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ment, I found reason to suppose that the hydrogen was not at
all concerned in liberating the chlorine from the silver.

When zinc is thrown into chloride of silver, diffused through
dilute sulphuric or muriatic acid, hydrogen is liberated, and
the chloride suffers decomposition. But the same effect takes
place if zinc be thrown into chloride of silver, diffused through
pure water, so that the hydrogen which escapes in the state of
gas, cannot, in its nascent state, have been the decomposing
agent. It may, however, be supposed that water is decom-
posed even when no acid is present, and that thus hydrogen is
still the agent. But I find that zinc decomposes chloride of
silver even more rapidly when unembarrassed by water, than
when water is present. Thus, if a little fused chloride of
silver and a sntall portion of zinc be heated in a glass tube, a
violent action takes place ; chloride of zinc is formed and
silver liberated, and the heat rises so high as generally to fuse
the silver ; or if dry chloride of silver in powder be triturated
in a mortar with zinc filings, the two bodies immediately act,
and a heat above that of boiling water is produced.

Zinc is not the only common metal which thus rapidly de-
composes chloride of silver, in the dry way. Tin acts even
more powerfully when triturated with it ; and copper and iron
have both of them affinities for chlorine strong enough to pro-
duce the same effect.

There is therefore no occasion to assume hydrogen as the
decomposing agent, when chloride of silver is reduced in con-
tact with zinc or iron (iron acts as zinc does in all these ex-
periments, though not so powerfully) ; for the metals, by their
attraction for chlorine, are sufficiently energetic to produce the
effect. Yet, as I had supposed, from general opinion, that
hydrogen could, by its attraction for chlorine, separate that
element from silver, I endeavoured to ascertain in what cir-
cumstances it had the power of doing so. If a stream of
hydrogen, rapidly generated from iron or zinc, be sent against
moist chloride of silver, in a dark place or by candlelight, it
appears to alter it ; but this effect must be due to metals or
impurities held in solution, for when purified it has no power



18^0.] On two new Compounds of Chlorine and Carbon. 33

of changing it out of daylight ; nor have I been able, even in
the sunshine of this month, to make hydrogen act on chloride
of silver in several hours.

Still, however, hydrogen may be allowed in certain circum-
stances to have the power of decomposing chloride of silver,
but the circumstances are not such as were, I believe, gene-
rally supposed to have place in the experiment first referred
to. When zinc, iron, tin, &c. are thrown into moist chloride
of silver, the first decomposition is occasioned by the action of
the zinc on the chloride, afterwards a voltaic circle is formed
by the zinc, the reduced silver and the water; water is de-
composed, the zinc takes oxygen, the hydrogen liberated at
the surface of the silver takes the chlorine from the chloride
in its immediate neighbourhood, and thus the reduction will
go on to the distance of an inch or more from the piece of
zinc, and the consequent products are silver and solution of
muriate of zinc. But as this is a case of decomposition entirely
different to the supposed one of the reduction of chloride of
silver by hydrogen, any denial of the latter is not at all invali-
dated by the truth of the former.



On two new Compounds of Chlorine and Carbon, and on a new

Compound of Iodine, Carbon, and Hydrogen*.

[Read Dec. 21, 1820.]

ONE of the first circumstances that induced Sir H. Davy to
doubt the compound nature of what was formerly called oxy-
muriatic acid gas, was the want of action of heated charcoal
upon it ; and considerable use of the same agent, and of the
phenomena exhibited by it in different circumstances with
chlorine, was afterwards made in establishing the simple nature
of that body.

The true nature of chlorine being ascertained, it became of
importance to form all the possible compounds of it with other
elementary substances, and to examine them in the new view
had of their nature. This investigation has been pursued with
such success at different times, that very few elements remain
uncombined with it ; but with respect to carbon, the very cir-

* Phil. Trans. 1821, p. 47, and Phil. Mag. lix. p. 337.

D



34 On two new Compounds [1850.

cumstance which first tended to correct the erroneous opinions
which, after Scheele's time, and before the year 1810, had gone
abroad respecting its nature, proved an obstacle to the forma-
tion of its compounds ; and up to the present time the chlo-
rides of carbon have escaped the researches of chemists.

That the difficulty met with in forming a compound of chlo-
rine and carbon was probably not owing to any want or weak-
ness of affinity between the two bodies, was pointed out by Sir
H. Davy ; who, reasoning on the triple compound of chlorine,
carbon and hydrogen, concluded that the attraction of the two
bodies for each other was by no means feeble ; and the dis-
covery of phosgene gas by Dr. Davy, in which chlorine and
carbon are combined with oxygen, was another circumstance
strongly in favour of this opinion.

I was induced last summer to take up this subject, and have
been so fortunate as to discover two chlorides of carbon, and
a compound of iodine, carbon and hydrogen, analogous in its
nature to the triple compound of chlorine, carbon and hydro-
gen, sometimes called chloric aether. I shall endeavour in the
following pages to describe these substances, and give the ex-
perimental proofs of their nature.

If chlorine and olefiant gas be mixed together, it is well
known that condensation takes place, and a colourless limpid
volatile fluid is produced, containing chlorine, carbon and
hydrogen. If the volumes of the two gases are equal, the
condensation is perfect. If the olefiant gas is in excess, that
excess is left unchanged. But if the chlorine is in excess, the
fluid becomes of a yellow tint, and acid fumes are produced.
This circumstance alone proves that chlorine can take hydro-
gen from the fluid ; and on examination I found it was with-
out the liberation of any carbon or chlorine.

That the action thus begun might be carried to its utmost
extent, some of the pure fluid (chloric aether) was put into a
retort with chlorine, and exposed to sunshine. At the first
instant of contact between the chlorine and the fluid, the latter
became yellow ; but when in the sun's rays, a few moments
sufficed to destroy the colour both of the fluid and the chlo-
rine, heat being at the same time evolved. On opening the
retort, there was no absorption, but it was found full of muri-
atic acid gas. This was expelled and more chlorine introduced,



1850.] of Chlorine and Carbon, $c. 35

and the whole again exposed to sunlight: the colour again
disappeared, and a few moist crystals were formed round the
edge of the fluid. Chlorine being a third time introduced, and
treated as before, it still removed more hydrogen ; and now a
sublimate of crystals lined the retort. Proceeding in this way
until the chlorine exerted no further action, the fluid entirely
disappeared, and the results were, the dry crystalline substance
and muriatic acid gas.

A portion of olefiant gas was then mixed in a retort with
eight or nine times its bulk of chlorine, and exposed to sun-
light. At first the fluid formed, but this instantly disappeared ;
the retort became lined with crystals, and the colour of the
chlorine very much diminished.

On examining these crystals, I found they were the com-
pound I was in search of; but before I give the proofs of their
nature, I will describe the process by which this chloride of
carbon can be obtained pure.

Perchloride of Carbon. A glass vessel was made in the
form of an alembic head, but without the beak ; the neck was
considerably contracted, and had a brass cap with a stopcock
cemented on ; at the top was a small aperture, into which a
ground stopper fitted air-tight. The capacity of the vessel
was about 200 cubic inches. Being exhausted by the air-
pump, it was nearly filled with chlorine ; and being then placed
over olefiant gas, and as much as could enter having passed in,
the stopcocks were shut, and the whole left for a short time.
When the fluid compound of chlorine and olefiant gas had
formed and condensed on the sides of the vessel, it was again
placed over olefiant gas, and in consequence of the condensa-
tion of a large portion of the gases, a considerable quantity
more entered. This was left, as before, to combine with part
of the remaining chlorine, to condense, and to form a partial
vacuum ; which was again filled with olefiant gas, and the pro-
cess repeated until all the chlorine had united to form the fluid,
and the vessel remained full of olefiant gas. Chlorine was then
admitted in repeated portions as before; consequently more
of the fluid formed ; and ultimately a large portion was ob-
tained in the bottom of the vessel, and an atmosphere of chlo-
rine above it. It was now exposed to sunlight. The chlorine
immediately disappeared, and the vessel became filled with



86 On two new Compounds [1820.

muriatic acid gas. Having ascertained that water did not
interfere with the action of the substances, a small portion was
admitted into the vessel, which absorbed the muriatic acid gas,
and then another atmosphere of chlorine was introduced.
Again exposed to the light, this was partly combined with the
carbon, and partly converted into muriatic acid gas ; which
being, as before, absorbed by the water, left space for more
chlorine. Repeating this action, the fluid gradually became
thick and opake from the formation of crystals in it, which at
last adhered to the sides of the glass as it was turned round ;
and ultimately the vessel only contained chlorine with the accu-
mulated gaseous impurities of the successive portions, a strong
solution of muriatic acid coloured blue from the solution of a
little brass, and the solid substance.

I have frequently carried the process thus far in retorts ;
and it is evident that any conveniently formed glass vessel will
answer the purpose. The admission of water during the pro-
cess prevents the necessity of repeated exhaustion by the air-
pump, which cannot be done without injury to the latter; but
to have the full advantage of this part of the process, the gases
should be as pure as possible, that no atmosphere foreign to
the experiment may collect in the vessel.

In order to cleanse the substance, the remaining chlorine and
muriatic acid were blown out of the vessel by a pair of bellows,
introduced at the stoppered aperture, and the vessel afterwards
filled with water, to wash away the muriatic acid and other
soluble matters. Considerable care is then requisite in the
further purification of the chloride. It retains water, muriatic
acid, and a substance which I find to be a triple compound of
chlorine, carbon and hydrogen, formed from the cement of
the cap ; and as all these contain hydrogen, a small quantity
of any one remaining with the chloride would, in analysis, give
erroneous results. Various methods of purification may be
devised, founded on the properties of the substance, but I
have found the following the most convenient : The substance
is to be washed from off the glass, and poured with the water
into a jar ; a little alcohol will remove the last portions which
adhere to the glass ; and this, when poured into the water,
will precipitate the chloride, and the whole will fall to the
bottom of the vessel. Then having decanted the water, the



1820.] of Chlorine and Carbon, $c. 87

chloride is to be collected on a filter, and dried as much as
may be, by pressure between folds of bibulous paper. It
should next be introduced into a glass tube, and sublimed by
a spirit-lamp : the pure substance with water will rise at first,
but the last portions will be partially decomposed, muriatic
acid will be liberated, and charcoal left. The sublimed por-
tion is then to be dissolved in alcohol, and poured into a weak
solution of potash, by which the substance is thrown down,
and the muriatic acid neutralized and separated ; then wash
away the potash and muriate by repeated affusions of water,
until the substance remains pure ; collect it on a filter, and
dry it, first between folds of paper, and afterwards by sulphuric
acid in the exhausted receiver of the air-pump.

It will now appear as a white pulverulent substance ; and if
perfectly pure, will not, when a little of it is sublimed in a tube,
leave the slightest trace of carbon, or liberate any muriatic
acid. A small portion of it dissolved in rether should give no
precipitate with nitrate of silver. If it be not quite pure, it
must be resublimed, washed, and dried until it is pure.

This substance does not require the direct rays of the sun
for its formation. Several tubes were filled with a mixture of
one part of olefiant gas with five or six parts of chlorine, and
placed over water in the light of a dull day ; in two or three
hours there v/as very considerable absorption, and crystals of
the substance were deposited on the inside of the tubes. I
have also often observed the formation of the crystals in retorts
in common daylight.

A retort being exhausted had 12 cubic inches of olefiant gas
introduced, and 24*75 cubic inches of chlorine : as soon as the
condensation occasioned by the formation of the fluid had
taken place, 21*5 cubic inches more of chlorine were passed in,
and the retort set aside in a dark place for two days. At the
end of that time muriatic acid gas and the solid chloride had
formed, but the greater part of the fluid remained unchanged.
Hence it will form even in the dark by length of time.

I tried to produce the chloride by exposure of the two gases
in tubes over water to strong lamp-light for two or three hours,
but could not succeed.

The perchloride of carbon, when pure, is, immediately after
fusion, or sublimation, a transparent colourless substance. It



38 O/i two new Compounds [1820.

has scarcely any taste. Its odour is aromatic, and approaching
to that of camphor, Its specific gravity is as nearly as pos-
sible 2. Its refractive power is high, being above that of flint-
glass (1*5767). It is very friable, easily breaking down under
pressure ; and when scratched has much of the feel and ap-
pearance of white sugar. It does not conduct electricity.

The crystals obtained by sublimation and from solutions of
the substance in alcohol and aether, are dendritical, prismatic,
or in plates ; the varieties of form, which are very interesting,
are easily ascertained, and result from a primitive octahedron.
It volatilizes slowly at common temperatures, and passes, in
the manner of camphor, towards the light. If warmed, it rises
more rapidly, and then forms fine crystals : when the tempera-
ture is further raised, it fuses at 320 Fahr. and boils at 360
under atmospheric pressure. When condensed again from
these rapid sublimations, it concretes in the upper part of the
tube or vessel containing it, in so transparent and colourless a
state, that it is difficult, except from its high refractive power, to
perceive where it is lodged. As the crust it forms becomes
thicker, it splits, and cracks like sublimed camphor ; and in a
few minutes after it is cold, is white, and nearly opake. If
the heat be raised still higher, as when the substance is passed
through a red-hot tube, it is decomposed, chlorine is evolved,
and another chloride of carbon, which condenses into a fluid, is
obtained. This shall be described presently.

It is not readily combustible ; when held in the flame of a
spirit-lamp, it burns with a red flame, emitting much smoke
and acid fumes ; but when removed from the lamp, combustion
ceases. In the combustion that does take place in the lamp,
the hydrogen of the alcohol, by combining with the chlorine of
the compound, performs the most important part ; nevertheless,
when the substance is heated red in an atmosphere of pure
oxygen, it sometimes burns with a brilliant light.

It is not soluble in water at common temperatures, or only
in very small quantity. When a drop or two of the alcoholic
solution is poured into a large quantity of water, it renders it
turbid from the deposition of the substance. It does not appear
that hot water dissolves more of it than cold water.

It dissolves in alcohol with facility, and in much greater quan-
tity with heat than, without;. A saturated hot solution crystal-



1820.] of Chlorine and Carbon, $c. 39

lizes as it cools, and the cold solution also gives crystals by
spontaneous evaporation. When poured into water, the chlo-
ride is precipitated, and falls to the bottom in flakes. If burnt,
the flame of the alcohol is brightened by the presence of the
substance, and fumes of muriatic acid are liberated. Solution
of nitrate of silver does not produce any turbidness in it, unless
it be in such quantity that the water throws down the substance;
but no chloride of silver is formed.

It is much more soluble in aether than in alcohol, and more
so in hot than in cold aether. The hot solution deposits cry-
stals as it cools ; and the crystallization of a cold solution, when
evaporated on a glass plate, is very beautiful. This solution
is not precipitated by water, unless the aether has previously
been dried, and then water occasions a turbidness. Nitrate of
silver does not precipitate it. When burned, muriatic acid
fumes are liberated, but the greater part of the chloride remains
in the capsule.

It is soluble in the volatile oils, and on evaporation is again
obtained in crystals. It is also readily soluble in fixed oils.
The solutions when heated liberate muriatic acid gas, and the
oil becomes of a dark colour, as if charred.

Solutions of the acids and alkalies do not act with any energy
on the substance. "When boiled with solutions of pure potash
and soda, it rises and condenses in the upper part of the ves-
sel ; and though it be brought down to the alkali many times
and reboiled, still the alkali, when examined, is not found to
contain any chlorine, nor is any change produced. Ammonia
in solution is also without action upon it. These solutions do
not appear to dissolve more of it than pure water.

Muriatic acid in solution does not act at all upon it. Strong
nitric acid boiled upon it dissolves a portion, but does not
decompose it : as it cools, part of the chloride is deposited un-
altered, and the concentrated acid, when diluted, lets more fall
down. The diluted portion being filtered, and tested with
nitrate of silver, gives no precipitate. It does not appear to be
either soluble in, or acted upon by, concentrated sulphuric acid.
It sinks slowly in the acid, and, when heated, is converted into
vapour, which, rising through the acid, condenses in the upper
part of the tube.

It is not acted upon by oxygen at temperatures under a, red



40 On two new Compounds [1S20.

heat. A mixture of oxygen and the vapour of the substance
would not inflame hy a strong electric spark, though the tem-
perature was raised by a spirit-lamp to about 400. When
oxygen mixed with the vapour of the substance is passed
through a red-hot tube, there is decomposition ; and mixtures
of chlorine, carbonic oxide, carbonic acid, and phosgene gases
are produced. A portion of the chloride was heated with per-
oxide of mercury, in a glass tube over mercury ; as soon as the
oxide had given off oxygen, and the heat had risen so high as
to soften the glass considerably, the vapour suddenly detonated
with the oxygen with bright inflammation. The substances
remaining were oxygen, carbonic acid, and calomel ; and I
believe there was no decomposition or action, until so much
mercury had risen in vapour as to aid the oxygen by a kind of
double affinity in decomposing the chloride of carbon.

Chlorine produces no change on the substance, either by
exposure to light or heat.

When iodine is heated with it at low temperatures, the two
substances melt and unite, and there is no further action.
When heated more strongly in vapour, the iodine separates
chlorine, reducing the perchloride to the fluid protochloride of
carbon, and chloriodine is produced. This dissolves, and if no
excess of iodine be present, the whole remains fluid at common
temperatures. When water is added, it generally liberates a
little iodine ; and on heating the solution, so as to drive off all
free iodine, and testing by nitrate of silver, chloride and iodide
of silver are obtained.

Hydrogen and the vapour of the substance would not inflame
at the temperature of 400 Fahr. by strong electrical sparks ;
but when the mixture was sent through a red-hot tube, the
chloride was decomposed, and muriatic acid gas and charcoal
produced.

The vapour of the perchloride of carbon readily detonates by
the electric spark with a mixture of oxygen and hydrogen
gases; but the gaseous results are very mixed and uncertain,
from the near equipoise of affinities that exists among the ele-
ments.

Sulphur readily unites to it when melted with it, and the
mixture crystallizes on cooling into a yellowish mass. When
heated more strongly, the substance rises unchanged, and



1820.] of Chlorine and Carbon, $c. 41

leaves the sulphur unaltered ; but when the mixed vapours are
raised to a still higher temperature, chloride of sulphur and
protochloride of carbon are formed. Sometimes there are ap-
pearances as if a carburet of sulphur were formed, but of this
I have not satisfied myself.

Phosphorus at low temperatures melts and unites with the
substance without any decomposition. If heated in the vapour
of the substance, but not too highly, it takes away chlorine,
and forms the protochlorides of phosphorus and carbon. If
heated more highly, it frequently inflames in the vapour with a
brilliant combustion, and abundance of charcoal is deposited.
Sometimes 1 have had the charcoal left in films stretching across
the tubes, and occupying the space where the flame passed.
The appearance is then very beautiful.

When phosphorus is heated with the vapour of the substance
over mercury, so as not to inflame in it, there is generally a
small portion of muriatic acid gas formed. If great care be
taken, this is in very minute quantity ; and its variable propor-
tion sufficiently shows, that the hydrogen which forms it does
not come from the substance. I am induced to believe that it
is derived from moisture adhering to the phosphorus. The
action of iodine on phosphorus shows that it is very difficult to
dry the latter substance perfectly.

A stick of phosphorus put into the alcoholic or sethereal
solution of the perchloride did not exert any action upon it. .

Charcoal heated in the vapour of the substance appears to
have no action upon it.

Most of the metals decompose it at high temperatures. Po-
tassium burns brilliantly in the vapour, depositing charcoal and
forming chloride of potassium. Iron, zinc, tin, copper and
mercury act on it at a red heat, forming chlorides of those
metals and depositing charcoal ; and when the experiments
are made with pure substances, and very carefully, no other
results are obtained. Some of the substance was passed over
iron turnings heated in a glass tube. At the commencement of
the sublimation of the chloride through the hot iron, the com-
mon air of the vessels was expelled, and received in different
tubes : but before one-third of the substance had been passed,
all liberation of gas ceased, and the remainder was decom-
posed by the iron, without the production of any gaseous mat-



42 On two new Compounds [1820.

ters. The different portions of air that were thrown out being
examined, the first proved to be common air, and the last car-
bonic oxide. This had resulted, probably, from the action of
the chlorine on the lead of the glass tube. An evident action
had taken place, and the oxygen evolved, meeting with the
liberated carbon, would produce the carbonic oxide. This
experiment has been repeated several times with, the same
results.

When the perchloride of carbon is heated with metallic
oxides, different results are produced according to the propor-
tions of oxygen in the oxides. The peroxides, as of mercury,
copper, lead and tin, produce chlorides of those metals, and
carbonic acid ; and the protoxides, as those of zinc, lead, &c.,
produce also chlorides, but the gaseous products are mixtures
of carbonic acid and carbonic oxide. I have frequently per-



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