William George Valentin.

Introduction to inorganic chemistry online

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Online LibraryWilliam George ValentinIntroduction to inorganic chemistry → online text (page 1 of 21)
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With 82 Engravings on Wood








THE encouraging reception which my Laboratory Text Book
met with in this country, as well as in America, and the expe-
rience which I since have had of its working with a large
class of chemical students, have induced me to render the
book still more generally useful by publishing it in two parts,
and by somewhat enlarging the first part. I am in hope that
this first volume may now take rank as a suitable text book
for elementary classes preparing for the chemical examina-
tions which are held annually under the Science and Art
Department. The admirable list of experiments, sketched
out by Dr. Frankland, in the Syllabus issued by the Depart-
ment, will be found interwoven throughout the text. This I
was able to do without deviating from the original plan of
the book, which consists mainly in deducing the fundamental
laws of chemistry from experimental facts, and thus to lay
a sound foundation for qualitative and quantitative analyses.
From my own laboratory experience, I can confidently recom-
mend this experimental method of teaching. Large classes
of students can be instructed with comparative ease, and
theoretical difficulties, which are usually overcome only by a
long course of chemical study, may be grappled with at the
earliest stages even. I have found the theory of atomicity
of chemical elements remarkably conducive to a quick and
thorough understanding of chemical* changes. Graphic
illustrations, I need scarcely remark, may be discarded as
soon as they have fulfilled their purpose, and as soon as the
pupils have become familiar with the use of the constitutional
bymbolic formulae employed in this work.



The Questions and Exercises, placed at the end of most
of the chapters, constitute an essential feature of the book.
They will be found of great use if the written answers are
examined by the teacher, and any shortcomings discussed
with the pupils. This en t ails \ no doubt, much labour, but it
forms, in my experience, the only safe means of controlling
and rendering the laboratory teaching thoroughly efficient.

Most of the experiments can be readily performed by
beginners, if the directions given in the text are attended to,
others again, are perhaps more suited to the lecture-room.
The selection may, however, be safely left to each teacher.

When the chemical instruction in schools or elementary
science classes has, of necessity, to be conducted by lectures
only, this little book will, when placed in the hands of the
pupils, also form a useful companion and guide for private

The final chapter contains a brief summary of all the
previous experimental facts, classified under four chemical
changes, a summary which, I trust, will recommend itself to
the practical teacher.

In conclusion, I have to thank Mr. A. J. Greenaway,
Junior Assistant in the Laboratory, for his kind help in pre-
paring a number of new wood-cuts.


Oct. 18, 1872.




Hydrogen. Properties of Hydrogen. Compound of Hydrogen with

Oxygen. Water . . . . 1


Oxygen. Properties of oxygen. Nitrogen. Composition of air. Com-
pounds of oxygen with metals, Oxides. Compounds of oxygen with
sulphur and phosphorus. Combustion of carbon in oxygen. Yolume
combination of hydrogen and oxygen . . . . . . . . . . 6


Physical states of matter solids, liquids, and gases. Mechanical mixture.
Chemical combination. Chemical reactions (combinations and decom-
positions). Binary compounds. Names and symbols of elements . . 19

Eeductions. Chemical affinity. Indirect oxidation. Eeciprocal affinities 26


Electrolysis. Constant volume proportions. Eudiometer. Composition
of water by weight and by volume. Allotropic state of oxygen. Ozone,
its preparation and properties . . . . . . . . . . . . 31


Constant combining proportions. Atomic theory. Table of combining
weights of the most important elements. Yolumetrical composition of
steam. Molecular volumes. Multiple proportions . . . . . . 37


Water. Natural waters. Distillation. Metallic and non-metallic oxides.

Acids. Alkalies. Salts. Basic oxides . . . . . . , . . . 45


Sulphur : its occurrence and properties. Allotropism. Dimorphism. Volume
combination of sulphur with oxygen. Compounds of sulphur with
metals, Sulphides. Compounds of sulphur with non-metals. Volu-
metrical composition of sulphuretted hydrogen. Metallic sulphides.
Precipitation, &c. .... . . . . . . . . . . . . 51




Chlorine. Properties of chlorine. Preparation of chlorine water. Action
of chlorine upon water. Hydrochloric acid. Metallic chlorides.
Hydrogen compounds of bromine, Iodine, and fluorine. Properties and
volumetrical composition of hydrochloric acid gas . . . . . . 62


Application of the theory of constant chemical combining proportions.

Quantitative chemical calculations . . . . .... . . 71


Atomicity or quantivalence of atoms. Volumetrical composition of hydro-
chloric acid. Polyad elements. Hydrogen, the unit of atomicity.
Representation of the atomicity of elements. Graphic representation
of atoms and molecules. Classification of elements according to their
highest atomicities. Use of thick type . . . . . . . . . . 75


Hydrates, metallic and non-metallic. Peroxides. Hydroxyl. Formation
of acids from anhydrides. Reactions in the wet way. Compound
radicals and metalloxyls . . . . . . . . . . . . . . 83


Hydrochloric acid. Conversion of metallic oxides into chlorides. Prepa-
ration of metallic chlorides. Action of hydrochloric acid upon metals. . 92


Formation of ternary oxy- compounds from metallic hydrates and oxy-
acids. Sulphurous and sulphuric acids and their salts. Haloid salts.
Oxy-salts 96


Carbon, its occurrence and properties. Preparation and properties of its
oxides carbonic anhydride and carbonic oxide. Carbonates, their
formation, and action of acids upon them. . . . . . . . . . 102


Oxides of nitrogen, their direct formation by electric discharges. Prepara-
tion and properties of nitric acid. Nitrates. Nitric peroxide. Nitrous
acid. Nitrites. Nitrous anhydride, its reducing and oxidizing action.
Preparation and properties of nitric oxide. Action of nitric acid upon
metals. Compounds of nitrogen and oxygen. Aqua regia. Chloro-
nitric gas. Use of nitric peroxide in the manufacture of sulphuric acid.
Metallic sulphates 109




Ammonia. Preparation of ammonic nitrate and laughing gas. Properties
of nitrous oxide. Composition and properties of ammonia. Ammo-
nium. Ammonoxyl. Preparation of ammonic hydrate. Ammonium
compounds . . . . . . . . . . . . . . . . . . 124


Oxides of chlorine. Chlorates. Hypochlorites. Hypochlorous, chlorous,

chloric, and perchloric acids. Perchlorates 131


Phosphorus. Phosphoric anhydride. Orthophosphates. Pyrophosphates.
Metaphosphates. Phosphorous anhydride. Phosphoretted hydrogen.
Arsenides. Oxides of arsenic. Arsenites and Arseniates . . . . 137

Boric anhydride. Orthoboric and metaboric acids. Borates . . . . 144


Construction of the blowpipe. Nature of a candle flame. Oxidizing
and reducing flame. Construction of gas lamps. Charcoal supports.
Platinum supports. Blowpipe reactions. Fluxes . . . , . . 146

Silicic anhydride. Orthosilicic acid . . . . . . . . . . . . 152


General properties of salts. Solubility of salts. Crystallisation. Water

of crystallisation and of constitution. Colour and taste of salts . . 155


Reaction of salts. Definition of a salt. Normal, acid, and basic salts.

Double salts. Alums . . . . . . . . . . . . . . 159

Definition of chemistry. Modes of chemical action . . . . . . . . 163





Experiment 1. Fill a glass cylinder or test-tube with water, and invert
it over a basin containing water, by first closing its mouth with a glass plate
(Fig. 1). Wrap up a small
piece of the metal sodium in
a little fine wire gauze, fas-
tened to a piece of wire. In-
troduce the sodium rapidly
underneath the mouth of the
cylinder (Fig. 2). Gas bub-
bles are observed to ascend
through the water, and to
collect in the upper part of
the cylinder. The evolution
of gas ceases after a few
moments, and the sodium is
found to have disappeared
entirely. By repeating this
operation, if necessary, the
whole of the water in the
cylinder may be replaced by
a colourless gas. This gas
is hydrogen.

A. few other metals,
such as potassium, ba-
rium, strontium, cal-
cium and magnesium,
decompose water like-
wise at the ordinary
temperature with the
evolution of hydrogen,
but the action is, for
the most part, much
slower, and has, in the
case of the latter metal,
to be assisted by em-
ploying hot instead of
cold water.

Some metals, such



FIG. 1.


manganese, cobalt, nickel, zinc, cadmium, tin, and antimony, which,
when cold, are, for the most part, without action upon water, are
yet capable of decomposing it when water, in the form of vapour or
steam, is slowly passed over the metals heated to redness in a por-
celain tube. They decompose it r however, more or less rapidly in
the cold, if a little hydrochloric acid be added to the water. A
brisk evolution of hydrogen ensues.

Other metals, again, such as copper, mercury, gold, and platinum,
even when placed in acidulated water, do not evolve any hydrogen.

Experiment 2. Larger quantities of hydrogen are most conveniently pre-
pared by acting upon zinc or iron with dilute hydrochloric acid. An apparatus,
represented in Fig. 3, consisting of a two-necked bottle so-callecl Woulfe's
bottle is employed, fitted up by means of perforated corks with a funnel and
delivery-tube. The funnel-tube reaches nearly to the bottom of the Woulfe's
bottle, and serves for the introduction of the acid. The delivery-tube, which
has been bent, as seen in Fig. 3, in the gas-flame of an ordinary fish-tail or bat's-
wing gas-burner, is fitted into the other hole, so as just to pass through the cork.
Sound and well-fitting corks should be selected for such experiments, and they
ought to be well squeezed before being bored. The glass funnel and delivery-
tube should readily pass through the holes, and yet fit perfectly air-tight. It is
best, therefore, to bore the holes by means of a sharp cork-borer of the size of
the glass tubing to be employed.

The delivery-tube dips under the water, and delivers the gas into the cylinder

inverted over water in a pneu-
matic trough.

Q-ranulated zinc (or strips of
sheet zinc) is introduced into
the bottle, and the cork and
delivery-tube adjusted properly.
Moderately concentrated hydro-
chloric acid is then poured
through the funnel-tube, when
the evolution of hydrogen begins
at once. The gas finding no
other outlet, passes through the
deli very- tube, and forces its way
through the water. The air
contained in the Woulfe's bottle
must first be displaced before
any of the gas is collected. In
order to ascertain whether the
air has been sufficiently dis-
placed, some of the gas is col-
lected over water in a test-tube

in the manner already described. When quite full, the tube is withdrawn by
closing the mouth with the thumb, or with a small watch glass or glass plate. If
the enclosed gas burns quietly, on applying a light to it, whilst the mouth of the
tube is held downwards, with a blue lambent flame, it may be considered safe to
collect the gas ; but should the gas in the tube burn with a slight explosion on
applying a light to it, it may be taken as an indication that the air has not been
sufficiently displaced from the generating apparatus.

In the place of the zinc we might have employed iron scraps,
nails, borings, or filings. Hydrogen gas, generated from impure
iron, possesses a most disagreeable odour, arising from the pre-
sence of carbon and sulphur in the iron, which elements, by
entering into combination with a portion of the hydrogen, form



gaseous compounds, called carburetted and sulphuretted hydrogen.
Pure hydrogen is inodorous, and is but very slightly soluble in
water ; 100 volumes of water dissolve only 1*93 volumes of the gas.

For storing up larger quantities of hydrogen, a gasholder, repre-
sented in Fig. 4, is usually employed, consisting of a cylindrical vessel,
A, made of zinc or copper, connected by means of two tubes, a and b,
with the open vessel, B, and supported by one or two more tubular
stays, c and c', as shown in Fig. 4 ; a and b can be shut off by means
of stopcocks. A glass gauge, as seen in g g' , indicates the height of
the column of water in A. By closing the opening, d, fitted with a
screw'-plug, and turning on the taps at a and b, as well as the de-
livery-tap at e, water which is poured into the vessel B makes its
way into the vessel A, till it fills it entirely, and runs over through
e. The taps at a, b, and c
are then closed, and the gas- '
holder may be charged with
gas by inserting the delivery-
tube through the opening at
d, after the removal of the
screw-pi Qg. The water runs
out from d as fast as the
gas enters. When full, the
screw-plug is replaced, and
the apparatus is ready for

By keeping the top ves-
sel, B, always well supplied
with water, the gas can be
discharged at pleasure from
A by turning on the tap a,
which conveys the water
down to the bottom of A,
and opening the tap e partly
or fully, as may be required.
The water which flows from
B to A presses upon the gas,
and forces it from .e. The top vessel, B, may also serve the pur-
poses of a pneumatic trough, and gas may be filled directly from the
gas-holder into an inverted cylinder by opening the tap 6, and
allowing the gas to escape through the water into the inverted

Now, what are the properties of the gas which has been collected ?

Experiment 3. The hydrogen gas collected in a test-tube, or glass
cylinder, as described in Experiments 1 and 2, can be readily removed from the
basin (Fig. 5), or pneumatic trough, by closing the opening of the cylinder with
the thumb or a glass plate.

On applying a lighted candle to the mouth of the cylinder, Fig. 6, the gas
burns quietly with a lambent, non-luminous flame. It is an inflammable gas.

On introducing a wax taper, as shown in Fig. 7, into the cylinder, the gas
burns at the mouth quietly with a bluish flame, giving very little light, whilst
the taper, on being moved upward through the flame into the hydrogen, as shown

B 2



FIG. 5.

in Fig. 8, is immediately extinguished ; on withdrawing the taper again, it ignites
once more when it readies the burning gas at the mouth of the cylinder. The
taper may be thus extinguished and rekindled several times in succession.

This proves that hydrogen cannot support combustion ; also, that it
burns, but only where it is in contact ivith the air (at the mouth of
the cylinder).

Experiment 4. A strong soda-water bottle, filled to about one-third its
bulk with water, is inverted over the gas delivery tube, Fig. 3, until all the water

Fl0 ' 6 -

FIG. 7.

. .

. expelled by the bubbles of gas. A mixture of air and gas in the proportion of
8 ' " ta^explodes

This proves that a mixture of hydrogen gas and air does not combine
he ordinary temperature, but explodes with violence on coming in
contact with a light.

ansm^ 5 ,'~ A fc e8t-tube or cylinder full of air is held, mouth down-
, ar some hydrogen is aUowed to pass into it from another tube, somewhat


FIG. 8. FIG. 9.

inclined, as shown in Fig. 9. On applying a light -to its mouth, an explosion
takes place, showing that this cylinder, which originally contained only air, con-
tains now a mixture of hydrogen and air a mixture which is highly explosive, as
proved by Experiment 4.

This shows that the gas ascended from the lower into the upper
cylinder, and that it must therefore have been lighter than air.
Accurate determinations have established the fact, that the gas is
ah out 14 times lighter than air, its specific gravity being '0691, as
compared with air = 1.

Owing to its lightness it is sometimes used for filling balloons.
Coal gas being, however, more easily procurable, although about
8 times heavier than hydrogen, is now usually employed for this

Experiment 6. The delivery tube of the gas-generating apparatus is con-
nected with a drying tube (containing calcic chloride, a substance which
possesses a strong affinity for water), and a glass tube drawn out to a point
(Fig. 10). After allowing the hydrogen to escape for some time, the jet may
be lighted without any
danger of an explosion. 9
The gas burns with a pale
blue flame, which, how-
ever, is exceedingly hot.
Invert a dry bell-jar over
the flame. It soon be-
comes covered with mois-
ture on its inner surface,
and drops of condensed
water collect and run
down. The same may
be shown by holding a
wide glass tube, about " ,

half an inch in diameter, over the jet. A musical note, high or low, according
as the tube is wide or narrow, will be heard, arising from a series of small explo-
sions, which follow one another in more or less rapid succession, as the tube is
raised or lowered over the gas flame. The upper part of the tube contains the
condensed water.

This proves that water is formed by the combustion of hydrogen in


air. Hence the name hydrogen given to the gas (from vSup, water ,
and ryei/i/aw, I generate), represented shortly by the symbol H.

Bodies which consist of hydrogen, together with another element
capable of burning in air, viz., carbon usually termed hydro-
carbons such as oil of turpentine, paraffin oil, petroleum ; and,
again, others which contain a third element, viz., oxygen, such as
common tallow, spirits of wine, wood, etc., produce all more or less
water, besides some products of combustion, which will be explained
hereafter. A tallow candle, ex. gr., produces rather more than its
own weight of water ; alcohol, or spirits of wine, yields a still larger
amount. This may be seen by holding a wide glass tube or a bell-
jar over a burning candle, in the manner shown in Experiment 6.
It is also perceived whenever water, or some, other cold liquid, is
heated over a spirit-lamp or gas-flame in a glass vessel (a retort or
flask). Drops of water produced by the combustion of the alcohol
or gas condense on the outside of the glass vessel, until the vessel
has been heated sufficiently long to prevent the condensation of the
water vapour or steam.

Summary.* Hydrogen is a very light gas. When pure it is
colourless, tasteless, and inodorous.

It is inflammable, evolving much heat, but giving little light ; it
does not support combustion. Water is formed by its combustion in
air. Although it has no poisonous properties, it cannot support life.



Experiment 1. Heat a little mercury
nearly to boiling in a small flask (Fig. 11) pro-
vided with a long glass tube, and shake fre-
quently. The bright metal gets slowly coated
over with a reddish-yellow film, which, on
shaking, adheres to the sides of the flask, and,
after heating for some hours, a portion of the
metal is converted into a red powder. (The
vapour of the metal mercury being poisonous,
care must be taken not to allow any to escape
into the room through the open condensing tube.)

On weighing the flask and metal be-
fore and after the conversion of some of
the latter into the red powder, an in-
crease in weight is observed. A ponder-
able substance must have been added
during the heating, which can only have
come from the air.

* The summaries placed at the end of this, as
\vc-ll as the next following seven chapters, should
be committed to ineivovv.


Experiment 8. Introduce a weighed quantity of the red powder so
obtained into a tube of hard G-erman glass (Fig. 12), and connect by means of a
cork with a delivery tube, which dips under water in a pneumatic trough. On
applying a strong heat to the tube by means of a Bunsen's gas burner, the


expands, and is forced out through the delivery tube. After a little time a
metallic coating is observed to form in the bend of the tube, and gas bubbles
begin to come off more briskly. Test the gas which bubbles up through the
water in the pneumatic trough by bringing a glowing chip of wood near it. If
the latter bursts into flame, this is due to the gas which comes off from the red
powder, as air would not inflame it. A glass cylinder, full of water, is then
inverted over the mouth of the delivery-tube, and some of the gas collected.
The cylinder becomes gradually filled with a colourless invisible gas. The
metallic mirror in the bend of the tube increases, and collects in heavy drops.
This liquid metal is mercury. When the whole of the red powder has been
volatilized, and converted by heat into a gas and a liquid metal, the lamp is
removed, and the delivery-tube taken out of the water. The condensed mercury
may now be weighed in a little counterpoised porcelain dish. It weighs less
than the red powder employed. Something, then, has been removed from the
latter, viz., the gas collected in the cylinder.

If the experiment be conducted with proper care, and in a per-
fectly suitable apparatus, it will be found that 100 parts by weight
of the red powder leave invariably 92 '59 of metallic mercury, or in
the proportion of 216 : 200, and conse-
quently yield 16 parts by weight of oxygen
gas from every 216 parts of the red powder.
The latter is a compound of mercury and oxy-
gen, and is called mercuric oxide.

What is this gas, and what are its properties ?

By closing the cylinder with a small glass plate, the
gas can be removed without loss, and on introducing a
glowing taper or ignited chip of wood into it, the taper
or wood bursts into flame (Fig. 13), and burns very

This gas, therefore, supports combustion
much more readily than the air from which
it was originally derived (comp. Exp. 7). It is Flo> 13>


called oxygen, or acid producer, from ov9, sour, acid, and
generate (because chemists thought, at one time, that oxygen entered
into the composition of every acid), and the symbol has been
assigned to it.

The metal mercury, .symbol Bg, from hydrargyrum, by combining
with the gas oxygen forms an oxide, mercuric oxide (red precipitate),
and the symbol HgO is used to express its composition.

Experiment 9, Introduce a small piece of phos-
phorus, dried between filter papa*, into a porcelain cruci-
ble, which floats on water, as seen in Fig. 14. Set fire
to the phosphorus, and rapidly invert an empty bell- jar
over the burning phosphorus, so that the combustion can
only take place at the expense of the air confined over
water under the bell-jar. The latter becomes filled with
dense white fumes, which gradually sink down, and are
absorbed by the water. A diminution of about one-fifth
in the volume of the air takes place, and in proportion as
the air disappears, the water rises in the bell-jar. As
soon as the combustion has ceased, the crucible may
be removed from beneath the glass vessel. By slipping
a glass plate over the mouth of the jar, it can be readily

_^ removed, and its contents examined. This is done by

FIG. 14. - PREPARATION OF introducing a lighted taper into the colourless gas left in
NITROGEN. the bell-jar. The burning taper is immediately extin-


The gas, therefore, no longer supports combustion. It is no longer
air. The phosphorus possessed a strong affinity for that constituent

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Online LibraryWilliam George ValentinIntroduction to inorganic chemistry → online text (page 1 of 21)