevic di-suhstitution products are
formed. If the hydrogen atoms represented in the above
formula be numbered consecutively from 1 to 6, it is
easily seen that (2) and (6) are similarly situated with
regard to (I), so that replacing (1) and (2) with,
say, Cl's, gives the same formula as is obtained by re-
placing (I) and (6). In the same manner (3) and (5)
are similarly situated; but, with regard to (1), (4) is
differently situated from (2), (3), (5), or (6). Only
three different formulas of di- substitution products are
possible, and this result is in accordance with the facts.
By a oeries of beautiful experimental investigations, the
relative positions of the substituted atoms have been
determined, and names have been assigned accordingly.
Thus (1) (2) (or (1) (6))'di-substitution products are
called ortho, e.g., ortho-dichlorbenzene ; (1), (3) products
are called meta, and (1), (4) para.

202. Nitro - substitution Products. — When

strong nitric acid acts on benzene, one or more of the
hydrogen atoms are replaced by the monad radical — NOj
[nitroxyl). Thus :

(1) CeHe + HNO3 = CeH^.NOa + H,0.

(2) CeHe + 2HNO3 = CeH,.(N02)2 + m^O.

Only one mononitrohenzene is known, but three isomeric
diniti'ohenzenes have been obtained. (How many tri-
nitrohenzenes are possible according to theory 1)

MoNONiTROBENZENE (CgHg.NOj) is manufactured on
the large scale in the preparation of aniline (CgHg.NHj).
It is a yellow, oily liquid smelling like oil of bitter
almonds. It is often sold as " artificial essence of mir-

236 ANILINE.

bane," or "artificial oil of bitter almonds ; " but as it is
poisonous and different in its physiological action from
the true oil, it should never be used in medicine in
place of the true oil. — Mononitrobenzene boils at 205° C.
Its specific weight is 1.2. It is insoluble in water. By
the action of nascent hydrogen it is reduced to aniline
(CeH5.NH,) :

CeH^.NOa + SH^ = CeHg.NH^ + 2H2O

Nitrobenzene is used to perfume cheap soaps and confec-
tionery, as well as in the manufacture of aniline. It
is sometimes mixed with oil of bitter almonds as an
adulteration. Its presence can be detected by reducing
to aniline by means of zinc and hydrochloric acid, and
then treating with filtered solution of bleaching powder,
with which aniline forms a beautiful purple colour.

Experiment 190- — Mix a few drops of benzene with a little
concentrated nitric acid. Warm very gently and note the smell
of nitrobenzene.

203. Aniline (Phenylamine). — C6H5.NH2. Was
first prepared from indigo [anil). It is found in small
quantities in coal tar, wood tar, and bone oil.

Preparation.— By the action of nascent hydrogen on
mononitrobenzene. The hydrogen is evolved from iron
and acetic or hydrochloric aoid. (Write the equations).

Properties. — Aniline is a colourless liquid of specific
weight 1.036. It boils at 184°.5. It is soluble in 31
times its weight of water, and the solution has p weak
alkaline reaction. It is more freely soluble in alcohol.
— Aniline unites with acids to form salts :

CeHg.NHa + HCl = CeHg.NHaCl.
Compare with NH3 + HCl = NH^Cl.

CARBOLIC ACID. 237

Aniline is a substituted ammonia, or amine, of the aroma-
tic series. Commercial aniline always contains toluidine
(CyHy.NHa^ a higher member of the same series; and,
when it is oxidised by means of arsenic acid or potassic
chlorate, the beautiful colour rosaniline (Q.^^■^^^.^ is
formed This is the first of the aniline dyes, the dis-
covery and manufacture of which have revolutionised
tlie dyer's art. They are comparatively innocuous when
pure, but arsenic acid is used in their manufacture, and
through carelessness or ignorance it is sometimes imper-
fectly separated.

Tests. — 1. To an aqueous solution of aniline add some
tiltered solution of bleaching powder. A purple colour results.

2, Dissolve a drop of aniline in strong sulphuric acid. (What is
formed ?) Stir in a porcelain dish with a drop of potassic bichro- ,

mate solution (KaCrgOy). A blue colour is produced.

204. Carbolic Acid (Phenol). — Q.U^.OYL. This
is in reality a tertiary alcohol, but it has very weak
acid properties. — It is found in small quantities in urine.
It is a product of the distillation of wood, coal, bones, &c.

Preparation. — From the heavy oil of coal tar. This
is treated with caustic soda solution, which dissolves the
carbolic acid, forming sodic carbolate, or phenolate,
(CgHg.ONa). The solution forms a layer separate fiom
the oil. It is decanted, and is then decomposed by hy- . «

drochloric acid :

CoHs.ONa + HCl = CeHg.OH + NaCI. '

The carbolic acid is purified by distillation.

Properties. — A colourless, crystalline solid, crystal-
lising in long needles. It has a strong, somewhat tarry
smell, not unpleasant when the carbolic acid is pure. It

238 CREOSOTE.

melts at 35°, and boils at 180^ It is dehquesconfc,
uniting with a small proportion of water to form a liquid.
This liquid is sparingly soluble in water (1 in 15), but
mixes with ether and alcohol in all proportions.

Experiment 191. — To a little solid carbolic acid add a drop
or two of water. They combine to form an oily liquid. Add a
little more water. The two do not mix. (Which is tlie
heavier?) JSow add much water, and the carbolic acid dis-
solves. Note taste and smell of this Hquid.

It is very poisonous, and the strong solution burns the
skin. It has a burning taste. The antidotes are olive oil,
castor oil, and a mixture of slaked lime witn 3 times
its weight of sugar, rubbed up with a little water. —
Carbolic acid is extensively used as an antiseptic in
surgery, &c. It was introduced into general use by
Lister, of Edinburgh, who devised a system by which
surgical operations were carried on in an atmosphere
containing no living putrefactive germs. The antiseptic
spray was combined with a minute cleanliness hitherto
unknown in surgery, and in all probability to this is due
in a great measure the success of Listerism. t

Test. — Mix the liquid with one-fourth its volume of am-
monia solution and add a few drops of clear bleaching powder
solution. The merest trace of carbolic acid will cause a blue
colour to appear.

205. Creosote. — Pure creosote is obtained by distil-
ing beech and other hard woods. It consists mostly of is-
omeric cresolsy CgH^"^^^. It resembles carbolic acid in
smell and taste. Carbolic acid is often sold as creosote ;
and the so-called " coal-tar creosote " is merely impure
carbolic acid.

PICRIC ACID. 239

To distinguish carbolic acid from creosote :

1. Dissolve in glycerine and add water. Carbolic acid
remains dissolved. Creosote is precipitated by the water.

2. Add to the liquid to be tested alcoholic solution of
ferric chloride. Carbolic acid gives a brown colour ;
creosote, green.

3. With aqueous ferric chlorid*^, carbolic acid turns
blue ; creosote is unchanged.

206. Picric Acid ( Trinitrophenol, or Carbazotic
Acid).—C,li,{OB.).(NO,),.

Preparation. — Experiment 192. — Dissolve some carbolic
acid in dilute nitric acid and add drop by drop about half
the volume of strong nitric acid. Dilute with cold water, and
picric acid is precipitated.

Properties. — A yellow crystalline solid sparingly
soluble in cold, easily in hot water, and in alcohol or ether.
It has a bitter taste and is poisonous. It explodes when
heated rapidly. Amnionic picrate (NH^.CgHaNgO;) is
used as an explosive. Picric acid has strong colouring
power, and is a good dye for silk and wool.

207. Benzylic Alcohol— CeHg.CHaOH. — Found

in balsam of Tolu and Peru, and in storax, as ethereal
salts of benzoic and cinnamic acids. When oxidised
it gives first benzoic aldehyde (CeHg.COH), and then
benzoic acid (CgHg.COOH).

208. Benzoic Aldehyde.--CeH6.C=0. A com-

ponent of amygdalin, a glucoside found in bitter

240 BITTER ALMOND-OIL.

almonds, in laurel leaves, cherry kernels, <fec. Amyg-
dalin ferments under the influence of synaptase (a fer-
ment present in the almond), forming benzoic aldehyde,
hydrocyanic acid, and dextrose :

C20H27O11N + 2H2O = C^HgO + HON + 2CeHi20e.

Oil of hitter almonds is prepared by fermenting bitter
almonds. The crude oil contains, besides benzoic alde-
hyde, hydrocyanic acid, and is therefore very poisonous.
It is purified by distilling with milk of lime (to retain
the pnissic acid), and fused calcic chloride (to retain the
water). Pure benzoic aldehyde is thus prepared.

Properties. — A colourless, bright liquid of pleasant
aromatic odour. Specific weight = 1.054. It boils at
180° C. It dissolves in 30 times its weight of water,
and mixes in all proportions with alcohol and ether. —
It is not poisonous ; but the so-called " artificial oil "
(nitro-benzene) is poisonous. A delicate test for nitro-
benzene in oil of bitter almonds is as follows : — Treat
with zinc and dilute hydrochloric acid, filter, and add
solution of potassic chlorate. A mauve colour appears,
if nitro-benzene is present. — Benzoic aldehyde is easily
oxidised to benzoic acid (CgHg.COOH).

209. Benzoic Acid. — CeHg.CO.OH. Benzoic acid
is found in gum benzoin, in balsams of Peru and Tolu,
&c. It is also present in the urine of some animals.

Preparation. — 1. By sublimation from gum benzoin,
formerly the chief source of benzoic acid.

2. From hippuric acid (OgHgOgN), which can be ob-
tained in large quantities from the urine of herbivorous
animals. This, when boiled with a dilute acid, decom-

BENZOIC ACID.

, , 241

poses into benzoic acir? nr^.i -j

(NH.,CH,.COOH) "^-'o-a^tic acid, o. gl,.^,u

A considerable proportion of th , ''^■''^^•^««H.
".erce is derived from this soured ""='" "' »■"-

3- A good deal of benzoic ,^- 1 •

C,H,.0H3 + 30 = C,H..COOH + H O
also from naphthalene ^C H ^ .,• .
yields a dibasic acid, pkZi f' "'^"^ "^"ised,
This acid when heated wS £ -^ (C.H.fCOOH),).'
»oid and calcic carbonate 7 ""^^ "? '"*« ''e''»>io

OaO + C.H.(COOH).=Ca003 + o,H.COOH

«o *he cooler part, of the tubo" ttotlrf'"^'^ "^^""^
PilOPERTIES - A v.*

tahery needles, of arlllrdot\^^^^^^^ scales or
It dissolves easily in alcohol. ' at 121^ c.

Experiment 194— Tr^f^ J. ,
;-« quantity of wator^H j Tie? ! «'"» •'-«'i'= -M in a
T^»t with htn>ns. Heat a stju „ ^ '? ^"""^ 'he solution
■"■oa. "nd inhale the fuaea J"''*"''' »* henzoio acid on

Benzoates R

-e mostly solubler wltef " "°"°'"'"<'' =">" '^^ »alta

Experiment IQfJ— p«i^
porcelain dish witriit^n "7" Vt«™ »' '■"monia i„ a

242 SACCHARINE.

crystals of amnionic benzoate (NH^.C^HjOj) are left. It is
necessary to add a little ammonia from time to time during
evaporation so as to keep the solution alkaline. When salts of
ammonia are evaporating a little ammonia always escapes.

Animonic benzoate is used in medicine. When taken
into the system it is eliminated in the urine as hippuric
acid, rendering the urine strongly acid. — Sodic benzoate
(Na.CyHgOa) can be prepared in the same way as am-
monic benzoate. It is used as a medicine.

Experiment 196. — Dissolve in a little water the ammonic
benzoate prepared in Experiment 195. To a small portion of
the solution add dilute hydrochloric acid. Benzoic acid is pre-
cipitated. To another portion add neutral solution of ferric
chloride. Ferric benzoate (Fe.^Bzg) is precipitated. Examine
it carefully, noting its colour, &c.

Tests. — See last experiment.

210. Saccharine. CeH^ZgQ ^NH. {Benzoyl sul-

phonic imide. — This substance is related to benzoic acid.

Benzosidphonic acid has the formula CJjH^HgQ ^g. If

the two hydroxyls are replaced by the dyad radical
=NH, the formula for saccharine is obtained. — This re-
markable substance was discovered a few months ago by
Dr. Fahlberg,

Properties. — A white crystalline solid, " 220 times
as sweet as cane-sugar." It has antiseptic properties,
and is said to be harmless when taken into the system,
passing away in the urine unchanged. It is difficultly
soluble in cold water, more freely in hot water, in alco-
hol, and in ether. It is proposed to use it instead of
cane-sugar in cases of diabetes mellitus.

dALLW ACID

wijitergreen." It j. ^ ^^H ''), or " oil of

«" - •>, the oxidHt.ro'rzr '™"' '-"■•''°'- -"•. -

monobasic acid, p„„«,f,.,, ~./ gl"eosule._^^ i, „

-Pecta to carbolic acid,C: 'r' ""'!"■'"''<' '" --o
"ssoes. ' ""S "ot so injurions to the

212. Gallic Acid /-T^-i ,

K various barks, ic. «'"'°'*''''' *» oak-galls,

Preparation —Fm

listened with water"" T,T' "'''«" "- Powdered.

^'■egaliic acid is then di so v :~' A"^- « -«'^^'

P«oPERT,t-s._A ]i<,hf . * """'""S ^»t<"-.

dissolves in joo p,,,f ', J^f ' 7»tellme solid. It

>'''"<"•; it is f,.eely soln.l ' '' '" ^ ?"■•'» of hot

^'Kerineand in etir"Si- ^^ -« ^P-'ngl, t'

^«3ts.-,. With . ■ K """"'""•" ""'"•

"-k precipitate, .olallrjif ^<= """''"^ " «<- a Mue-
^•"<.oe.„otc„.,,.,3„,„ti„„,,,,^^„^^^_.^^^^ .

213. Tannic Acid n tt ^ ««• .

*'•* of gallic acid, !id Us :^'"^V .'""' " - ««%-

"^^-''^o -id b, ti. subsi^:?: ::r r ^™"' '^'

o,„. ^ nioJecuIe of water •

90 TT rx Tannic acid.

^C'HeO, - H,0 = c,,H, O

^PREPARATION -Fr

-'- 3 or 4 da,s andThef 'xt^rtf "' ^'"^■"^ «'- »

^^fci'tcfcing witli ether.

244 TERPEN ES.

pROPKKTiES. — A white or yellowish solid, of acid,
astringent taste, soluble in water, and in a nuxtiire of
water with alcohol or ether. — Tanidyi is the glucoside,
present in oak-galls, <fec., which produces gallic and
tannic acids by its decomposition. Glucose is formed
at the same time, and commercial tannic acid generally
contains glucose. Tannic acid forms gallic acid when
boiled with dilute acids.

Tests — 1. With aqueous solution of ferric chloride, ;i black
colour is produced (ink).

2. With ferrous sulphate, it slowly blackens.

3. Tannic acid coagulates solution of gelatine or white of
egg. This illustrates the process of tanning.

Note. — Tannic acid is a good local astringent, while
gallic acid is a remote astringent.

214. Terpenes. — CioHjg. These form a series of is-
omeric hydrocarbons found in pines, firs, and other trees.
— Turpentine is an oily liquid (like honey), which flows
from incisions in firs, larches, &c. When distilled it
yields " oil," or " spirits " of turpentine, and a rosin
(resin) which remains in the retort. Rectified oil of tur-
pentine is prepared by mixing the crude oil with caustic
soda and distilling it. It is a limpid, colourless liquid
of pungent smell and bitter taste. When exposed to
the air it partly volatilises and partly oxidises to resin.
It dissolves resins, and is hence used in preparing var-
nishes. — Resins are oxidation products of terpenes. Bal-
sams are similar compounds. Resins consist largely of
acids, and form soaps with alkalis. They are used in
soap-making.

CAMPHOR. 245

215. Oamphor.— Ci„Hi«0. Is prepared by distil-
ling camphor wood with water. The camphor laurel
grows in China and Japan.

Properties. — A white, crystalline solirl, melting at
175°. It volatilises slowly at ordinary temperatures.
It is slightly soluble in water (40 grains in a gallon),
freely in alcohol, and in oils. Specific weight -- 0.98. —
Liquid camphor, or camphor oil (CouH.tjO) is the essential
oil of the camphor laurel. It yiekls cami)hor wh.en oxid-
ised by exposure to air. — Borneo camphor {Q^^^^O) is
obtained from Dryobalanops camphora. " Oil of Borneo
camphor " (so-called) is in reality a terpene.

216. Oinnamic Acid— C6H5-CH=CH-COOH,

or CgHgOj. Found in liquid storax, and in balsams of
Peru and Tolu. It can be prepared by oxidation of
oil of cinnamon, which consists largely of cinnamic aide-
hyde (C^HeO).

217. Essential Oils {volatile oils) — The essential
oils are the substances which impart fragrance and
flavour to different parts of plants. They generally con-
tain compounds resembling camphor or turpentine, along
with ethereal salts of benzoic, cinnamic, and other a^-o-
matic acids. They are obtained from the leaves, flowers,
fruit, &c., of plants, by distilling with water, or by ex-
pressing. Oil of cinnamon and oil of cloves are good
examples.

Experiment 197. — Distil some ground cloves with water and
obtain oil of cloves. Receive in a cold t. t.

246 INDIGO.

218. Indigo Blue (IndigotinJ.—CiJJ^^'N.fi^. Pre-
pared from certain plants which contain a glucoside,
indican. This yields indigo when fermented and oxid-
ised by the air. Indigo is also made artificially by a
complicated process, including the formation of cinnamic
acid.

Properties. — A dark blue solid, insoluble in water,
in dilute acids, alkalis, and ether ; but soluble in parafiin
oil and in hot alcohol. When indigo is heated it vola-
tilises, forming a beautiful purple vapour. If it is pure
(as it rarely is), there is no residue. — Indigo is soluble
in concentrated sulphuric acid, forming sulphindylic, or
sulphindigotic acid. A dilute solution of this is used as
a test for nitric and chloric acids, which oxidise it and
destroy the colour. — Indigo is reduced to indiyo white
by green vitriol and other reducing agents. Indigo
white is soluble in water, a very important fact for the
dyer. Calicos, &c., are printed or dyed vdth the colour-
less solution of indigo white and then exposed to the air.
The oxygen of the air unites with the ind'go white
forming the insoluble indigo blue, and thus a fast colour
is produced. — Indigo is often adulterated with Prussian
blue, which leaves a bulky reddish residue when heated.

Experiment 198. — Heat a little indigo i 1 a porcelain dish or
on mica.

Exporiment 199- —Try to dissolve a little indigo in water.
Add some solutions of ferrous sulphate and caustic soda, and
heat. Steep a piece of white cotton in the solution and expose
it to the air for some time.

219. Naphthalene.— CioHg. Naphthalene is related

GLUCOSIDES. 247

to benzene in the manner indicated by the structural
formula :

1 1

H-

-0

1 II

C-

-H

H-

1 II

-c ■

C-

-H

' c

1' ' ■ ■

It is prepared from the heavy oil of coal-tar by frac-
tional distillation. — It is a colourless solid, crystallising
m thin plates. It melts at 79°.2 and boils at 216°.6.
It is insoluble in water, but soluble in alcohol. When
oxidised it yields phthalic acid, C6H4(COOH)2, from
which benzoic acid is manufactured.

220. Anthracene. — Ci4Hio. Is also obtained from
the heavy oil of coal-tar. It is the starting point in the
preparation of alizarin, or artificial madder.

221. GluCOSideS. — These are substances found in
plants, which readily undergo fermentation, with a glu-
cose as one product. The other products of the fermen-
tation are various, but generally an aldehyde or an alcohol.
The ferment is present in the same plant with the glu-
coside, but appears to be enclosed in separate cells, and
thus does not set uj) fermentation until the cells are
broken down by grinding, <fec.

1. Amygdalin has bee.u tJready described (Art. *^'jS).

248 SALICIN — DIGirALIN.

2. Salicin (CigHigO^). Found in willow bark and in
poplar leaves and bark.

Preparation. — Boil willow or poplar bark with milk
of lime, filter, decolourise with bone-black, evaporate the
filtrate to dryness, and extract the salicin with alcohol.

Properties. — A white solid, soluble in alcohol ^nd
in hot water, but not in ether. It dissolves readily in
solutions of alkalis or of alkaline carbonates.

Experiment 200. — Boil a little salicin for some time with
water and a few drops of sulphuric acid, and then test for
glucose.

When salicin ferments, it unites with water, thus form-
ing salicylic alcohol and dextrose :

CisHisO^ + Ha^ = ^6H4{cHaOH + CeHiaOg.

Experiment 201; — Dissolve a little salicin in solution of
potassic carbonate. Neutralise with hydrochloric acid. The
salicin is precipitated.

A solution of salicin with potassic carbonate is said to
be valuable in cases of diabetes.

Tests. — 1. Mix on a porcelain plate with concentrated sul-
phuric acid. A red colour is produced.

2. See Experiment 200.

3. Heat with potassic bichromate and dilute sulphuric acid,
and observe the odour of salicylic aldehyde. It is like that of
heliotrope.

3. PiGiTALiN. — A mixture of several glucosides. It is
the active principle of foxglove. When boiled with dilute
acids it yields glucose and digitaliretin. — Digitalin is a
white, inodorous solid, of very bitter taste. It is almost

ALKALOIDS. 249

insoluble in water and in etber, but soluble in alcohol
and in acids. It leaves no residue when burned. It is
poisonous, one-sixteenth of a grain being sometimes fatal.

Test. — Mix with weak aqueous solution of dried ox-bile, and
add concentrated sulphuric acid. A deep red colour is formed.

4. Jalapin (C^HggOie), glycyrrhizin [Q^Jln^O^), and
hellehorin {Q.2^^^0^^ are glucosides found in jalap, liquor-
ice, and the hellebore respectively. — Cerehrin is a gluco-
side present in the brain and other nervous tissues.

222. Alkaloids. — As the name implies, alkaloids are
substances having the properties of alkalis, i.e., of the
volatile alkali, ammonia. They are, in fact, amines the
molecules of which are of complex structure and in
most cases not yet known. They are for the most part
products of vegetable growth. Their names are gen-
erally derived from those of the plants from which the
alkaloids are obtained, the terminations -ine and -ia
being used interchangeably, e. g., strychnine, or strychnia,
derived from Strychnos nux vomica. — The alkaloids all
contain nitrogen, and many of them oxygen, in addition
to carbon and hydrogen. Those whicli contain no
oxygen are mostly liquids, which clxi be distilled ; those
containing oxygen are crystalline solids and cannot be
distilled. Most of them are insoluble, or sparingly
soluble, in water, but unite with acids to form soluble
salts. The alkaloids dissolve in alcohol, ether, chloro-
form, benzene, &c. Their tas';e is generally intensely
bitter. — They are usually extracted from the plants with
water or dilute acid ; and the solution is then decom-
posed with an alkali. The volatile alkaloids are dis-
tilled, while the solid ones are filtered off.

250 MORPHINE.

General Tests. — 1. All alkaloids give a precipitate with
phoaphomolybdic acid.

2. All alkaloids give a precipitate with solution of potassic
mercuric iodide (Hgl2.2KI).

3. Most of the alkaloids give a precipitate with potassic
iodide solution of iodine,

223. Volatile AlkaXoida.— Conine (CgHi^.NH) is

the active principle of poisonous hemlock {Gonium macu-
latum). It is a colourless liquid, boiling at 168° 0. It
dissolves in 100 parts of water, forming a strongly alka-
line solution. It unites with acids, forming salts, e.g.,
C8Hi4.NH2Cl. It is a narcotic poison. — Nicotine
(CioHi4N2) is found in tobacco, from which it can be ob-
tained by distilling with solution of caustic potash. It
is a narcotic poison.

224. Morphine. — C17H19NO3.II2O. This is found
in opium, associated with narcotine and other alkaloids.
It is combined with meconic acid.

Preparation. — The meconate is dissolved out with
water and treated with solution of calcic chloride. Mor-
phine chloride remains in solution while calcic meconate
is precipitated. From this solution the morphine is pre-
cipitated by ammonia.

Properties. — A white crystalline solid, insoluble in
ether, sparingly soluble in water and in cold alcohol,
and soluble in hot alcohol and in dilute acids. It unites
with acids, forming crystallisable, soluble salts. The
chloride (hydrochlorate, or muriate), sulphate, and acetate
are used in medicine. — Morphine and its salts are nar-
cotic poisons.

QUININE — CINCHONINE. 251

Tests. — 1. If solid, add a little water ; if liquid, evaporate
nearly to dryness. Stir with a drop of neutral ferric chloride
solution. A dirty blue colour appears.

2. Moisten the solid substance with strong nitric acid. It
gives a bright orange-red colour.

225. The Alkaloids of Peruvian Bark (Cin-
chona).

1. Quinine (CaoHj^NA-SHaO). The alkaloid itself is
a wliite, crystalline powder. It is sparingly soluble in
water (1 in 900), but easily soluble in alcohol and ether.
The solutions have an alkaline reaction. Sulphate of
quinine is the salt generally used in medicine, but pre-
parations of citrate and chloride are also used. The sul-
phate is only sparingly soluble in pure water, but dis-
solves readily in water containing sulphuric acid (a solu-
ble acid salt being formed).

Experiment 202. — Try to dissolve quinine or quinine sul-
phate in water. Add sulphuric acid. Note the fluorescence of
the solution.

Experiment 203. — Add an alkali to a solution of quinine
sulphate. What is precipitated ?

Quinine and its salts are antipyretic (lower the tempera-
ture when taken internally) ; and also antiperi -lie (pre-
vent the return of periodic fevers, <fec. )

Test. — Add chlorine water and then a considerable quantity
of ammonia solution. A bluish-green colour appears. If potas-
sic ferrocyanide be added before the ammonia, a red colour ap-
pears for a moment, but soon fades.

Note. — Quinine and its salts are sometimes adulterated with

salicin.

2. CiNCHONiNE (C20H24N2O) is less soluble in alcohol
than quinine, and is thus separated from it in the process

252 STRYCHNINE — COCAINE.

of preparation. It is similar to quinine in its properties,
but is insoluble in ether. It is not so good a febrifuge
as quinine.

Tests. — Cinchonine does not give the greenish-blue colour
with chlorine water and ammonia. It is sometimes used to
adulterate quinine. To detect it, make the following test ;
'* Into a glass tube or bottle put ten grains of the suspected salt,
dissolve in 10 minims of dilute sulphuric acid, and 60 minims of
distilled water ; to this add 150 minims of pure ether, 3 minims
of spirits of wine, and 40 minims of a solution of soda (1 of
caustic soda in 12 of water). Agitate well and set aside for
12 hours, when, if the slightest trace of quinidine or cinchonine
be present, they will be seen at the line of separation between
the ether and the solution of sodium sulphate."

3. Quinidine, cincbonidine, &c., are other alkaloids
found in Peruvian bark.

226. Strychnine. — C.^iH.,2N202. Is found in Strych-
no8 nux vomica, along with hrucine (C23H26N2O4). —
Strychnine is a white crystalline solid, sparingly soluble
in water and intensely bitter in taste. It is soluble in
spirits of wine, but not in absolute alcohol or ether.
The solution generally used in medicine is made with
hydrochloric acid, rectified spirits, and water. It is
very poisonous.

Tests. — 1. Dissolve the solid in pure sulphuric acid and atir
with a drop of potassic bichromate solution. A violet colour is
produced, which soon changes to red and yellow.

2. The solution, when treated with hydrochloric acid and
mercuric chloride (HgCla), gives a clotted white precipitate.

3. Pure strychnine gives no colour with nitric acid. Brucine
is turned deep red.

227. Cocaine. — Ci7HoiN04. Obtained from cocoa
leaves {Erythroxylon coca). The hydrochlorate (C17H21

ARTIFICIAL ALKALOIDS. 253

NO4.HCI) is used as a local ancesthetic. When a little
of it is put into the eye, it causes insensibility to pain in
tlmt part, and operations can thus be performed without
administering chloroform or ether.

228. Atropine, (C17H23NO3), and hyoscyamine

(C15H23NO3), are poisonous alkaloids found in common
plants ; atropine in belladonna, the thorn-apple, <fec., and
liyoscyamine in henbane,

229. Artificial Alkaloids. — Several antipyretic

alkaloids have lately been made by synthesis from coal-
tar products. Tht^y promise to be very valuable as
medicines.

1. Kairine (C10H13NO) is made from aniline by a
series of rather complicated reactions. It unites with
acids to form soluble salts. The chloride (C10H14NO.CI)
is sold as a substitute for quinine. It lowers the tem-
perature in fevers, but this action is only of short con-
tinuance. On the other hand, it has none of those un-
pleasant effects associated with the antipyretic action of
quinine. :

2. Antipyrine (CnHioNoO) is also manufactured from
aniline as a starting point. It is a powerful antipyretic,
but not antiperiodic. It is a white, tasteless, odourless,
crystalline solid, easily soluble in cold water. It is used
uncombined with acids.

3. Thalline (C10H11NO5), a recently discovered arti-
ficial alkaloid, is said to be a specific for yellow fever.

There are many alkaloids prepared from coal-tar, the
physiological actions of which have not been investigated.
The results already obtained show the fruitfulness of a

254 ALBUMINOIDS.

combination of the chemist's investigations witli tliose of
the physician. An illustration of the necessity for tliis
is the fact that cocaine was known ten years before the
peculiar power of its hydrochlorate was discovered.

230. Albuminoids, or Proteids. — These are
nitrogenous substances of a very complex character.
They are the basis of all living matter. They are
similar in composition, but vary slightly. Tlioy contain
carbon, hydrogen, oxygen, nitrogen, sulphur, aiid, gen-
erally, phosphorus. Their percentage composition is as
follows :

Carbon from 51. 5 to 54. 5

Hydrogen. .
Oxygen ....
Nitrogen.. . .

Sulphur

Phosphorus.

6.9 " 7.3

20.9 " 23.5

15.2 " 17.0

0.3 '' 2.0

0.4

The proteids are built up by plants out of the simpler
compounds which form their food. Animals have no
power of synthesising I .^m, and must therefore obtain
them ready-formed from plants.

Experiment 204. — Beat ^^p the white of an egg with water,
allow the solution to settle, aiid pour off the clear liquid. Heat
a small quantity. It coagulates before it begins to boil. Try
another portion after adding a little caustic soda. Test other
portions with nitric, hydrochloric, and sulphuric acids, and with
alcohol ; also with acetic and tartaric acid. To another portion
add a very small drop of cupric sulphate solution and then a
large quantity of caustic soda. A purple colour is produced.
This reaction is characteristic of proteids.

Experiment 205. — To small quantities of the solution of
white of egg add solutions of plumbic acetate, cupric sulphate.

QUESTIONS AND EXERCISES. 256

and mercuric chloride (corrosive sublimate). Collect the pre-
cipitates on filters, and wash them three or four times by pour-
ing distilled water on them. Then pour a little ammonic sul-
phide solution on each of them. Tney are blackened, showing
the presence of the metallic salts. This explains the action of
white of egg as an antidote.

Proteids are all colloid substances, and have very little
power of passing through animal membranes. Hence,
albuminuria indicates something radically wrong in the
kidneys. — Many proteids are soluble in pure water, but
others require a small quantity of sodic chloride to keep
them in solution. After they have been coagulated,
they can be dissolved by the action of dilute acids
aided by a ferment, as in the process of digestion. Al-
kalis keep in solution many proteids insoluble in neutral
or acid solutions. Thus milk, naturally alkaline, coagu-
lates when it becomes sour. — Proteids are very unstable
chemical compounds, readily undergoing fermentations
and other chemical changes.

QUESTIONS AND EXERCISES.

1. Compare the preparation of benzene with that of marsh
gas,

2. Explain the action of milk of lime in purifying oil of bitter
almonds.

3. Write the formulas for chloride, sulphate, and acetate of
morphia. (Its molecule is equivalent to one molecule of am-
monia).

4. How would you test for salicin in a specimen of quinine ?

5. How would you distinguish between specimens of morphine
and brucine ?

6. Calculate the percentage composition of acetylene (CgH,),
and of benzene (CgHg).

7. Is carbolic acid a true acid ? (Note . — Ethyl alcohol forms
alcoholates, CgH^ONa, &c.)

25.6 SILICON.

8. The flowers, &c., of the Cherry Laurel contain amygdaliu.
Is that plant poisonous ?

9. What is the relation of saccharine to benzoic acid ? Would
you expect it to be nutritive ?

10. Why is indigo-blue reduced to indigo- white in dyeing?
How is it re-oxidised ?

11. Indigo is ^.ften adulterated with Prussian blue. How
would you detect this ?

12. How would you make an aqueous solution of quinine
sulphate ?

13. A specimen of urine gives a white precipitate with strong
nitric acid. What is the cause of it ?

CHAPTER XV.

SILICON AND BORON.

231. Silicon (Si^^ = 28).

Occurrence. — The greater part of the earth's crust is
made up of compounds called silicates, composed of sili-
con, oxygen, and metals. Silicon is never found free in
nature, but always in the form of silica (SiO^), either
uncombined (sand, quartz, &c.), or combined in silicates.
Minute traces of combined silicon are present in the
urine, blood, bones, (fee, of man.

Preparation. — By heating potassic Jluosilicate
(KoSiFfi) in iron tubes with potassium or aluminium.
When potassium is used, the silicon is obtained as an
amorphous powder ; with aluminium, it crystallises :

2KF.SiF4 + 4K = 6KF + Si.

Properties. — Two allotropic forms, one crystalline,
the other amorphous. There is perhaps a third form

SJUCON DIOXIDE.

»e.nWes carbon in ife chen.ic-d I. ' '^^ ^"''=»" 'o-

-"' hy.l.ogen, chlorine bZ^T'^- '^""'Vonu,.
'';"■""«' -i"- ...eti,ane, 'a^cTsin' ""*'A:<""« «- '"•own,
;- mo., ccnpiicto;. con,foi,''^.V, ''^'■'' «"'>

«'ieon seems able to replace cIX„! ^ '^^'" '^"•^'- "'"'
"'■■'»y organic compound, •'' ""'•''''" "^'o-'t in

232. Silicon Dioxide _^,n

".":' '^''h'lrous sUicic acid T • '^''° """'"' "««,
silicon knoH-a. ' ^' '^ «'« only oxi.le of

«»'. J-per, cbalceC diatl " '?"'" ^^"''' '^''^<-
^«"- Uniee. with L : S oT ' f r "" '- ''-
*o «.-eat .iWson of minerals, S i~' ^'-'^ ^orms

-TilOPERTlES .P

'mating .*V«'«oJ";HroT-r' ft'' "'"-'-'"' by

»'«oh,ble in water and in : ,' \ ''«■"' ^^^ Powder^

(«^)- /^ « easily i ,:^' Xr ""''' '^''"•^'"'-

ft decomposes sodic carbonatf k'' "'"'" '" """"onia.

-- dissolved in water rsoli^'V''^^'^'' "''' ''

■■■'loa are used in glass and ,0 "°"' ^orms of

-H- and cemenl; o, ;e,„rr"f"*""' '" ""-"^
'--- pestles used if t:LSingt::tiS;-

000 rM.,. .

233. Silicic Acid and Silicates.

Experiment 206.-Fnse a litti ,

258 SlLIClC ACID.

weight of anhydrous sodic carbonate (Na.^COg). Coutinue
heating tintil a clear li(|uid is obtained. Pour this out on a
piece of clean iron, and, when it has cooled, break it up and dis'
solve it iu water by boiling for some time.

Tn tliis oxperiment ftodic silicate (NsiySiO.,) is formed :

NaaCOg + SiOj = NaaSiO^ -f CO2.
(Have you observed the escape of the carbon dioxide 1)

Experiment 207. — To a little of the solution of sodic silicate
add dilute hydrochloric acid ; collect the gelatinous precipitate
on a filter and wash it with hot water. It is silicic acid. Heat a
little of it on mica and obtain silica. Try the solubility of silicic
acid iu alkalis, and in acids. Write the equation for the de-
composition of sodic silicate by hydrochloric acid.

Silicic acid has not been obtained of any definite com-
position free from water. There are numerous classes of
silicates, corresponding to a great number of theoretical
acids; e.g., ortho-silicates, salts of an acid, H^SiO^; and
meta-silicates, from HoSiOa. — Silicic acid is insoluble in
water, but an unstable solution, which easily gelatinises,
can be obtained by careful manipulation (compare dia-
lysed iron). — The silicates of the alkalis are soluble in
water (soluble glass) ; all other silicates are insoluble.
Mica, felspar, garnet, serpentine, and clays, are exam})les
of natural silicates. Felspar is a double silicate of
aluminium and potassium. By the action of air and
water it is decomposed into potassic carbonate and hy-
drated aluminium silicate, or clay. In this way a fertile
soil is gradually formed by the " weathering" of felspar.—
The silicates are most conveniently represented as com-
posed of oxides of metals united with one or more mole-
cules of silica, e.g., Na-P.SiOa, 3Mg0.2SiO.^, &c.

""- "f silict.,. ,f the'.;, t- r^'"';"'', '--Pi'-.te wit,, ,„,„.
''^' '"»'«! for. " "'■"•"'J' «i'l. "ilica nee.l not

234. Fluosilicic Acid.-H,8iF,

;''h about t..o;t,S"r;,tf!rr^'"'"" '^'■■'^ -" '

Wio mixture i„ a t. t. or (Usk '^7"'-'^'''' ./''""• »/«»■ (Oap , ,,
--it. a„„ .nunciatei/t;^;--;- strong -■•"■urL „!

» t; t. h»lf-full of water. h1 I ^"^ """ '''l'P"'« '"to

:7'r"' '""•'"- through the : Lr: ^- , ^"."'vi^iwo t-... i,

3..i«ta„eo. Collect s,„„e of this a^ '1,™* ' """'"' " ""''y "''ito
;;■' to « li«l.t white „„waer. U^J^^ "V" '"""• ^' ''"-
the water.-The .lelivery tube In Tl "" "" ■''''"•tion of

experiment must then eea,,e. "°°'"°' °'"'''«' "P. »...! the

Jn tins ex|>eri,„ent, three chemical -.cti . ,
- -presented b, the following e^'uiC '' ''''""'

2 t^abO, + 2HF.

Silicon

(2)4HF + sio *«*^"";--ie.

OrthoHilcic pi„ ....

/Qj Qcj-n . acid *'»').silicie

(^; 3S1F4 + 4H2O = H 4^ . "'"'•

■' . the end „f th„ experi,ne u « - b1 «r"" "'^ "'"^
»■'- acid, ablution of ..osiJLcS^i^ilir"-

"itOPERTfES -A f

Ao«W., a're soluble i"ln?'t "''• *^°^' "^ *«

(K=siF,, and wi::.r;; ;;~/«-

I ^aoii^ ^ ) are only sparingly

'260 BORON — nonic ^cin.

soluble. For this reason fluoKilicic acid is used to sepa-
rate these metals froui others present v/ith them in solu-
tions. — i'Y^^osilicic acid is silicic acid with fluorine instead
of oxygen^ 6 atoms of fluorine replacing 3 of oxygen.

235. Boron (B'» = 11).— The chief compound; of
this element occurring in nature are borax {N'a,.J^^O^.
ICH.^O), and boric, or boracic, acid (H^BOg). Borax is
found principally' in the plains of Thibet, and in the
borax lakes of California. Eerie acid issues along with
steam from fissures in the sides of volcanic hills in Tus-
cany. — The element, boron, is of little importance. It
can be pre}>ared by methods similar to those used in the
preparation of silicon, which element it resembles in its
properties.

236. Boric Acid. — H3BO3. Derived from the la-
goons of Tuscany, into whicli tiie boric acid comes from
volcanic fissures or from holes bored for the purpose.

Prkparation. — The water of these lagoons is evapo-
rated by the heat of the steam which issues from the
earth, until tiie acid crystallises out. The crystals are
collected, dried, and purified by recrystallisation. Before
tJie discovery of the presence of borio acid in the Tuscan
lagoons, it was prepared fr&dti borax, by treating a hot
saturated solution with strong hydrochloric acid. T^e
boric acid crystallised out on cooling :

iNaaB^O^ 4 2HC1 -j- 6H2O - 2NdCl -j- 4H3BO3.

Since tli*- discovery ol' the borax lakes of California, buiic
ac'l is again made in this way .

BORAX.

261

■txperiment 209— Dissn]u»

a P<>.-cdaiu ,lish a.ul set (ire t„ it I 'f »'™l""'c mhM.m i„to

fame Boric .aci,, volatilise., with aklt, '^''•°" "'""'"' "' "«'
t"e hot flame. i,„parti„g the 1" , ' "'"' '" ''"-"I"«-l in

^.ueous solution, an., tr/its actfor; hi;;:",;::;'- -"""'= ""•

r-entad a. co,„pou,.cI« of" r^""' V "" '"' ■"■
«'io«*, e.g., 3Mg0.4B.,0.. ''^''''''' ^'"^ *<"«»

"".s the borax of co:n„,erce !!^ 'I '"'"''• ^™'"

«™-oH,,ofg.e.j;zrre:r;2:r""7^

4H3BO3 + Na^CO, = N. R n .

-TROPERTIES.— Bor V -o ^

::--"••- -,.io.n. ,,,- ^---. J

262 TESTS FOR BORIC ACID.

Experiment 212. — Heat a small piece of borax in a dry t. t.
Water condtMi.ses in the tube (Whence has it come?), and the
borax swells up. Heat a little borax on a platinum wire, until
it fuses to a clear bead, then allow it to cool, moisten it, touch
it to some powdered cupric sulphate, fuse it again, and note the
colour when it has cooled.

When borax is heated, it loses its water of crystallisa-
tion, and, if tlie temperature is high enough, fuses to a
clear liquid. At high temperatures the borax bead dis-
solves metallic compounds, forming borates which give
characteristic colours to the beads. Borax is used in
this way to test small quantities of solid substances.
— Borax is soluble in glycerine;, and a glycerine of borax
is used as a lotion and gargle.

Tests for Boric Acid and Borates.— 1. Mix the sub-
stance with strong sulphuric acid and alcohol in a porcelain dish,
and set the alcohol on fire. It burns with a green Hame. Or,
fuse some of the substance on a platinum wire, moisten it with
strong sulphuric acid or glycerine, and hoM it in the Bunsen
flame. It gives a green colour to the flame.

2. Acidify the solution with hydrochloric acid, dip in it a
strip of turmeric jyaptr, and dry the paper at a gentle heat. It
is turned brown.

3. Add a few drops of ])aric chloride (BaCla) to a solution of
a borate. A white precipitate is formed. It is ,olubI'> in
hydrochloric acid.

QUESTIONS AND EXERCISES.

1. Compare silicon and carbon, (a) with regard to chemical,
and (b) with regard to physical, properties.

2. What is soluble glass ?

3. Explain the term jlnosilicic, acid.

4. Balance the following ecpiation :

K.,SiFe + Al = KF + A1.,F., + Si. -

METALS. 263

5. It is found that alkaline solutions eat away glass. Explain.

6. Mention an acid and a base which will dissolve sand.

7. How can it be proved that silica is an acid-forming oxide ?

8. With what does the delivery- tube become choked up in
Experiment 208 ?

9. Boric acid (H3BO3) is tribasic. Write the formula for
normal sodic borate. Is this the ordinary salt ?

10. Borax is an acid salt, and yet its solution is alkaline.
Account for this.

11. How can borax be used to test for glycerine ?

12. In the preparation of boric acid from borax, sodic chloride
is formed. How is the boric acid separated from it ?

CHAPTER XVI.

THE METALS.

238. General Ohaiacters. -Tho only charactei-
istic common to all metals is the power of taking the
place of the hydrogen of acids to form salts, or in otlier
words, the power of forming bases. But most metals
have a bright and peculiar appearance called metallic
lustre ; as a rule, they are specifiically heavier than
water ; they are good conductors of heat and electricity ;
and most of them are malleable and ductile.

239. Ores of Metals. — The noble metals (i.e., the
least oxidisable) are generally found uncombincd
(native) ; native copper also occurs. Sometimes the
baser metals are found free ; but in most cases they occur
combined with other elements, from which they are
separated by the processes of metallurgy. Common
metals such as lead, iron, tin, ikc, are found very gener-

2G4 METALLURGY.

ally as sulphides and oxides. In many cases salts of
the metals are found in nature. If the metals of the
alkalis be excepted, it may be stated as a general rule
tliat metallic ores are insoluble in water. — The processes
by which metals are obtained from tlieir ores are various.
A common way, applicable to oxides and some oxygen
salts, is to heat to a high temperature with some form of
carbon (coal, charcoal, &c.). In many cases sulphides
are first roasted to convert them into oxides, and then
reduced by means of coal or charcoal. In other cases
sul[)hides are partially oxidised at a comparatively low
temperature, and then heated to a higher temperature, at
which the oxygen and remaining sulphur combine, set-
ting the metal free. Lead and copper aie obtained in

this way :

(1) PbS + 30 = PbO + SO2.

(2) PbS -f- 2PbO = 3Pb + SO2.

1. Metals reduced by heating the ores with coal, char-
coal, &c. : Na, K, Rb, Sn, Cd, Zn, Fe, Mn, Sb, Cr, Ni.

2. By pa7'tial oxidation arid subsequent Jusiori : PI),
Cu, Bi.

3. By heating with sodium or potassium : A), Mg, Ca,
Be.

4. By electrolysis of fused salts : Ba, Ca, Sr, Li, Cs.

5. By distilling in a current of air : Hg.
G. Native : Cu, Ag, Au, Pt, Hg, &c.

This is only a general statement, and not intended to
be exhaustive.

240. Alloys. — Metals usually combine with eacli
other when fused together. In many cases the combina-

ALLOYS. 265

tion takes place in definite proportions, and chemical com-
pounds are formed. In other cases, the proportions may
be varied, and it is not easy to decide whether or not there
is any chemical action. Compounds of metals with each
other are called alloys. The properties of alloys are not
the mean between those of the metals present. Alloys
generally melt at lower temperatures than any of the
constituents. Thus, Rose's fusible metal (tin, 1 [)art ;
lead, 1 part; and bismuth, 2 partS) melts at 1)5° C. ;
while tin melts at 235°, lead at 334°, and bismuth at
270°. Many alloys are in common use, e.g.

Solder, tin and lead in various [)roportions. «

Brass, 65 parts zinc, and 137 parts coppcu-.

Gold coin, 1 1 parts gold and 1 part copper.

Silver coin, 40 parts silver and 3 parts copper.

Gun metal, 9 parts copper and I part tin.

Bell metal, 4 parts copper and 1 i)art tin.

Type metal, 4 parts lead and I part antimony.

Briti rmia jnetal, copper, zinc, tin, antimony.

Pewter, 4 parts tin, and 1 part lead.

Bronze, tin, copper, and zinc.

German silver, 5 parts copper, 2 parts nickel, and 2
})arts zinc.

Wood's fusible metal (melting at G8°), 8 parts lead, 5
[)arts bismuth, 4 parts tin, and 3 parts cadmium.

Amalgams are alloys of mercury with other metals.

241. Compounds of Metals.— The compounds of
metals are classified into (1) binarif compounds, including
oxides, sulphides, chlorides, bromides, iodides, fluorides.

266 OXIDES OP METALS.

(fee. (Note the ending — ide) ; and (2) oxygen salts, ttc,
such as sulphates, sulphites, nitrates, phosphates, <fec.

242. Oxides of Metals. — Each metal has at least
one basic oxide ; several have acid-forming oxides ; and
many have oxides which are neither Vjase-forming nor
acid-forming, hence called indifferent oxides.

1. Basic Oxides. — These may be classified as follows:

(a) General formula MX> : — Li.^O, NaaO, KgO, Rb.^O,
Cs^O ; Ag,0, Hg,0, Cu^O ; Tl^O, Au,0. .

(b) General formula MO ;— CaO, SrO, BaO ; PbO,
HgO, CuO, SnO; FeO, MnO, ZnO, NiO, CoO, CrO ;
PtO, &c.

This includes nearly all the basic oxides (the rarer
metals being left out of consideration). — It will be
observed that some metals have more than one basic
oxide. Some dyad metals (Hg, Cu) have oxides in
which they seem to play the part of monad metals.
There is reason to believe, however, that the molecules of
the corresponding chlorides must be represented as fol-
lows: HgjClj, and Cu^Cly. The metals must, then, be
dyad in these compounds, and the structural formulas

Hg\ Cu .
for the oxides and chlorides are | O, \ ^O, and

Hg— CI Cu— CI

I , I . — Gold and thallium are monad and triad.

Hg— CI Cu— CI

Thus gold forms aurous oxide, AugO, and auric oxide,

AujOg. — Iron, cobalt, and manganese, have two basic

oxides, e.g. ferrous oxide, FeO, and ferric oxide, Fe,,0;,.

In the lower oxides these metals are dyad. The specific

OXIDES OB^ METALS. 267

weight of ferric chloride in the gaseous condition shows

Fe/S

tiiat its forniuhi is Fe.^Clg, or grapliicallv | >^{ . Ferric

' Fe { ci
Ici

Fe =0

oxide must then be represented as | ^ O, and in the

Fe =0

ferric compounds iron is tetrad. So witli m^inganose,

cobalt, aluminium, and cliromium, which have also basic

sesquioxides. The first group of sesquioxidos, Sb.jO;), (kc,

correspond to chlorides, SbCl.,, &c., so that the metals

must be represented as triad, e.g. O — Sb - O - Sb = O. —

There are hydroxides corresponding to most of the basic

oxides.

2. Acid-forming Oxides. — The basic oxides of imper-
fect metals, such as antimony, have also weak acid charac-
ters ; but there are also distinct acid-forming oxides of
tliese metals, e.g. antimony pentoxide, Sb.^Oj. Chromium,
manganese, &c., also form acids. The acid- forming oxides
always contain a greater proportion of oxygen than the
basic, and, as a rule, readily give up their oxygen to
reducing agents, becoming transformed to basic oxides.

3. Indifferent Oxides, — These are such oxides as
manganese dioxide (MnO.^), having neither acid nor basic
properties. They generally contain a greater proportion
of oxygen than the basic oxides, and are hence often
called joer-oxides.

243. Sulphides of Metals. — These correspond
closely to the basic oxides of the metals, e. g., LigS, Na.jS,
&c. The imperfect metals have sulphides corresponding
to their acid-forming oxides, e. g., Sb.^8-, SnS.,, ifec. As a

268 CHLORIDES, etc. — OXYGEN SALTS.

rule, wlien a basic oxido of a motal is soluble in wat(!i',
the corresponding sulphide is also soluble, — and so for
insolubility. Thus, both the oxides and the sulphides
of lithium, sodium, potassium, &r., are soluble in water.

244. Chlorides, &C. — There are chlorides corres-
ponding to the basic oxides of the metals. In writing
the formulas of chlorides, it must be remembered that 2
atoms of chlorine replace 1 atom of oxygen. Thus,
given the formula of aluminic oxide, Al.^Og, the formula
for aluitdnic chloride is written, Al^Clg. It could be
written more simj)ly, AICI3, but, for reasons similar to
those stated above for ferric chloride, the simpler formula
is doubled. The formula for bismuth trioxide is Bi-.O^;
replacing O3 by CIj, we get as the formula for the chlor-
ide, Bi.,Clg, but its specific weight in the gaseous state
shows that its molecule contains only half the number of
atoms represented here, so that the formula for bisinuth
trichloride is BiClg.

245. Oxygen Salts. — The oxygen salts of the
metals have been already noticed along with the various
acids. To derive the formula of an oxygen salt from the
formula of an oxygen acid, it is necessary to know the
atomicity of the metal, and, also, whether or not two
atoms of the metal play the part of a single atom as in
the case of mercurous salts (Hg._,(N03)2, tkc), and the

ferric, salts (Fe.2(N03)o, tfec). For example, given the
formula of sulphuric acid as H.2SO4, and knowing the
at micity of calcium to be 2, it is easy to write the for-
mula for calcic sulphate, viz,, CaS04. Again, bismuth
is triad ; and, therefore, 1 atom of bismuth replaces 3 of
liydrogon. In order to replace the hydrogen of su!

ANALYSIS — PKECIPITATION. 2G9

pliiiiic Jicid by hisinuth, vo must take SPLSO^. The
G iitoms of hydrogen ai( ;quivalent to 2 of bisinutli ;
and, tlierefore, the formula for bismuth sulphate is
Bio(S04):5. The atomicity of iron in the ferric salts is 4,
but 2 atoms of iron are united in the molecules of ferric
salts so that their joint atomicity is 6 ; i.e., Fe., replaces
6H. The formula for ferric sulphate is thus Fe._,(S04)3.
— To many oxygen salts there are corresponding sulphur
salts, e.g., K2CS3.

246. Classification of Metals — Analysis. —

The method of classification to be adopted here is that
which is employed in the jn'ocess of examining unknown
substances to discover the elements of which they are
composed. These processes constitute analysis in the
broad sense of the term. The substances are not always
— indeed, not generally — decomposed into their ele-
ments, but such evidence is obtained as enables the ana-
lyst to be certain of the presence of the elements. This
is qualitative analysis. If the quantities of the elements
in a compound, or the quantities of the elements and
compounds in a mixture, are to be determined, this is
clone by quantitative analysis. A great deal of the work
in both qualitative and quantitative analysis consists in
preparing insoluble compounds of the metals (and acids)
by precipitation from solutions. In order to understand
the operations of analysis it is necessary to know the
solubilities of chemical substances. Such knowledge is
also of great importance to the prescriber of medicines.
A physician who is not well acquainted with this part of
chemistry is very likely to produce '' muddy mixtures."

Precipitation. — When two chemical compounds are
brought together in solution, there is usually chemical

270 CLASSIFICATION OP METALS.

action, consisting in exchange of parts of tlie molecules.
If this exchange causes the formation of an insoluhle
substance, the latter is precipitated, or thr'own to the bottom.

Experiment 213. — Mix solutions of cupric Huliihatc. (Cu8(),)
and baric chloride (BaCla). A white precipitate of Itaric ml-
phate (BaSO^) falls, while cuprir chloride (CuClg) remains in
solution.

Such a cliemical action is called a double decomposition,

because the two salts decompose each other, the metals

changing places :

CuSOJ _ (BaSO^
Bad, I ~ |CuCl.,

Group Reagents. — Insoluble compounds can gener-
ally be obtained by precipitation. We have seen in
studying groups of compounds, such as chlorides, sul-
phides, carbonates, &c., that each group may be classified
into (1) soluble, and (2) insoluble. Thus, there are three
insoluble chlorides (PbCL,, AgCl, HgyCl.,), and the rest
are soluble. If a complex solution containing salts of all
the metals were treated with hydrochloric acid, these
three chlorides would be formed and precipitated. Thus,
a separation would be effected of lead, silver, and mer-
cury from the rest of the metals. Hydrochloric acid
is a group reagent ; and, in analysing substances, the
first step is to determine by the use of group reagents to
what group or groups the substances under examination
belong.

GROUPS OF METALS.

I. Lead,* silver, and mercury (mercurows salts).
Chlorides precipitated by hydrochloric acid. .

* Plumbic chloride is sparingly soluble, so that lead appears in Crroups
and II.

QUESTIONS AND EXERCISES. 271

II. Lead, mercury (nierciiric salts), copper, cadmium,
bismuth, mitimony, \avseuic\, tin, gold, platinum, and
some rare metals. Siilj)hides precipitated by hydric
sulphide from neutral or acid solutions.

III. Iron, cJiromium, aluininium, zinc, manganese,
cobalt, and nickel. Sulphides precipitated only in pre.s-
ence of an alkali. Amnionic sulphide is the group re-
agent.

IV. Calcium, strontium, and barium. Precipitated as
carbonates from solutions (in presence of amnionic chlo-
rides) by amnionic carbonate.

V. Magnesium. Precipitated as phosphate, by sodic
phosphate. Magnesium is often included in Group IV.

VI. Lithium, sodium, potassium, ammonium, rubi-
dium, and ccesium. Salts mostly soluble.

Groups I., II., and III., include the common metals
in everyday use. They are the heavy tnetals. Group IV.
is made up of the metals of the alkaline earths. Group
VI. includes the metals of the alkalis.

QUESTIONS AND EXERCISES.

1. Metala generally feel cooler than other substances. Why
is this ?

2. What is an ore ?

3. Are alloys compounds or mixtures?

4. What class of metallic compounds does the ending -ide
mark ?

5. Why write the formula for chromic chloride Cr.^Clo, and
not CrClg ?

6. Mercury is a dyad metal, but it has an oxide HgjO. How
is this explained ? What non-metal forms numerous compounds
in the same way ?

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272 « METALS OF GllOUP I.

7. Bismutli has an oxide, the formula of which is Bi^O.;.
Ferric oxide is represented by Fe^O.,. The first is caJled his-
tnuth trioxitlc ; the second, iron sestjuiox'uk. Is there any rea-
son for this difference of momenclature ?

8. Write the formulas for the chlorides corresponding to SnO,
Or^O.,, K2O, BiaOa, BaO, CuO, GuaO, Ag.,0, and AU2O3.

9. The formula for oxalic acid is H20y04. It is dibasic.
Write the formulas for the normal oxalates of barium, sodip'*!,
ammonium, iron (ferrous and ferric), chromium, and copper.

10. Will the groj'p reagent of Group II. precipitate the mem-
bers of Group I. as sulphides '! Try.

1 1 . Have you observed any regularity in the atomicities of
the groups of metals? Write the formulas for the oxides of
Groups IV. and VI.

CHAPTER XVII.

METALS OF GROUP I.
Lead, Silver, and Mercury.

247. General Characters.— The metals of this

group are heavy and soft (mercury is liquid). They are
easily reduced from their ores by lieating with charcoal.
Their sulp/ddes are black and insohible in water and
in dilute acids. The oxides are earthy compounds in-
soluble in water. The chlorides (except mercuric chlo-
ride), bromides, iodides, carbonates, and phosohates, are
insoluble in water.

. LEAD (Plumbum).

248. Lead.— (Pb"= 20G.4. Specific weight =11.352.
Melting point = 334° C. Specific heat = 0.0315). The

«»

LEAD. 273

cliief ore of lead is galena (PbS). It is very common in
Canada, occurring in crystalline masses, of a brilliant,
metallic appearance.

Experiment 214. — Examine a specimen of galena, noting ita
colour, hardness (scratch with a knife), specific weight, &c.
Mix a little of the powdered mineral with sodic carbonate,
mijibten, and heat it on charcoal before the blow-pipe, or on a
cliarred splinter in the reducing flame of the Bunsen burner.
Extract the metallic bead, and examine it carefully as to its
hardness, malleability, &c. It is lead.

Galena generally contains silver, sometimes only in
small traces, but often in considerable proportion.

Preparation. — The galena is partially oxidised by
heating in air, and then more strongly heated to set the
lead free. (Art. 239).

Experiment 215. — Put a piece of zinc in a solution of plum-
bic acetate, and allow it to remain for some time. Pouv otF the
iii^uid, dry the metal which remains, and melt it by heating it
ill a closed porcelain crucible with a little charcoal dust. Ex-
amine it. It is lead.

Properties. — A heavy, dull metal, soft, tough, easily
tarnislied. A small quantity of antimony or arsenic
alloyed with it renders it hard and brittle. Lead is
easily set free from compounds in solution by the action
of iron, zinc, <fec., as in Experiment 215. This method
is sometimes employed for impure ores.

Experiment 216. — Warm some small scraps of lead with

dilute nitric, dilute hydrochloric, and dilute sulphuric acids.

Divide the solution obtained with nitric acid into two portions.

To one add some hydrochloric, to the other a little sulphuric

acid. Heat bits of lead with strong hydrochloric and sulphuric

acids.

'27A OXIDES OP LEAD.

Experiment 217. — I'ut pieces of bright lead into 4 test
tubes, la])elled (1), (2), (3), and (4). In (1) put distilled water,
in (2) water containing amnionic nitrate, in (3) vinegar, and in
(4) tap water. Set aside for a day and then test the liquid con-
tents of the tubes for lead. '

Lead is attacked and dissolved by distilled water (and
rain water) owing to the action of the dissolved oxygen
and carbonic acid. Water containing ammonium salts
(es})ecially ammonic niti ate) dissolves lead. Water con-
taminated by sewage generally contains ammonium salts,
and is therefore dangerous on this account as well as on
others. (Does vinegar dissolve lead]) Water contain-
ing lime and magnesia salts does not attack lead, so that
ordinary river and well waters may be carried safely
through lead pipes.

•

249. Oxides of Lead. — Lead forms several oxides
(Pb,0, PbO, Pb,0;„ Pb.,04, PbO,). Of these the impor-
tant ones are lead monoxide (PbO), and red-lead (P 1)304).

1. Lead Monoxide (PbO). — Also called litharge, or
massicot, according to the methot- by which it is pre-
pared.

Experiment 218- — Heat some thin shavings of lead in an
open porcelain crucible. They oxidise to a greyish yellow sub-
stance. This is the monoxide. Remove it and try the solu-
bility of portions of it in dilute acetic, nitric, hydrochloric, and
sulphuric acids. (Do you notice any change with hydrochloric
and sulphuric acids ?)

Litharge is used for giving a glaze to earthenware,
and in making flint glass. It is also used in preparins;
red-lead, lead acetate, nitrate, <fec. " Drying oils " are
prepared by boiling the raw oils with litharge.

Experiment 219. — Heat some lead monoxide with aolution
of sugar. It is dissolved.

SALTS OF LEAD. 275

*
Experiment 220. — Try the solubility of lead monoxide in
water, and in solutions of sodic, potassic, and calcic hydroxides.

2. Rrd-lead, or Minium (Pb304). — This is prepared
hy heating litharge or massicot in air until it becomes
further oxidised :

3PbO -f O = Pb304.

It is a heavy red powder, used as a paint, and in the
manufacture of flint glass. It is often adulterated with
hriok dust, ferric oxide, &c.

Experiment 221- — Heat a little red-lead in a porcelain dish
and note any changes.

Experiment 222. — Warm a some red lead with dilute nitric
acid to which a little sugar has been added. It is completely
dissolved, if pure, a solution of plumbic nitrate being obtained.
(What is the object of the sugar ? What becomes of the oxygen
in excess of 3PbO ?)

250. Salts of Lead. — There are two basic oxides of
lead, P'jO and Pb.O;,, but the sesquioxide forms unstable
salts of no importance The ordinary salts of lead are
derived from the monoxide, PbO ; and in these salts Pb
takes the place of 2H. Moist lead oxide, as well as the
hydroxide, turn red litmus blue. Salts of lead have a
sweetish metallic taste.

251. Plumbic Acetate, or Sugar of Lead,

Pb(CoH30.2).2.3IL20. Prepared by dissolving litharge or
massicot in acetic acid. (See Experiment 163.)

Experiment 223. —Examine carefully a specimen of sugar of
load. (Why called siujai' ?) Dissolve it in warm distilled water.
(It is soluble in I^ parts.) Test it with blue litmus. Note the
odour of the solution. If the solution is turbid, add acetic acid
until it is clear.

276 PLUMBIC NITRATE — WHITE LEAD.

Goulard's Extract is a solution of sub-acetate, or
basic acetate, of lead, Pb(C^H.02),,.PbO, made by boiling
solution of the normal acetate with litharge.

Experiment 224. — Boil some solution of plumbic acetate for
some time with litharge in a porcelain dish. Filter, and test a
little of the filtrate with red litmus. Leave the rest exposed to
the air. It becomes turbid owing to the formation of plumbic
carbonate. Try its action on gum arabic mucilage.

252. Plumbic Nitrate, Pb(N03).,.— The nitrate of
lead has already been prepared in several experiments.

Preparation — By dissolving litharge or massicot in
warm dilute nitric acid, filtering, and evaporating to
crystallisation :

PbO + 2HNO3 = Pb(N03)2 + H2O.

Properties. — A white crystalline solid, of astringent
metallic taste. It dissolves in twice its weight of water,
but is only sparingly soluble in alcohol. — It is an irritant
poison. It has been used as a disinfectant and deodor-
iser. Its action as a deodoriser is due to the fact that
it reacts witli sulphuretted hydrogen to form the sulphide
of lead (PbS). Ledoyeiis Disinfecting Fluvd contains
a drachm of lead nitrate to an ounce of water.

Experiment 225. — Shake up a solution of plumbic nitrate
with an equal volume of hydric sulphide water. Note the ab-
sence of bad smell in the solution. What is the black pre-
cipitate formed ?

253. White Lead.— 2PbC03Pb(OH),, a basic car-
bonate of lead.

Preparation. — 1. Dutch process. Expose sheets of
lead to the conjoint action of the fumes from vinegar and

PLUMBIC CHLORIDE 277

tlie carljoii dioxide from decaying tan-bark. An acetate
is formed first, and thia is decomposed by carbon dioxide.

2. Milners process. Grind litharge with common
salt and water :

PbO + H2O + NaCl = Pb j gjj + NaOH.

Pass in carbon dioxide till the solution is neutral.
The basic carbonate is formed.

Properties. — A soft, heavy, white powder, insoluble
in water, but easily dissolved by dilute nitric or acetic
acid with effervescence of carbon dioxide. It is poisonous.

Experiment 226 —Pour some hydric sulphide water on a
little white lead in a porcelain dish. Explain the blackening.

Experiment 227.— Dissolve a little white lead in acetic acid.
(What substances are formed? Write the equation.) To por-
tions of the solution add hydrochloric acid, solution of potassic
iodide, and dilute sulphuric acid respectively. (Note the ap-
pearance of the precipitates and write the equations.)

White lead is used as t:, paint. It is used in medicine
in the form of an ointment ( ungueiitum plumbi carbon
atis). It is ver}'^ often adulterated with baric sulphate
(BaSO^), and gypsum ; but, as both are insoluble in
nitric or acetic acid, they are easily detected.

254. Plumbic Chloride. - PbClo. Occurs in nature

as horn lead.

*
Experiment 228. — To a little solution of lead acetate add

excess of hydrochloric acid. Plumbic chloride is precipitated.
Filt?r, and transfer the precipitate to a t. t. ; Hll the t. t. half-
full of pure water and heat to boiling. The chloride dissolves
completely, if there is enough water. Allow to cool, and observe
crystals. — Add to the solution a drop or two of hydrochloric
acid to see that it gives no further precipitate. Now add a few
drops of "idphuric acid, and white sulphate of lead (PbSO^)

278 PLUMlilC IODIDE — LEAD PLASTER.

is precipitated. (What conclusion do you draw as to the sohi-
bility of plumbic chloride ?)

Plumbic chloride is also s[>ariiigly soluble in pure water.

255. Plumbic Iodide.— Pblj. (In what experi
ment has this been already formed ?)

Experiment 229.— To some solution of plumbic acetate a<l.i
solution of potassic iodide (KI), collect the precipitate of plum-
bic iodide on a filter, and wash it with cold water. Note its
colour, &c. Transfer it to at. t., fill half- full of water, boil, and
allow to cool. The iodide dissolves in hot water, and crystal-
lises beautifully on cooling.

Plumbic iodide is used in medicine in the forms of
plaster and ointment.

256. Lead Plaster. — This consists of oleate of lead
and lead salts of other fatty acids.

Preparation. — Boil at a gentle heat for 4 or 5 hours,
4 pounds of litharge with 1 gallon of olive oil and 3 }^ pints
of water, adding water as it evaporates. The glycerine
dissolves in the water, and the oleate of lead forms an
insoluble gummy mass. Lard is sometimes used instead
of olive oil.

257. Plumbic Sulphate.- PbSO^.

Experiment 230- — Warm a little litharge with concentrated
sulphuric acid, it dissolves. Cool the solution carefully and
then dilute with watc"" Plumbic sulphate is precipitated.

Plumbic sulphate is soluble in strong, but insoluble in
dilute, sulphuric acid.

Experiment 231. — Mix solutions of magnesic sulphate and
plumbic acetate. Plumbic sulphate is precipitated :

PbAa + MgSO^ = PbSO^ -f MgAg.

LEAD POISONING. 279

Try its solubility in hot water, and in nitric and hydrochloric
acids.

Commercial oil of vitriol often contuiiia sulphate of
lead. It is precipitated on dilution.

258. Oommercial Preparations of Lead.

1. Basic Carbonate. — White lead, flake white, ceruse,
mineral white, Newcastle white, and Nottingham white.
Also some hair dyes.

2. Sulphate. — Miniature painter's white, white preci-
pittite of lead.

3. Chromates. — Chrome yellow (PbCrO^), cl:* ome red
(PbCr04.PbO).

4. Basic Chloride. — Turner's yellow, or Cassella yel-
low (PbCl,.7PbO), and Pattinson's white (PbC!.OH).

5. Litharge and various salts of lead are constituents
of hair dyes.

6. Minium (Pb304). — Red lead.

259. Lead Poisoning. — Nearly all compounds of

lead are poisonous ; but the insoluble compounds are at
least very slow in their action. The soluble compounds
are irritant poisons. The antidotes are soluble sul-
phates, such as Epsom salts. Lead is a cumulative
poison. Minute quantities taken repeatedly remain in
the system, and at length accumulate to such an extent
as to produce symptoms of poisoning, as in painter's
colic. The treatment in such cases is to administer
antidotes and to remove the lead from the skin by re-
}>eated sulphur baths, which convert the soluble salts into
plumbic sulphide, and this can be rubbed oflf the skin.

280 SILVER.

200. Tests.

1. If the solution is not too dilute, kijd rochluric acid gives a
white precipitate insoluble in a further (j[uautity of the acid and
unchanged by ammonia.

2. Sulphuretted hydrogen gives a black precipitate (PbS) in-
soluble in solution of ammonic sulphide, partly dissolved,
partly whitened by strong nitric acid. . ■

3. Sxdphuric acid gives a white precipitate (PbS04).

4. Potassic iodide (KI) gives a yt3llow precipitate (Pbla).

5. Potassic bichromate (K2Cr207) gives a yellow precipitate
(rbCr04).

6. Insoluble compounds are detected by reducing on charcoal
with sodic carbonate, dissolving tlie metallic bead in nitric
acia, and making the above tests.

SILVER (Argentuvi).

261. Silver. — (Ag' = 107.06. Specific weight --
10.5. Melting point = 1040° C. Specific heat =
0.057.)

Occurrence. — Native, often in large masses ; tlic;
principal ores are silver glance (Ag^S), rubi/ silver
(AgaSbSg), silver copper glance (Ag.^S.Cu.^S), and horn
silver (AgCl).

Preparation. — 1. Silver is extracted from argenti-
ferous lead by Pattinson's process, wliicli consists in
melting the lead and then cooling it slowly. Pure lead
crystallises and sinks to the bottom. This is ladled out,
until the remaining molten lead contains a considerable
percentage of silver, when the process is finished by
cupeUation. The lead is melted in bone-ash cupels, or
shallow vessels, and subjected to a blast which oxidises
the lead and leaves the silver.

ELECTHOl'LATING. 281

2. Ainalgamatio7i Process. — The silver is extructed
with mercury, which is distilled, leaving the silver free.

3. The silver is dissolved out o'^ its ores by acids,
sodic thiosulphate, &c., and then procipitated by scraps
of copper.

Properties. — A pure white metal, the best conductor
of heat and electricity known ; very tough and ductile ;
and very soft when pure.

Note. — Keep all residues from experiments with silver.

Experiment 232 — Cut small pieces of silver from a silver
coin, and try their soiubility in dilute hydrochloric, nitric, and
sulphuric acids. Try the strong acids with the aid of heat.

Silver is soluble in nitric acid, argentic nitrate being
formed. It is insoluble in hydrochloric, and in dilute
sulphuric acid ; but it dissolves in strong, hot sulphuric
acid, with the formation of argentic suli)hate (Ag.2S04)
and sulphur dioxide :

2Ag + 2H2SO4 = AgaSO^ + 2H2O + SO2.

Silver is easily reduced from its comj)ounds.

Experiment 233. — Put a scrap of zinc in a small (quantity of
argentic nitrate solution in a porcelain basin. After a short
time, a dark powder is formed in its place. Fuse this on char-
coal with the blow-pipe. A bright silver bead is obtained.
Dissolve it in nitric acid, and keep the solution to test.

Silver is much used for plating inferior met;ds. This
is now generally done by means of electricity, in the
process known as electroplatirig. The object to be
plated is fastened to the negative wire of a galvanic
battery, and immersed in an aqueous solution of the
double cyanide of silver and potassium (AgCN.KCN),

282 LUNAR CAUSTIC.

through which the electric current is paH8e<l. The silver
is de[)osited in an even layer on the object. — Silver iH
easily tarnished by sulphur or hydric sulphide, argentic
sulphide (AgjS) being formed. This can be removed by
washing with solution of ammonia, or of sodic thio-
sulphate.

262. Oxides of Silver.— There are throe (Ag,0,
AgjO, Ag202), but only one of importance, viz., argentic
oxide, AgjO.

Experiment 234. — To solution of argentic nitrate, add a
little caustic soda. Argentic oxide is precipitatud. Filter,
wash, dry, and heat on mica. The oxygen is driven otf and
metallic siver remains :

(1) 2AgN03 -f- 2NaOH = 2NaN03 + Ag,0 + H^O.
■ (2) Ag,0 = 2Ag 4- O.

. Argentic oxide is used in medicine. It is less liable
than argentic nitrate to colour the skin.

263 Salts Cf Silver.— The only salt used in medi-
cine is the nitrate.

Argentic Nitrate (AgNO;,), or lunar caustic, is pre-
pared by dissolving pure silver in dilute nitric acid with
the aid of a gentle heat, evaporating to dryness, and
fusing.

Properties. — A colourless solid ; sold either in
sticks or as tabular crystals. It has a strong metallic
taste, and is a violent, irritant poison. Antidotes —
soluble chlorides, especially common salt.

Experiment 235.— To a little argentic nitrate solution add
solution of common salt :

AgNO.^ + NaCl = AgCl -f NaNOg.

MERCURY. 283

Test the 8oluhility of the precipitate (AgCl) in nitric acid, and
in ammonia.

Argentic nitrate is very hclublo in water (2^ parts in
1), and in alcohol. The solid substance ia used as a
caustic. If nitrate of silver be administered in small
doses for a long time, it may produce permanent colora-
tion of the skin. It. darkens the skin when applied ex-
ternally.

264. Tests.

1. To a small ((uantity of argentic nitrate solu^'.ion a<ld hydro-
chloric acid. A curdy white precipitate (AgCl) fc.rms. Divide
it into three portions. To one add nitric acid ; no change. To
another ammonia ; dissolved. Let the third stand ; it darkens.

2. Sulphuretted hydrogen gives a black precipitate (Ag.^S),
insoluble in amnionic sr'phide

3. Heat with solution of ferrous sulphate. Metallic silver is
precipitated. T'he ferrous sulphate is oxidised.

4. Potassic bichromate (KgCraOy) gives a bright, reddish
purple precipitate of argentic chromate (AgjCrO^).

5. Potassic iodide (KI) gives a yellow precipitate of argentic
iodide (Agl), insoluble in nitric acid, and whitened, but not dis-
solved, by ammonia. Potassic bromide (KBr) similarly. These
salts of silver, especially the latte'', are used in photography.

Note. — Many salts of silver a'e insoluble in water, and as
they have characteristic colours and other properties, argentic
nitrate is I'sed as a group reagent in testing for acids.

MERCURY (Hydrargyrum).

265. Mercury (Hg" = 199.8. Specific weight =
13.595. Melting point -. - 39° C. Boiling point =
357° C. Specific heat - 0.0319.) The principal ore of
mercury is cinnabar (HgS), from which the mercury is

284 * . AMALGAMS.

obtained by roasting in a current of air and condensing
the vapours of niercui-y in a series of cool chambers. It
is purified by distillation.

Note. — Keep all residues from experiments with mer-
cury.

Sxperiment 236. — Put a little mercuric sulphide (vermilion)
in a small hard-glass tube open at both ends. Uold the tubo
aslant and heat the sulphide until it disappears. Met all: j mer-
cury collects in the upper part of the tube :

HgS 4- Oa = Hg + SOa.

Properties. — Mercury is commonly called quicksilver,
which means living silver. It is brilliant when pure
and does not readily tai-nish in air. If it is impure
(containing, lead, antimony, &c.), it soon gets a grey
coating, and when allowed to run over white paper leaves
a " tail." — When rubbed up with chalk, fats, and other
substances, it becomes partially oxidised and very finely
divided. It is in this way that mercury ointments and
pills are made. — The specific weight of gaseous mercury
is 6.93 (air =1). (Calculate the number of atoms in
the molecule). Mercury evaporates slowly even at low
temperatures, and it should, therefoie, always be kept in
closed vessels. — On account of its high specific weight it
is used for barometers, areometers, <fec.

Amalgams. — Mercury unites with all metals but iron
to form amalgams. From these the mercury can be
driven ott by heat. This property is utilised in silvering
by means of a silver amalgam. Cadmium amalgam
(HgaCd) is very brittle, heavier than mercury, and has
the property of hardening gradually. It is used for
filling teeth. Copj)er amalgams are brittle at ordinary
temperatures, but soften at 100° C. They are used for
filling teeth and for sealing bottles, &c.

CATiOMKL. 285

2()G. Mercurous Compounds. — In tliese com-

poiiiuls two atoms of mercury act as a dyad radical,

Hg—

I . The salts arc insoluble, or sparingly soluble, in

Hg—

water, and can be converted by oxidation, &c., to mer-
curic salts.

267. Mercurous Nitrate.— Hg.,(N03)2.

Experiment 237. — Pour some dilute uitric acid over a glo-
bule of mercury, and allow it to stand for some time. The
metal gradually dissolves, forming a solution of mercurous
nitrate. Keep this for further examination.

Mercurous nitrate is soluble in water, but with a
large proportion of water it is partially decomposed, with
the formation of a yellow basic nitrate :

Hg,(N03)2 + H^O = Hg2.NO3.OH + HNO3. -'

268. Mercurous Chloride (Hg.^Clj). Also called

calomel. This name is from the Greek, and means beau-
tiful black.

Experiment 238. — To a small quantity of mercurous nitrate
solution (Exp't 237) add hydrochloric acid. A white precipitate
of mercurous chloride is thrown down :

Hg^iNOa)^ + 2HCI = Hg.Cl, 4- 2HNO3.
To this add lime water until the chloride is blackened. This is
the black wash of the Pharmacopoeia :

Hg,Cl, 4- Ca{OH), = Hg,0 + H^O + CaCl,.

Calomel is usually prepared by subliming a mixture
of mercuric sulphate (HgS04), mercury, and sodium
chloride :

HgSO^ + Hg + 2NaCl = HgaClg + Na2S04.
The sodic sulphate is not volatile.

286 MERCUROUS IODIDE.

Properties. — A white, tasteless, inodorous powder,
insoluble in water, and in acids. (Try with a specimen
of calomel.) It is turned black by alkalis, owing to the
formation of mercurous oxide (Hg-^O), the active consti-
tuent of black wash. Precipitated calomel is more active
as a medicine than that prepared by sublimation, owing
to its finer state of division ; but great care should be
taken, in preparing it by precipitation, that no basic
nitrate be present. This would dissolve readily in the
acid juices of the stomach and might cause mercurial
poisoning In order to guard against this, warm the
precipitated calomel with dilute hydrochloric acid, filter,
and wash well. — Calomel may be administered in doses
up to 6 grains.

269. Mercurous Iodide, Hgals, green iodide of
mercury, or protoiodide of mercury. — A dull green
powder, prepared by rubbing together iodine and mer-
cury (In what proportions?), occasionally moistening
with spirits of wine.

Ezperiment 239- — Add solution of potaasic iodide to solution
of mercurous nitrate. A greenish precipitate of mercurous
iodide appears :

2KI + Hg,(N03), = Hg,l2 + 2KNO3.

Mercurous iodide readily changes into mercuric iodide
(HgTa) and mercury. As the mercuric salt is more
readily dissolved than the mercurous (and therefore
more active as a poison \ care should be taken that it be
absent from the preparation. The mercurous iodide
should be kept away from the light, which tends to
bring about this decomposition :

Hgal^ = Hg4-Hgl2.

MERCURIC NITRATE. 287

270. Tests for Mercurous Compounds.

1. White precipitate with hydrochloric acid, blackened by
ammonia :

Hg^Cl^ + 2NH3 = HgaCl.NHa + NH^Cl.

2, Insoluble compounds disappear when heated on mica, and
are blackened by caustic soda.

271. Mercuric Compounds. — Tn these com-
pounds a single atom of mercury acts as a dyad (HgZl).

They are more soluble than the mercurous compounds,
and are generally deadly poisons.

272. Mercuric Nitrate, Hg(N03)o, is prepared by

boiling mercury with excess of nitric acid until the solu-
tion no longer gives a precipitate with hydrochloric acid.
(What is the precipitate 1)

Experiment 240. — Heat a globule of mercury in a porcelain
dish with nitric acid diluttd with an equal volume of water.
From time to time take out a drop of the solution with a glass
rod, and mix it with a drop of hydrochloric acid. Continue
heating, adding more acid if necessary, until the drop remains
clear on mixing with hydrochloric acid. Evaporate to dryness.
Examine the residue, dissolve part of it in water, and test it
with lime water. It turns yellow :

Hg(N03)2 + Ca(0H)2 = HgtOH)^ + CalNOg),.-

Heat a little of the dry salt carefully in a dry porcelain capsule,
lied fumes are evolved, and red oxide of mercury, or mercuric
oxide (HgO), remains.

An acid solution of this salt is used in medicine as a
caustic. It is an irritant poison.

273. Mercuric Sulphate, HgSOi, is prepared by

dissolving mercury in hot, strong sulphuric acid :
Hg + 2H2SO4 = HgSO^ 4- 2H2O -f SOj.
(Calculate the proportions to be used.)

288 CORROSIVE SUBLIMATE.

Experiment 241. — Heat a drop of mercury in a small po;'-
celain vessel with about 7 or 8 times its volume of cjncentrated
sulphuric acid, stirring constantly. The mercury dissolves.
When cold, test a small portion of the salt with caustic soda.
It is turned yellow :

HgSO^ 4- 2NaO]l = HgCOH)^ + Na^SO^.

Morcuric sulphate if> used in the preparation of cor-
rosive sublimate (HgCl.,). • .

274. Mercuric Chloride, HgCU, or corroAve sub-
limate^ is prepared by subliming a mixture of mercuric
sulpliate and common salt, a little manganese dioxide
being added to make sure of the absence of mercurous
salts. (How?):

HgSO^ + 2NaCl = HgCla + NagSO^

Propertiks. — Heavy colourless crystals, having a
biting mc allic taste (Examine a specimen) ; soluble in
water (7 > ts in 100), more so in alcohol, and still
more so in ether. It volatilises more readily than
calomel when heated. The medicinal dose is ^j^ to \
of a grain. In larger doses it is a violent poison. The
antidotes are white of egg, flour, &lq. Stannous chlmnde
(SnCl.j) may be given :

SnClg 4- SHgCla = SnCl^ + HgaCla
(How does this prevent the poisonous action ?)

Experiment 242. — Mix solutions of mercuric and stannous
chlorides. What is the precipitate formed ?

Experiment 243. — To solution of corrosive sublimate add
lime water. A yellow precipitate is formed :

HgCl, 4- Ca{OH), - Hg(OH), -f CaCl.,.

This is the yeUoxo wash of the Pharmacopana.

MERCURIC IODIDE. 289

Corrosive sublimate is an excellent antiseptic, even in
very dilute solution, and is largely used instead of car-
bolic acid.

275. Mercuric Oxide. — HgO. There are two
varieties, the differences depending on the fineness of
division. Red oxide of mercury is prepared by heating
mercury with mercuric nitrate :

Hg + Hg(N03)2 = 2HgO + 2N0a.
It is a heavy, red powder, soluble in those acids which
form soluble mercuric salts. (What is the effect of a
strong heat upon it 1) — The yellow oxide is prepared by
precipitation. A solution of mercuric chloride is treated
with solution of caustic soda, and the precipitate of mer-
curic hydroxide (Hg(0H)2) is washed, and dried at
100°. This method of preparing the hydroxides and
oxides of the heavy metals is very generally employed.
In several cases, the soluble base used as a precipitant is
ammonia instead of soda.

276. Mercuric Iodide, Hglj. Also called red iodide

of mercury.

Experiment 244. — To solution of mercuric chloride add solu-
tion of potassic iodide drop by drop. A yellowish precipitate
appears, but immediately turns red :

2KI 4- HgCl, = Hgl^ + 2KC1.

Add more potassic iodide. The precipitate of mercuric iodide
redissolves, a soluble double salt {Hgl2.2KI) being formed
This solution, with caustic soda added to it, constitutes NesM-
kr's reagent, a very delicate test for ammonia, used in water
analysis. Try it with a drop of ammonia dissolved in about half
a litre of distilled water. A brown colour or precipitate ap-
pears :

NH3 4- 2Hgl2 + 3NaOH = NHgJ + 3NaI + SHjO.
20

290 WHITE PRECIPITATE.

Mercuric iodide is a brilliant cryst^Uine powder of a
vermilion colour. It turns yellow when heated care-
fully. It is very slightly soluble in water, sparingly in
alcohol, quite freely in ether and in aqueous solution of
potassic io'Mde. It resemb' s corrosive sublimate in its
poiscmous action.

277. Infusible White Precipitato, or mercuric

ammonium chloride, NHgHjCl.

Experiment 245- — Add ammonia solution to solution of
mercuric chloride. A white precipitate falls ;

HgCla 4- 2NH3 = NHgHjCl + NH^Cl.

278. Fusible White Precipitate, or mercuric di-

ammonium chloride, Hg(NH3Cl)2, is prepared by adding
solution of mercuric chloride to a boiling solution of am-
monic chloride and ammonia. — These two compounds
diflfer as their names indicate. The infusible precipitate
decomposes without fusing when heated ; the fusible
precipitate fuses and then decomposes.

279. Mercuric Sulphide, HgS, is found in nature

as a heavy red mineral, cinnabar. It can be prepared
by subliming mercury and sulphur together, when it is
obtained as a red or black powder, vermilion, or jEthiops
mineral. Or, it can be prepared as a black powder by
precipitation.

Experiment 246- — Add hy'dric sulphide to solution of mer-
curic chloride. A white precipitate ai)pear8 (2HgS.HgClo), but
this rapidly passes through shades of colour until it becomes
black (HgS). (Write the equation). Divide the precii)itate
into three parts and try its solubihty ( 1 ) in ammonic sulphiile,

(2) in boiling dilute nitric acid, and (3) in aqua regia. He
suits (1) (2)

(3)

MERCURIAL POISONING. 2S1

280. Tests for Mercuric Compounds.

1. See Experiment ?46.

1,\ Sodic hydroxide solution gives with solutions of mercuric
salts a yellow precipitate (Hg(0H)2) not rediasolved whtn more
of the reagent ia added.

3. Btannoua chloride (SnCl^ > gives a white precipitate (HgaClj),
turning grey (Hg) with more of the reagent.

4. A bright copper wire is silvered when put in a mercuric
solution. This applies to mercurous solutions also.

General Test for Insoluble Mercury Compounds.
— Mix with dry sodic carbonate and charcoal powder, and heat
in a matrass. Metallic mercury is obtained as a mirror in the
tube. — All mercury compounds volatilise when strongly heated.

281. Mercurial Poisoning. — The soluble com-
pounds of mercury are violent irritant poisons. A
characteristic symptom is the increased flow of saliva
{salivation). The insoluble compounds are not so poison-
ous, but are still dangerous. Even metallic mercury in
a finely divided state will cause symptoms of poisoning,
especially when it is breathed as a vapour. Therefore,
it is dangerous to boil mercury, or to sublime compounds
of mercury, into the atmosphere of an inhabited room.
As mercury and its compounds are very extensively used
in arts and manufactures, as well as in many patent and
quack medicines, numerous cases of poisoning occur.
The antidotes are albuminous substances, such as white
of egg, flour, &c., and stannous chloride.

292 QUESTIONS AND EXERCISES.

QUESTIONS AND EXERCISES.

1 . Is there any reason why ^-aiu water should not be stored in
J.ead-liued tanka ?

2. In what liq d<\s is lead soluble, and in what insoluble ?

3. Muntion some liquids which will, and some which will not
dissolve litharge.

4. A white crystalline solid is given you. How would you
determine whether it is sugar of lead?

5. What proportions of plumbic acetate (Pb(C2H30.^)2.3HM())
and litharge (PbO) must be combined to form the subacetate of
lead?

6. Why should solution of subacetate of lead be kept well
closed from the air ?

7. What chemical action takes place when white lead is taken
into the stomach ?

8. In what acids is mercury soluble ?

9. Why is mercurous chloride called calomel ?

10. What chemical compounds are present in black wash ? In
yellow wash ?

11. Write formulas for mercurous sulphate, mercurous bromide,
and mercuric cyanide.

12. How would you prepare a specimen of mercuric hydroxide^.

13. Black mercuric sulphide becomes red when rubbed. Can
you account for this ?

14. Explain the action of stannous chloride as an antidote to
poisoning by corrosive sublimate. Woiild stannic chloride
(SnCl^i) do ?

15. Argentic cyanide is insoluble in water, but soluble in
solution of potassic cyanide What happens when a drop of
argentic nitrate solution is added to a considerable quantity of
potassic cyanide and shaken up with it ?

CHAPTER XVI

293

II.

METALS OF .iftoUP n.

[lead, Mercury] Pn.. ^

y< Un, [Areemci, Oold, PUuinum, ,fe.

feclissolved by a f„,.tl,p,. ' ' ' '""'"'"« of them are

"*'** can be prepared hy CLTT !'='^'""'>'>- ~ The
"■e earthy substances insoluble ° '^^''"•o^ides. They

stances insoluble in water ^'""^''"'^ ''■•e '"arthy sub.
T'"« group is subdivided into two •
A- Mefcals having siilnh.vi • ,
""'"'ine sulphides :%;!'" ""°'"'"« '» -'"tions of

7'^- In analysis, me S/Xl ""'";'""' "'"' *-
class, "" ^"s are included in this

R Metals havi'n^ snlnl.;,i
^"'ne^iphides:', riiV^o'f'^ '" ^lutions of
««, and some rare metX ' ''"■''"'"J' ^''^''' P^'-

COPPER ^P„^,„

-» J. Copper (Cu" = fiq I „

Mdting point = 1090O n q f "" "^"'S^" = 8.92

^- Specific heat = 0.0952). '

294 COPPER.

Occurrence, — Free ; soiuotiines in great musses. The
ores of copper are very iiunierous. The commonest one
is copper pyrites, or chalcopyrite (CuFeS^). Copper is
found in the liver and kidneys of man and of domestic
animals.

Preparation. — The smelting of copper is a very com-
plicated process, but it is the same in principle as that
of lead, viz., a partial oxidation of the sulphide and sul)-
sequent fusion at a higher temperature. Poor ores are
worked up by dissolving in acids and precipitating with
iron.

Experiment 247. — Pip the poiut of * knifo blade in a little
solution of cupric sulphate. It becomes coated with copper :

CUSO4 4- Fe = FeSO^ + Cu.

Properties. — A red metal, heavy, very tough, malle-
able, and ductile. Next to silver it is the best conductor
of heat and electricity. Its solubility in nitric and sul-
phuric acids has been already proved. (See Arts. 86
and 1 15).

Experiment 248. — Try the solubility of copper in hydro-
chloric acid, strong and dilute. Put a piece of brighb copper
wire in dilute acetic acid, so that it is half covered with the
acid. Leave it for a day, and then examine it. Test the acid
for copper. Verdigris, or basic cupric acetate, has been formed.

Experiment 249. — Put pieces of bright copper wire in test
tubes or beakers containing (I) distilled water, (2) dilute solu-
tion of common salt, (3) butter or fat, and (4) solution of sugar.
After 24 hours, examine the condition of the copper and test
the solutions for copper.

Copper is gradually dissolved by water, especially
when the water contains ammonium salts or chlorides.
Vinegar, fats, oils, and syrups, with the aid of air and

BLUR VITRIOL. 295

moisture, dissolve copper. Thus occur frequent cases of
poisoning, from copper kitchen utensils, taps for liquors,

284. Compounds of Copper. — Copper resem))les
mercury in forming two classes of compounds, (I) cup-
rous, in which two atoms of copper act as a dyad radical

("u-
I , and (2) cupric, in which one atom of copper replaces

(_'u —

two of hydrogen. — The cup'ous salts are so easily oxidised
that it is difficult to keep them. Cuprous oxide (Cu.^O)
has been already noticed. (See Sugars). Cuprous
chloride (CU.2CI2) is remarkable as being a solvent for
acctvlene and carbon monoxide.

285. Cupric Sulphate.— CUSO4.5H2O. Also called
blue vitriol and blue stone.

Preparation. — Copper pyrites is roasted so as to form
cupric oxide (CuO) and ferric oxide (Fe.203). The cupric
oxide is then dissolved out by hot sulphuric acid, in
wliich ignited ferric oxide is insoluble. The solution is
evftporated, and the salt crystallised. The commercial
salt always contains a little ferrous sulphate (FeSO^.
THjO). Blue vitriol is obtained as v. secondary product
in the refining of silver by precipitation on copper. (In
what way has it been already prepared 1)

Properties. — Cupric sulphate is generally sold in
large blue crystals. These are soluble in water (2 parts
in 5).

Experiment 250. — Carefully heat a crystal of cupric sulphate
in a t. t. It turns whit«3, and water gathers on the sides of the
tube. The crystal falls to a powder, because it has lost its
water of crysiallisaiion. When the t. t. is cool, pour a few

296 CUPRIC OXIDE.

drops of water ou the atii jJrouM xalt. Note signs of heat.
Anhydrous cupric sulphate is used in tenting li(iuida for water.
Tt turns blue when acted on by water.

Experiment 261. — Dissolve a little cuj ric sulphate in water,
and test the solution with blue litmus paper. 1'he basic part (if
the salt is comparatively weak. Taste the solution. Test it
for sulphuric acid.

Blue vitriol is used in medicine as a caustic, and also
as an emetic. In small doses (up to 2 grains) it is not j
poisonous, but acts as a tonic and astringent. In large)'
doses it is poisonous, unless it exerts its emetic action.
Antidotes, white of egg, <fec. Cupric sulphate is an anti-
dote to phosphorus.

286. Cupric Oxide. — CuO. This is the black oxide
of copper.

Experiment 252. — Heat a little powdered cupric sulphate
strongly on mica. Black oxide of copper is left :

CuSO^.SH^O = CuO + SO3 + 5H./).

Cupric oxide is a black hygrosco[)ic powder, soluble
in acids, insoluble in water. It is used in organic
analysis to supply oxygen to oxidisable substances.

287. Commercial Preparations of Copper.

1. Scheele's green. (See Arsenic.)

2. Schweinfurth rreen, or emerald green. (See
Arsenic.)

3. Brighton green, a mixture of impure cupric acetate
and chalk.

4. Brunswick green, oxychloride of coppei', or car-
bonate of copper mixed with chalk.

CADMIUM. 297

6. Mountain green, or mineral green, is a native car-
bonate of copper.

6. Green verdites, a mixture of ciipric oxide and car-
bonate with chalk.

7. Verdigris, a basic acetate.

Many alloys of copper are used, e.g., brass, tombac,
Muntz metal, bronze, <fec. (See Art. 238.)

288. Tests.

1. Acidify a solution of cupric sulphate with hydrochloric
acid, and add hydric sulphide. A black precipitate of cupric
sulphide (CuS) falls :

CuSO, -f H,,S = CuS + HaSO,.

Filter, wash, and teat the solubility of a portion of the precipi-
tate in yellow amnionic sulphide. It is insoluble (in reality,
sparingly soluble). Heat another portion in a porcel^Jn dish
with dilute nitric acid. It is dissolved. Heat a third portion
with dilute sulphuric acid. It is undissolved.

2. Add ammonia solution gradually to cupric sulphate solu-
tion. A light blue precipitate is iirst formed. When more am-
monia is added, this dissolves to a deep blue solution containing
a compound, CuS0^.4NH3.

3. Potassic ferrocyanide gives a reddish-brown precipitate, or,
with very dilute solutions, a reddish colour.

4. Insoluble compounds may be tested by heating a little of
the substance on a platinum wire with a borax bead. The bead
is green while hot, blue when cold. If it be moistened with
solution of stannous chloride and heated in the inner (reducing)
zone of the Bunsen ilame, it becomes coppery red when cold.

CADMIUM.

^ 289. Cadmium.— (Cd" = 111.6. Sp. wt. = 8.5.

Melting point = 315"C. Boiling point = 860°C. Sp.
heat = 0.0567).

298

("ADMIC NITKATK.

Ot'cuRUKNCK. Al«)iiji[ willi zinc oroH. In mniiliing
zinc or<\s, otuliuinni voIatiliHo.s first (Conijmn; boiling
points^ burna whon it. roaohi^s tlu^ air, and tho oxido
(OdO) oolleots as a brown dust in the rtuo of tho furnace.

PiiBPAHATioN. — The inij3ure cadmium oxide is dis-
solved in hycirocliloric acid, and tho ca<lniium is then
precipitated as sulphide (CdS) by sul[>hurett(Hl hydrogen,
the zinc salt reniainijig in solution. The sulphide is dis-
solved in strong hydrochloric acid, and the carbonate
(CdCO.,) is obtained by precipitating with sodic carbonate.
By heating the carbonate, pure cadmium oxide is formed,
and this is then reduced by heating in iron tubes with
charcoal.

PiioPKHTiES.-- A white metal, somewhat like tin. It
crackles when bent. It is harder than tin, malleable and
ductile, and takes a good polish. (Cadmium is soluble in
hot dilute hydrochloric acid, and in suli>huric acid. It
is very easily dissolved by nitric acid.

(1) Cd -f 2H01 - CdCla -f H2

(2) Od -f H2SO4 = CdSO^ -f H2

(3) 3Cd + 8HNO3 = 3Cd(N03)2 + 2N0 + 4H2O.

290. Compounds of Cadmium.— Cadmium has
only one oxide ^OdO), a brown solid, mentioned abovu-
The salts of cadmium are mostly colourlesSj and resemble
those of zinc both in chemical properties and in physio-
lojrical action. Solutions of the normal salts have an
acid reaction. •

291. Cadmic Nitrate, CdCNOa).^, is prepared by
dissolving the metal in nitric acid and evaporating the
solution. It is a deliquescent white salt, used for pre-
paring other salts, and in chemical experfments.

CADMU: IODIDE. 299

292. Oadmic Sulphate, .'UMHO^.H!!/), w prepared
from the nitrate or cliloride.

Experiment 253. — "our Holutiou of cadmic nitrate or cldoride
into sodic carbonate nolution :

Cd(NO„)a -f NaaCO„ = OdCOg -f 2NaN0„.

Kilter off the precipitate of cadmic carbonate, waah it, and dis-
Holve it in dihite sulphuric acid, taking care not to use too
much. Evaporate to cryatallisation, and examine the cryHtals :

CdCOa + HjSO^ = CdSO, + H,() -f CO,.

This method of pasHing from one soluble Halt of a metal to
another is often employed. Sometimes the hydroxide is pre-
cipitated instead of the carbonate.

Sulphate of cadmiiun is a colourless salt^ resembling
sulphate of zinc in its physiological actions, but it is
more powerful. It is used as a wasli for diseases of the
eye. It is soluble in about one and a half times its
weight of water,

293, Oadmic Iodide, Cdl.^, is pre[)ared by digesting
the metal with iodine and water, until the colour of the
iodine diduppears. \ solution is obtairied which, on
evaporation, deposits thin pearly j)lates of the iodide. It
is soluble in about an equal weight of water. — Cadmium
iodide is used in medicine in the form of an ointment.
It is also used in jdiotography in preparing the sensi-
tive plates, as it is one of the few iodides soluble in
alcohol and ether. A solution in alcohol and ether is
mixed with a collodion solution and spread in a thin
layer upon the plate. The liquids quickly evaporate and
leave a thin layer of collodion impregnated with cadmium

300 BISMUTH.

iodide. When this is dipped in a bath of argentic nitrate,
double decomposition takes place :

Cdia -^ 2AgN03 - 2Agl -|- Cd(N03)3.

Tnis is the sensitive plate.

294. Tests.

1. To a cadmium solution add hijdric sulphide. A yellow
precipitate of cad mic' sulphide (CdS) is formed. This is insoluble
in yellow ammonic sulphide. It resembles arsenic trisulphide
(As^Sg) and stannic sulphide (SnS^), but these are soluble in
ammonic sulphide. Cadmic sulphide is soluble in hot dilute
sulphuric and nitric acids.

2. To a solution of a cadmium salt add ammonia gradually.
A white precipitate of cadmic hydroxide, Cd(0H)2, appears, but
redissolves in more of the reagent, forming a colourless solution.

BISMUTH.

295. Bismuth. (Bi"' ^ = 210.— Sp. wt. = 9.8.—
Melting point = 270°.— Sp. heat = 0.0305.)

Occurrence. — Rather rare, chiefly in the free condi-
tion. It is found often with ores of cobalt.

Preparation. — Generally as a by-product in smalt
works, being separated in the metallic state from the
sulphide of cobalt by smelting with iron scraps. The
commercial metal nearly always contains arsenic. For
medicinal use it must be freed from this by melting with
a little saltpetre, which oxidises the arsenic, but does not
attack the bismuth.

Properties. — A hard, lustrous, brittle metal, of a
reddish tint. It expands on solidifying, and gives this
property to its alloys, some of which are used in stereo-
typing. It decomposes steam at a red heat. It oxidises

BISMUTH NITRATE. 301

slowly in the air. Bismuth is not dissolved by cold
dilute hydrochloric or sulphuric acid.

Experiment 254. — Dissolve a little bismuth in hot, strong
sulphuric acid :

2Bi + 6H2SO4 = Bi2(S04)3 + 3SO2 + 6H2O.

It dissolves easily in nitric acid and in aqua regia. —
Alloys of bismuth, lead and tin, made to melt at par-
ticular temperatures, are used as safety plugs for boilers.

296. Compounds of Bismuth. — Bismuth unites
with oxygen in four proportions (Bi.^O.,, Bi203, BijO^,
BiaOg), but only one of the oxides, viz , the trioxide^
(BijOg) is of importance medicinally. It is a basic oxide.
Tho pentoxide (BijOg) is acid-forming. The others are
indifferent.

297. Bismuth Trinitrate, Bi(N03)3.3H20. Also

called nitrate of bismuth.

Experiment 255- — Dissolve a little bismuth in nitric acid
diluted with about three-fourths its volume of water :

Bi -f 4HNO3 = Bi(N03)3 -f NO + 2H,0.

Evaporate the solution to crystallisation. Colourless delique-
scent crystals are obtained. Any arsenic present remains dis-
solved in the mother liquor.

298. Bismuth Subnitrate, or basic nitrate of bis-
muth, BiN 03(0 11)2!. Also called white bismuth.

Preparation.— Experiment 256.— Add a few drops of
water to the crystal i of trinitrate obtained in Experiment 255,
so as to form a solution, and pour it into a beaker of distilled
w?*" r. A white precipitate falls :

Bi{N0,)3 4- 2H2O = BiNO^iOH), + 2HNO3

t The composition of this salt varies with the amount of water used in its
preparatio .1.

302 BISMUTH TRIOXIDB.

(Many salts of weak bases can be thus decomposed by water.)
Filter oflF, wash, and dry the precipitate. Keep the filtrate.

Properties. — A heavy white powder, insoluble in
water, but soluble in moderately strong nitric acid. It
is again precipitated from this solution by the addition
of water.

Experiment 257- — Dissolve a little bismuth subnitrate in a
few drops of nitric acid and a drop or two of water. Then add
more water.

Experiment 258. — Dissolve a little bismuth subnitrate in
sulphuric acid diluted with an equal volume of water. To this
add a few drops of ferrous sulphate solution. A black colour or
precipitate is formed (BiaOa).

Subnitrate of bismuth is much used in medicine. It
is not poisonous, but it sometimes contains the tri-nitrate
or arsenic compounds, and then gives rise to symptoms
of poisoning. It should be carefully distinguised from
the trinitrate. It is also used as a cosmetic, and to givo
an iridescent glaze to porcelain.

299. Bismuth TriOXide, BijOg, is prepared by boil-
ing subnitrate of bismuth with solution of caustic soda :

2BiN03(OH)2 + 2NaOH = 2NaN03 + BiaOg + SHjO.

The precipitate is collected on a filter, washed, and dried.

Properties. — A lemon-yellow powder, insoluble in
water, but soluble in nitric and hydrochloric acids, with
the formation of the trinitrate and the trichloride (BiClg)
respectively. It is a basic oxide. — It is used instead
of the subnitrate in many cases, and is to be preferred
on account of its purity.

300. Bismuthyl Carbonate.— 2(BiO)2C03 . 11,0.

BISMUTHYL CARBONATE. ' 303

Preparation. — Experiment 259- — Pour solution of bis-
muth trinitrate into cold solution of amnionic carbonate, A
white precipitate falls :

3(NH JaCOg 4- 2Bi(N03)3 =

(BiO)2C03 -f GNH.NOg + 2CO2.

Collect the precipitate on a filter and wash it.

Properties. — This salt, commonly called carbonate of
bismuth, is a white powder, insoluble in water, but soluble
in nitric acid with effervescence. It is also soluble in
sulphuric acid, and the solution should not respond to
the test for nitric acid. If it does, the carbonate has
contained subnitrate. The carbonate of bismuth is often
administered in place of the subnitrate, on account of its
more ready solubility in the acid juices of the stomach,
and also because of its antacid properties :

(BiO)2C03 + 6HC1 - 2BiCl3 + CO2 + 3B.^0.

In this salt the radical ~ Bi = O plays the part of a
monad metal. Other salts of bismuthyl are known, e.g.,
bismuthyl chloride (BiOCl), formed when the trichloride
of bismuth is acted on by much water :

BiClg + H2O = BiOCl + 2HC1.

301. Tests.

1, To the filtrate from Experiment 256 add hydric sulphide.
A brovn-black precipitate of bismuth trisidphide (Big S3) falls :

2Bi(N03)3 + 3H2S = BiaSg + GHNO3.

It is insoluble in yellow ammonic sulphide, but soluble in hot
dilute nitric acid.

2. Solutions of bismuth salts give with ammonia a white pre-
cipitate (Bi(0H)3), not dissolved by more of the reagent. If this
precipitate be filtered off and dissolved in as little as possible of

304 ANTIMONY.

hydrochloric acid, the solution is turned milky on the addition
of much water. This precipitate is not dissolved by tartaric
acid.

3. Potassic iodide gives with bismuth solutions a brown pre-
cipitate (Bilj,).

4. Caustic potash gives a white precipitate (Bi(0H)3), insoluble
in excess.

5. Insoluble bismuth compounds can be tested by dissolving
them in nitric acid and diluting with water. (Experiment 256.)
The precipitate obtained is insoluble in tartaric acid. (Com-
pare Aniimony.)

ANTIMONY {Stibium).

302. Antimony (Sb»*-^- = 120. Sp. wt. - 6.7 to
6.86. Melting point = 425°C. Sp. heat = 0.0523).—
The chief ore of antimony is stihnite (SbjSg). This
occurs in black, shining, crystalline masses.

Preparation. — Stibnite, purified by fusion, is reduced
by heating with iron :

SbgSg -f 3Fe = 2Sb + 3FeS.

Properties. — A silvery metal, generally in masses of
laminated crystals, hard and brittle ; it can be ground to
a powder in the mortar. When heated in air, it burns,
forming the tetroxide (SbgO^). It is soluble in nitric
acid and in aqua regia. It is also soluble in hot, strong
sulphuric acid, antimonic sulphate being formed :

2Sb -f 6HaS0^ - Sb2(S04)3 -f 3SO2 + 6H2O.

In this salt antimony plays the part of a trivalent metal. —
Antimony black is finely divided antimony prepared by
reducing the metal from a solution of the chloride by

ANTIMONY TRISULPHIDE. 305

means of zinc. It is used for giving to plaster casts, (fee,
the appearance of iron or steel. — Antimony is a con-
stituent of many useful alloys. (Art. 240.)

303. Oompounds of Antimony. — Antimony

combines with oxygen in three proportions. The trioxide
(Sb.^0;,) is both basic and acid-forming ; the pentoxide
(SbyOg) is acid-forming, antimonic acid (H3Sb04) and the
antimonates being similar to the corresponding compounds
of phosphorus and arsenic; the tetroxide >Sb204) is also
acid-forming.

304. Antimony Trisulphide, SUS;,, is found in

nature as stibnite. The mineral is purified by fusion,
and is used as the starting point in the^ preparation of
antimony compounds. It is also called black antimony
and crude antimony. — It is a greyish-black crystalline
powder, soluble in hot, strong hydrochloric acid, with
evolution of hydric sulphide.

Experiment 260- — Heat a little black sulphide of antimony
with strong hydrochloric acid. Keep the solution :

SbgSg + 6HC1 = 2SbCl3 + SHgS.

Experiment 261- — Boil a little sulphide of antimony with
solution of sodic hydroxide. It dissolves :

2Sb2S5 + 4NaOH = NaSbOj + SNaSbSg + 2H2O.

Add dilute sulphuric acid until a precipitate appears :

NaSbOa + SNaSbSj, + 2H2SO^ =

2Na2S04 -f 2SbaS3 + 2H2O.

The substances formed when antimony trisulphide is dissolved
iu caustic soda are sodic antitnonite (NaSbO.^) and sodic sulphanti-
monite (NaSbSa). When the acid is added the trisulphide is
again precipitated, but it is orange-red. Prepared in this way
it always contains a little of the trioxide, and is called sulphurated
antimony, or golden sulphide of antimony.
21

306 POWDER OP ALGAROTH.

305. Antimony Trichloride (SbCl.,) is prepared

as in Experiment 260. By evaporating such a solution

the trichloride is obtained as a crystalline, colourless,

solid, melting at 72° (" butter of antimony "). It is very
deliquescent.

Expe ' Jient 262. — Dilute a small part of the solution pre-
pared iu Experiment 260. A white precipitate of antimony I
chloride, or powder of Algaroth (SbOCl) is formed :

SbCla -h HaO - SbOCl + 2HC1.

Filter, and test the filtrate for antimony and for hydrochloric
acid. To two other portions add considerable quantities of
strong hydrochloric acid and tartaric acid respectively, and dilute
them as before. To a strong solution of antimony trichloride
add a little dilute hydrochloric acid. A precipitate forms ; the
dilute acid has the same eflFect as water. Add more acid and
the precipitate is redissolved.

Antimony trichloride is a powerful caustic. It is a
corrosive poison, acting like a strong solution of hydro-
chloric acid. (Explain this.)

306. Antimony Trioxide (SbgO ), also called

flowers of antimony, is prepared by diget^ting powder of
Algaroth (SbOCl) with sodic carbonate, and washing
with hot water. — It is a greyish-white powder, insoluble
in water, sulphuric and nitric acids, but readily soluble
in alkalis, and in hydrochloric and tartaric acids :

SbaOg + 6HC1 = 2SbCl3 + 3H2O.

When heated strongly in air it fuses and, absorbing
oxygen, becomes changed to the tetroxide (SbaOi). —
Antimonial powder is a mixture of 1 part of antimony
trioxide with 2 parts of calcic phosphate (Ca3(P04).2).

307. Tartar Emetic, SbO.K.C^HiOg, is antimony I
potassium tartrate, already mentioned (Art. 189).

TARTAR EMETIC. 307

Experiment 263. — DissoW** some tartar emetic in as little as
possible of hot water. Dilute the solution. It does not turn
milky. The explanation is as follows : — The antimony is already
combined as a soluble antimonyl compound. (What experiment
above does this explain ?)

It will have been observed that antimony shares with
bismuth the tendency to form so-called oxysalts, in which
a radical, in this case, aritimonyl, - Sb = O, acts the
part of a univalent atom.

Experiment 264- — Examine a specimen of tartar-emetic care-
fully. Taste it. Heat a small portion on mica or platinum.
It chars and burns, leaving a white solid.

In large doses trHar emetic is a [)oison. Antidotes^
freshly precipitated ferric hydroxide, tannic acid, or any
vegetable infusion containing tannin, e.g., tea.

308. Tests.

1. To a solution of an antimony salt, acidified with hydrochloric
acid, add hydric sulpJiide. An orange precipitate falls. Filter
off the precipitate and test the solubility of parts of it in yellow
ammonic siilphide and in hot strong hydrochloric acid. It
dissolves in both. Dilute the hydrochloric acid solution. — The
ammonic sulphide solution contains amvionic sulpfiantimonite
(NH^SbS^). Treat it with hydrochloric acid, and the sulphide
is reprecipitated.

2. Test for antimony as in Marsh's teat for arsenic (Art.
146). Antimony has a gaseous compound with hydrogen,
stihine, or nntimoniuretted hydrogen (SbH,). Spots are obtained,
similar to those of arsenic, but they are turned orange by am-
monic sulphide, and are not dissolved by bleaching powder
solution. (Compare ^r«ewic.)

3. Put a scrap of zinc in a solution c£ tartar emetic, collect
the precipitated antimony, and test its solubility in hot hydro-
chloric acid. It is insoluble. (Compare Tin.)

308 TIN.

4. Strong solutions of antimony trichloride give a white pre-
cipitate with water or dilute hydrochloric acid, 8<dul)le in tar-
taric acid ; but thit; test does not answer with tartar emetic or
alkaline solutions.

5. Insolul)le antimony compounds can be dissolved in hydro-
chloric or nitric acid, and the solution then treated as above.

TIN (Stannnm).

309. Tin (Sii*"^ = 117.8. Specific weight .^ 7.739.
Melting point = 235°. Specific heat = 0.0r)48).—Tin
is prepared almost exclusively from tin-stone (SnO.j), by
smelting the purified ore in a blast furnace with anthra-
cite :

SnOa + 2C = Sn + 2C0.

1'he impure metal is piuified by liqnation, i.e., by melt-
ing gradually. The pure metal melts fiist and flows
away from its impurities. Commercial tin may contain
arsenic, antimony, bismuth, zinc, lead, copper, and iron.

Properties. — A bright white metal, crackling when
bent, harder than lead, softer than gold. It is iiialleablo
and ductile at 100° C. It does not tarnish readily in
air, and is therefo-e used for covering sheet iron in the
manufacture of ' om" utensils. It is soluble in hvdro-
chloric and dilute nitric acids, and is oxidised, but not
dissolved, by strong nitric acid. — Tin forms some useful
alloys. {See Alloi/8.) ^'m ama^^am is used for silvering
mirrors.

Experiment 265. — Pat a bit of zinc in an alkaline solution
of tin (SnCl2 and NaOH). Tin is gradually deposited in crystals.

310. Compounds of Tin. — Tin forms two series
of compounds : (1) Stanno?ts (SnO, SnS, SnCl.,, &c.) in

STANNIC OXIDE. 309

which the element is dysitl ; and (2) stanntc (SnO.j, SnSo,
SnCl4, ikc), in which it is tetrad. Stannous oxide (SnO)
is basic, forming suits with acids, e.g., Sn(N03)2, BnSO^,
(fee. Stannic oxide (SnO.^) is acid-forming (also weakly
basic), and the stannates are analogous to the carbonates
and the silicates, e.g., sodic stannate, Na-^SnOg.

311. Stannic Oxide (SnOs) is found in nature as
tin-sto7ie.

Experiment 266. — Pour some strong nitric acid on a few
scraps of tin. Ked fumes are evolved, and a wliite powder is
formed. This is stannic acid (HySnOg) :

. Sn + 4HNO3 = HgSnOg -f 4NO2 + H2O.

Try its solubility in hydrochloric acid, and in caustic soda. It
dissolves in both, forming stannic chloride (SnCl4) and sodic
stannate (Na^SnO;,) respectively. — Heat a little stannic acid on
mica. A' white powder remains (yellow when hot), 'i'his is
stannic oxide (8n0.j). Try its solubility in hydrochloric acid
and in caustic soda.

312. Stannous Chloride (SnCl.,)

Experiment 267. — Dissolve some scraps of tin in hydro-
chloric acid diluted with an equal volume of water. Stannous
chloride is formed :

Sn + 2HC1 = SnCla + H2.

Put in more tin and evaporate on the water bath to crystallisa-
tion. "Tin Salt" (SnCl2.2H20) is obtained — Dissolve a little
of this salt in a small quantity of water. It forms a clear solu-
tion. Add more water ; it becomes turbid, owing to the for-
mation of a basic chloride :

SnCla 4- H2O = SnCl.OH + HCl.

The same precipitate is formed when a solution of stannous
chloride is exposed to the air :

3SnCl2 + O + H2O = SnCl^ + 2SnC10H.

310 STANNIC CriLORIDE.

StaimouH Halts ha v«an Jisiringent metallic taste, Tliey
are eiiHily oxidiseil, and must he kttjjt from the air.
They are powerful reducing agents, precipitating gold,
silver, and mercury from their solutions. — The nitrate
(Sn(N()3).j) and sulphate (SnSOi) can he prepared by
dissolving tin in the dilute acids. Solutions of stannous
salts are acid in reaction. They are poisonous ; anti-
dote, solution of ammonic carbonate.

3i:V Stannic Chloride (SnCl^) can be prepared by
passing dry chlorine gas over tin foil, or by distilling
tin with mercuric chloride [H^^i'A.^). It can also be pre-
pared in solution as follows :

Experiment 268. — Boil solution of stiumous chloride with
nitric and hydrochloric acids, using only a small (piautity of the
substances. Keep the solution.

Properties. — A colourless, heavy, fuming liquid. It
solidifies when mixed with one-third its weight of water,
forming "butter of tin" (SiiCl4.5H,0). With much
water it is decomposed :

SnCl^ 4- SHgO - HaSnOa -f 4HC1.

Many compounds of tin are similar in composition to
compounds of silicon, e.g., potassic Jluo-stannate (K.^SnF,),
and the stannateii (Na^SnO^, &c.).

Closely allied to tin are three rare metals, titanium,
zirconium, and thorium.

314. Tests.

Stannic Salts.

I. To a solution of stannic chloride add hydric sulphide. A
yellow precipitate (SnSa) falls :

SnCl^ + 2H2S = -SnSa -f 4HC1.

TESTS FOR TIN. 311

This precipitate is soluble in ainmonic sulphide and iu strong, hot,
hydrochloric acid. (Filter it off and try.) — Stannic 8ulphide(iinS,)
combines with alkaline sulphides to form aulphoatayivutes, e.g. :

SnSa + (NH^^aS = {NH^)aSnS,.

These are soluble salts, easily decomposed by acids. (Try with
hydrochloric acid.)

2. Caustic soda gives with stannic salts a white precipitate
(HaSnOg), soluble in excess of the reagent.

3. To a little stannic chloride solution in a porcelain dish add
a scrap of zinc and warm. Wash the precipitated tin, dissolve
it in warm hydrochloric acid, and add to the solution a drop of
mercuric chloride. A white precipitate of calomel (Hg.^Cl,^) or
a grey precipitate of mercury is formed :

2HgCl2 + SnCla = HgaCla + SnCl^.
HgCla + SnCla = Hg -f SnCl^.
This test applies also to stannous salts.

Stannous Salts.

1. To solution of stannous chloride add hydric sulphide. A
brown p»ccipitate of stannous sulphide (SnS) is formed. Collect
on a filter or wash by decantation, and test its solu' ility in
yellow ammonic sulphide. It dissolves. To the solution add
hydrochloric acid. Stannic sulphidt is precipitated. — Explana-
tion : Yellow ammonic sulphide coni.uns a persulphide of
ammonium (NH4)2Sa ; this unites with stannous sulphide to
form ammonic sulj)hostannate :

(NH4)2S2 + SnS = (NHJaSnSa,

wiiich is decomposed by hydrochloric acid as follows :

(NH4)2SnS3 4- 2HC1 = 2NHiCl + SnSj + H^S.

2. Caustic soda gives with stannous solutions a white pre-
cipitate (Sn(OH)a) soluble in excess.

3. Same as for stannic salts ; but stannous salts give a white
(HgaCla) or grey (Hg) precipitate with mercuric chloride, with-
out the preliminary treatment with zinc, &c.

Insoluble tin compounds can be got into solution by
reducing on charcoal and dissolving in hydrochloric acid.

312 GOLD.

GOLD (Aurum),

315. Gold. (Au' »'• = 196.2.— Sp. wt. =^ 19.265.—
Melting point = 1037^— Sp. heat = 0.03244.)

Occurrence. — Gold is usually found free or alloyed
with silver, platinum, <kc. It is found associated with
quartz and pyrites mostly.

Preparation. — It is obtained from quartz by crushing,
and washing away the lighter mineral. It is obtained
from turiferous sand and gravel by sinple \\ashing.
Gold is extracted from pyrites, <fec., by treating with
aqua regia, and precipitating the gold with green vitriol.

Froperties. — Gold is of familiar appearance, and need
not be described. It is softer than silver, and must be
hardened by alloying with copper before it is suitable for
use. It is the most malleable and ductile of all metals.
A ^olu wire can be drawn so tine that 10,000 feet (about
1| mile) weigh only 15 grains. Gold is not attacked by
any simple acid, excepting selenic (H.2Se04). It is attacked
by caustic potash, caustic soda, and saltpetre. The best
solvent for gold is aqua regia, which dissolves it as tri-
chloride (AuClg). Gold is very easily precipitated from
solutions by reducing agents such as stannous chloride,
ferrous sulphate, oxalic acid, mercurous nitrate, &c.
Purple of Gassius is formed jy precipitating with stan-
nous chloride. It consists of finely divided gold and
some compound of tin.

316. Compounds of Gold. Gold forms two
oxides, aurous (Au.^0), and auric (Au^Oa). Both are
decomposed into gold and oxygen at 250°C. Both are
basic, but auric oxide is also a weak acid-forming oxide. —
The aurous salts (AuCl, A al, <fec.) are very unstable,

PLATINUM. 313

readily decomposing into gold and auric salts. Potassic
aurous cyanide (KCN.AiiCN), is, however, quite stable,
and is used in electro-gilding. — Auric chloride (AuOlg)
unites with hydrochloric acid to form chlorauric acid
(HAUCI4). This is the solution generally used and
called ter chloride of gold.

317. Tests.

1. Solutions of gold acidified with hydrochloric acid give a
brown precipitate (AujSy), soluble in amnionic sulphide.

1\ Solutions containing gold give a purple colour or precipitate
with stannous chloride or ferrous sulphate.

PLATINUM, &c.

318. Platinum (Pt»*^ = 196.7.— Sp. wt. = 21.5.—
Melting point about 2600°,— Sp. heat = 0.03243).

Occurrence. — Platinum is found in the metallic state,
alloyed with palladium, osmium, iridium,, <fec. It is
found in the Ural Mo" ntains, S. America, Australia,
Borneo, and California. It has lately been discovered in
British Columbia. It is generally present in small
quantity in gold and silver.

Preparation. — The crude platinum l . dissolved in
aqua regia, and precipitated as ammonium chloroplati-
nate, (^"114)2 PtClg, by ammonic chloride. From this
compound it is obtained by heating :

(NH4)2PtCle = 2NH^C1 -f Pt + 2Cla.

It generally contains about 2 % of iridium.

Properties. — A tin-white metal, soft, very heavy and
malleable. It fuses only at an intense white heat. It
has the power of condensing gases on its surface, and, in

314 PLATINUM.

the finely divided state of spongy platinum and platinum
black, it is used to bring about the oxidation of alcohols
to aldehydes, sulphur dioxide to trioxide, (fee. Platinum
is attacked by few chemical substances. It combines,
however, with the halogens, and is dissolved slowly when
heated strongly with caustic potash, caustic soda, potassic
nitrate, or potassic cyanide. It is attacked by oxides
and sulphides of easily reducible metals, such as lead,
copper, bismuth, (fee, as well as by these metals them-
selves. These substances should never be heated in a
platinum crucible.

Uses. — Platinum is of the greatest importance in
chemistry. " Without platinum the composii'ion of most
minerals would have yet remained unknown." — (Liebig.)
It is used for crucibles, as it resists the action of most
chemicals. It is pIso used in the manufacture of chemical
balances and many other instruments of precision. The
surgeon employs it, heated by a current of electricity or
by alcohol vapour, using it instead of a knife.

319. Compounds of Platinum. Platinum forms
two series cr" compounds, platinous (PtO, PtClg, PtS, <fec.),
and platinic (PtOj, PtCl^, (fee). The platinous compounds
are unimportaxit. When platinum is dissolved in aqua
regia the solution contains chloroplatinic acid (HjPtClg).
This is the solution generally called " solution of tetra-
chloride of platinum^ It is a well-marked dibasic acid,
and forms characteristic sparingly soluble salts (chloro-
platinates) of potassium, ammonium, amines, and alka-
loids. These salts are of a golden yellow colour, and are
sparingly soluble in water. — As the sodium salt(Na2PtClj)
is very soluble in water, chloroplatinic acid is used in
analysis to separate sodium from potassium.

PALLADIUM, <kc. 316

320. Tests.

It is precipitated along with the other members of this group
by hydric sulphide. Platinic sulphide (PtSj ) dissolves in amroonic
sulphide. — A solution containing platinic salts gives a golden
yellow precipitate with ammonic chloride. — Solid substances
containing platinum are extracted with aqua regia and tested as
above.

321. Palladium is similar to platinum, but is soluble
in nitric acid. It is used instead of gold by dentists. —
Iridium is alloyed with platinum to make standard
weights and measures. The alloy is very hard, and as
elastic as steel. — Osmium forms a remarkable acid-forming
oxide (OsO^), which is volatile and very poisonous.
Osmic acid (HjOsOg) is much used in practical histology.
It stains fats black. An alloy of osmium and iridium
{osmiridium) is used for tipping gold pens. Osmium is
the heaviest substance known (sp. wt. = 22.477). It
has never been fused. — Tungsten and molybdenum,
although not nearly allied to the metals of this group,
are mentioned here because their sulphides are precipitated
by hydric sulphide and dissolve in ammonic sulphide.

QUESTIONS AND EXERCISES.

1. "The hydroxides of Group II. are precipitated from solu-
tions of salts by alkaline hydroxides." Illustrate this utatement
by examples.

Illustrate from the members of this group the Law of Dulong
and Petit.

3. What experimental proof can you bring to show that iron
haf^ a stronger attraction for salt radicals than copper has, i.e., is
a more positive radical ?

4. How would you prepare crystals of cupric nitrcUe ?

316 QUESTIONS AND EXERCISES.

5. Why is it dangerous to eat food which has been for some
time in contact with brass ?

6. Is there any danger in using brass taps for vinegar and
cider casks ? Explain.

7. How can cadmic chloride be prepared from cadmic nitrate ?
(Both salts are soluble.)

8. The specific weight of cadmii i vapour is 3.94 (air = 1).
Calculate its molecular weight. How many atoms in the mole-
cule of cadmium ?

9. Why should we expect bismuth carbonate to be more
soluble in the gastric juice than the subnitrate ?

10. Compare bismuth and antimony (1) as to the properties of
the elements themselves, (2) as to their compounds.

11. Bismuth trinitrate is poisonous, and large doses cause
symptoms of nitric acid poisoning. Explain this.

12. How would you distinguish by a jst bismuth subnitrate
from bismuthyl carbonate ?

13. Compare antimony and arsenic with regard to their com-
pounds.

14. Balance the following equations :

(1) SbClaOH 4- H2O = SbaOg + HCl

(2) SbaOg + KHC^H^Oe = SbOKC^H^Oe + HjO.

(3) SbClg + H2S = SbaSa + HCl.

(4) SbaOg + Ha = SbHg + H3O.

15. What substances are formed when tin is dissolved in very
dilute nitric acid ?

16. When solution of stannous chloride (SnClj) is added to
auric chloride (AuCl 3), metallic gold is precipitated and stannic
chloride remains in solution. Write the equation.

17. What is the chemical composition of "butter of *in,"
" butter of antimony," " butter of arsenic," and *' tin salt f "

18. Why is it necessary to use ammouic sulphide containing
excess of sulphur to dissolve stannous sulphide ?

19. A solution of chlorauric acid in water oxidises ferrous sul-
phate. How is this possible ? Does chlorauric acid contain any
oxygen ?

METALS OP GROUP III. 317

CHAPTER XIX.

METALS OF GROUP III.

Iron, Chromium, Aluminium ; Zinc, Manganese, Cobalt,
and Nickel. \^Rare metals oj the Cerium class. \

322. General Characters. — The metals of this

group are mostly reducible from their oxides by smelt-
ing with charcoal, but are more difficult to reduce than
those of the preceding group. With two exceptions
(aluminium and zinc) they have two oxides having the gen-
eral formulas MO and M.^Oj. Besides these, chromium
and manganese have well-marked acid-forming oxides.
Their sulphides are not precipitated by hydric sulpliide
from acid solutions ; but are precipitated by alkaline sul-
phides (two exceptions will be noted further on). Both
sulphides and oxides are insoluble in water, but soluble in
dilute acids (nickel and cobalt sulphides with difficulty).
Tiie hydroxides, carbonates, and phosphates are insoluble
in water, and can all be prepared by precipitation. The
hydroxides are easily changed to oxides by heat. The
sulphates, chlorides, nitrates, and acetates are soluble in
water, and their solutions have an acid reaction. The
sulphates form characteristic double-sulphates with those
of the alkali metals, e.g., K2SO,.FeSO,.6H.,0. The
alums form an interesting group of these double sulphates.

For convenience of analysis this group is subdivided
into : A. Metals forming stable hydroxides, M.j(0H)6, in-
soluble in ammonia : iron, chromium,, and aluminium ;

318 TRON.

and B. Metals, the most basic hydroxides of which have
the general formula M(0H)2 and are soluble in am-
monia : zinc, maiiganese, cobalt, and nickel. In analysis
the cerium metals, as well as uranium, zirconium, and
thorium fall here.

IRON (Ferrum).

323. Iron (Fe "^^ = 56.— Specific weight = 7.844.
Melting point = 1600°. Specific heat = 0.11379).
Occurrence. — Rarely free, and then generally 'of

meteoric origin. Meteors composed mostly of iron have
been found weighing several tons. The principal ores
of iron are red hcematite (FejOg), brown haematite
(2Fe203.3H20), magnetic iron ore (Fe304), spathic iron
ore (FeOO,), clay ironstone (FeCOj, with clay or sand),
and black band (FeCOg, with coa ). — Iron is present in
the sun and in many fixed staio. — Iron is an essential
constituent of the bodies of plants and animals. In the
latter it is chiefly found in the hcemoglobin of the blood.

Smelting of Iron. — The ores are first calcined, if
necessary, to drive off water, <fec., and then placed in a
tall, somewhat spindle-shaped, furnace {blast furnace],
with alternate layers of coal and limestone. The lime-
stone combines "with the siliceous impurities to form a
fusible slag. The coal burning at the bottom of the
furnace (where a blast of hot air feeds the combus-
tion) forms carbon dioxide, which, passing upward,
unites with carbon to form carbon monoxide. Ferric
oxide (FejOs) is then reduced by the carbon monoxide :

FcaOa -f 3C0 = 2Fe + SCOg.

IRON. 319

This is repeated with the successive layers. The iron, as
it falls toward the bottom of the furnace, combines with
carbon and silicon and becomes more fusible. It melts
and falls into the hearth of the furnace, the slag forming
a layer above it. The molten iron is run off into chan-
nels made of sand, and solidifies into bars of pig iron.
Pig iron contains from 76 % to 96 % of pure iron, from
1 % to 20 % of manganese, and from 1 % to 7 % of car-
bon. It melts with comparative ease, and is used in
manufacturing stoves, (fee, by the process of casting. It
• is hence called cast iron. It is more brittle than pure
iron and lighter.— Wrovyht iron is prepared from cast
iron by removing the carbon and silicon. This is done
by subjecting the molten metal to a hot oxidising blast
in the process of puddling. In the Bessemer process the
iron is kept hot by the oxidation of its impurities.
Wrought iron contains up to 0.3 % of carbon. It is
lieavier than cast iron and very tenacious and malleable.
— Steel is intermediate in com[)osition between cast and
wrought iron. It is now generally prepared by the
Bessemer process, modified more or less. The impurities
are burned away until the composition is that of wrought
iron. Then enough cast iron is added to bring up the
percentage of viarbon to about 1.5 %. — Spongy iron, the
ferrum redactum of the Pharmacopoeia, is prepared by
heating pure ferric oxide in a current of hydrogen :

FeaOg + 3H2 - 2Fe + SHaO.

It is valuable as a medicine, and as a filter for water,
since it possesses the power of destroying impurities.

Properties. — Pure iron is almost as white as silver.
It is the most tenacious of all metals, except nickel and

320 OXIDES OF IRON.

cobalt. Iron is soft at a red heat, and can be welded
at a white heat. Borax, sand, <kc., are used to clear
away the oxide from the surfaces to be welded. This
they do by uniting with it to form fusible slags (silicate
and borate of iron), which are easily scraped off. Iron
is attracted by magnets, and can be made magnetic by
the influence of electricity or of other magnets. It does
not rust in dry, but does in moist, air. The rust is a
compound of ferric oxide with ferric hydroxide (Fe./),,.
Fe2(OH)8). The rusting of iron can be prevented by
coating it with tin, or with a layer of the black oxide
(FeijO^) by exposing it to tlie action of steam at 650''
(BarfT's process). Galvanised iron is covered with a
layer of zinc, which protects the iron by rendering it
electro-neyative. — Iron dissolves in dilute acids, and thus
forms ferrous salts and hydrogen (Expt's 28 and 29).
It is also slowly eaten away by water in the presence of
air. Part of lie iron dissolves as acid carbonate, and
part of it forms rust. Caustic soda and potash prevent
this.

Experiment 269. — Put a piece of bright iron wire in a beaker
of tap water, and another in water containing caustic soda.
Examine after 24 hours.

324. Compounds of Iron. — Iron forms three
oxides : ferrous (FeO), ferric {¥e,f)^, and tlie hlack
(Fe304), or ferrosoferric oxide {YqO.Yq^O^). The latter
is formed when iron is heated strongly in air, and is the
chief constituent of the black scales of the smithy. It
can also be prepared by adding caustic soda to a solution
containing a ferrous and a ferric salt, and then applying
heat. It then forms a black p^-ecipitate, attracted by the
magnet. Ferrous and ferric oxides are basic, and thus

FERROUS SALTS. 04^1

there are two classes of iron salts to be considered. In
the Pharmacopceia. the names of the fen-ic salts are
distinguished by the syllable per-, e. g., perchloriJe of
iron, instead of ferric chloride.

1. Ferrous salts correspond to the oxide FeO, in which
Fe takes the place of Hj. They are easily oxidised, and
it is difficult to preserve them unchanged. They are
light green, or colourless ; have a sweetish, inky, as-
tringent taste ; and are powerful reducing agents.

2. Ferric salts correspond to the oxide FcjOg, and are
prepared mostly by the oxidation of the corresponding
ferrous salts. They are colourless when anhydrous, but
when hydrated they are yellow or brown. They have
an astringent, chalybeate taste, and can be reduced to fer-
rous salts by the action of nascent hydrogen, <fec.

FERROUS SALTS.

325. Ferrous Sulphate (FeSO^ . TH^O). — Also

called green vitriol and copperas (copper rose, from its
supposed identity with the green rust of copper).

Preparation. — By slow oxidation of iron pyrites
(FeSj) piled in heaps and exposed to the weather ;

FeSa -}- 70 -f H2O = FeSO^ + H2SO4.

The acid drainage from these heaps is treated with

scrap iron :

HaSO^ -f Fe = FeSO^ -f H3.

On evaporation, crystals of green vitriol are obtained.

Experiment 270. — Dissolve a few iron tacks in dilute sul-
phuric acid. (What is the black substance remaining ?) Keep
the solution for further experimerts.
2?

322 FERROUS SULPH\TE.

Properties. — A green crystalline substaace (Examine
a specimen carefully), often rust-coloured on the surface
from the oxidising action of the air. It is soluble in
water (70 parts in 100), insoluble in alcohol.

Experiment 271. — To a portion of the solution from Experi-
ment 270 add caustic soda. A precipitate falls, which is at
first white, but rapidly turns green. It is ferrotis hydroxide
(Fe(OH),) :

FeS04 + 2NaOH = Fe(0H)2 -f NaaSO^.

Close the 1. 1. with the thumb, and shake vigorously. Note that
the thumb is pushed inwards showing that the pressure inside
has decreased, and that the hydroxide has become rust-coloured :

2Fe(OH)2 + O + H2O = Fe2(0H)e .

If ferrous hydroxide is precipitated in an atmosphere
free from oxygen, it is white. When heater" it loses
water, and iorm.% ferrous oxide (FeO), a black powder :

Fe(0H)2 = FeO + HgO.

Experiment 272- — Boil a little of the solution of ferrous
sulphate with nitric acid. Red fumes are evolved, and the solu-
tion becomes red, owing to the formation of ferric sulphate
(Fea(S04),) and nitrate (Fea(N'03)e) :

6FeS04 4- 8HNO3 =

2Fea(SOj3 -f Fe2(N03)e + 2N0 + 4H2O.

Add caustic soda to this solution ; a red precipitate of ferric hy-
droxide is thrown down :

Fe2(S04)8 + 6NaOH = Fea(OH)e + SNaaSO^.

Experiment 273. — Pour a small quantity of hot saturated
solution of ferrous sulphate into an equal volume of alcohol.
Shake or stir. Ferrous sulphate is precipitated in a granular
condition (Ferri sulphas granulata).

FRUROUS ARSENATE. 333

Experiment 274. — Heat a crystal of green vitriol very gently
in a t. t. It loses water of crystallisation and falls to a white
powder {Ferri nulphas exaiccata).

In large doses ferrous 8ul[)hate may act as poison,
but in smaller doses it is a useful medicine. — Mohr'a
salt is amnionio-ferrous sulphate (NH4)2SO^.FeS04.6H.jO.
It does not become oxidised as readily as green vitriol.

326. Ferrous Carbonate (FeCOg).

Experiment 275. — Heat some solution of ferrous sulphate to
boiling, and add to it solution of amnionic carbonate (best made
with recently boiled water). A precipitate falls, which is at first
white but rapidly becomes green by oxidation. It is ferrous
carbonate (F&GO ^) :

(NHJ2CO3 + FeFO^ = FeCOg + (NHJaSO^.

Ferrous carbonate is so easily oxidised that its pre-
paration is attended with some difficulty. In medicine
it is used mixed with sugar {Ferri carbonas aaccharatd).
Griffith's mixture is another preparation of ferrous car-
bonate. They must be kept in well stoppered bottles.
Ferrous carbonate, on account of its easy solubility in
the gastric juice and its mild action, is a favourite pre-
sc iption of iron.

327. Ferrous Arsenate (Fe3(A804)2).

Preparation. — By adding solution of ferrous sulphate
to one of sodic arsenate (NajHAsO^) mixed with sodic
acetate, ferrous arsenate is precipitated as a greenish
readily oxidisable substance :

2Na2HA804 + 2NaC2H302 + 3FeS04 =

Fe3(A804)2 + SNa^SO^ + 2HCaH30a.

It is always partially oxidised in the process of prepara-
tion.

324 FKNROUB IODIDE.

328. Ferrous Phosphate (FejiPOJ.,).

Preparation. — This compoimd is prepared in much
the same way as ferrous arsenate.

Experiment 276 — To solution of ferrous sulphate add some
sodic acetate, and then sodic phosphate. Ferrous phosphate k
precipitated. (Write the equation.)

The object of adding sodic acetate in these processes
is to provide that the acid which is set free in the reac-
tion shall not be a solvent for the phosphate. Note
that, while sodic phosphate is an acid salt, the iron salt
is normal. If the sodic acetate were not added, some of
the phosphate would remain unprecipitated, being solubl
in sulphuric acid. But it is insoluble in. acetic acid.

Properties. — Similar in appearance to the arsenate
(Art. 144), but inclining to blue in colour. It is in-
soluble in water, but soluble in hydrochloric acid. — To
distinguish the phosphate from rhe arsenate, dissolve in
hydrochloric acid and test with hydric sulphide. The
arsenate gives a yellow precipitate, the phosphate none.

329. Ferrous Iodide (.Felj). — This is the green

iodide of iron, prepared by warming together 3 parts of
of iodine, 1 ^ of iron, and 1 2 of water, until the iodine dis-
appears, then boiling, filtering, <fec. It is a deliquescent
green salt. — Ferrous Bromide (FeBr^) is prepared simi-
larly. — Ferrous Chloride (FeClj) has been already
noticed (Exp't 29).

FERRIC SALTS.

330. Ferric Chloride (Fe^Clg). — Also called per-
chloride of iron.

FERRK! CHLORIDE. 326

Preparation. — Experiment 277. — Disnolve some iron
tacks in dilute hydrochloric acid in a porcelain dish with the
aid of a gentle heat. Let there be insufficient acid to dissolve
the tacks completely. Filler the solution. (What is the black
substance ?) Add a small (piantity of nitric acid and a little
hydrochloric acid, and heat (quickly until red fumes are evolved.
Evaporate on the water bath.

Ferrous chloride (FeCl.^) is formed by (H8.solving iron
in hydrochloric acid :

Fe + 2HC1 = FeCla + Hg.

This is changed to ferric chloride by the addition of
chlorine produced by the action of nitric on hydrochloric
acid :
(JFeCla + 6HC1 + 2HNO3 = SFeaCle + 2N0 + 4H2O.

Properties. — The solution obtained in Experiment
277, when evaporated to a syrup and allow^ed to cool,
solidifies to a yellowish ma8.s of the liydrate, Ye^G\.
I2H3O. — Anhydrous ferric chloride can be prepared as a
steel-black deliquescent solid by heating iron in a curr( ut
of dry chlorine gas. — Fe^ic chloride dissolves in water,
forming a dark red solution which becomes yellow on
dilution. The solution has an astringent taste. Ferric
chloride is soluble in alcohol, but the solution [tincture
of iron) tends to deposit ferric hydroxide, and has no
virtues to recommend it above the cheaper aqueous solu-
tion. — Ferric chloride dissolves terric hydroxide, and
thus forms soluble basic salts, milder in their action than
the normal salt. By dialysis of ferric chloride, soluble
ferric hydroxide (dialysed iron) can be obtained. It is
an excellent antidote for arsenic poisoning, and is the
best preparatioTi of iron for a delicate stomach. It un-
fortunately gelatinises after a time.

326 FERRIC NITRATE.

Experiment 278. — Make a small boat of parchment paper,
fill it about one-fourth with dilute solution of ferric chloride,
float it in a basin or beaker of distilled water, and leave it for
24 hours. Examine the water for hydrochloric acid, by taste,
litmus, &c. Taste the iron solution. It has lost much of its
astringency. Boil some of it in a t. t. I^erric hydroxide is pre-
cipitated.

In this experiment water decomposes ferric chloride :
FeaCle + 6H-0 = Fea(0H)6 + 6HC1.

The crystalloid hydrochloric acid passes through the
membrane, while colloid ferric hydroxide remains.

331. Ferric Sulphate (Fe,(S04)3).--This salt has

been already noticed (Exp't 272), If it is desired to
prepare the pure sulphate, sulphuric acid must be added
according to the equation :

CFeSO^ + 3H2SO4 + 2HNO3 = 3Fe2(S04)3 -h 2N0 + 4H2O.

It forms a reddish-brown solution, of strongly acid reac-
tion. — Ferric sulphate unites with potassic sulj)hate and
water to form iron alum, K2S04.Fe.2(S04)3.24H20.

332. Ferric Nitrate (Fe,(N03)6).— When iron dis-
solves in cold very dilute nitric acid, ferrous nitrate
(Fe(N03)2), and ammonic nitrate are formed :

4Fe + IOHNO3 = 4Fe(N03)2 + NH4NO3 + 3HaO.

But when the action is hastened by heat or by using a
stronger acid, ferric nitrate is one product, and some
oxide of nitrogen another, e.g. :

2Fe + 8HNO3 = Fe2(N03)e + 2N0 -f 4HaO.

It forms a solution of a reddish-brown colour, the ferri
pernitratis liquor of the Pharmacopoeia.

FKRRIC HYDROXIDE. 327

333. Ferric Hydroxide (Fe,(0H)6). This is pre-
pared as in the second part of Experiment 272, but am-
monia is generally n.. 1 instead of caustic soda. It is a
reddish bro'.'^n substance vhich gradually undergoes
change even when kept in water. It loses water when
dried in the air, forming a hydroxide of the composition
FejOg.HjO. The same decomposition goes on under
water, and the dehydrated compound is less active, e.g.
it does not combine with arsenic trioxide.

Experiment 279.--Heat a small quantity of ferric hydroxi(te'
on mica until it is converted into the oxide (FeaOg). Try to
dissolve this in hydrochloric acid. (Is the hydroxide soluble in
hydrochloric acid ?)

Ezperiment 280. — Add solution of sodic carbonate to one of
ferric chloride. Ferric hydroxide is precipiT;ui.3d. It is so weak
a base that it does not form salts with weak acids :

FejCle + SNaaCOg + SHjO = .

Fe2(0H)8 + 6NaCl -f 300^.
(Did you observe the evolution of carbon dioxide ?)

334. Ferric Oxide (FegOg). This compound has
been already noticed several times.

Experiment 281. — Heat a few crystals of green vitriol
strongly in a porcelain crucible. Ferric oxide remains as a red
powder, called colcothar, crocus, rouge, or Venetian red. Try to
dissc-ive some of it in strong acids. It is insoluble.

Igni^/cd ferric oxide should never be used in medicine
instead of the hydroxide described in Art. 333, as it
is insoluble in acids, and therefore useless for prescription
as an iron preparation.

335. The "Scale" Compounds of Iron.—

Certain organic acids (citric, tartaric, <kc.,) prevent the
precipitation of ferric hydroxide by ammonia.

328 THE "scale" compounds.

Experiment 282. — To a solution of ferric chloride add tar-
taric acid, and then ammonia until the liquid is alkaline. No
precipitate forms.

This is due to tlie formation of a soluble basic tartrate
of iron and ammonium. If ferric hvdroxide is dissolved
in tartaric Sicid, ferric tartrate is formed. When ammonia
is added to this and the whole evaporated to dryness, a
basic salt is obtained in red amorphous scales. Similarly
with citric acid. Quinine and other alkaloids are added
to these scale preparations. They contain variable
quantities of iron, and are rather difficult to prepare.

336. Tests.

Ferrous Salts.

1. Solutions of ferrous salts give with ammonia a greenish
precipitate (Fe(0H)2), turning rust coloured when shaken up
with air.

2. Amtnonic sulphide gives a black precipitate (FeS), soluble
in dilute hydrochloric acid :

FeS + 2HC1 = FeCla -f H2S.

3. PotaAsic ferrocyanide {K^VeiGN)^) gives a white or light
blue precipitate of potassic ferrous ferrocyanide i

■ K4.Fe(CN)e + FeSO^ = KaFe.FeCCN)^ + K2SO4. .

This quickly turns blue by oxidation, fortaing Prussian blue.

4. Potassic ferricyanide (K3Fe(CN)a) gives a deep blue pre-
cipitate (or colour, according to the strength of the solution)
(KFe.Fe(CN)e). (TurnbuU's Blue.)

5. Ferrous solutions, when heated with nitric acid, turn red,
and will then give a reddish-brown precipitate with ammonia.

Ferric Salts.

1. Ammonia gives a reddish-biown precipitate of ferric hy-
droxide, insoluble in excess. .

CHROMIUM. 329

2. Amnionic sulphide gives a black precipit vte of ferrous sul-
phide mixed with sulphur :

FegCle + 3(NH4)2S = 2FeS + S + 6NH4CI.

This is soluble in dilute hydrochloric acid, the sulphur remain-
ing undissolved.

3. Potasaic ferrocyanide gives a deep blue precipitate of Prua-
siatt b/ue.

4. Potassic ferricyanide gives a greenish-brown colour, but no
precipitate.

5. With hydric sulphide ferric salts give a white precipitate of
sulphur. FeaCl, -f HaS = 2FeCl2 -f 2HC1 + S.

6. Insoluble iron compounds are tested by the borax bead,
which with iron is yeilow in the oxidising, colourless or blue in
tb ?■ reducing flame.

CHROMIUM.

337. Chromium (Cr "• '^•^' = 52.4).— The metal it-
self is of no imj)ortance. The principal ore is chrome
ironstone, or chrornite (FeO.Cr.^Og). — The name Chromium
is derived from a Greek work meaning colour, because
all chromium compounds are coloured. The metal is re-
duced from its ores with great difficulty. Chromium
ores are sometimes added to iron ores, because chromium
imparts great hardness to steel. CAromiwrn «<ee/ requires
to be worked at comparatively low temperatures.

338. Compounds of Chromium. — Chromium

unites with oxygen in three portions, forming two basic
oxides, — chromovs (CrO), and chromic (CroOg); and one
acid-forming oxide, — chromium trioxide (CrOg). — The
chromous salts (CrCl2, CrS04, <fec.) are very unstable,
becoming oxidised even more readily than feiTous salts. —
The chromic salts (CrjCl^, Cr2(S04)3, «fec,) are similar to
ferric salts in composition and properties. They are the

330 POTASSIC BICHROMATE.

ordinary salts of chromium. — Besides these two series of
compounds there are the chromates, salts of chromic acid
(H^CrO,). ,

339. Potassic Bichromate {'K.firf>^ = KjO.

2Cr03). — This salt is the starting point in preparing
chromium compounds.

Preparation. — Chrome ironstone is roasted, ground,
and heated with lime and potassic carbonate, with con-
stant stirring so as to allow oxidation to go on. The
object of the lime is to economise alkali, and to prevent
fusion, so that the air may penetrate into the mass :

CrgOa + 2K2CO3 + 30 = 2K2Cr04 -j- 2CO2.
CraOa + 2CaO + 30 = 2CaCr04.

When oxidation is complete, the potassic and calcic
chromates are dissolved in water, and to the solution
potassic sulphate (K2SO4) is added to precipitate calcium :

KaSO^ + CaCrO^ = CaSO^ -|- K2Cr04.
To the strong solution of potassic chromate thus obtained
sulphuric acid is added to form the less soluble bichromate:

2K2Cr04 + H2SO4 = K^Gt^O^ + K2SO4 + H2O.

The object of this operation is to separate the chromium
salt from the impurities present in the solution.

Properties. — Potassic bichromatf crystallises in large
garnet red prisms, soluble in water (8 parts in 100). It
is a strong oxidising agent, especially in the presence of
acids. An instance of this has been already described
(Aldehyde).

Experiment 283. — To a solution of potassic bichromate
acidified with sulphuric acid add sulphuretted hydrogen. The
red colour changes to green, and sulphur is precipitated :

INSOLUBLE CHROMATES. 331

KgCraO^ + 4H2SO4 + 3H2S =

K2SO4 + CraCSOJg + 7H2O + 3S.

In this action chromium trioxide is an oxidising agent,
and the hydrogen of hydric sulphide is oxidised to water.
Leaving the acid out of considei-ation the action can be
represented more simply :

2Cr03 + 3H2S = CraOj -f- 3H2O + 3S.

Experiment 284. — To 50 c. c. of saturated solution of potassic
bichromate add 5 or 10 drops of sulphuric acid, and then sul-
phurous acid until the coloui is bright green. Evaporate to a
small bulk and set aside. The solution contains chrome alum
(K2SO^.Cr,(SOJ3.24H,0):

K2Cr207 -f HaSO^ + SSOa = K2S04.Cr2(S04)3 + H2O.

Potassic bichromate, on account of its oxidising power,
is a corrosive poison. The antidote is ferric chloride,
which forms the sparingly soluble ferric chromate.
Alkaline sulphites should also be antidotal, (Whyl)

Potassic bichromate is used in the preparation of other

chromates. The following are insoluble in water but

soluble in dilute acids : baric (BaCr04), plumbic

(PbCrO^), argentic (A-gjCrOi), mercurous (Hg2Cr04),

ferric (Fe2(Cr04)3), and others.

Experiment 285. — Add solution of potassic bichromate to
solutions of the following salts, note the colour of the precipitates
and test their solubility in acetic and nitric acids, viz., baric
chloride (BaCla), plumbic acetate (Pb(C2H302)2). argentic nitrate
( AgNOg ), and merctirous nitrate (HgalNOg) 2). Normal chromates
are precipitated, and acid is set free in each case. (Write the
equations.)

Plumbic chromate (PbCr04) \l used as a paint {chrome
yellow). Chrome red is a basic chromate of lead pre-
pared by boiling the normal chromate with lime water.

332 CHROME ALUM.

Experiment 286. — t)ip a piece of white cotton in dilute solu-
tion of pi imbic acetate, soak it well, wring it, and then dip it in
dilute solution of potassic bichromate. It is dyed yellow, and
the colour is fant, being precipitated within the fibres of the
cotton. Boil the cotton with lime water ; it becomes orange
red.

340. Chromic Acid.

Experiment 287. — To a cold saturated solution of pota38ic
bichromate add one and a half times its volume of concentrated
sulphuric acid, taking care to stir well. Set in a cool place.
Chromium trioxide (CrOg) separates oui* in beautiful red crystals.

Chromium trioxide dissolves in water, forming a strongly
acid Bolution, but no definite acid has been separated
from this. The normal chromates are analogous to the
sulphates in composition, e.g. K2Cr04, PbCr04, (fee, so
that chromic acid may be supposed to have the formula
HgCrO^. Potassic bichromate is then an anhydrous
acid salt.

341. Chrome Alum (K,S04.Cr,(S04)3.24H20).

This salt is prepared as in Experiment 284. It is a by-
product in some operations in which potassic bichromate
is used as an oxidising agent, e.g. in the manufacture of
alizarine. It is soluble in water, and crystallises from
cold solutions in violet crystals isomorphous with those
of common alum. If a crystal of common alum be placed
in a saturated solution of chrome alum it grows by addi-
tion of layers of the chrome alum. Solutions of chrome
alum undergo a peculiar change on being heated. The
colour changes from violet to green, and this solution
does not crystallise. It slowly returns to its former
condition. This property is common to all chromic

CHROMIC HYDROXIDE. 333

galls. — Chrome alum is used in tanning, dyeing, and
calico-printing.

342. Chromic Hydroxide (Cr,(OH)«).

Experiment 288. — Add ammonia to a solution of chrome
alam. Collect the precipitate of chromic hydroxide on a filter
and wash it. Try the soluhility of portions of it in hydrochloric
acid, caustic soda, and ammonia. Heat part of it on mica.

Chromic hydroxide is of a dirty green colour. It dis-
solves in hydrochloric acid, forming chromic chloride
(CrjClg). It is also soluble in caustic soda, forming a
green solution from which it is reprecipitated by boiling.
When heated it loses water, and chromium sesquioxide
(CraOg) remains. This oxide is used as a paint (chrome
green). Guignet's green has the composition, Cr203.2H20.
It is also sold as chrome green.

343. Tests.

Chromaies.

1. Baric chloride gives a yellow precipitate insoluble in acetic
acid, soluble in nitric acid.

2. Acidified solutions of chromates are turned green by hydric
sulphide.

3. Solutions of chromates are reduced by ammonic sulphide,
which precipitates chromic hydroxide, so that this group reagent
is a test for chromates as well as for chromic salts.

4. Insoluble chromates can be tested for by the borax bead,
to which they give an emerald green colour.

Chromic Salts.

1. Ammimia precipitates chromic hydroxide, insoluble in
excess.

2. AmmOTiic sulphide gives a dirty green precipitate of hy-
droxide :

Cr^CSOjg + 3(NH JaS + SH^O =

Cr2(OH)e + SCNHJ^SO^ + SH^S.

334 ALUMINIUM.

3. Caustic soda gives a green precipitate soluble in excess, re-
precipitated by boiling.

4. Insoluble chromium compounds can be detected by the
borax bead, or by heating in the oxidising flame with a sodic
carbonate bead, to which they give a yellow colour, due to the
formation of sodic chromate. If the bead be dissolved in water
the yellow colour appears strongly.

ALUMINIUM.

344. Aluminium (Al'^ = 27.3. ~Sp. wt. = 2.67.—
Melting point = 700°.— Sp. heat = 0.2143).

Occurrence. — Compounds of aluminium form a very
considerable proportion of the earth's crust, being found
in clay, granite, gneiss, mica, felspar, &c.

Preparation. — From bauxite, a hydroxide of alum-
inium and iron. Aluminium chloride (AljClg) is obtained
by a series of operations, and from this the metal is set
free by sodium. Lately the metal has been obtained
more economically by electrolysis.

Properties. — A light, tin-white metal, malleable,
ductile, and sonorous. When pure it does not tarnish in
air, but the impure metal soon tarnishes ; and this is one
difficulty in the way of the economical manufacture of
the metal. It decomposes water at 100°, and dissolves
easily in most acids and alkalis. Obviously, it cannot
be used for cooking utensils. It is very useful wherever
lightness and durability are required, as in optical instru-
ments, &c. Aluminium, bronze is an alloy of aluminium
with 90 % of copper. It has the appearance and many
of the qualities of gold.

ALUMINA. 335

345. Alumina (AI2O3). This is the only oxide of
aluminium.

Occurrence. — As corundum, ruby, sapphire, emery,
(fee. ; and combined in many silicates, &c.

Preparation. — Experiment 289.— To a solution of alum
add ammonia. Collect on a filter, and wash, the gelatinous pre-
cipitate of aluminic hydroxide, Ala(0H)9 :

6NH4OH + Al2(SOj3 = Al2(0H)e + 3(NH4)2S04.

Heat a portion of the precipitate on mica. It decomposes into
water and aluminic oxide :

Al2(0H)6 = AlaOs + SHaO.

Properties. — A whit« powder, insoluble in acids after
it has been ignited. Crystalline alumina is next to
diamond in hardness, and in the form of emery is used
in grinding and polishing hard substances.

Aluminic hydroxide^ Al2(0H)g, is a, weak base, and
also a weak acid. . -

Experimont 290. — To ia solution of alum add caustic soda, a
little at a time. Aluminic hydroxide is precipitated and re-
dissolved:

Al2(0H)e + 6NaOH = Ala(0]Sra)e + eHjO.

Aluminic hydroxide dissolves in solutions of caustic
soda and caustic potash, forming aluminates. It does not
dissolve in solution of ammonia. — It has the power of
extracting colouring matters from solution, and is used
as a clarifier, decolouriser, and as a mordant in dyeing.

346. Aluminic Salts. Aluminium salts are mostly
colourless, and, when the acid is a strong one, of an
astringent, acid taste. They resemble ferric and chromic
salts in composition, e.g. AljClg, Al2(S04)3, Al2(N03)g, &c.

336 ALUMS.

Like chromium and iron (in ferric compounds), aluminium
does not form salts of such weak acids as carbonic.

347. Alums. Aluminic sulphate (Al2(S04)3) com-
bines with potassic sulphate (KqSO^) and water to form
potash alum, K2S04.Al.j(SOj3.24H20. It also unites
with ammonic sulphate to form ammonia alum
(^Yi^)^^O^.A.\{%0^)^.UVL^O. The alums are a group of
compounds similar in properties and composition, and
exactly alike in crystalline form. A crystal of any one
alum will increase in size when placed in a saturated solu-
tion of any other ; the alums are isomorphous. A gen-
eral formula may be written thus :

MaS04.M'2(S04)3.24Hj,0.

M = K, NH4, Na, Rb, Cs, Ag, or Tl.
M' = Al, Fe, Cr, In, or Ga.

Preparation. — Potash and ammonia alum,s are the
ones in common use. They are prepared mostly from
shale, which contains clay (a silicate of aluminium) and
iron j)yrites (FeSj). The shale is burned in heaps, when
aluminic and ferrous sulphates are formed. By lixivia-
tion a solution of aluminic sulphate is obtained. To this
potassic or ammonic sulphate is added, and the alum is
obtained by evaporation, and purified by recrystallisation.

Properties. — Potash and ammonia alums are colour-
less solids, generally sold in large crystals. They are
exactly alike in appearance, and can only be distin-
guished by a chemical test. They have an acid, sweetish,
astringent taste. They are soluble in water (12 parts in
100), the potash, a little more so than the ammonia,
alum. They effloresce slowly in air, owing to the action

PORCELAIN. 337

of the ammonia of the air in forming basic salts. — Potasli
ahim is now the one generally sold.

Experiment 291. — Heat a crystal of potash alum in at. t. ^
and observe the loss of water of crystallisation. The white
powder which remains is anhydrous alum, or burnt alum {alumen
tidum).

348. Aluminic Sulphate (Al2(SO,)3.l8H20). This

salt, known as concentrated alum, or alum cake, is pre-
pared on the large scale by the action of sulphuric aci<l
on certain clays, the products being alurainic sulphate
and silicic acid. It replaces the more expensive alum in
many of the uses to which that substance has been put.

349. Porcelain, &C. Porcelain is made fiom a
pure white clay {kaolin, or china-clay), a hydrated silicate
of aluminium (Al.2O3.2SiO2.2H2O). In the process of
burnirtg, the water is driven off. The glaze is felspar,
borax, bone ash, or red lead. — Stoneware, earthenware,
and common pottert/, are made from impure clays.

350. Tests.

1. Ammonia precipitates aluminic hydroxide, insoluble in
excess.

2. Amnionic sulphide gives the same precipitate :

Al2(S04)3 + 3(NH4)2S + 3H2O =

Al2(0H)e + 3(NH4)2S04 + 3H2S.

.3. Caustic soda precipitates aluminic hydroxide, but rcdissolves
it. (Experiment 290.) From this solution aluminic hydroxide
is precipitated by avimonic chloride :

Al2(ONa)6 + 6NH4CI = Al2(0H)e + 6NaCl + 6NH3.

4. Insoluble aluminium compounds are detected by moistening
with cohaltous nitrate, Co(N03)2, and heating with the blowpipe
on charcoal. A deep blue colour is imparted.
23

338 ZINC.

B
ZINC.

351. Zinc (Zn" = 64.9.— Sp. wt. = 6.9.— Melting
point = 433".— Boiling point = 1040°.— Sp. heat =
0.09555).

Occurrence. — The principal ores of zinc are calamine,
or zinc spar (ZnCOg), zinc blende (ZnS), franklinite
(ZnO.Fe.2O3), and red zinc ore (ZnO).

Preparation. — The ore is roasted, and reduced by
heating with j.ounded coal in clay retorts. The metal
distils over and is condensed in iron tubes :

ZnO + C = Zn + CO.

Commercial zinc contains lead, carbon, iron, <fec., as im-
purities. Arsenic is often present, a fact to be remem-
bered in making Marsh's test.

Properties. — Zinc is of a bluish white colour when
pure. When heated strongly in air it -iurns, forming
zim; oxide (ZnO). Commercial zinc is brittle at ordinary
temj)eratures, but is very malleable and ductile between
100° and 150°. It is easily oxidisable, and dissolves
readily in acids. Alloyed with copper it forms brass. —
Zinc is used in the manufacture of various utensils, in
galvanizing iron, in generating electricity, in preparing
hydrogen, &c.

352. Zinc Oxide (ZnO). — Zinc forms only one
oxide, known in commerce as zinc white.

Preparation. — (1) By boiling zinc and burning its
vapour. — (2) The British Pharmacopceia directs it to be
prepared by heating zinc carbonate in a loosely covered

ZINC CHLORIDE. 339

crucible, until a portion taken out does not effervesce

with acids :

ZnCOg = ZnO + CO3.

This method of preparing oxides of metals is often
employed.

Properties. — A soft, white powder, tasteless, and in-
odorous. It is insoluble in water. It is used in medicine
and as a paint.

XiXperiment 292. — Heat a small ([uantity of zinc carbonate
in a porcelain crucible for 15 minutes. Test a part of it with
dilute sulphuric acid. Note that the oxide is yellow while hot.

353. Zinc Salts. The salts of zinc are colourless,
unless the acid is coloured. The soluble salts have an
acid reaction in solution, and a nauseous metallic taste.
They are poisonous and act as emetics.

354. Zinc Chloride (ZnCl^). — This salt is known
as " butter of zinc."

Preparation. — The soluble salts of zinc are usually
prepared from the commercial metal, and the method of
preparation is similar for most of the pharmaceutical
preparations.

Experiment 293. — Dissolve some granulated zinc in dilute
hydrochloric acid by warming in a pi.rcelain dish. Boil, filter,
and add chlorine water to convert ferrous to ferric chloride.
Add zinc carbonate until a brownish precijjitate appears :

3ZnC03 + FeaCle + 3H2O =

SZnClj + Fe2(OH)6 + SCOg.

Filter again, and evaporate until oily. Set aside for a day and
observe.

Properties. — A white, fusible solid, very deliquescent.
It has strong caustic i)roperties, and the anliydrous salt

340 ZINC SULPHATE.

chars sugar, &c. It dissolves easily in water, alcohol,
and ether. — It is used for weighting cottoi. goods. In
surgery it is employed as a caustic and antiseptic. —
Burnett's disinfecting fluid is a solution of zinc chloride.
It is very poisonous, and has sometimes been swallowed
by mistake. The chemical antidotes are chalk, magnesia,
sodic carbonate, &c. (Explain the action of these anti-
dotes.)

355. Zinc Sulphate (ZnSO,. 7 H^O),— generally
known as white vitriol.

Preparation. — Dissolve zinc in dilute sulphuric ?cid,
and then proceed as with zinc chloride.

Properties. — A white crystalline salt, very much
resembling Epsom salts (MgS04.7H./3), with which it is
isomorphous. (These two salts can be readily distin-
guished by their taste.) It effloresces when exposed to
air. It is an irritant poison when taken in large doses.
The antidotes are albumen, tannin solutions (tea, &c.),
and sodic carbonate. — Zinc sulphate dissolves readily in
water (1 part in 2 of water).

356. Zinc Carbonate (ZnCOg). The normal car-
bonate of zinc is difficult to prepare. Zinci carbonas of
the Pharmacopoeia is a basic salt (ZnCO3.2ZnO.3H2O).

Experiment 294. — Add sodic carbonate to solution of zinc
sulphate. Basic zinc carbonate is precipitated. Note itg appear-
ance. (What gas i." evolved ?) Filter, wash, test solubility in
acids. (Has this salt any taste ?)

357. Zinc Acetate (Zn(C,H302),.H20).

Preparation. — Experiment 295—- Dissolve zinc carbonate
in acetic acid until no more will dissolve, filter if necessary,

MANGANKSE. 341

evaporate to small bulk, adding a few d^opa of acetic acid from
time to time, and set aside to crystallise.

Properties. — A colourless solid, crystallising in thin,
pearly plates. It is soluble in water, and the solution
has a sharp, unpleasant, metallic taste.

358. Tests.

1. Ammonia gives a white precipitate of zinc hydroxide
(Zn(0H)3), soluble in excess.

2. Ammonic sulphide gives a white precipitate of zinc stilphide

(ZnS) :

ZnSO^ + (NH4)2S = ZnS + (NHJaSO^.

This is soluble in dilute hydrochloric acid.

3. Caustic soda precipitates zinc hydroxide, and then redis-
solves it :

ZnSO^ + 2NaOH = NaaSO^ + Zn(0H;2.
Zn(0H)2 + 2NaOH = Zn(ONa), + 2H2O.

This solution gives no precipitate with ammoni"^ chloride (because
zinc hydroxide is soluble in ammonia), but gives a white pre-
cipitate of zinc sulphide when treated with hydric sulphide.

4. Zinc compounds insoluble in water can be dissolved in
dilute sulphuric or hydrochloric acid, and tested as above.

MANGANESE.

359. Manganese (Mn" '^ ^ = 54.8.— Sp. wt. = 8.—)

Compounds of manganese are widely distributed in small
quantities. They give the colour to many otherwise
colourless minerals, e.g. many silicates ; and are found in
minute Quantities in both plants and animals. — The
chief orr,i> of manganese are pyre i^ite, or black oxide of
ma/nganese (Mn02), hraunite (Mn-^Og), hausmannite
(MugOi), psilomelane (BaO.MnOa), and r hodocrozite

342 MANGANESE DIOXIDE.

(MnCOg). The metal is of little importance. It can be
prepared by reducing manganous oxide (MnO) with
charcoal at a very high temperature. It decomposes
warm water. Its presence in iron renders that metal
very hard.

360. Oxides of Manganese. Mang^mese unites
with oxygen in four proportion, forming owo basic, —
manganous oxide (MnO), and manganic oxide (Mn.^Og) ;
and two indifferent oxides, — red oxide of manganese
(MugOi^ and manganese dioxide (MnO.^). It unites with
oxygen and hydrogen to form two acids — manganic
(H2Mn04), and permanganic (HMn04). There is some
evidence of the existence of an oxide (M.i\.f)^) corres-
ponding to permanganic acid :

2HMn04 = H2O + MnaO^.

361. Manganese Dioxide (MnO.^). This sub-
stance is found in large quantities as the mineral pyro-
lusite, or black oxide of manganese. It is the most
important compound of manganese, being used in the
manufacture of bleaching powder and glass, and in the
preparation of oxygen, chlorine, potassic permanganate,
&c.

Properties. — A brownish black solid. When heated,
it gives off one-third of its oxygen :

SMnOg = MugOi + O2.

Strong hot sulphuric acid causes it to lose half its
oxygen :

MnOa -f H2SO4 = MnSO^ + O + H2O.

The action of hydrochloric acid has been already studied.
(Art. 92.) — Manganese dioxide is sometimes fraudulently

MANGANATKS. 343

mixed with coal dust and charcoal powder. This makes
it explosive when heated :

2Mn02 + C - 2MnO + CO2.

362. Manganous Salts- In these salts manganese
is bivalent (MnCl^, MnSO^, &c.). The soluble salts can
be prepared by dissolving manganese dioxide or man-
ganous hydroxide (Mn(0H)2) in the acids ; and the
insoluble salts by precipitation. Manganous salts are
usually pink or rose-coloured, and are not easily oxidised
to manganic salts, (Compare with ferrous and ferric
salts.)

Experiment 296. — Heat a little manganese dioxide with con-
centrated sulphuric acid. Observe the evolution of oxygen. A
solution of manganous sulphate (MnS04) is obtained. There is
usu^'Jly a reddish residue oi ferric oxide, nearly always present in
manganese dioxide as an impurity. The solution contains ferric
sulphate as an impurity. This can be removed by heating the
impure manganous sulphate to redness, and thus decomposing
the ferric sulphate. Manganous sulphate can then be dissolved
out.

363. Manganic Salts. Unlike the corresponding
salts of iron and chromium, manganic salts very readily
lose oxygen, &c., and become converted into manganous
salts. For example,

MnaCSOJa + H2O = 2MnS04 + O -f- H2SO4.

364. ManganateS- The manganates are similar to
the sulphates and chromates in composition, and are also
in many cases isomorphous with these salts. The most
important manganates are potassic (K2Mn04), and sodic
(NajMnO^).

Preparation. — Experiment 297. — Fuse manganese dioxide

344 PERMANGANATES.

in a porcelain basin with one and a half times its weight of caustic
potash, and stir for some time with a glass rod so as to expose
the mass to the oxidising action of the air :

2Mn02 + O2 + 4K0H - 2K2Mn04 + 2H2O.

Lixiviate the blue mass with water. A solution of potassic man-
ganate is obtained, (Keep the solution.) By using caustic soda
a solution of sodia manganate can be prepared in the same way.

Properties. — The magnanates of potassium and
sodium form dark green solutions from, which the solid
substances can be obtained by evaporation. They are
stable only in the presence of free alkali. (See Exp't 298.)

Condys green disinfecting fluid is an alkaline solution
of sodic manganate, generally containing permanganate
in small proportion. The manganates are powerful
oxidising agents, and to this they owe their valuable
disinfecting and deodorising properties. — Manganic acid
(H2Mn04) is not known apart from its salts.

365. Permanganates. These are salts of perman-
ganic acid (HMnO^). The potassium and sodium salts
are of most importance.

PhEPARATION. — Experiment 298.— To the clear solution
of potassic marganate (Exp't. 297) add carefully dilute sulphuric
acid until the cc lour change: to purple. This takes place as soon
as the free alkali is neutralised :

3K2Mn04 + 2H2O = 2KMn04 + MnOa + 4K0H.

If this solution is evaporated, it deposits first potassic sulphate,
and then potassic permangandte (KMnO^).

Properties. — Potassic permanganate crystallises in
needle-shaped crystals of a dark purple colour, and a
somewhat steely lustre. It is soluble in water (I part
in 15) and has e lormous colouring power.

PI'RMANGANATES. 345

The permanganates are strong oxidising agents, and
are of great value as disinfectants and deodorisers.
Condy'a redjiuid is a solution of more or less pure sodic
permanganate. (NaMnO^).

Experiment 299. — To a solution of potassic permanganate
add sulphurous acid. The colour disappears :

2KMn04 + 5SO2 + 2H2O = KaSO^ + 2MnS0, -f 2HaS0^.

Test this solution for sulphuric acid. — Decolorise acidified solu-
tions of potassic permanganate with other reducing agents, e.g.,
ferrous sulphate, hydric sulphide, amnionic sulphide, &c. (Write
the equations).

Potassic and sodic permanganates oxidise many or-
ganic substances, especially those which are offensive and
noxious.

Experiment 300- — Bubble the air from the lungs through a
dilute solution of potassic permanganate, using a glass tube.
The purple colour disappears and a reddish precipitate of hy-
drated dioxide of manganese (MnO(OH)2) is thrown down. — Re-
peat the experiment, first acidifying the solution with dilute
sulphuric acid. The colour is discharged, and no precipitate ap-
pears.

366. Tests.

Manganous Salts.

1 . Ammonia gives a white precipitate of manganous hydroxide
(Mn(OHa)), soluble in excess.

2. Ammonic sulphide gives a salmon-coloured precipitate of
manganous sidphide (MnS), soluble in dilute hydrochloric acid.

3. Caustic soda gives a white precipitate of manganous
hydroxide, insoluble in excess, and oxidising to brown manganic
hydroxide (MnaOa(OH)a) when shaken up with air :

2Mn(0H;a + O = MngOaCOHja + HaO.

4. Insoluble compounds can be tested by heating with a sodic

346 COBALT.

carbonate bead iu the oxidising zone of the Bunsen flame. Th(;
bead is coloured green by the formation of sodic manganate.
The borate bead is coloured amethyst by manganese compounds.

Manganates and Permanganates.

1. Hydric sulphide reduces them, and precipitates manganous
sulphide if the solution is alkaline.

2. Ammonic sulphide reduces them, and precipitates manganouR
sulphide.

COBALT.

367. Cobalt (Co " '^ = 58.6.— Sp. v t. = 8.5.—
Melting pt. = 1100°.— Sp. heat = 0.10696.)— Cobalt
occurs combined with nickel, iron, arsenic, and sulphur. It
is always accompanied by nickel. It is also found in
meteoric iron, and is present in the atmosphere of tlio
sun. It is an unimportant metal. Cobalt ores are used
chiefly in the manufacture of smalt, a powdered blue
glass used as a paint.

368. Oxides of Cobalt. Cobalt forms three oxides,
parallel with those of iron. They are cohaltous (CoO),
cobaltic (Co.^Og), and cohaltcso-cobaltic oxide (C03O4, or
C0O.C02O3). They are all stable.

369. Salts of Cobalt. There are two series of
salts, cohaltous and cobaltic. The latter are very unstable,
being readily reduced to the former. — Cohaltous salts
(C0CI2, C0SO4, Co(N03)2, &c.) are violet or blue when
anhydrous, but rose coloured when hydrated.

370. Cobaltous Nitrate (Co(N03)2.6H20) is a

reddish, crystalline salt, prepared by dissolving cobaltoso-
cobaltic oxide or cobaltous carbonate in nitric acid, and

NICKEL. 347

evaporating the solution. It is freely soluble in water,

and the solution has an acid, astringent taste. — Cobiltous

nitrate is used in testing substances by means of the

blowpipe. (Art. 350, i). It is decomposed by a strong

heat :

30o(N03)2 = C03O4 + 6N0a + Oj.

371. Oobaltous Chloride ( CoCl,. 6 H,0) is a rose-
coloured salt prepared by the same method as that used
for the nitrate. Its solution has an acid reaction, and
ia used as a sympathetic, or invisible ink.

Experiment 301. — Write with a solution of cobaltous chloride
80 dilute that the writing is invisible when dry. Hold the
paper near a flame. The writing appears in blue characters.
(Explain.)

372. Tests.

1. Ammonia gives a blue precipitate (basic salt) soluble in ex-
cess to a brownish solution.

2. Amnionic sulphide gives a black precipitate of robaltous
■lulpfdde (CoS) * insoluble in cold dilute hydrochloric acid, but
soluble in aqua regia.

3. Caustic soda gives a blue precipitate insoluble in excess
and turning reddish when shaken up with air.

4. Insoluble compounds are tested by the borax bead, to which
cobalt gives a deep blue colour.

NICKEL.

373. Nickel (Ni"- 1'^- = 58.6. Specific weighs = 8.9.
Melting point = 1500°. Specific heat = 0.10863).

Nickel is found generally along with cobalt. The

* In reality the hydro-sulphide, Co(SH)a.

348

SALTS OF NICKEL.

principal ore is kup/er-nickel (NiA.8). Nickel ores gen-
erally contain cobalt, copper, iron, and arsenic.

It is a white metal, somewhat like steel in appearance,
hard, ductile, and not easily oxidised by air. It decom-
poses steam slowly at a red heat, and is soluble in dilute!
acids. On account of its permanence in the atmosphere
it is used for electro[)lHting other metals. — Nickel coim\
are made of an alloy of 75 parts of copper with 25 of I
nickel. This alloy is hard and wears well. — Genmnl
silver is an alloy of copper, nickel, and zinc in various
proportions. It is harder than copper, but more easily
attacked by acids.

374. Oxides of Nickel. Nickel forms two oxides,
nickelous (NiO), and nickelic (Ni^Og). Nickelous oxide I
is basic, while nickelic is indifferent. (Compare witli
iron, <fec.) The former occurs in nature as Bunsenitt\
It can be prepared by strongly igniting nickel nitraiA
(Ni(N03),):

Ni(N03)2 = NiO + 2N0a + O.

It is a green powder, permanent in air, and soluble in i
acids.

375. Salts of Nickel. — There is only one series of!
nickel salts, and they are derived from the basic oxide,
NiO. They are mostly green in colour, but are yellow
when deprived of water of crystallisation. The faolublej
salts (NiClg, NiS04, Ni(N03)2, &c.) form acid solutions of I
an astringent taste. They are prepared usually by dis-
solving the metal in dilute acids.

376. Nickel Sulphate (NiSO,.7H20) is a greenl

CERIUM. 349

salt, isomorphous with Epsom salts, prepared by dissolving
nickel in dilute sulphuric acid :

Ni + H3SO4 = NiSO^ + Ha.

It is soluble in water (2 parts in 5). It combines with
ammonic sulphate to form ammonio-nickel sulphate
(NiS04.(NH4)2S04.6H20), used in nickel-plating. In
this compound, as in Mohr's salt, and other double sul-
phates of the same class, a molecule of alkaline sulphate
replaces one of the seven molecules of water of crystal-
lisation.

377. Tests.

1. Ammonia gives a green precipitate (Ni(0H)2), soluble in
excess of ammonia to a blue solution.

2. Ammonic sulphide gives a black precipitate of nickel hydro-
mlphide (Ni(SH)2), insoluble in cold dilute hydrochloric acid.
This precipitate is somewhat soluble in excess of ammonic sul-
phide, which should therefore be sparingly used in precipitating
solutions containing nickel. It is better to use freshly prepared
sulphide free from excess of sulphur.

3. Caustic soda gives a green precipitate of nickelous hydroxide
(Ni(0H)2) insoluble in excess.

4. Insoluble nickel compounds are tested by the borax bead,
to which they give a reddish-brown tint. The test is, however,
easily obscured by the presence of other metals.

378. Cerium (Ce •"• = 141 .2).— This is the most impor-
tant of the Cerite metals, a group of rare metals, allied
to the group under consideration. They have recently

been discovered in large quantities and may assume con-
siderable practical importance in medicine. Cerium
forms two oxides (CcjOg and CeOj), both basic. The
cerous salts are of most importance in medicine. Cerov^

350 QUESTIONS AND EXERCISES.

nitrate (Ce(N03^3.GH20), and cerous oxala'". (Cej'CjOJj)
are used. The nitrate is easily soluble in water, tlie
oxalate very sparingly. They are both colourless.

QUESTIONS AND EXERCISES.

1. In what experiments already made has green vitriol been
one product ?

2. Wliat weight of 70 % nitric acid is required to oxidise 1 tb.
green vitriol to ferric sulphate ? How much pure sulphuric acid
must be added ?

.3. Why would you expect ferrous carbonate to be less irritat-
ing to the stomach than ferrous sulphate ?

4. How much iron in one-eighth of a grain of ferric arsenate?
To what weight of ferric chloride is it equivalent ? • ^ '

5. What causes the red fumes in the preparation of ferric
chloride? iv •■! » ; r' > .■'■■ v • ;.■ • ^ »■ ■■•-'■■ •

6. Why must ferric hydroxide be freshly precipitated when
used as an antidote to arsenic ? -v ,.. - . -

7. In what respects are iron and chromium alike ? In what
respects do they diflfer ?

8. The third equation in Art. 339 represents calcic sulphate
(CaS04) as being precipitated from aqueous solution. Is this
strictly correct ?

9. Is there any resemblance between chromium and sulphur ?

10. Chrome yellow dissolves in solution of caustic potash.
What substances are formed ?

11. Does chrome alum contain aluminum? Why is it called
" alum" ? Write the formulas of all the alums which have been
mentioned.

12. Why cannot aluminium be used for making cooking uten-
sils ?

13. How would you distinguish aluminium bronze from gold ?

14. Write the formula for eois'mm alum ?

METALS OP GROUP IV. 351

15. Whiit is the composition of kiMtnt alum ?

16. Can aluina be represented by a simpler formula than that
given in Art. 347 ?

17. Common alum is a good antidote to lead salts. Explain.

18. How would you distinguish a solution of aluminic from
one of zinc sulphate ?

19. What is zinc white ?

20. What resemblance is there between manganese and sul-
phur ?

21. Calculate the percentage of oxygen in potassic permanga-
nate. What weight of potassic permanganate will oxidise the
sulphurous acid obtained by burning 10 g. of sulphur ?

22. Explain the explosive nature of a mixture of charcoal,
manganese dioxide, and potassic chlorate ?

23. Write a short essay on the general resemblances r.nd dif-
ferences among the metals of Group III. with regard to ;he salts
which they form.

24. Explain the antiseptic properties of a solution of potassic
permanganate. Will it disinfect the atmosphere ? /

25. How would you prepare cobaltous nitrate from cobaltous
sulphate? 'j -

26. What differences have you noticed in the chemical charac-
ters of nickel and cobalt ? -, - , ,

CHAPTER XX.

METALS OF GROUPS IV. AND V.
Calcium, Strontium, Barium ; Magnesium.

379. General Characters. — Calcium, strontium,

barium, and magnesium are the metals of the alkaline
earths. Formerly, any insoluble earthy substance which

352 MRTALS OF GROUP IV.

remained unchanged \vhon heated was called an earth; so
that substances such as lime, silica, phosphates, (be,
were classed under this terra. Then it was noticed that
some of these earths, viz., lime, strontia, baryta, and mag
neaia were somewhat soluble in water, and had alkaline
properties. They were therefore called alkaline earths,
and were held to be elements until metals were obtained
from them. The metals have very strong chemism and
are difficult to separate from their compounds. Cal-
cium, strontium, and barium are prepared by the elec-
trolysis of their fused chlorides or cyanides. Magnt'-
sium can be prepared in the same way, ^ ut is prepared
on the large scale by reducing its chloride by means
of sodium. These metals oxidise so readily that they
must be protected from the action of the air by naph-
tha. They are bright, easily fusible, and decompose
water at ordinary temperatures. They are all dyad, and
each has only one basic oxide (CaO, SrO, BaO, MgO).
These oxides unite directly with water, forming spar-
ingly soluble hydroxides (Ba(0H)2, Sr(0H)2, Ca^OH),,
and Mg(0H)2 ; — in the order of their solubility begin-
ning with the most soluble). The sulphides (CaS, SrS,
BaS, MgS) are decomposed by water, and cannot be pre-
pared by precipitation. They are prepared by heating
the sulphates with charcoal, e.g. :

CaSO^ + 4C = CaS + 4C0.

The carbonates (CaCOg, SrCOg, BaCOg, MgCOg), sulphates
(MgSO^, CaSO^, SrSO,, BaSO^, in the order of their
solubility : — magnesic sulphate is freely soluble.), and
phosphates (Qa2,{V0^\, <fec.) are insoluble (or sparingly
soluble) in watei*. The chlorides, nitrates, &o., are
soluble.

LIMK. 353

CALCIUM.

380. Oalcium (Ca»- = 40).

OccuuRENCE. — AlwayB in combination. Its com-
pounds occur in vast quantities, and include limestone,
marble, chalk, coral, dolomite, gy)»8U!n, apatite, <fec. It
is present in natural waters, in the bodies of plants and
animals, and in the sun and fixed stars.

381. Calcic Oxide (CaO). — Calcium combines with
oxygen in two proportions (CaO, CaO.^), but the mon-
oxide (CaO) is the only important oxide.

Preparation. — It is prepared on the large scale by
strongly heating limestone. Impure calcic oxide {([uick
/me) is obtained :

CaCOs = CaO + COa.

Experiment 302. — Wrap several times around a small frag-
ment of calc spar a platinum wire, one end of which is fastened
in a handle of glass (by fusing the glass and sticking the wire
into it). Thrust the calc spar into the centre of a Bunsen flame,
and hold it for two or three minutes just above the point of the
central bluish green zone. Remove it and observe the change in
its appearance. Put a drop of water on it, and observe the
change. Wash it into at. t., shake it up with water, and add a
little red litmus. See whether calc spar affects red litmus.

Properties. — Calcic oxide is a white solid, not fused
by the intense heat of the oxy -hydrogen flame.

Experiment 303. — Place a lump of good quick lime on a

clean iron or porcelain plate, and pour over it one-third its

weight of water. Note the heating of the mass. Whence

comes the heat ? This process is called the slaking or slacking of

lime :

CaO + HaO = Ca(OH)a.

(Keep the slaked lime for Experiment 305).
24

354 SLAKED LIME.

Experiment 304. — T/eavc a small lump of quick lime exposed
to the air for two or three days. Note any changes iiif its ap-
pearance. Test it for carbonic acid.

Quick lime absorbs moisture and carbon dioxide from
the air and becomes changed at length to calcic carbon-
ate. Quick linie is often used to ke-p the air of an
apartment dry and pure.

382 Calcic Eydroxide (Ca;OH),), bIso called

slaked lime, is prepared as in Experiment 303. Much
heat is given out during the combination of the lime and
the water. Fires liave been caused by the accidental
slaking of large quantities of quick lime.

El'.perinieilt 305. — Put about equal quantities of recently
slaked iime in two test tubes ; to tue one add about 100 parts of
water, ar,d to the other 100 parts of water and 2 of sugar.
Shake both for some time and observe that the sweetened water
dissolves much more slaked lime than the pure water does.
Filter off the solution in pure water, and try its taste and action
on red litmus. ■

Calcic hydroxide dissolves in wat :r to the extent of 1
part in 700 of water. The solution is called lime water.
Calcic hydroxide is more soluble in cold than in hot
water. (Heat a little of the filtered solution prepared in
Experiment 305.) S'ig«^ increases the solubility of lime
in water. Sacckarated solution of lime contains about
1 part by weight of calcic hydroxide and 2 of cane sugar
dissolved in 20 of water.

Experil ent 306. — Leave a few cubic centimetres of lime-
watv.r m an open vessel for two or three day?, stirring it from
time to tima. Then, try its action on rud litmus Pour off the
liquid, add a few drops of hy^V'^chloric acid to the sediment,
and obssrve the result. What is the sediment ?

CALCIC CARBONATK. 355

Lime water is used in medicine as an antacid, (kc, and
as r.n antidote to poisoning by acids, particularly oxalic.
— Milk of lime is water shaken up with more shiked
lime than it can dissolve.

383. Oalcic Carbonate (CaCOg).

OccuRRErcE. — Calc spar is nearly pure crystallised
calcic carbonate. It is colourless and transparent.
Aragonite is another crystalline form of calcic carbonate.
This comj)ound is therefore dimorphous ; it crystallises
in two forms. Calcic carbonate is found more or less
pure, as marble, limestoae, chalk, coral, &c. It forms a
considerable part of the mass of egg-shells and of the
shells of molluscs.

Preparation. — Calcic carbonate occurs so abundantly
in nature that it is not necessary for most purposes to
prepare it artificially. In medicine, however, it is pre-
pared by precipitation ( calcis carbonas precipitata) in
order to obtain it in a fine state of division.

Sxperiment 307. — To a hot solution of calcic chloride
(CaCla), add solution of sodic carbonate until no more precipitate
is formed on further addition of the carbonate. Filter and wash
the precipitate :

NajCOs + CaCla = 2NaCl + CaCOg.

Properties. — Precipitated calcic carbonate is a white
powder, plightly granular, insoluble in water, soluble
with eff vvescence in hydrochloric and other acids (Ar .
152). Its solubility in water containing carbonic acid
has been already referred to (Art. 1L3). It is used as
an anti^ot > to poisoning by acids, and also to correct
acidity oi the stomach.

356 CALCIC SULPHATE.

384. Calcic Chloride (CaCl,.6H20).

Preparation. — Experiment 308- — Dissolve in a porcelain
dish a few fragments of calc spar in hydrochloric acid, and
evaporate the solution on the water bath until it forms a pellicle
on the surface. Then heat it over the Bunsen burner, placing
the dish so far above the flame that it may not be touched by it.
When the salt is quite dry, apply the flame to the dish until
moisture ceases to come off". Leave this fxined ca^ric chloride,
(CaCla) exposed to the air for 24 hours, and observe the result.

Properties. — Calcic chloride is a colourless salt very
soluble in water. The fused chloride contains no water
of crystallisation. It is very hygroscopic, and is used
for drying gases. Solution of calcic chloride is used as
a test reagent, and also as a medicine.

385. Calcic Sulphate (CaSO^).

Occurrence. — Crystallised as gypsum, alabaster, or
selenite (CaS04.2H20), and anhydrite (CaS04). It is
present in sea and other waters.

Preparation. — Experiment 309.— To solution of calcic
chloride add dilute sulphuric a i, fil^or, and wash the p'c-
cipitate with hot water. (Write the equation.) The precipitate
is gypsum.

Properties. — Gypsum is a white solid of sp. wt. 2.3.

Experiment 310. — Heat a small quantity of gypsum in a t. t.
and observe. Heat a larger quantity in a porcelain basin until
moisture ceaseS to escape. Let cool, and mix the anhydrous
salt with water on a piece of broken porcelain or smooth wood.
(What proportion of water should be used tc form gypsum?)
Observe change after a few minutes.

Anhydrous calcic sulphate is called j^laster of Paris,
or sometimes simply plaster. It is used as a cement, for
making plaster casts, &c., and in surgery for making stiff

BLEACHING POWDER. 357

bandages. - (jryj)sum is less soluble in hot than in warm
water. It is most soluble at 35°C.

Experiment 311. — Heat a saturated solution of gypsum to
boiling.

One part of gypsum requires 500 of water to dissolve
it.

386. Bleaching Powder. {''Chloride of Lime:')

This substance has been already referred to at p. 105.
It is probably a mixture of calcic hypochlorite and
chlor.'de in molecular proi)ortions, Ca OCl)^ + CaCl^ ;
but it always contains calcic hydroxide.

Preparation. — Slaked lime is spread on a series of
shelves in large closed compartments, and exposed to the
action of chlorine gas. The chlorine is generated by the
action of crude hydrochloric acid on manganese dioxide :

4HC1 + MnOa = MnCla + CI2 + 2H2O.

Its action on the slaked lime may be represented as
follows : .. :

2Ca(OH)2 -I- 2012 - Ca(OCl)2.CaCl2 + 2H2O.

Properties. — A white powder, having a chlorous
smell. The odour is due to the liberation of hypochlorous
acid by the action of the carbon dioxide and moisture of
the air :

Ca(0Cl)2 + H2O + CO2 - CaCOg + 2HC10.

It is one of the best known decdorisei*s and disinfectants,
and is esp(?cially useful because of the volatility of hypo-
chlorous acid, a substance which deodorises and disinfects
the atmosi>here into which it escapes.

Expenment 312.— l^jxatnine a specimen of bleaching powder,

358 CALCIC PHOSPHATE.

noting its colour and odour. Shake up about 10 grains of it with
50 to 100 cubic centimetres of water and filter. The filtrate
contains calcic chloride and hypochlorite. It is the Liquor calcls
chloratm of the pharmacopoeia. Add a few drops of it to a
solution of sulphate of indigo. Try with acidified litmus solution,
and with potassic bichromate solution .

Experiment 313. — Pour some dilute sulphuric and hydro-
chloric acid over small portions of bleaching powder in watch
glasses, and note evolution of chlorine :

CaCla + Ca(OCl).^ + 2H^S04 = 2CaS04 + 2CI2 + 2H.^0.
CaOla + Ca(0Cl)2 -|- 2HC1 = 2CaCl2 -f- 2CI2 -f 2H2O.

When bleaching powder is heated, the hypochlorite is decom-
posed into chlorate and chloride :

6Ca(OCl)2 = Ca(C103)2 + 5CaCl2.

3«7. Calcic Phosphate {p-Si^{VO,\). This com

pound has been already studied. (Arts. 128 and 132.)

Occurrence. — It is found in the minerals apatite
(3Ca3(P04), + Ca[Cl2, F,]*), phosphorite (Ca3(PO,)2),
tsombrerite (Ca3(P04)o.2HoO), &c., and in bones. Bone
ash contains about 80 % of calcic phosphate.

Preparation. — Experiment 314.— Digest bone ash with
dilute hydrochloric acid, filter, dilute to double volume, add
ammonia to alkaline reaction, filter, and wash the precipitate
with hot distilled water.

The hydrochloric acid acts on the phosphate to form
calcic chloride and calcic tetrahydric phosphate :

CaalPOJa + 4HC1 = CaH4(P04)2 + 2Cani3.

The ammonia reprecipitates the calcic phosphate :

CaH^CPOJa + 2CaCl2 + 4NH3 = Ca3(P04)2 + 4NH4CI

* When sj'iiibola are put within sqnare brackets and separated by a comma,
it signifies that the elements are present in varyinjf proportions.

MORTARS AND CEMENTS. 359

It is plain that any impurities in the bone ash which are
soluble in hydrochloric acid may be precipitated along
with calcic phosphate.

Properties. — A light, white powder, insoluble in
water, soluble in dilute hydrochloric, nitric, or phosphoric
acid. From this solution calcic phosphate is again pre-
cipitated when an alkali is added. (Experiment 314.)
Thus, an acid solution of calcic phosphate might be mis-
taken for an aluminium salt; but the former gives a
white precipitate (calcic oxalate) on the addition of sodic
acetate and amnionic oxalate, while the latter does not.

388. Mortars and Cements. — Ordinary mortar
is a mixture of slaked lime ((^a(0H)2), sand (SiO.^), and
water. It hardens by the formation of calcic carbonate,
carbon dioxide being absorbed from the air. The process
of hardening continues for years. There appears to be
no combination of the lime with the silica. — Hydraulic
mortar, or Roman cement, is prepared by carefully heat-
ing a mixture of lime and clay. It hardens under water,
and the hardening seems to be due to the formation of
silicate of lime and alumina. Portlaoid cement is made
by carefully heating a levigated mixture of clay and
chalk. These cements deteriorate when kept exposed to
the air, because the lime in them unites with carbon
dioxide.

389. Tests.

1. Solutions of calcium salts give a white precipitate with
ainmonic carbonate. If tlie solution is acid it must be neutralised
with ammonia. The precipitate is soluble with effervescence in
nitric acid.

2. Sodic phosphate gives a white precipitate with neutral or

360 STRONTIUM.

alkaline solutions of calcic salts (in practice the solution is made
alkaline with ammonia) :

aCaCla + 2Na2HP04 + 2NH3 =

Ca3(P04)2 + 4NaCl + 2NH4CI.

3. Ammonic oxalate gives a white precipitate of calcic oxalate
even with very dilute solutions of calcium salts :

CaCl2 + (NHJaCaO^ = CaCaO^ + 2NH4CI.

This precipitate is soluble in dilute nitric or hydrochloric acid,
but is insoluble in acetic acid. ■ ,

4. Calcium compounds insoluble in water can be tested by
dissolving in hydrochloric acid, adding sodic acetate (so that the
acidity may be due to acetic acid), and then adding ammonic
oxalate. Or, they may be tested by moistening them with
strong hydrochloric acid end bringing them by means of a plati-
num wire into the Bunsen I'ame. A bi'ick red colour is imparted
to the flame by calcium compounds.

STRONTIUM.

390. Strontium (Sr»- = 87.2). — Compounds of
strontium are found in considerable quantities in nature.
The most commonly occurring are celestine (SrS04), and
strontianite (SrCOg). The inetal is prepared by electro-
lysis. — Strontium compounds have not yet found a place
in the pharmacopoeia. The nitrate (Sr(N03).2) and other
salts are used in making fire-works. Tliey give a fine
red colour to flames.

Experiment 315. — Mix a little atrontic nitrate with powdered
charcoal and sulphur, put the mixture on a piece of mica or por-
celain and touch it with a hot wire. (What causes the rapid
combustion ?)

The soluble salts are prepared by dissolving strontia-
nite in the acids, or by reducing celestine to strontic sul-

• BARIUM. 361

phide (SrS), and dissolving this in the respective acids.
StroiAtic oxide (SrO), and hydroxide (Sr(0H).2) are simi-
lar to the corresponding calcium compounds, but the
hydroxide is more soluble than calcic hydroxide. Stron-
tium compounds are mostly colourless. The sulphate
(SrS04) is less soluble than calcic, but more so than
baric, sulphate.

391. Tests.

1. Amiiionic carbonate gives a white precipitate (SrCOg) with
neutral or alkaline solutions of strontium salts. The precipitate
is soluble with eflFervescence in dilute nitric acid.

2. Sodic phosphate (with ammonia) gives a white precipitate
(SrgfPOJ,).

3. Ammonic oxalate gives a white precipitate of strontic
oxalate (SrCjO^), soluble in nitric and sp/iringly soluble in acetic
acid.

4. Calcic fiulphate gives a white precipitate (SrS04) after some

time :

CaSO, -f- SrCl^ = SrSO^ + CaCl,.

5. Insoluble strontium compounds can be tested by moistening
with strong hydrochloric acid and bringing on a platinum wire
into the Bunsen flame. A carmine red colour is imparted to the
flame. The test is more delicate if the substance be held for a
few moments in the reducing flame, then moistened with hydro-
chloric acid, and held in the oxidising flame.

BARIUM.

392. Barium (Ba» = 136.8).— The principal com-
pounds of barium found in nature are witherite (BaCO,),
heavy spar (BaS04), and psilo7nelane{\M.n, BajO.MnOj).
The metal can be prepared by electrolysis of the fused
chloride or cyanide.

362 BARIUM CHLORIDE.

. 393. Oxides of Barium. — Barium, like calcium
and strontium, unites with oxygen in two proportions,
forming the monoxide (BaO), and the dioxide (BaOj).

1. Barium monoxide (BaO) is prepared by heating
the nitrate :

Ba(N03)2 = BaO + 2NO2 + 0.

It unites with water, and forms barium, hydroxide, or
baryta (Ba(0H).2). This compound is more soluble than
either calcic or strontic hydroxide. Baryta water, used
in analysis, is a solution of barium hydroxide. The
hydroxide is prepared on the large scale from heavy spar,
for use in suijar refininj;. It forms an insoluble com-
pound with cane sugar.

2. Barium dioxide (BaOj) is a white solid prepared by
heating the monoxide to a red heat in a current of oxygen.
It is used in the preparation of hydrogen dioxide.

394. Baric Chloride (BaCl,.2H,0).

Preparation. — By dissolving baric carbonate or sul-
phide in hydrochloric acid :

BaCOg + 2HC1 = BaCla + H3O + CO2.

It is also prepared from heavy spar, which is firet reduced

to sulphide (BaS), and then decomposed by hydrochloric

acid :

BaSO^ + 40 = BaS + 4C0.

BaS + 2HC1 = BaCla + HgS.

Properties. — A white crystalline solid, soluble in
water (35 parts in 100), sparingly soluble in alcohol.

Experiment 316. — Examine carefully a specimen of barium
chloride, noting taste, &c. Dissolve it in a little distilled water,
and to a small portion of the solution add about twice the volume

BARIUM NITRATE. 363

of strong uibiic acid. Baric chloride is only sparingly soluble in
strong nitric acid. To another portion add magiiesic sulphate.
Baric sulphate is precipitated :

MgSO^ + BaClg - BaSO^ + MgClj.

Baric chloride, in common with the other .soluble com-
pounda of barium, is very poisonous. Solution of mag-
nesium sulphate is a good antidote. (How does it act 1)

395. Baric Nitrate (Ba(N03)a). Is prepared by
the same methods as those used in preparing the chloi'ide.
It is much used in pyrotechny, being mixed ^vUh char-
coal and sulphur to form "green fire." ;

Experiment 317. — Mix carefully with little friction small
quantities of baric nitrate, sulphur, and ground charcoal. Put
the mixture on a piece of mica, a flat stone, or a piece of porce-
lain, and touch it with a red hot wire.

396. Tests.

1. Ammonic carbonate gives a white precipitate (BaCOg),
soluble with eflfervescence in dilute nitric acid.

2. Sodic phosphate (with ammonia) gives a white precipitate
(Ba3(P0,),).

3. Ammonic oxalate gives a white precipitate (baC.^O^), soluble
in ddute nitric, sparingly soluble in acetic acid.

4. Calcic sulphate gives at once a white precipitate (BaSO^).
Baric sulphate requires -400,000 parts of water for its solution.

5. Insoluble compounds are tested for as in Art. 391 (5).
Barium compounds give a greenish colour to the flame.

MAGNESIUM.

397. Magnesium. (Mg"=23.95). '

Occurrence. — Magnesium compounds are very abun-

364 MAGNESIUM SULPHATE.

dant and widely distriV)uted. Mountain limestone, or
dolomite, ([Mg, Ca] CO.,,) forms whole ranges of moun-
tains. Other commonly occurring compounds are mag-
nesite (MgCOg), kieserite (MgS04.H20), carnallite (MgCl...
KC1.6H.,0), spinelle (MgO. AljOg), asbestos ([Mg,(Ja]SiO.,),
Epsom salts (MgS04.7H20) &c. Magnesic phosphate
(Mgg' P04)2) is found in the V>ones, &c., of animals.

Preparation. — By heating together a mixture of mag-
nesium chloride, calcium fluoride, and sodium. The
sodium displaces the magnesium :

MgCla + 2Na = Mg + 2NaCl.
The metal is purified by distillation.

Properties. — A soft, silvery metal ; it tarnishes in
moist air; sp.wt. = 1.75 ; melts at red heat, and boils
above 1040*^ ; when heated in air it catches fire and
burns with a dazzling white light. The magnesium light
is used in photography, signalling, &c.

Experiment 318. Bum a piece of magnesium wire, dissolve
the white ash (MgO) in a drop of dilute sulphuric acid, evaporate
on a watch glass, and obtain crystals of Epsom salts.

398. Magnesic Sulphate (MgSO^.TH.O).- Mag-
nesium sulphate is generally sold as Epsom salts, crystal-
lised with seven molecules of water to the molecule of
sulphate. It occurs in nature crystallised with one
molecule of water, as kieserite (MgSO^.HjO.)

Preparation. — Epsom salts are now prepared mostly
from kieserite, by heating in water. The sparingly
soluble kieserite apparently combines with more water
and becomes changcjd to the much more soluble hei^tahy-
drated salt. This is then purified by ci-ystallisation.

MAGNESIUM CARBONATE. 365

Properties. — A colourless, crystalline solid, isomorph-
ous with zinc sulphate (ZUSO4.7H2O), which it resembles
very closely in appearance ; it has an un])leasant bitter
taste. It is soluble in water, 35 parts in 100.

Experiment 319. Compare specimens of Epsom salts and
crystallised zinc sulphate, noting general appearance and taste.
Dissolve them separately in water, and add ammonium chloride
and a drop of ammonia to each.

Magnesium sulphate is used in medicine as a purgative.
It is a " saline purgative," i.e., it acts by promoting the
diffusion of water into the intestinal canal.

399. Magnesic Carbonate (MgCOa).— Found in

nature in large quantities, as magnesitfi. It was formerly
used in preparing Epsom salts. The carbonate of mag-
nesia of the pharmacopoiia is a basic salt (4MgO. 300.2.
5H,0).

Preparation. — By the action of solution of sodic car-
bonate on solution of magnesic sulphate.

Experiment 320- To a hot solution of magnesium sulphate
add hot solution of sodic carbonate. Basic carbonate of mag-
nesium is precipitated. Filter, wash the precipitate, and dry it
in a glass or porcelain dish. Note the appearance of the dried
salt. It is the heavy carbonate of magnesia, or magnesia alba
ponderosa. Repeat the experiment, but use cold solutions, and
boil for a few minutes after precipitating. The dried precipitate
is very light. It is magnesia alba levis.

Properties. — The carbonates of magnesia are white
powdery solids insoluble in pure water, but soluble in
dilute acids (with effervescence), in solutions of am-
monium salts, and in water containing carbonic acid.

Experiment 321. — To solution of magnesic sulphate add
ammonic carbonate ; a white precipitate falls (unless the am-

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366 MAGNESIA.

monic carbonate consists mostly of the acid salt, in which case a
little ammonia must be added). Add ammordc chloride ; the
precipitate is dissolved.

Experiment 322. — Put a little magnesia alba in a consider-
able quantity of distilled water in a flask or beaker, and pass
carbon dioxide through the water for some time. If the car-
bonate does not dissolve completely, filter. Boil a little of the
clear solution ; it becomes milky owing to the pre " "^itation of
magnesic carbonate.

The solubility of magnesic carbonate increases with
the pressure of the carbon dioxide. Liquor magmsice,
carhonatis is a solution made by using carbon dioxide
under considerable pressure. It contains about 1 3 grains
of " carbonate of magnesia " to the fluid ounce.

400. Magnesic Oxide (MgO). — Magnesium forms
only one oxide. It is known in pharmacy as magnesia,
or magnesia usta.

Preparation. — By heating strongly the carbonate of
magnesia. A light or heavy magnesia is obtained cor-
responding to the carbonate used.

Experim 3Ilt 323. — Heat a small quantity of magnesia alba
for some time in a porcelain crucible. Try the action of hydro-
chloric acid on the residue. It dissolves without eflfervescence,
if the heating has been continued long enough:

MgU + 2HC1 = MgCla + HaO.

Properties. — A light white powder, almost insoluble
in water (1 part dissolves in about 55,000) ; soluble in
acids, salts of magnesium being formed ; tasteless ; when
moistened, turns red litmus blue. It is thus a well-
marked basic oxide. It is a good antidote to arsenic
poisoning; it forms insoluble arsenite or ai'senate, and
neutralises tlje acid of the gastric juice.

QUESTIONS AND EXERCISES. 367

401. Tests.

1. Ammonic carbonate gives a white precipitate, bohible in
acids, and in solution of ammonium chloride. The carbonates
of barium, str&ntrum, and calcium are not soluble in solution of
ammonium chloride.

2. Sodic phosphate (with ammonia) gives a granular white pre-
cipitate (Mg.NH^.PO^), which forms in lines on the walls of
the t. t. when the solution is stirred with a glass rod :

MgSO^ 4- NHj + Na.HPO^ = Mg.NH^.PO, -f- Na^SO^.

3. Compounds insoluble in water are dissolved in hydrochloric
acid and tested by (1) and (2).

QUESTIONS AND EXERCISES.

1. In what way does calcic carbonate act as an antidote to
acids ? To zinc chloride ?

2. What substances does quick lime absorb from the atmos-
phere ?

3. What weight of water will 10 lbs. of quick lime absorb ?
What volume of air at 20°C saturated with water vapour will
supply this amount of water ?

4. Explain the " setting " of plaster of Paris.

5. Why does bleaching powder become moist when exposed to
the air ? Why must it be kept in well closed vessels ?

6. Calculate the weight of limestone to furnish 1 ton of lime.
What volume of carbon dioxide would be driven from it into the
atmosphere in the process of burning ?

7. What substances are formed by the action of hydrochloric
acid on barium sulphide (BaS) ? Write the equation.

8. How would you distinguish a specimen of zinc sulphate
(white vitriol) from one of Epsom salts ?

9. When potassic hydroxide Rolution is added to solution of
magnesic sulphate a white precipitate falls. What is it ? Write
the equation.

368 METALS OF THE ALKALIS.

10. How would you prepare baric nitrate from baric chloride ?

11. Baric sulphate is often used by painters as a substitute for
white lead. Why is it preferable ?

12. What substances are formed when solutions of sodic sul-
phate and baric nitrate are mixed ?

CHAPTER XXL

METALS OF GROUP VI.

Lithium, Sodium, Potassium, Rubidium, CcEsium,

\Ammonium\

402. General Characters. The metals of this

group form freely soluble hydroxides, called alkalis (from
alkali, the Arabic name for the plant from the ashes of
which potash was first prepared). The Tnetals of th"
alkalis form a series, similar in properties, but showing
that gradation always found in chemical series. Thus
the hydroxides increase in basic character from lithium
to caesium ; the oxidisability of the metals increases in
the same order, while ttoir melting points increase from
csesiuni to lithium. The metals are all univalent, and
are difficult to separate from their compounds. Each
forms only one basic oxide (NajO, KjO, Li.^O, <fec.), which
can be obtained by burning the metal in air. The oxides
combine with water to form hydroxides (NaOH, KOH,
(fee), from which the water cannot be driven off by heat.
The salts of the alkali metals are mostly soluble in water.
— The metals will be treated generally in the order of
their importance.

SODIUM CHLORIDE. 369

SODIUM.

403. Sodium (Na' = 23. Sp. wt. = 0.97. Melting
point --95°. 6).

Occurrence. — Compounds of sodium are univeraally
diffused, so that it is very diffi'^ult to get any substance
free from them. The compounds occurring in greatest
abundance are sodic chloride (NaCl), and Chili nitre

(NaNOg).

Preparation. — By strongly heating in iron tubes a
mixture of sodic carbonate, slack coal, and chalk :

Na^COg + 2C = 2Na + 3C0.

The sodium distils, is received in iron pots, and immedi-
ately sealed up to prevent oxidation.

Properties. — A bright, white metal, soft, and very
easily tarnisliod. In moist air it remains bright only a
few seconds. It readily burns in air, and forms sodium
monoxide, NaaO, along with some dioxide, Na202 (Exp't
26). It decomposes water, even in the form of ice, the
products being sodic hydroxide and hydrogen (Exp't 30):

Na + H2O = NaOH + H.

Sodium forms liquid and solid amalgams with mercury.
A. liquid amalgam is used in extracting gold from quartz.

404. Sodic Chloride (NaCl).

Occurrence. — In masses in the earth, as rock salt ; in
sea- water to the extent of 2.6 % ; in salt springs; and
in small quantities very widely diffused.

Preparation. — (1) By mining, as in Poland, Ger-
many, <fec.; (2) by allowing water to run down shafts ex-
tending into the salt beds, and pumping up and evapor-
25

370 SODIUM SULPHATE.

ating the solution formed ; (3) by evaporating the water
from salt springs; and (4) by evaporating sea- water. ]
This latter operation is often conducted in shallow bays !
(salterns) in which the water is left to evaporate by the i
heat of the sun ; hence the name bay salt. The mother j
liquor (bittern) contains chloride, bromide, sulphate, and |
iodide, of magnesium, sodium, potassium, and calcium ; 1
and is used as a source of bromine and iodine. Com- |
mon salt contains, as impurities, sodium and calcium i
sulphate, and magnesium chloride.

Properties. — Colourless cubical crystals. Specific
weight = 2.16 ; melting point = 776°; soluble in water,
the solubility increasing slowly with the temperature ;
100 parts of water at 5°C dissolve 35.63 parts of the
salt— at 50°, 37 parts— and at 100°, 39. 16 parts.— Sodium
chloride forms an essential constituent of blood and other
animal liquids. It seems to be necessary to keep in
solution certain albuminous compounds which are insolu-
ble in pure water. — It is used in medicine as an antidote
to nitrate of silver. (What is the action 1)

405. Sodic Sulphate (NajSO,).

Preparation. — From common salt by the action of
oil of vitriol ; enormous quantities are in this way pre-
pared as " salt cake," in the manufacture of soda (sodium
carbonate). Common salt is treated with sulphuric acid
in furnaces so constructed that half the salt is decom-
posed at a comparatively low temperature :

2NaCl + H2SO4 = NaHSO^ + HCl + NaCl.

and the remainder by transferring the mixed salts to a
hotter part of the furnace : • .

NaESO^ + NaCl = NagSO^ + HCl.

SODIUM CARBONATE. 371

The hydrochloric acid escapas up a flue, and is dissolved
by water descending in a shower. Tlius is obtained the
impure hydrochloric acid of commerce. — Sodic sulphate
is sometimes a by-product in the manufacture of nitric
acid, but the acid sulphate (NaHSO^) is generally
obtained.

Experiment 324. — Warm a small quantity of common salt in
a porcelain basin with about an equal weight of sulphuric acid,
dissolve the residue in water, and evaporate tc crystallisation.
The crystals have the composition represented by Na^SO^. lOH^O.
They are called Olaiiber's salt. Drain them and leave them
exposed co the air for a day.

Properties, — Crystallised sodic sulphate (Na^SOi.
lOHgO^ is a colourless salt, of bitter saltish taste. It is
efflorescent, and is soluble in water (35.96 parts in 100
at 15°). Its solubility is greatest at 34°C, and is only
42 in 100 at 100°. It is very sparingly soluble in
alcohol. — Sodic sulphate is much used in Europe as a
saline purgative. It is also used as an antidote in cases of
poisoning by salts of lead and barium. (How does it aot'i)

406. Sodic Carbonate (NaaOOg.lOHjO). Also

called carbonate of soda, soda, and washing soda.

Preparation. — 1. Bv Leblanc's process, in three
stages :

(a) The salt cake process. (Art. 393.)

(b) The black ash process, in which the salt cake is
strongly heated with limestone and slack coal. A certain
proportion of quick lime is also generally added. The
following equations represent the principal chemical
actions which take place :

NaaSO^ 4- 40 = NaaS + 4C0.
NaaS + CaCOg = NaaCOg + CaS.

372 THE AMMONIA SODA PROCESS.

Calcic sulphide is insoluble, and the sodium carbonate is
extracted from the " black V)all " by

(c) Liociviation. The strong solution thus obtained is
evaporated and the soda allowed to crystallise. It may
be purified by recrystallisation.

2. By the Ammonia-Soda process. A. saturated solu-
tion of common salt is saturated with ammonia, and then
a current of carbon dioxide is passed through it. Sodic
hydric carbonate is precipitated :

NH3 + COa + NaCl + H2O = HNaCOg + NH^Cl.

The ammonia is recovered by distilling the mother liquor
with magnesia :

MgO + 2NH4CI == MgCl2 + 2NH3 + H2O.

The magnesia is recovered (as hydroxide) by treating the
chloride with superheated steam :

MgClg + 2H2O = Mg(0H)2 + 2HC1.

Sodic hydric carbonate is easily converted into the car-
bonate by the action of heat :

2NaHC03 - NaaCOa -f H2() + COa.

Properties. — Sodic carbonate is sold in large crystal-
line lumps, or in the form of a white powder. The
crystals are efflorescent, and are readily soluble in water
(60 parts in 100). The solution is alkaline in reaction,
and neutralises strong acids.

Experiment 325- — Heat gently a crystal of washing soda iu
a t. t. and note the escape of water. Dissolve a fragment in
water and test with red litmus. Add sulphuric acid to a solu-
tion of washing soda.

Experiment 326.— Heat some washing soda in a porcelain

CAUSTIC SODA. 373

capsule until the liquid at first formed dries up to a cake. This
is dried carbonate of soda. Powder and preserve it in a stop-
pered bottle.

407. Sodic Hydric Carbonate (NaHCOg). —

Also called bicarbonate of soda, and baking soda.

Preparation. — By exposing washing soda crystals to
the action of carbon dioxide evolved by the action of
hydrochloric acid on marble or limestone :

NaaCOg.lOHaO + COa = 2NaHC03 + GHgO.

It is also prepared from common salt by the ammonia
soda process (Art. 406).

Properties. — A white powder, soluble in water, and
in hydrochloric and other acids, with much efferves-
cence. It is decomposed by heat (Art 406.) It is much
less soluble in water than the normal carbonate, 100
parts of water at 15°, dissolving only 10.5 parts.

408. Sodic Hydroxide (NaOH). — Also called

sodium hydrate and caustic soda.

Preparation. — Experiment 327. — Dissolve some washing
soda in about six times its weight of water, heat to boiling in a
porcelain dish, add, a little at a time, slaked lime equal to about
half the weight of the washing soda, keeping the liquid at the
boiling point, and adding water as it boils away. Allow to
settle, pour off the clear liquor, and test it with hydrochloric
acid. It should give no effervescence. Test the precipitate
with hydrochloric acid. It effervesces :

Ca(OH)a 4- NaaCOa = CaOOa + 2NaOH.

This solution {liquor sodas) prepared on the large
scale in this way is boiled down in iron pots until a red
heat is attained, when the molten caustic soda is run

374 SODIUM NITRATE.

into iron cylindei-s and sealed up. — Causfcic Boda is also
formed when sodium decomposes rvater. (Exp't 30).

Properties. — A brittle white solid, of specific weight
2.13. It melts at a dull red heat, but is not decomposed
until an intense white heat is attained. It is delique-
scent, and when exposed to the air soon becomes changed
to carbonate. It dissolves readily in water, with the
evolution of heat.

Experiment 328- — Put a small piece of caustic soda in a
porcelain dish, leave it a few days, and then test it with hy-
drochloric acid.

Experiment 329- — Pour a little water upon a piece of cftastio
soda in a t. t. Note the heat. Add more water, and note the
taijteand action on the skin of the resulting solution.

Caustic soda has a strong corrosive action on animal
tissues. It is therefore very poisonous. — Solution of
caustic soda disscdves glass and porcelain. This goes on
gradually even with very dilute solutions. — Caustic soda
has many usee. Combined with fatty acids it forms
hard soaps ; and on account of its solvent action on fats,
<kc., it is used in cleansing rags, grass, tkc, in the manu
facture of paper. In medicine caustic soda is used as an
escharotic. In the chemical laboratory it is often used
to precipitate insoluble metallic hydroxides.

409. SodiC Nitrate (NaNOg). — Also called cubic
nitre and Chili saltpetre. This salt is found in large
quantities in Peru and Bolivia. It is obtained by min-
ing, and purified by solution and crystallisation. Its
crystals when perfect are nearly cubical. It is very
soluble in water (84 parts in 100), and somewhat deli-
quescent. In dissolving, it renders much heat latent.

aODlUM PHOSPHATE. 375

This accounts for its cooling taste. It is used as a fer-
tiliser, and in the manufacture of nitric acid and inferior
blasting powders.

410. Sodic Sulphite (Na^SOa.THjO).

Preparation. Divide a solution of sodium carbonate
into two equal parts. Saturate one with sulphur di-
oxide, add the other, and evaporate to crystallisation.
Sodic hijdric sulphite (NaHSOg) is first formed :

Na2C03+2S03 4- HaO - 2NaHS03 + CO2.

Tliis is then converted into the normal sulphate :

2NaHS03 + NaaCOg = 2Na2S03 + COa + H2O.

Properties. — A colourless crystalline salt; soluble in
water ( 1 part in 4). The solution is alkaline. Both the
normal and the acid sulphite are used in medicine.
They are used especially to destroy sarcince ventriculi,
minute parasitic plants sometimes present in the stomach.
The acid of the gastric juice sets free sulphur dioxide,
which has an antiseptic action :

NaaSOg + 2HC1 = 2NaCl + SO^ + HjO.

Sodic sulphite must be kept well stoppered, as it absorbs
oxygen from the air and becomes oxidised to sulphate.

411. Sodic Phosphate (N9^HP04.12H,0).— This

is ta(! ^^ common" or '^^ rhombic" phosphate of soda. It
was first prepared from urine, and is present in the
blood and in other animal liquids.

Preparation. — Bone ash is decomposed with sul-
sulphuric acid :

Ca3(r04)2 H-3H2S04 = SCaSO^ + 2H3PO4.

376 sotnuM bbomide.

The solution of phosphoric acid is separated from tho
sparingly soluble gypsum, and treated with sodic car-
bonate :

n3P04 -f NaaCOg = NaaHPO^ + HaO + CO2.

The solution is then evaporated to crystallisation.

Properties. — A colourless salt, soluble in water (14
parts in 100). Its solution is alkaline in reaction. Its
taste closely resembles that of common salt.

Experiment 330- — Dissolve a little sodic phosphate in water.
Note the taste of the solution. Test with red litmus. Add a
few drops of argentic nitrate to a little of the solution. Note
the yellow precipitate (Ag3P04) :

SNaaHPO^ f eAgNOa = 2Ag8P04 + 6NaN0^ -f HgPO^.

412. Sodic Bromide (NaBr).^Thi3 salt is pre-
pared by dissolving bromine in solution of caustic soda :

6NaOH + 3Br2 - 5NaBr -f- i.aBrOs + 3H2O.

evaporating to dryness, and heating with a little char-
coal to d ecompose the broraate :

2NaBr03 + 3C = 2NaBr + 3CO2.

It is a soluble, colourless, crystalline salt, similar to the
potassium salt. It is propoi^^ed to use it in medicine in
place of potassium bromide, since it is equally efficacious,
and causes none of the unpleasant symptoms resulting
from the continued use of the potassium salt.

413. Sodic Sulphide (Na-^S). — Can be prepared
impure {liver of sulphur) by heating sodic sulphate with

charcoal :

Na.,S04 -^40 = Na.,S -f 4C0.

To prepare solution of sodic sulphide, take two equal

GLASS. 377

quantities of a solui/ion of caustic soda, saturate the one
with hydrogen sulphide :

NaOH + H,S = NaSH + IIjO,

and then add the other :

NaSH + NaOH = ]Sra,S ^ H,0.

The same method is used for preparing solutions of po-
tassmm and ammonium sulphides. — Solution of sodium
sulphide is used to precipitate and dissolve sulphides of
heavy metals. It combines with the .sulphides of arsenic,
antimony, tkc, to form soluble sulphur salts; e.g.:

SNa^S + Sb^Sg = 2.Na3SbS,.

414. GlaSF — Grlass is a mixture of silicates. The
materials used are (1) silica, in the form of quartz,
ignited flint, white sand, or red sand; (2) alkali, purified
potashes, refined soda ash, or salt cake ; and (3) calcic
carbonate, (Lc. — calcspar, marble, chalk, or limestone, and,
for flint glass, red lead or litharge. There are several
varieties of glass :

1. Bohemian Glass. — Silicates of potassium and calci-
um. It fuses with difficulty and resists the action of
chemicals better than tlie other kinds of glass.

2 Window's, or Crown, Glass. — Silicates of sodium and
calcium. It is more fusible than Bohemian Glass, and
more easily acted on by chemicals.

3. Bottle Glass. — Silicates of sodium and calcium, but
made from cheap materials. Its colour is due to iron
compounds.

4. Flint Glass, Crystal, or Strass. — Silicates of potas-
sium and lead. It is heavy, fusible, and has a bright

378 POTASSIUM.

liiBtre. It is used for ornamental purposes, and ore vari-
ety {paste) is used for imitating diamonds.

The properties of glass make it very useful in chemical
operations. It is transparent, not readily fused, and
only slowly and sparingly soluble in most chemical
substances. It can be fused at a red heat, and can then
be moulded into any desired form.

415. Tests.

Very few salts of sodium are insoluble, so that the tests are
mostly negative. Sodic metantimonate is insoluble, and a solu-
tion of the potassium salt is sometimes used as a test for sodium;
but the test chiefly relied upon in analysis is the exclusion of
other metals, and the yellow colour given to the Bunsen flame
when sodium compounds are brought into it.

POTASSIUM.

416. Potassium (K' = 39.04. Specific weight =
0.875. Melting point = 62°.5).

Occurrence. — Is found almost universally, but always
in combination. It forms from 1.5 to 3.1 % of granite, and
occurs in many double silicates. Potasf'i felspar is. a
double silicate of potassium and aluminium (KjO.AljOj.
GSiOj), which " weathers " and thus forms clay. The
chief source of potassium compounds is the mineral de-
posits of Stassfurth, which contain silvine (KCl), carnal
lite (KCl.MgCl2.6H2O), &c. Potassium compounds are
present in sea water, in soils, and in plants and animals.

Preparation. — In the same way as sodium, but
special precautions must De taken on account of the
formation of an explosive compound of potassium and
carbon monoxide.

POTASSIC CARBONATE. 379

Properties. — A silver white metal, resembling sodi-
um, but it is more easily oxidised. Its chemical pro-
perties are very like those of sodium, but more pro-
nounced. It is used in })reparing boron, silicon, magne-
sium, <fec.

417. Potassic Carbonate.— (K2CO3). Also called

carbonate of potash, potashes, and salt of tartar (was form-
erly prepared by igniting * cream of tartar ').

Preparation. — 1. From potassic chloride (KCl), and
sulphate (R^SOi), by the same process as that employed
for sodium carbonate (p. 371).

2. From wood ashes, by leaching, evaporating, and
calcining. The residue is impure potassium carbonate
(potashes). It is purified by recrystallisation, and is
theti called pearl ash.

3. From the waste liquors of the beet suyar industry,
)by evaporation and repeated crystallisation.

4. From the washings of sheep's wool, technically
called " suint." The washings are evaporated to dryness
and distilled. An illuminating gas, and an ammoniacal
liquor, are obtained. The fixed residue is lixiviated, <fec.,
for potassium carbonate. Commercial carbonate of pot-
ash is rarely pure. It can be purified by treating a sat-
urated aqueous solution with carbon dioxide, and collect-
ing and heating the acid carbonate thus precipitated :

K2CO3 -{- CO3 + H2O = 2KHCO3.
2KHCO3 = K3CO3 -\- H2O -t- COa.

Properties. — A white granulated powder, or a pasty
iiiass, very deliquescent, very soluble in water (106.4
parts in 100), sparingly soluble in alcohol. The aqueous

380 BICARBONATE OF POTASH.

solution has an alkalina reaction, the properties of the
strong base being only partially neutralised by the weak
acid. Potassic carbonate is used in medicine as an ant-
acid, and to promote the solution of uric acid stones. Its
taste is very disagreeable. It is also used in the manu-
facture of soft soap, crystal glass, potassium ferrocyanide,
bichromate, and cyanide.

Experiment 331. — Scatter a few grains of dry potassium
carbonate upon a sheet of paper and examine after a few hours.
1. 1, e a solution, and try the taste and action on red litmus.

418. Potassic Hydric Carbonate (KHCO^).-

Also called bicarbonate of potash.

Preparation. — By passing a current of carboii diox-
ide for several houi-s through a cold saturated solution of
potassium carbonate. The sparingly soluble acid carbon-
ate is precipitated.

Properties. — Colourless crystals, of a Sdltish taste ;
soluble in water (25 parts in 100), giving a slightly alka-
line solution, decomposed by heat, even when in solution :

2KHCO3 = K2CO3 4- H2O -f CO2.

This salt has none of the corrosive action of the normal
carbonate. It is used as an antacid and antilithic. Li-
quor potasses effervescens, or potash water, is a solution
of potassium bicarbonate into which carbon dioxide uas
been introduced under a pressure of seven atmospheres.

419. Potassic Hydroxide (KOH), also called
potassium hydrate, and caustic potash. — This compound is
prepared from potassium carbonate by the same method

POTASSIC CHLORATE. 381

as that used for sodic hydroxide, which it resembles in
its properties. It is, however, more strongly corrosive
in its action on the skin &c. Potash lye is an aqueous
solution of impure potassic hydroxide.

420.— Potassic Chlorate (KCIO3), also called
chlorate oi potash.

Preparation. — Milk of lime is saturated with chlo-
rine, and part of the water is evaporated :

6Ca(OH)2 + 6CI2 = Ca(C103)2 + Sr'aCla + 6H2O.

Potassium chloride is added (In what proportion V), and
the solution is boiled down and allowed to cool, when
potassic chlorate crystallises out :

Ca(C103)2 + 2KC1 = CaCl2 + 2KCIO3

In this way the whole of the potassium is obtained as
chlorate. The old method is wasteful (Expt. 76).

Properties. — Colourless, flat crystals, or a white
granular powder. It has a cooling acid taste, and is
sparingly soluble in water (6 parts in 100). When
heated to 352° C. it decomposes into oxygen, chloride,
and perchlorate :

2KCIO3 = O2 + KCl + KCIO,.

At a higher temperature the whole of the oxygen is
driven off. It is a powerful oxidising agent, but is not
capable of supplying oxygen to the blood.

Experiment 332. — Carefully mix some dry sugar with about
one-fourth its weight of powdered potassic chlorate, place the
mixture on a stone or a piece of poroelain and touch with a glass
rod dipped in concentrated sulphuric acid. (Explain the action).

421. Potassic Nitrate, (KNO3).— Also called salt-
petre, and nitre.

382 POTASSIC BROMIDE.

OocURRENCE. — As efflorescence on the soil in hot dry
countries, such as Bengal and Egypt. Has been obtained
by lixiviating certain porous rocks (hence the name, sal
petrce). Its formation in the soil is due to the slow oxi-
dation of nitrog'^nous matter in the i)resence of potassic
carbonate or silicate. Nitric acid is first formed and this
decomposes the j)otassium carbonate, &c.

Preparation. — It is prepared from the soil incrusta-
tion by lixiviation and crystallisation. Much saltpetre
is now prepared from potassic chloride by dissolving along
with an equivalent (Calculate the proportions) of sodium
nitrate in hot water until the specific weight is 1.5. Sodi-
um chloride is precipitated, and potassium nitrate sepa-
rates out when the solution cools :

KCl + NaNOa = KNO3 + NaCl.

(Compare the solubilities of these four salts.)

Ph I'ERTIES. — Long colourless crystals, of a cooling
bitter taste, soluble in water (26 parts in 100). It is an
oxidising agent and plays this part in gun powder and in
many coloured fires. Its uses in medicine depend princi-
pally on its cooling properties.

422. Potassic Bromide, (KBr).

Preparation. — Experiment 333 —Gradually add dilute
solution of potassic hydroxide to a drop of bromine under water,
until the colour of the bromine disappears. Evaporate the solu-
tion to dryness in a porcelain dish and ignite the residue. Potas-
sic bromide remains :

6K0H -f 3 Bra = KBrOg + 5KBr -f 3HaO.
KBrOa = KBr 4- 30.
Dissolve in a little hc^fc water and crystallise.

Properties. — Translucent, colourless, cubical crystals,

POTASSIO IODIDE — AMMONIUM. 383

resembling those of potassic iodide, but not so porcelain-
like ; taste, sharp and saline ; readily soluble in water,
somewhat sparingly in alcohol.

423. Potassic Iodide, ^KI).

Preparation. — Experiment 334 —Repeat Expt. 333,
using iodine instead of bromine. Potassic iodide is obtained.
(Write the equations).

Properties. — Potassic iodide is very like the bromide
in its properties. It crystallises in cubes, which are
opaque and porcelain-like when deposited from a hot
solution, but clear when crystallised cold. It is very
soluble in water (140 parts in 100'. (Examine carefully
and compare crystals of potassium bromide and iodide).

424. Tests.

1. Tartaric acid gives a white crygtaline precipitate of potassic
hydric tartrate, especially on stirring with a glass rod.

2. Platinum tetrachloride gives a yellow crystalline precipitate
(KjjPtCle). Make this test by stirring together a drop or two of
the solutions on a watch glass.

3. Potassium compounds give a violet colour to the Bunsen
flame.

AMMONIUM.

425. Ammonium Salts- — These are compounds
containing the radical ammonium (NH^ — ), which acts
the part of a monad atom. They are generally prepared
by neutralising the appropriate acids with solution of
ammonia. This solution may be supposed to contain
ammonium hydroxide (NH^OH), which acts towards
acids as sodic hydroxide does, e.g. :

NH4.OH + HCl = NH^.Cl -f H2O.
Compare KOH + HCl = K.Cl + HaO.

384 AMMONIC CHLORIDE.

The ammonium salts resemble those of sodium and potas-
sium, especially the latter, but can all be decomposed
by heat.

426. Ammonic Sulphate, ((NH4)jS0,).

Pre '\RATiON. — By heating i,a8 liquor with lime, and
receiving the evolved ammonia in dilute sulphuric acid.
The solution thus obtained is evaporated to crystallisation.

Properties. — A colourless salt, generally in small
crystals, soluble in water (75.5 parts in 100). When
heated strongly it volatilises completely.

Experiment 335. — Heat a little ammonic sulphate in a dry
glass tube. Dissolve another portion in water and test it for
sulphuric acid.

Ammonic sulphate is used as a fertiliser. It is the
starting point in the manufacture of other ammonium
salts.

427. Ammonic Chloride, (NI14CI), also called

sal ammoniac.

Preparation. — Experiment 336. — Neutralise a small
quantity of dilute hydrochloric acid with solution of ammonia
and evaporate to dryness. Ammonium chloride remains :
NHj 4- HCl = NH^Cl.

Ammonic chloride is also prepared by subliming a
mixture of the sulphate and common salt :

(NH4)aS04 + 2NaCl = 2NH4CI + NajSO^.

It is purified by re-sublimation.

Properties. — Colourless crystals, either in tougli
masses of flexible fibres, or in grains. It has a sharp
cooling taste, and is freely soluble in water (35 parts in
100). When the aqueous solution is boiled, ammonia

AMMONIL'M CARBONATE. 385

escapes and the solution becomes acid. Ammonium chlo-
ride lenders latent a great deal »/f beat when dissolving.
It is an excellent cooling a'^ent.

Experiment 337 — Dissolve some ammonic chloride in a little
water and note the low temperature produced. Heat a small
quantity of the solid in a dry glass tube. It sublimes and leaves
no residue, if it is pure.

428. Ammonic Carbonate. — The normal carbon-
ate (NH4)2C03) is diflBcult to prepare and keep. It loses
ammonia and becomes converted into the acid carbonate
(NH4HCO3). The " sesqui carbon ate " of commerce is a
compound of the acid carbonate with ammonium car-
bamate (NH4.CO2.NH2).

Preparation. — By subliming a mixture of chalk and
sal ammoniac or ammonium sulphate :

CaCOs + (NH4)2S04 = (NHJaCOg + CaSO^.

The salt which sublimes is, however, not the normal car-
bonate represented in the equation, but the " sesquircar-
bonate " ^so called) :

NH4HOO3.NH4NH2CO2

Experiment 338- — Heat a mixture of ammonium sulphate
and ground limestone in a dry test tube. Scrape out a little of
the sublimate, observe its odour, and note that it eflfervesces
with hydrochloric acid.

Properties. — Commercial carbonate of ammonia {sal
volatile) is sold in hard translucent crystalline masses.
It smells of ammonia, and, if exposed to the air, is soon
changed to tho acid carbonate by losing ammonia and
gaining water :

NH4.NH2.CO2 + H2O = NH^HCO^ 4- NH3.

It is soluble in water (27.5 parts in 100), and the solu-
26

.\HC) AMMONIUM SUM'IIIIH'

tion is alkaline. Aromatic npirit of aniinonia is a prepa-
ration of tlie carbonate

429. Amnionic Phosphate, (NHJ.HPO^.

PREPAR.onoN. — By neutralising solution of [)hos})horic
acid with ammonia solution, and crystallising :

2NH3 + H3PO4 = (NH4)2 HPO^

Properties. — Colourless crystals, soluble in water,
insoluble in. alcohol.

430. MicroCOSmic Salt. — Is hydric sodic ammonic
phosphate (H.Na.NH4.P04.4H20.) first noticed as crystal-
lising from concentrated uiine. It is a colourless crystal-
line salt prepared by mixing hot strong solutions of
sodium and ammonium phosphates and allowing to crys-
tallise. By heat it decomposes as follows :

HNaNH4P04.4H20 = SHgO + NH3 + NaPOg.

The non-volatile sodic metaphosphate remains.

431. Amnionic Sulphide, ((NH4)2S.)

Preparation. — In the some way as solution of sodic
sulphide (Art. 413).

Properties. — Forms a colourless solution which gradu-
ally turns yellow, owing to the absorption of oxygen,
which sets free sulphur. Ammonium sulphide solution
dissolves sulphur, and thus forms "yellow ammonium
sulphide," used in analysis to dissolve stannous sulphide.

Experiment 339. — Add hydrochloric acid to a few drops of
yellow ammonium sulphide, and observe the precipitation of
sulphur and the evolution of hydric sulphide :

(NH JaSx + 2HC1 = 2NH4CI + H2S -f- xS.

Ammonic sulphide is poisonous.

I-ITIIHTM. 387

432. Tests.

1. Heat in a test tube with caustic ao'lp solution, o})8erve the

odour, and hold over the mouth of tlie teat tube a glass rod

moistened with dilute hydrochloric acid. White fumes are

formed :

NH» 4- HCl = NH«C1.

(What is the object of the caustic soda ?)

2. Platinum tetrachloride gives a yellow precipitate
((NHjaPtClo). (Art. 424 (2)).

LITHIUM.

433. Lithium (Li' = 7.0 1. —Specific weight = 0.59.—
Melting point = 180°.) The metal is prepared by elec-
trolysing the fused chloride (LiCl). It resembles sodium
and potassium in its properties, but is much lighter, and
has not so strong an attraction for oxygen. Lithium
compounds are widely diffused, but i*^ small quantities.
They are found in most mineral waters, and in river and
spring water generally. The compounds of lithium re-
semble those of sodium and potassium, but the hydroxide
(LiOH), carbonate (LioCOg^ and phosphate (Li3P04), are
much less soluble in water.

434. Lithic Carbonate, (LiaCOg).— This is the
most important compound of lithium, as it is much used
in medicine in treating gout, stone, &c.

Preparation, — Experiment 340- — To a small qni.ntity of
solution of ammonium carbonate in liquor ammoniae add a small
quantity of a strong solution of lithium chloride. Lithium car-
bonate is precipitated :

2LiCl -h (NH J2CO3 = LiaCOg + 2NH^C1.
Warm, filter, and wash with cold water.

388 , m:mi)irM c/Ksilm.

Pkopkutiks. — Jiitliiimi cMihonatci i.s u white crystalline
)»ow(ler, RiMii'iiigly .soliil)le in watijr (0.78 parts in 100 .
It is more soluble if carbonic acid 1h5 added, as the bi-
carbonate (LiHCO.,) is formed, of which 5,25 parts dis-
solve in 100 of water. When this solution is exposed to
the air, it loses ct.rhon dioxide and the normal car'oonatc
is precipitated. (What other carbonates behave sinii
larly 1)

Lithium carbonate is prescribed for gout, stone, i''c. It
is preferable to the potassium salt. (Art. 167).

435. Tests.

Lithium compounds can be recognised l)y the spectrum of the
beautiful red colour which they give to the Bunseu flame.

436. Rubidium, (HV = 85.2).— Compounds of this

rather rare alkaline metal are found in mineral springs,
and in some minerals. The metal can be prepared by the
same process as that for the preparation of sodium and
potassium. It is like these in properties, but has greater
chemism for oxygen than potassium has. Its compounds
are similar in com{)osition and {)roperties to those of
potassium, e.g., Rb.^O, RbOH, KbCl, &c.

437. Caesium (Cs'= 132.5). — Ctepium compounds

were discovered in 1860 by Bunsen, by means of the
spectroscope ; and this discovery was the first fruit of
spectrum analysis. When white light is passed througli
the edge of a wedge-shaped piece of glass [prism), it is
spread out in such a way that the waves of different
lengths fall on different parts of a retina receiving them.
The sensation is one of a band of coloured I'ghts ranging
from red to violet. Such a band is called the spectrum

QUKSTIONS AND KXKHCISKS. 380

and in the spectrum each colour has its fixed phice.
Now, each element in the state of a hot vapour gives a
light corresponding to particular lines in the spectrum ;
and if, when looking thiough a prism (appropriately ar-
ranged in a spectj'oscope), we see in a flame bands or
lines, we can recognise these as l^eing due to the presence
of some known element. Bunsen, when looking at a
flame in which was volatilising the solid residue of the
water from a mineral spring, saw lines produced by no
known element. He thus discovered the metals caesium
and rubidium. — Cesium was prepared in 1881 by Carl
Setterborg by electrolysing the fusc^d cyanide (CsCN*.
It melts at the temi)erature of the hand, and exceeds
rubidium in its chemism for oxygen. Its compounds are
very like those of rubidium and potassium, e.g., Cs.^O,
CsOH, CsCl, Cs-pO.,, ifcc.

QUKSTiONS AND EXERCISES.

1. Calculate the percentage of water in washing soda.

2. How much dried sodium carbonate is etiuivalent to 100
grains of washing soda ?

3. What substances are antidotes to caustic soda and caustic
potash ?

4. "Sodium nitrate gives, weight for weight, more nitric acid
thanpotassic nitrate does." Show the truth of this statement.

5. How would you distinguish (practically) sodium carbonate
from potassium carbonpte.

6. Solution of normal sodic sulphite is alkaline in reaction.
How do you account for this ?

7. Show that, weight for weight, lithium carbonate will dis-
solve a larger quantity of uric acid stone than will potassium
carbonate.

390 ELECTRICITY.

8. How much potassium chlorate (KC'lOa) ca.i be obtained
from 10 lbs. of cau^uic potash (KOH)— (1) by the method of
Art. 101, ami (2) by that of Art. 420?

8. What would you use as an antidote to poisoning by am-
monium sulphide ?

9. Arrange the metals of the alkr.iis (I) in the order of their
atomic weights, and (2) in the order of their chemism for oxygen.

CHAPTER XXII.

ELECTRICITY.

438. Voltaic Batteries. — If a plate of copper helj
by a glass rod (an insulator) be touched by a zinc plate
similarly held, and then withdrawn, the two plates will
be found to be in a peculiar condition, such that they
produce exactly opposite effects on electrified bodies.
What the copper attracts the zinc repels, and vice versa, —
the zinc is positively, the copper negatively, electrified.
The condition is one analogous to a difference of temper-
ature. If a drop of sulphuric acid be placed between
the plates, a similar condition is produced. And, if the
dry ends of the plates be now connected by a copper
wire, so as to complete the circuit, the copper and zinc
tend to assume the same electrical condition by a trans-
ference of electricity through the liquid from the zinc to
the coppei. At the same time sulphuric acid is decom-
posed into H2 and SO4, the hydrogen appearing at the
surface of the copper plate, and the salt radical (SO4)
attacking the zinc plate and for^^iing zinc sulphate. While
this takes place in the liijuid there passes round the rest
of tlie circuit a disturbance of some sort, called, for lack

ELECTIUCITY. 31)1

of a better term, a current oj eleetricUjf. The source of
this form of energy (which can be used to drive ma-
chinery, to heat a wire, tkc.) is the chemical action be-
tween the zinc and acid. If no electricity were produced,
e.g. if the zinc were put alone into 8ul[)huric acid, an
amount of lieat equivalent to the electricity would appear
in the li(|uid for the same amount of zinc dissolved. This
is the simjjlest form of voltaic cell. The zinc is called the
positive element, tlie copper, the iiegative element. As a
rule, when any two suV)stances are brought together in
this way, the one assumes the j)Ositive condition and the
other the negative. The chemical elements can thub be
arranged in an electro-cliemical series, beginning with the
most positive, and ending with the most negative ele-
ments. In this series, any element is positive as regards
succeeding, but negative as regarding preceding, elements.

Electro-chemical Series : Cs, Rb, K, Na, Li, Ba, Sr,
Ca, Mg, Al, Mn, Zn, Fe, Ni, Oo, Cd, Pb, Sn, Bi, Cu, Ag,
Hg, Pt, Au, H, Si, Te, Sb, C, B, Cc, As, P, I, Br, CI, F,
N, Se, S, O.

439. Electrolysis. — Most compounds which can be
got in the licjuid condition, either by fusion or by solu-
tion, can be decomposed by a current of electricity allowed
to pass through the liquid between two wires dipping into
it. Compounds decomposable by electricity are called
electrolytes. In such decompositions, one portion of tbo
compound is set free at the wire (^the negative pole) com-
ing from the positive element of the battery, and the
other at that (the positive pole) connected with the nega-
tive element. If the liquid is a metallic compound the
metal always appears at the negative pole (Art. 261), and
the non-metal, or negative radical (NO^, SO^, <fec. ) at the

392 KLECTUIC'V.

positive pole. The positive part of a compound goes with
the current. The wires or plates used for conductin*,'
the current into and out of the liquid are generally
called electrodes. The positive electrode is often eaten
away by the negative product of electrolysis. Plat-
inum resists in most cases, Vmt is attacked by chlorine,
(fee. Various secondary actions occur when solutions are
electrolysed. For example, when a solution of sodium
sulphate is electrolysed, sodium is set free at the negative
I)ole, but immediately decomposes water, and thus hydro-
gen and caustic soda are the final [)roducts. At the nega
tive jiole, oxygen and sulphuric acid appear, since the
radical SO4 cannot exist by itself. Generally, when solu-
tions of alkaline salts are electrolysed, an alkali and
hydrogen appear at the negative electrode, while an acid
and oxygen ap[)ear at the positive. The nascent hydrogen
and oxygen may exert reducing or oxidising action on
the other substances present in the solution. — The liquids
of the human body contain salts of sodium and potas-
sium, so that when a current of electricity passes thiougli
any part, f Ikali collects around the negative, and acid
around the positive, needle. The alkali exerts its well-
known solvent action on the tissues, while the acid co-
agulates the albuminous substances and thus causes the
needle to become more or less firmly fixed in the tissues.
Advantage is taken of these phenomena in the destruc-
tion of tumors, <fco., by electrolysis of the diseased tissue.

SY.STliMATIC TliSTlNU. 393

CHAPTER XXIII.

ANALYSIS— TOXICOLOGY.

440. Systematic Testing. — Most of the sub-
stances whicli are met yith in i)ractice can be arranged
under the three heads of bases, acids, and salts. In sys-
tematic testing of unknown substances, two cases may
occur: (1) the substance may be pure — a chemical in-
dividual, or (2) it may bo t»ixe<l — including two or more
chemicj,l individuals. The first case is the only one
which admits of treatment here ; the case of mixtures
requires more space than we have at our disposal. For
purposes of system;! tic testing, the metals are classified
as at p. 270, and the first step is to determine, by the
use of group reagents, to which of the six groups the
metal whose base or salt is under examination belongs.
This determined, further testing shows which metal of
the group is present. The acids can be arranged in four
groups :

1. Organic acids, which char when heated : — Tartaric,
citric, succinic, 'benzoic, &,c.

2. Inorganic acids, the barium salts of which are in-
soluble or spai'ingly soluble : — Sulphuric, carbonic, phos-
phoric, oxalic, boric, sulphurous, chromic, &c. The group
reagent is barium nitrate.

3. Inorganic acids, the silver salts of which are in-
soluble : - Ferrocyanic, ferricyanic, hydrocyanic, hypo-
chlormis {chloride precipitated), hydriodic, hydrobromic,

094 DISSOLVING THE SUBSTANCE.

hydrochloric, thiosulphuric, nitrous, [boric, oxalic, sul-
phurous]. Argentic 7iitrate is the group reagent.

4. Acids which give no precipitate with the group
reagents : — Nitric, chloric, acetic, and (in sufficiently
dilute ssolutions) oxalic, boric, sulphurous, and nitrous.

Note. — In testing for the acids, the nature of the
metal (already discovered) must be considered. For
example, a solution of plumbic acetate might char on
evaporation and ignition. On the addition of calcic
chloride, a white precipitate would a})pear at once. This
might lead to the conclusion that the acid is tart^-'--
whereas the precipitate is plumbic chloride. In i

cases, the metal must be removed as carbonate, by boil-
ing with solution of sodic carbonate, filtering, and neu-
tralising part of the filtrate with nitric acid, to test for
all acids but nitric and chloric, and another with hvdro-
chloric acid, to test for these two acids.

441. Dissolving the Substance.— Try the solu-
bility of small portions of the substance in water, in hy-
drochloric acid, in nitric acid, and in aqua regia. If a
solution is obtained in any of these solvents, make the
analysis according to the following tables. If the sub-
stance is insoluble in water, but soluble in hydrochloric
acid, it may be a phosphate, oxalate, or citrate, in which
case it would be re-precipitated by ammonia (Table B),
and might then be mistaken for alumina. In such
cases, these thiee acids must be tested foi* separately (see
articles 132, 184, 190\ If the substance is insoluble in
all the above-mentioned solvents, it is probably one of
the following : — Baric sulphate, strontic sulphate, silica,
calcic Jluoridc alumina, stannic oxide, anjetitic chloride,

PRACTICAL HINTS — CHEMICAL TOXICOLOGY. 395

plumbic sulphate, carbon, ferric oxide. TJiese are all
^vhite, excepting the last two. They may be tested for
by special tests, described in the preceding pages (see
Barium, <fec.)

442. Practical Hints.— Use small quantities, both
of reagents and of liquids, to be tested. Add the re-
agents a little at a time. Remember that in chemical
actions, equivalents of the substances must be used in
order to complete the actions.

Excess of a reagent means more than enough to com-
plete the chemical action which the reagent brings about.
It does not necessarily mean a large quantity. Chemi-
cal actions take time, and when solutions are very cold
the time is longer. This is a matter to be considered
m the more delicate tests.-Work slowly, and handle
apparatus gently. Clean apparatus as soon as possible
after using it, as it is more difficult to clean after standing
for some time. Explain every test, and write equations
where possible.

443. Chemical Toxicology. - Poisonous sub-
stances may be conveniently classified as follows :—

1. ^orro^fm.— Corrosive sublimate, concentrated acids
(sulphuric, nitric, hydrochloric, oxalic, &c.), alkaline sub-
stances (caustic potash, caustic soda, ammonia, and the
carbonates of these bases), acid, alkaline, and corrosive
salts of the metals (potassium bi-sulphate, alum, atiti-
mony trichloride, silver nitrate, &c.), and carboxic acid.

2. /rn^an^s.— Arsenic comppunds, dilute acids, phos-
phorus, many metallic salts, e.g., those of antimony, lead,
zinc, copper, and chromium, and many organic sub'

396 CHKMICAL TOXICOLOGY.

stances, e.g., elaterium, gamboge, aloes, colocynth, croton
oil, caiitliarides, ikc.

3. Xeurotics. — Prussic acid, opium (including the
opium alkaloids, e.g., morphine), strychnine, aconite,
belladonna, &c

4. Gaseous Poisons. — Chlorine, bromine, hydrochloric
acid, hydrofluoric acid, sulphur dioxide, nitrogen oxides,
ammonia, carbon dioxide, carbon monoxide, coal gas
(carbon monoxide and acetylene), sulphuretted hydrogen,
anesthetics, vapours of hydrocarbons (e.g., of mineral
naphtha).

Tests for most of these substances have been described
in the preceding pages. These tests can be applied with-
out an}^ difficulty where a definite chemical substance is
to be examined, but in many CHses, the substance to be
tested for poisons is a complicated mixture, such as the
contents of a stomach, or some article of diet. In such
cases, special methods must be used, in order to separate
the })oison from the organic matter which would obscure
the tests. A very useful method is that of dialysis,
since all poisonous substance diffuse through a moist
membrane, while albuminous substances do not. The
following method may be employed in testing for the
common poisons. Boil with hydrochloric aicid for some
time, filter, and heat a portion of the clear filtrate for
half an hour with a small piece of bright copper. Any
mercury, arsenic, or antimony present will be deposited
on the copper. Remove the copper, wash, and dry it
carefully, and heat it in a narrow glass tube held aslant.
Mercury forms a metallic, coat on the tube, arsenic oxid-
ises and forms a white crystalline deposit at some dis-
tance from the metal, while antimony forms a white de-

CIIKMICAL TOXlCOr.OGY. 3!)7

posit near the metal. Marsli's t<'st {\)\). 161 and 307)
may be ap|)lie(l to other portions of the liquid. To test
for lead and copper, [)ass sulphuretted hydrogen through
the warm liquid for some time. A black })recipitHte
may be PbS or C'uS. Filter, wash, dissolve the [)reci|)i-
tate in aqua reyia, and test as at pp. 280 and 297.
Zinc is tested for by treating .the liquid with excess of
ammonia, filtering, and adding sulphuretted hydrogen to
th(5 filtrate. A white })recipitate (ZnS) indicates zinc.
Chromium is detected as at p. 333. — Acid and alkaline
substances can be tested for by observing whether a large
quantity of alkali or acid is required to render the sub-
stance neutral. For hydrocldoric, nitric, and sulphuric
acids, see pp. 103, 86, and 133. As small quantities of
the salts of these acids are naturally present in articles
of food, (fee, only large quantities should be looked upon
as abnormal. — To test for oxalic acid, precipitate the
clear liquid with lead acetate, collect the precipitate,
wash, mix with water, decompose with sulphuretted
hydrogen (PI 0,0, "f H,S = PbS + H.^Cp,), and test
the filtered liquid for oxalic acid (p. 210). — Prussic acid
can often be recognised by its smell, especially when the
substance is treated with a little sulphuric acid. The
tests at p. 184 can be made by mixing the suspected sub-
stance with sulphuric acid in small porcelain dishes, and
placing over these inverted dishes or watch glasses
moistened with argentic nitrate, caustic soda solution,
and ammonium suljdiide res})ectively . The acid is vola-
tilised upon these, and the tests are completed as at p.
184. — Any substance containing free phosphorus is lum-
inous in the dark. The luuiinosity is especially apparent
when the substance is distilled along with water in the

398 CHKMICAL TOXTr'OLOOy.

dark. A luminous ring a})poars in tlie neck of the con-
denser. — The examination of an organic mixture for
poisonous alkaloids is a process too extensive for treat-
ment here. They can be tested for separately as at pp.
250, 251, and 252.

Note. — The following Analytical Tables are to be used in
examining solutions containing not more than one metal and one
acid.

ANALYTK'AL TABLK.S.

399

r—i

Xi
ci

•l-H

too

ANALYTICAL TABLES.

PQ
<

-o
a
<a

O
iz;

;z;

.5 -t "o c .
^ 9* V 4> .«-

3 O.S 4*

5
I

■ o

t-i

1) --e iM

1-2

5 3

4) c

ox;

P. *

c
o

• d ■

Si J 3 ..

T3J=

ft 3 w S
<«5 O 4J.S

-^a

CD O fO

1 2

TJ-^

^ 4J ht-^

4> -

CLS S 3

O 4) O

-o

=,. «_^

00 f^

0) «8 CO

hogO

S ®-»^

■r3 X

M C «

s
o
O

tiD

rtl

-kj

i.'

■p<

c«

AN'ALYTrCAL TAFU.R.S.

40 i

402

ANALYTICAL TABLES.

H
m

H g

O fci
^ o

I— I » ^

c
I, w

S3 H

o o

B
O

et
O

<»
0)

o
o
a

-s

B
O

O
5-t

(/3

p.
o

a
o

1 ^

eS C

Sao

G1]

S
P .

«^

B
O

O
O

B
O

i-i

B
O

S o

s
c

o
o

ANALYTr(;AL TARLKS.

403

5d ..

-" * 2 3 E m .3 S
iV OD * 41 «« C"

e3 C -

«V

«
c
o
O

N . C •

~ o J2 "5 +>

-•iq

c
o

:?K 3.fc ''^

c
o
u

»t

c
o

o
H

5
-So

*■

404

ANAhYTICAT/ TABLES.

PQ
<

-s

e
o
'■C

3^ a"
o2 S

■5.
o

o
;zi

§:

(z;

♦J I. iJ-O s i" « « "

21-

-Z &?

!*;

c .
o a
o

-»3
O

;z;

jz;

tient wht. ppt.
ed on heating,
Add to O. S.

Perma
dissolv

4) » -

OJ o

f s

5 9**

e«.2-S

;2'x.-*

^fc^g

.«)-?

r** ~

0) r** ~

Sq9

t-i 55

a— .>!' "= '^

-- a 2: c .

9
I

4
'%

•S

355

*«•*

itf

•«->

•s

«<>d

-*?

•o

■^

«H

-w

■+*

APPENDIX.

TABLE OF SOLUBILITIES.

100 parts (by weight) o) water at 15°G dissolve of

NAMES.

Acetic Acid

Alcohol, ainyl

•' ethyl

" methyl

Alum, ammonia <

" chrome

" potash

Ammonia

Ammonium carbonate . . . .

Ammonic chloride

" chloroplatinate

" nitrate

" oxalate

" sulphate

Antimony trichloride

" trioxide

Argentic chloride

" nitrate.. .. . .. .

** oxide

Arsenic acid

'• trioxide

Baric carbonate

♦' chloride

' ' fluosilicate

" hydroxide

" nitrate

•• phosphate

•• sulphate

Benzene

Benzoic acid

" aldehj'de

Bismuth trichloride

" trinitrate

" subnitrate

Boracic acid

Borax

Bromine

Cadraic chloride

" sulphate

Calcic carbonate

" chloride

" citrate

FORMULAS.

CjH.Og

CsH,,d

C,H,6

CH.O

(NH,.)j,Al„(SO,)..24HgO

KaCrj(SO«)«. 24H2O

KjAlaCSOJi. 24H;,0

te°'::;;:;::::::::

(Nrf.),PtCl«

NH.NO.,

(muhc.,o,.H.,o

(NH,),S6,

SbCl,,

Sb^O,

Ajrci

AgNO,

A^^O

H,As04

ASvO,

BaCdg

BaC1^.2H20

BaSiFg

Ba(OH\

Ba(NO.,),

Ba.,(P6j2

BaSO^ •

CeHg

C.Hj.COOH

CgHj.COH

BiCla

Bi(N03),.3H^O

BiN03(6H)2

HjBO,,

N'a^B^Oj.lOH^O

Br.'.

CdCl^

CdSO^

CaCOg

CaOl.,

Ca3(C«H,0,),.4H,0

PARTS.

all proportions.

25.00

all proportions.

11.4

14.3

12.3

59.7

27.6

35.

0.666

200

4.22
75.5

loot*

0.001 (1)
0.00

loot

0.033

loot

3.33

0.0071
45.

0.0263

3,4

8.1

0,00

0.00025

0.1
' 0.6

3 32

loot
loot

0.00
3.00
5.3
3.226
140
58

0.0018
75.
0.1 (?)

* loot means very soluble.

406

APPENDIX.

NAMES.

Calcic hydroxide

*' oxalate

" phospliate

" sulphate

'• tartrate

Camphor

Carbolic acid

Carbon bisulphide

" dioxide

" monoxide

Chloral hydrate

Chlorine

Chloroform

Citric acid

jobaltous chloride

" nitrate

" sulphate

Cupric nitrate

" sulphate

Dextrin

Ether (ethylic) .

Ferric chloride

" sulphate

Ferrous "

*' amnionic sulphate

Gallic acid

Glycerine

Hydrochloric acid

hydrocyanic "

Hydrogen

" peroxide

Iodine

Iodoform

Lithic carbonute

" chloride

" urate

Magnetic chloride

" oxide

*' am. phosphate . .

" sulphate

Manganous carbonate

'* chloride

" sulphate

Marsh gas

Mercuric chlorfde

" oxide

Mercurous chloride

" nitrate

" oxide

" sulphate

Morphine

" chloride.

Nickel sulphate

Nitric acid

Nitrobenzene

Nitrogen

" monoxide

Oxalic acid

FORMULAS.

Ca,OH)^

CaC,04.2H20

Ca,(P04)„

CaSO.. 211^0

CaC.H40«.iH.,0

c.„H,„o.... :

CeH^.OH

CS^

CO J,

Cj,HCl.,O.H^O

cf....:.....

CHCl,

c«hA.h.o

C0CL.6H0O

Co(NO,)j6Hi,0

CoS0..7H^O

Cu(N0.,)5j 3H^O

CuSO^.SHaO...

CgHioO.

(C,H.),6

Fe,cr«

Fejj(S04)„

FeSO^.TH^O

Fe(NH4MS04)^6H20.

C,He04.H,0

C,H,(OH}.,

HCl...

HCN

H.O,

CHI3

LijjC'O,

LiCl..'

Li,C,H,N.O.,

MgCf,

MgO

MgNH^PO^.eH^O .
MgSO^.TH^O......

MnCO.,

MnClsUH^O

MnS04.4H20

OH4

Hg.Cl,

HgO

Hg.Cl,

Hgj'NO,),

Ug.^0

Hg.SO,

C.jH.»NO,,.H.,0..,
C,,H,»N0;.HC1..,

N1SO4.7H2O

HNO.,

C«H,.NO,

N..O

C.:Ha04.2HaO

PARTS.

0.137
0.00
0.00
0.238
O.Oltt
0.1
6.67
0.1

0.19744
0.00305
100 (?)
0.751.5
0.1 (•!)
133.00

loot
loot

33.5

loot

39.5

loot

11.00

loot
loot

70.
19

1.00

all proportions.
7572
all proportions.

0.00017
all proportions.

0.182

0.01 (?)

0.8

I 10 (?)
130.

0.0018

0.0067
67.5

0.013
200.00
130.00

0.00286

6.98

0.00

loot

0.00

0.2

0.05

6.00
67.0
all proportions.

0,1 (?)

0.0023

0.1633
11.

APPENDIX.

407

NAMES.

Oxygen..

Phosphoric atud

Plumbic ac^etate

" bromide

" carbonate

" chloride

'• iodide

•' nitrate

*' sulphate

Potassic bichromate

" bromide.

" carbonate

" hydric carbonate

" chlorate

*' chloronlat.nate • .

" chloriae

" chromate . . . . .

" cyanide

" fluosilicate

" ferricyanide . .. .

" ferrocyanide . . . .

" hydro -xide

" iodide

" nitrate

" oxalate

" hydric oxalate.. .

*' permanjfanate . . .

'* sulphate

" tartrate

" hytlric tartrate. .

•' sodic ••

" urate . .

" acid urate

Quinine

" sulphate

" bi -sulphate

Salicylic acid

Sodic acetate

" carbonate

" hydric carbonate. .

" chlorate

" chloride

"* hydroxide

" nitrate

*' phosphate

" sulphantimonate . . .

" sulphate

*' thiosulphate

Stannic chloride .........

Stannous chloride

Starch

Strontic carbonate

*' chloride.

'* hydroxide

" nitrate

" phosphate

" sulphate

Strychnine

FORMULAS.

PARTS.

H.^PO.

Pb CjH.v)^ .,.H.,0.
PbBr ....". ...?.. '...

PbCO;

PbCl.;

Pbl,

PbNO., .^

PbSO/.

K.,Cr^Oj

KBr

K„CO.,

KHCO.,

KCIO,,".

KjPtClfl

KCl

KjCrO,.
KCN...

,SiF„

..,Fe(CN>«.

.311^0.

K^FeiCN g.

KOH

KNO,,

K.,C.,04.H:;0

KHd.Oi.HaO

KMnO^

K2SO4

KjC^H.O^

KHC^H.O«

KNaC^H.O„.4HaO

K,C,H N.O.,

KHCsH^N.O.,

c.,„h;,nA-"3H,o....

C,„H,.N,0,>^.H„SO,
C2.,H,,N,0,.H2SO,. .

C-HfiO.,

NaC.,H.,0...3H..O

Na.,0o;.l6H2O'

NaHCO,

NaClOa".

NaCl.."

NaOH

NaNO,

Na.,HP04.12H20

Na;;8bS4.9H.,0

Na;;SO4.10H:,O

Na.,S203.5H;0

SnCL,.". ...."

SnCl.,.2H20

C«H,oOft

SrCO.,

SrCl ■

SnOH).

SnNOJa.

Sr.,'PO,).,
SrSO« ...*....
C„.H,,N,0,.

0.0057
l(K)t
."iH.OO

0.05 t?)

0.002

0.9

0.082
53.00

0.0044
10.3
100 ?)
KM). 4
25.00

6.00

1.10
32.8
62.0

loot

0.12
40.5
30.00
213.
140.
26.
33.

4.8

6.6

9.2
151.5

0.453
59.

2.24

0.125

0.05

0.14
10.0

0.5 (?;
30.
60
10.5
95.
35.76

loot

84.
14.
34.5
35.96
116.

loot

270.

0.(M)

0.00554
50.00

457
55.

0.00

0.0145

0.05

408

APPENDIX.

NAMES.

FORMULAS.

PARTS.

Strychnine chloride

Cj.,H2.,N.,02.HCl

5. (h
300.

Sucrai'. Cane

** Grape

75.

" Milk

C,2H220,,.HjjO

20.

Sulphur

0.00

Sulphuretted hydrogen

Sulphur dioxide

H.,S

0.4918

SO a

14.33

Sulphuric acid

H2SO4

all proportions.

7.0 {1,
138-

Tartar emetic

Tartaric acid

2iKSbOC4H40„ .HjjO

C,H,0

Turpentine (oil)

P* T?""

0.05 H)

Urea .•

CON.H.

100.00

Uric acid

C;,H^N^O,

0.0067

Zinc carbonate

znc6,.*. "..:.........:.

0.00

" chlorde

ZnCl.." .'

loot

'• oxide

ZnO."

0.00

" sulphate

ZnSO^.TH^O

.50.5

INDEX.

Acetates, 205.
Acetone, 201.
Acetylene, 180.
Acetylene series, 174.
Acid, acetic, 193, 204,
" antimonic, 305,
" arsenic, 159
" arsenious, 156, 157.
'' benzoic, 239, 240.
" boric, or boracic, 260, 2C2

broinic, 111.
" butyric, 193, 207.

nuosilicic, 259
•; formic, 192, 202, 203.
" gallic, 243.
" hippuric, 240, 242.

nydriodic, ll4.
" hydrobromic, 110.
" hj'drochloric, 101.
" hydrocyanic, 182, 183.
^, hydrofluoric, 117, 257.

hypobronious. 111.
'\ hypochlorous, 104, 105.
hypophosphorous, 151.

«<
<<
i<

hyposulphuruus, 127,
Iodic, 116.
lactic, 193, 214.
manganic, 344.
me«onic, 250.
raetaphosphoric, 146. 149
muriatic, 101.
nitric, S3,
nitrous, 94.
oleic, 207.

orthophosphoric, 146.

osmie, 315.

oxalic, 171, 203, 208, 211

palmitic, 207.

perchloric, 108.

phosphoric, 35, 86, 146, 147

phosphorous, 146, 150.

picric, 86, 239.

propionic, 197.

prussic, 100, 182.

pyrophosphoric, 149.

salicylic, 243.

selenic, 140, 312.

selenious, 140.

silicic, 257. 258.

stearic, 207.

succinc. 211. fl3l.l34

sulphuric, 85. 127, 129, 13(»,

Add, sulphurous. 35, 125, 126, 128.
tannic, 243.
'' tartaric, 214, 216.
thiosulphuric, 134.
uric, 188.
7 valerianic, 196, 207.
Acids, 35, 153

" dibasic, 132.
" haloid, 103.
Air, composition of, 72.
Air, impurities of, 75.
Albuminoids, 254.
Alcohol, amylic, 194, 196.
benzylic, 239.
' butylic, 196.
;; ethylie, 177, 192, 193, 195.
methylic, 190.
propylic, 196.
salicylic, 248.
Alcohols, 190.
" diacid, 208.
" isomeric, 197.
Aldehyde, acetic, 195, 200,
benzoic, 239.
" cinnamic, 245.
^1 salicylic, 248.
valerianic, 196.
Aldehydes, 200,
Alkaline earths 352,
Alkaline reaction, 80.
Alkalis, 368.
Alkaloids, 249,

" artificial. 263.
Allotropv, 53.
Alloys, 264.
Alum, ammonia, 336.
" chrome, 332.
" iron, 326.
" potash, 336.
Alums, 332, 336.
Alumina, 335.
Aluminium, 334.
" bronze, 334.
" chloride, 334.
" sulphate, 337.
Amalgams, 284.
Amides, 187.
Amines, 198, 249.
Animonia, 76, 80.
Ammonio-cupric sulphate. 162
Ammonium, 82, 383.
'* benzoate, 242.
bromide, HI.

410

INDEX.

Ammonium carbonate, 385,
'* chloride. 384.
" cyanate, 185.
" formate, 183.
«• hydroxide, 383.
•• nitrate, 87, 00.
" oxalate, 210.
" phosphate. 386.
" picrate, 239.
sulphate, 384.
sulphide, l(K), 386.
Amyifdalin, 239, 247.
Amyl nitrite, 196.

" acetate, 197.
Amyloses. 220, 227.
Anmsthetics, 177, 200.
Analysis, 138. 269, 393.
Aniline, 236.

dyes, 232, 237.
Anthracene, 247.
Antidotes, 145, 254.
Antimony, 101,304.
•' butter of. 306.
" pentoxide, 305.
" sulphate, 304.
" tetroxide, 3()4, 305,
•• trichloride, 306.
" trioxide, 217. 305, 306.
" trisulphide, 136,305.
Antimoniuretted hydrogen, 307.
Antimony 1, 217, 307.
chloride, 306
" potassic tartrate, 217, 306.
Antipyrine, 253.
Antiseptics, 193, 238.
Apatite, 142, 358.
Aqua Fortis, 83.
Argentic salts (nee silver).
Argol, 215.
Aromatic series, 232.
Arsenic, 61, 155.
•* antidotes to, 158.
*' flowers of, 156.
'* pentoxide, 1.56.
•• sulphides, 160.

trichloride, 132, 162.
" tri- iodide, 162.
" trioxide, 155, 156, 157, 159.
Arsenical wall paper, 162.
Arseniuretted hydrogen, 161.
\tmosphere, 67, 68.
, omic heat, 48.

" weights, 47, 48.
theory, 44.
Atomicity, 62.
Atoms, 44, 47.
Atropine, 25a.
Avogadro's Law, 45,

Balsams, 244.
Barium, 361.

Barium dioxide, 64, 362.'
" fluosilicate, 259.
nitra>L, 363.
sulphate, 132, 361.
Barometer, 67.
Bases, 36, 37.
Basicity, 86, 87, 203.
Beer, 194.
Beet sugar, 379.
Benzene, 2:53
Benzene series, 232
Bismuth, :iOO.

*' carbonate, 303.
" chloride. M'L
" oxide, 301.
" nitrates, 301.
" trioxide, 302.
" trisulphide, 303.
Bismuthyl carbonate, 302.

chloride, 303.
Black ash, 371.

wash, 285.
Blue vitriol, 295.
Bleaching, 100. 106, 125.

powder, 105, 138, 1 77, 202, .S.^7
Bf'iling points, 23.
B ,;e ash, 143, 147, 358.
bla<:>k, 14h.
oil, 143, 168.
Bones, 142.
Borates, 261.
Borax, 260, 261.
Boron, 260.

trioxide. 261.
Boyle's Law, 69.
Brimstone, 121.
Bromides, 111.
bromine, 98, 108.
Brucine, 252. «

Brunswick green, 296.
Burtictt's disinfecting fluid, 340.
Butter, 206.

Cadmium, 297.
" amalgam, 284.

compounds, 298, 299.
Cffisium, 388.
Calcium, 353,

acetate, 204.
" carbonate, 3.55.
" chlorate, 381.
" chloride. 3.56,

citrate, 218, 219.

fluoride, 117, 118.
" hydroxide, 354.
" hvpophosphite, 151.

oxalate, 209.
" oxide, 353.
•' phosphate, 358.

sulphate, 98 132. 356.
" thiosulphate, 123.

INDEX.

, Calomel, 285.

Calculations, chemical, 50
Camphor, 245.
Caramel, 222

Carbohydrates, 220
Carbon, 164.

bisulphide, 113, 144 172
^^ compounds, 167.
.. dioxide, 43. 75, 77, 168.

monoxide, 43, 171.
Carbonates, 170 171
Carbonyl chloride, 187
Carboxyl, 203.
Celluloid, 231.
Cellulose, 230.

Cerium and its comfwunds, 349.
Charcoal, 35, 165, 166.
Chalk, 355.
Charles' Law, 70
Chemical action, 1, 6.
Chemism, 38.
Chemistry, l.

n>!i ,°^8^a"'c,lfi7, 185.
Chloral, 201.

Chlorates, 107,

Chlorides, 101,' 103.

Chlorme, 98, 99.

;] ojddes, 104.

r.u. o.\5'gen acids, 105.

Chloroform, 177, 178, 202

Chromates, 331, 332

Chrome alum, 331, 332.

yellow, 279,
Chrommm, 329
II chloride, 333
^^ hydroxide, 333.

sesquioxide, 333.

trioxide, 332.
Chromyl chloride, lie
Cmchonine, 251
Clay. 258, 337.

SriS." ^'■"""''' ""^ ^'■'"'"'''" 1«2-
Coal tar, 232.
. Cobalt, 346.

chloride, 347
'* nitrate, 346.
Cocaine, 252
Collodion, 231.
Combination by volume, 45
Combining weights, 42, 57
Combustion, 34, 38. 59, 76."
Compounds, 6.
Conine, 250.
Conservation of matter. 41

Condy's fluids, 344, 345 "
Copper, 293.

Copperas, 321

Coprolites, 142.

Corrosive sublimate, 288
Cream of tartar 215
Creosote, 191, 238, 239.
Cresols, 238.

411

Crystallisation, 3, 24, 27
Crystalloids and colloids. 326
Cupric nitrate, 86.
'■ oxide, 296.
sulphate, 295.
Cuprous chloride, 172, 296
iodide, 11.5.
" oxide, 222, 296.
Cyanides, 181, 183, 184.
Cyanogen, 181.

decomposition, doable, 270

l^eflm+e Proportions. Law of, 42. 44

Deliquescence, 27 '

Dextrin, 225, 229,

Dextrose, 225, 248.

Dialysis, 63, 326.

Diamonds, 164.

Diffusion, 62, 63
Digitalin, 248.
Dimorphism, 356.
Dissociation, 131.
Distillation, 3, 80.
Donovan's solution, 162
Dulong & Petit, Law of. 48
Dynamite, 86, 213

Earths, 352.

Effervescing powders. 219

Efflorescence, 27

Electricity, 29. 390.

Electrolysis, 392.

Electroplating, 281. 313.

Elements and Compounds, 5. 6

E ements. Table of the, 39.

ii-lutriation, 2.
Emery, 335.
Epsom salts, 120, 3()4.
Equations, chemical, 49.
Equivalents. 42.
Essence of mirbane. 235
Essences, artificial, 197.
Ether, acetic, 195.
" ethyl (sulphuric), 198, 200.
'' nitrous. 195. ' ^'

Ethers, 198.
Ethylene, 178.
Evaporation, 21, 23, 24
Explosion, 60.

Fatty acids, 202. 207.
Fats and oils, 207.
Fehling's test, 223 226
Ferments, 76, 192.
Fermentation, 192, 193.
Ferric arsenite. 158.
'I chloride. 158, 324.

hydroxide, 158, 325, 327

412

INDKX.

Ferric nitrate, 322, 326.

" oxide, 320, 327.

" Hulphate, 322, 326.

" sulphocyanate, 186.
tartrate, 328.
Ferrous ai senate, 159, 323.

'* bromide, 324.

" carbonate, 181, ;;23.
iodide, 324

*• lactate, 215.

" nitrate, 326.

'• oxalate, 210.

" oxide, 320, 322.

" phosphate, 160, 324.
sulphate, 321.

" sulphide, 136.
Filtration, 2.
Flame, 176.
Fluorides, 117, 118.
Fluorine, 117.
Fluor spar, 117, 259.
Fluosilicates, 259.
Formulas, 48, 49. 62.
Freezing and melting, 18.
Freezing mixtures, 26.
Fusel oil, 194, 196, 197.
Fusion, 4.

Galena, 120, 273.
Gas liquor, 80.
Gas, olefiant, 17&
Gases, 2.

" Lawof Diffusion, 64.

" Molecular weight of, 47.

♦' Solubility in water, 34.

" volume of, 51, 70, 71, 72.
German silver, 348.
Glass, 274, 377.

" etching of, 118.

" soluble, 258.
Glauber's salt, 371.
Glucose, 194, 220, 225, 226, 244.
Glucoses, 225.
Glucosides, 227, 247.
Glycerine, 203, 211. 213.

" of borax, 262.
Glycogen, 229.
Glycol, 208.
Gold, 312.

Goulard's extract, 276.
Gram-molecule, 51, 71.
Graphite, 164.
Green vitriol, 321.
Group reagents, 270.
Guano, 188.
Gum, British, 229.

•• benzoin, 240, 241.
Gums, 230.
Gun-cotton, 80, 230.
Gun -powder, 88.
Gypsum, 24, 98, 120, 356.

Halogens, 98.
Heat. 12.

" expansion by, 14.
latent, 20, 23, 26.

" specific, 21.
Hydrocarbons, 173.

" saturated. 176.

" unsaturated, 178.
Hydrogen, 55, 58, 60, 61.

" dioxide, 64, 65.

" persulphide, 139.
sulphide, 136.
Hydroxides, 58, 190.
Hvdroxy-acids, 214.
Hydroxyl, 58, 190.
Hydroxylamine, 83.
Hypochlorites, 105, 106.
Hypophosphites, I'^l, 152.
Hyposulphites, 127.

Indigo, 128. 134, 246.

Infusion, 27, 28. . '

Iridium, 315.

Ink, 244. 347.

Inosite, 227. v

Innlin, 228.

Iodides, 112, 116.

Iodine, 98, 112, 113, 126, 135.

" chlorides, 116.

" pentoxide, 116.
Iodoform, 178, 195.
Iron, 56, 318.

dialysed, 325.

" galvanised, 320.
rust, 320.

pyrites, 120, 121, 124, 155, 321.
Isomerism, 179, 180.
Isomorphism, 159, 332, 336.

Jalapin, 249,
Jet, 167.

Kairine, 253.
Kaolin, 337.
Kelp, 108, 112.
Ketones, 197, 201.

Lactose, 223.
Lamp-black, 165.
Latent heat, 20, 23.
Lau£:hing gas, 90.
Lead, 272.

" acetates, 103, 206, 276, 276.

" black, 164.

** bromide. 111,

INDEX.

413

Lead chloride, 103, 277.
'I '•hromate, 331.'

hydroxide, 88.
, iwlide, 11.5.

nitrate, 85, 87. 95, 276.
oxtdes. 274, 275.
phosphate, 147.
^^ plaster, 212. 278
poisonin^r, 279.
red, 274. 276.
sulphate. 132, 278.
' white, 276.
Ledoyen's disinfecting fluid 276
Levulose. 22.5. 227. '

Lime, chloride of, 357
millc of, 355.
quick 353.
slaked, 354.
Liquids, 2.
Liaterisni. 238.
Litharfire, 205, 274.

Lithium and ooinpound.s, 387.
Litmus, 35. . oi.

Maceration, 27.
Mag-nesia, 366.'

alba, 365.
Magnesium, 363.

carbonate, 365.
citrate, 219.
)' oxide, 366.

sulphate, 98, 364.
Manganates. 343.
Manganese, 341.
;' dioxide,'33, 99, 341, 342.
salts, 343.
Mareh gas, 175.
Marsh's test, 161.
Massicot, 274.
Matter, three states of. 2
Mercurial poisoning, 291
Mercuric chloride, 288

iodide, lis. 162, 289.
nitrate, 287

oxide, 32, 112, 287, 289.
su phate, 285. 287, 288.
sulphide. 290.
Mercurous bromide, 111.
chloride, 103, 285,
iodide, 115. 286.
nitrate, 103. 285.
sulphate 132.
Mercury. 283.
Metallurgy, 263.
Metals, 39, 263.
I' classifieation of, 269
compounds of, 265.
Methane, 175, 176.
ethyl, 192.
«' amine, 198.
*' chloride, 198.

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^Jt'tjiyj salicylate, 191, 24.1

Methylated spirit, 191

Microcosmic salt, 148, 386.

Minium, 274.

Mi-xtures, separation of, 2.

Mohr s suit, 323.

Molasses, 221.

Molecules, 45, 46.

Morphine. 250,

Mortars and cements, 3.59

Mucilages, vegetable, 230 '

[90.

Multiple proportions'. Law of. 43, 44]
N.

Naphthalene, 246.
Nessler's reagent, 289.
Neutralisation. 88
Nickel, 347, 348.
Nicotine, 250.
Nitrates, 85, 86, 88.
Nitre, (see Saltpetre)
Nitrites, 94.
Nitrobenzene, 2.35, 240
Nitrogen, 72, 79.

compounds in air, 76.

dioxide, 92, 93, 129, 173
monoxide, 90, 91
I pentoxide. 9.5.
" tetroxide (peroxide). 95
trioxide, 93.
Nitroglycerine. 86, 213.
Notation, chemical, 47,

Oil of bitter almonds, 236, 240
cinnammon, 245.
cloves, 245.
vitriol, 129, 130.

wintergreen, 243.
Oils, drying. 274.

Oils, essential, 245.

Olefines, 174, 178

Olein, 212.

Orpinient, 160. ,

Osmium, 315.

Osmose, 63.

Oxalates, 210.

Oxides, 35.

Oxidising agents, 65.

Oxygen, 32, 33, 34, 73.

Oxymel, 223.

Oxy -salts, 307.

Ozone, 52.

Palladium, 315.
Palmitin, 212.
Paraffin oil, 174.
p '' wax. 137, 174.
Paraffins, 168, 174.
Paris green, 1,58.

414

INDKX.

Pearl ash, 37».
Percolation, 28.
Penuan^'anates, 344.
Peroxides, 2(i7.
Petirolemn, 168.
Phenol, 237.
Phosphates, 142, 148.
Phosphine, 152.

Phosphoretted hydrofjen, 150, 152.
Phosphorus, 35, 142, 143.
"' oxides of, 145.
" pentachloride, 153, 100.
" pentoxide, 43, 146.
" testa for, 146.
tribroniide, 110.
trichloride. 150, 158.
trioxide,. 43.146.
Phosphoryl, 153.
Photoj,'raphy, 136, 299.
Plaster of Paris. 356.
Platinum, 60, 3i3.
Plumbago, 1(J4.

Plumbic compounds (see Lead).
Poisons, 395.
Porcelain, 337.
Potash lye, 381.

Potassium, 378. [330.

" bichromate, 33, 65, 115, 143,
bromide, 110, 382.
carbonate, 379.
acid carbonate, 380.
chlorate, 32, 99, 104, 107, 381.
chloride, 98.
cyanide, 182.
ferrlcyanide, 328.
ferrocyaiiide, 171, 181.
fluosilicate, 107, 256, 259.
hydroxide, 380.
hypobromite, 111.
iodide, 112, 115, 278, 383.
manganate, 343.
nitrate, 381.
perchlorate, 108.
permanganate, 344.
sulphate^ 83.
sulphocarbonate, 173.
sulphocyanate, 185.
Potato oil, 196.
Pottery, 337.
Powder of Algaroth, 306.
Precipitation, 269.
Proteids, 254.

Prussian blue, 181, 246, 328.
Ptyalin. 223.
Pure substances, 2.

Quantivalence, 62.
Quicksilver, 284.
Quinine, 251.

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Radicals, coni|)ound, 58.
Realgar, 160.
Reducing agents, 125.
Reduction, 36.
Resins, 244.
Respiration, 77.
Rochelle salt, 216.
Rosaniline, 237.
Rouge, 327.
Rubidium, 388.

Saccharine, 168, 242.

Saccharoses, 220.

Sago, 228.

Sal ammoniac, 80, 384.

Salicin, 243, 248, 251.

Salt cake, 370.

Salt in air, 76.

" of sorrel, 210.

" of tartar, 379.

" radical, 89.
Saltpetre, 24, 79, 86, 381.

Chili, 83, 374.
Salts, 37, 88, 89.

" ethereal, 192.

" normal and acid, 133.

" oxygen, 268.

" sulphur, 269.
Sal volatile, 385.
Saponification, 212.
Scale compounds. 327.
Scheele's green, 158.
Sea water, 98.
Seidlitz powder, 216.
Selenium. 140.
Silica, 256. 257, 259.
Silicates, 256, 257.
Silicon, 25C.

dioxide, 257.

" tetrafluoride, 259.
Silver, 280.

bromide, 108, 111. •
chloride, 103, 135.

" cyanide, 281.
iodide, 115.
nitrate, 103, 282.
sulphate, 132, 281.
sulphide, l.'S2.
Smalt, 300, 346.
Soaps, 208, ^11, 212.
Soda, baking, 373

" caustic, 373.

" washing, 371.
Sodium, 369.

" a(>etate, 175, 206.

" antimonite, .305

" arsenate, 159.

INDKX.

ScKliuin arsenite, 158.
benzoate, 242.
biborate, 261.
broiuifle, 376.
carbolate, 237.
^^ f-arbonate, 112, 371
bi-carbonate, 373.
chloride, 369.
cyanide, 181.
hydroxide, 57, 373.
„ hypochlorite, 1{)6.
,, bypoaulphite. 128.
nianganate, 343.
nitrate, 83, 374.
nitrite. 94.
oxalate, 209.
,^ oxides, 369.

phosphate, 375.
^^ silicate, 258.

sulphantiuionite, 305.
sulphate, 370.
bi-sulphate, 84.
sulphide, 376.
,1 sulphite, 1-26. 375.
thiosulphate 135

Solids, 2^^''"''"'^*^' 1^«' 207.
Solubility, 25.
Solution, 3, 24.

chemical, 25.

latent heat of, 26

saturated, 25.

supersaturated, 26,
Specific heat, 21.

<j«l* weight, 8, 9, 10.
spectroscope, 389.
Spectrum analysis, 388.
opirit, proof, 195.
Spirit, sweet, of nitre, 195
spontaneous ifrnition, 38. '
stannic chloride, 309 310
'' oxide, 309. '
sulphide, 311.
stannous chloride, 288, 309
oxide, 309.
sulphide, 311.
Starch, 227, 228.
Stearin, 212.
Strontium, 360.
II hydroxide, 361 .
^^ nitrate, 360.
,^ oxide, 361.

C!f., u sulphate, 132, 361.
Strychnine, 252.
Sublimation, 3.
Substitution, 179, 232
Sugar, beet, 221, 379

cane, 221.

fruit, 227.
^^ grape, 225.

invert, 221, 225.

inalt, 224

415

Sujrar, milk, 223.

Sulphates, 120, 13»
S» phides, 120. ISO."
Sulphites, 128.

Sulphostannates; 311
Sulphur, 35. 120.

bromides, 140.

chlorides, 139.

dioxide. 103, 124.

flowers of, 121.

iodide.s. 140. '•

liver of, 376.

milk of, 123.

o.videsof, 124.

oxygen acid of. 127

precipitated, 123.

salts, 160, 269.

trioxide, 126.

Synthesis, 180. '

Tannin. 244.
Tartar, 215.

Tartar emetic, 217. 306.
lellurium, 140.

Temperature, 15, 16.

)' absolute, 70.

^^ critical, 34.

' of ignition, 37.
Terpenes, 244.
Thalline 253.
Thermometers, 16 17
Thiosulphates, 13.5.
Tin. .308.

Tin, butter of. 310.
Tin .salt. 309.
Tinctures. 28.
Tlncal. 261.

ToxiTOlogy, chemical, 395
Tiirnbull's Blue, 328.
Tur[)entiiie, 244.

Urates, 189.

Urea, 111. I86, 187, 188.

Urine, 188.

Valence, 61, 62.
Ventilation, 170.
Verdigris 206, 294, 297
Vermilion, 290.
Vinegar, 204.
Vitriol, blue, 144, 295
;; grreen, 121, 134, 321.
white, 340.

410

Water, action on lootl 274
analysis, 289.
boilinjf noint, 22.
„ composition of, 30

'• disSffI*'- °'- ''^ 2«-

•' fSntoV'ii^^"'''^*'^^-
'I in air, 75.

latent heat of, 20.
Weights, combining 42

WKu '^"'i. measures. 6,' 7.
White precipitate. 2f)o
Wines, 194.
Wine, spirits of,. 192.

INDK.V.

y^ood, distillation of, loi 204
spirit, 191.
tar, 108.

Yellow wash, 288.

Zinc, 56, 57. 338.
" acetate, 340.
II butter of, 339,

carbonate, 340.

chloride. .J39.

oxide, 37, 338.

sulphate, 37, 207, 340, 365.

THB COPP, CLARK COMPANV, LIMFTBD

'. PRIXTER8. COLBORNK STRBET, T0R0N"r0.