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ceived the smell of phosgene gas, on passing the chloride over
oxide of zinc ; and as the substance easily liberates chlorine at
high temperatures, it will be readily seen how a small portion
of that gas may be formed. It also happens, sometimes, that
the protoxides become blackened from the deposition of char-
coal.

When the vapour of the chloride is passed over lime, baryta
or strontia, heated red-hot, a very vivid combustion is produced.
The oxygen and the chlorine change places, and both the me-
tals and the carbon are burnt. Chlorides are produced, car-
bonic acid is formed and absorbed by the undecomposed parts
of the earths, and carbon is deposited. In these experiments
no carbonic oxide is produced. When passed over magnesia,
there is no action on the earth, but the perchloride of carbon is
converted by the heat into protochloride.

In these experiments with the oxides no trace of water could
be perceived.

Having thus far described the properties of the substance, I
shall now give the reasons which induce me to consider it a
true chloride of carbon, and shall endeavour to assign its com-
position. My first object was to ascertain whether hydrogen
existed in it or not. When phosphorus is heated in it, a small
quantity of muriatic acid is generally formed ; but doubt arises
as to the cause of its production, from the circumstance that
the phosphorus, as already mentioned, may be the source of



1820.] of Chlorine and Carbon, $c. 43

the hydrogen. When potassium is heated in the vapour of the
substance, there is generally a small expansion of volume, and
inflammable gas produced ; but it is very difficult to cleanse
potassium both from naphtha and an adhering crust of moist
potash ; and either of these, though in extremely minute quan-
tities, would give fallacious results.

A more unexceptionable experiment made with iron has
been already described ; and the inferences from it are against
the presence of hydrogen in the compound.

Some of the substance in vapour was electrized over mercury
by having many hundred sparks passed through it. Calomel
was formed and carbon deposited. A very minute bubble of
gas was produced, but it was much too small to interfere with
the conclusions drawn respecting the binary nature of the com-
pound ; and was probably caused by air that had adhered to
the sides of the tube when the mercury was poured in.

The most perfect demonstration that the body contains no
hydrogen, and indeed of its nature altogether, is obtained from
the circumstances which attend its formation. When the fluid
compound of chlorine and olefiant gas is acted on by chlorine
and solar light in close vessels, although the whole of the chlo-
rine disappears, yet there is no change of volume, its place
being occupied by muriatic acid gas. Hence, as muriatic acid
gas is known to consist of equal volumes of chlorine and hydro-
gen, combined without condensation, it is evident that half the
chlorine introduced into the vessel has combined with the
elements of the fluid, and liberated an equal volume of hydro-
gen ; and as, when the chloride is perfectly formed, it condenses
no muriatic acid gas, a method, apparently free from all fallacy,
is thus afforded of ascertaining its nature.

I have made many experiments on given volumes of chlorine
and olefiant gases. A clean dry retort was fitted with a cap
and stopcock. Its capacity was 25 '25 cubic inches. Being
exhausted by the aiivpump, it was filled with nitrogen (24'25
cubic inches being required), and being again exhausted, 5
cubic inches of olefiant gas, and 10 cubic inches of chlorine,
were introduced. It was then set aside for half an hour, that
the fluid compound might form, and afterwards being placed
again over a jar of chlorine, 19'25 cubic inches entered; so
that the condensation had been as nearly as possible 1Q cubic



44 On two new Compounds [1820.

inches, or twice the volume of the olefiant gas (barometer 29*1
inches). It was now placed for the day (Oct. 18) in the rays
of the sun ; but the weather was not very fine. In the evening
the solid crystalline substance had formed in abundance, and
very little fluid remained. When placed over chlorine, not
the slightest change in volume had been produced. The stop-
cock was now opened under mercury, and a small portion of
the metal having entered, it was agitated in the retort, to
absorb the chlorine ; the neck of the retort was left open under
the mercury all night, and the whole agitated from time to time.
Next morning (barometer 29*6) the mercury which had en-
tered, being passed into the neck of the retort, stood at a
certain mark 6 inches above the level of the mercury in the
trough, occupying 1*25 cubic inch, and leaving 24? cubic inches
filled by the expanded muriatic acid gas and nitrogen. These
volumes, corrected to the pressure of 29*1 inches, give 5*78
cubic inches for the chlorine absorbed, and 19*47 cubic inches
for the muriatic acid gas, &c. These absorbed by water left 1*2
cubic inch of nitrogen ; so that the gases in the retort, after
the action of solar light, were,

Cubic inches.
Muriatic acid gas . .;.... . 18*27

Chlorine : . . . . 5-78

Nitrogen, &c 1*2

and before that action,

Chlorine \ ,.^ . . 29-25

Olefiant gas . . . ..;,.,. . 5*0
Nitrogen .'*,* . . 1*0

Hence 23*47 cubic inches of chlorine had disappeared, and
9*18 of these had entered into combination with an equal
volume of 9*13 cubic inches of hydrogen liberated from the
5 cubic inches of olefiant gas, to form muriatic acid ; and con-
sequently 14*34 cubic inches of chlorine remained combined
with the carbon of the 5 cubic inches of olefiant gas. Here
the volume of chlorine actually employed is not quite five times
that of the olefiant gas, nor the volume of muriatic acid gas
produced equal to four times that of the olefiant gas ; but
they approximate ; and when it is remembered that the con-
version was not quite perfect, and that the gases used would



1820.] of Chlorine and Carbon, c. 45

inevitably contain a slight portion of impurity, the causes of
the deficiency can easily be understood.

In other experiments made in the same way, but with smaller
quantities, more accurate results were obtained : 1 cubic inch
of olefiant gas with 1'25 cubic inches of chlorine, produced
by the action of light 3*67 cubic inches of muriatic acid gas,
4*963 of the chlorine having been used. 1*4 cubic inch of
olefiant gas with 12*5 cubic inches of chlorine produced 5*06
cubic inches of muriatic acid gas, 6*7 cubic inches of chlorine
having been used. Other experiments gave very nearly the
same results ; and I have deduced from them, that one volume
of olefiant gas requires five volumes of chlorine for its conver-
sion into muriatic acid and chloride of carbon ; that four vo-
lumes of muriatic acid gas are formed ; that three volumes of
chlorine combine with the two volumes of carbon in the olefiant
gas to form the solid crystalline chloride ; and that, when chlo-
rine acts on the fluid compound of chlorine and olefiant gas,
for every volume of chlorine that combines, an equal volume of
hydrogen is separated.

I have endeavoured to verify these proportions by analytical
experiments. The mode I adopted was, to send the substance
in vapour over metals and metallic oxides at high tempera-
tures. Considerable care is requisite in such experiments ;
for if the process be carried on quickly, a portion of fluid chlo-
ride of carbon is formed, and escapes decomposition. The
following are two results from a number of experiments agreeing
well with each other.

Five grains were passed over peroxide of copper in an iron
tube, and the gas collected over mercury ; it amounted to 3*9
cubic inches; barometer 29*85; thermometer 54 Fahr. Of
these nearly 3'8 cubic inches were carbonic acid, and rather
more than '1 of a cubic inch was carbonic oxide. These are
nearly equal to '5004 of a grain of carbon. Hence 100 of the
chloride would give 10 of carbon nearly, but by calculation 100
should give 10*19. The difference is so small as to come
within the limits of errors in experiment.

Five grains were passed over peroxide of copper in a tube
made of green phial glass, and the chlorine estimated in the
same manner as before. 17*7 grains of chloride of silver were
obtained, equal to 4*36 grains of chlorine. This result ap-



46 On two new Compounds [1820.

preaches much nearer to the calculated result than the former;
but there had still been action on the tube, and a minute por-
tion of the substance had passed undecomposed, and condensed
at the opposite end of the tube in crystals.

Experiments made by passing the perchloride over hot lime
or barytes, promise to be more accurate and easy of perform-
ance. In the mean time, the above analytical results will, per-
haps, be considered as strong corroboration of the opinion of the
nature of the compound, deduced from the synthetical experi-
ments; and the composition of the perchloride of carbon will be

Three proportions of chlorine .... =100'5
Two ,, carbon . . . . = 11*4

111-9

Protochloride of Carbon. Having said so much on the
nature of the perchloride of carbon, I shall have less occasion
to dwell on the proofs that the compound I am about to de-
scribe, is also a binary combination of carbon and chlorine.

When the vapour of the perchloride of carbon is heated to
dull redness, chlorine is liberated, and a new compound of that
element and carbon is produced. This is readily shown by
heating the bottom of a small glass tube, containing some of
the perchloride in a spirit-lamp. The substance at first sub-
limes ; but as the vapour becomes heated below, it is gradually
converted into protochloride, and chlorine is evolved.

It is not without considerable precaution that the protochlo-
ride of carbon can be obtained pure; for though passed through
a great length of heated tube, part of the perchloride frequently
escapes decomposition. The process I have adopted is the
following : Some of the perchloride is introduced into the
closed end of a tube, and the space above it, for 10 or 12
inches, filled with small fragments of rock-crystal ; the part of
the tube beyond this is then bent up and down two or three
times, so that the angles may form receivers for the new com-
pound ; then heating the tube and crystal to bright redness,
and dipping the angles in water, the perchloride is slowly sub-
limed by a spirit-lamp, and, on passing into the hot part of the
tube, is decomposed ; a fluid passes over, which is condensed
in the angles of the tube, and chlorine is evolved ; part of the
gas escapes, but the greater portion is retained in solution by



1820.] of Chlorine and Carbon, $c. 47

the fluid, and renders it yellow. Having proceeded thus far,
by the careful application of a lamp and blowpipe, the bent
part of the tube may be separated from that within the furnace,
and the end closed, so as to form a small retort; and on di-
stilling the fluid four or five times from one angle to the other,
all the chlorine may be driven off without any loss of the sub-
stance, and it becomes limpid and colourless. It still, however,
always contains some perchloride, which has escaped decom-
position ; and, to separate this, I have boiled the fluid until
the tube was nearly full of its vapour, and then closing the
end that still remained open, by a lamp and blowpipe, have
afterwards left the whole to cool. It is then easy, by collecting
all the fluid into one end of the tube, and introducing that end
through a cork into a receiver, under which a very small flame
is burning, to distil the whole of the fluid at a temperature
very little above that of the atmosphere. The solid chloride
being less volatile does not rise so soon, and the pure proto-
chloride collects at the external end of the tube. To ascertain
its purity, a drop may be placed on a glass plate ; it will imme-
diately evaporate, and if it contains perchloride, that substance
will be left behind ; otherwise, no trace will remain on the
glass. The presence or absence of free chlorine may be
ascertained by dissolving a little of the fluid in alcohol or
aether, and testing by nitrate of silver.

The pure protochloride of carbon is a highly limpid fluid,
and perfectly colourless. Its specific gravity is 1*5526. It is
a non-conductor of electricity. I am indebted to Dr. Wollas-
ton for the determination of the refractive power of this chlo-
ride, and for the approximation to the refractive power given
of the perchloride. In the present case it is 1*4875, being
very nearly that of camphor. It is not combustible except
when held in a flame, as of a spirit-lamp, and then it burns
with a bright yellow light, much smoke, and fumes of muriatic
acid.

It does not become solid at the zero of Fahrenheit's scale.
When its temperature is raised under the surface of water to
between 160 and 170, it is converted into vapour, and re-
mains in that state until the temperature is lowered. When
heated more highly, as by being passed over red-hot rock-
crystal in a glass tube, a small portion is always decomposed ;



48 On two new Compounds [1820.

nearly all the fluid may, however, be condensed again ; but it
passes slightly coloured, and the tube and crystal are blackened
on the surface by charcoal. I am uncertain whether this de-
composition ought not to be attributed rather to the action of
the glass at this high temperature than to the heat alone.

It is not soluble in water, but remains at the bottom of it in
drops, for many weeks, with oat any action.

It is soluble in alcohol and aether, and the solutions burn
with a greenish flame, evolving fumes of muriatic acid.

It is soluble in the volatile and fixed oils. The volatile oils
containing it burn with the emission of fumes of muriatic acid.
When the solutions of it in the fixed oils are heated, they do
not blacken or evolve fumes of muriatic acid. It is therefore
probable, that when this happens with the solution of the per-
chloride in fixed oils, it is from its conversion by the heat into
protochloride and the liberation of chlorine.

It is not soluble in alkaline solutions, nor is any action appa-
rent after several days. Neither is it at all soluble in, or
affected by, strong nitric, muriatic, or sulphuric acids.

Solutions of silver do not act on it.

Oxygen decomposes it at high temperatures, forming car-
bonic oxide or acid, and liberating chlorine.

Chlorine dissolves in it in considerable quantity, but has no
further action, or only a very slow one, in common daylight ;
on exposure to solar light, a different result takes place. I
have only had two days, and those in the middle of November,
on which I could expose the protochloride of carbon in atmo-
spheres of chlorine to solar light ; and hence the conversion of
the whole of the protochloride was not perfect ; but at the end
of those two days the retorts containing the substances were
lined with crystals, which, on examination under the micro-
scope, proved to be quadrangular plates, resembling those of
the perchloride of carbon. There were also some rhomboidal
crystals here and there. After the formation of these crystals,
there was considerable absorption in the retort ; hence chlorine
had combined ; and the gas which remained was chlorine un-
mixed with anything else, except a slight impurity. The
solid body, on examination, was found to be volatile, soluble in
alcohol, precipitable by water, and had the smell and other
properties of perchloride of carbon. Hence, though heat in



1820.] of Chlorine and Carbon, $c. 49

separating chlorine from the perchloride of carbon produces
its decomposition, light occasions its reproduction.

It dissolves iodine very readily, and forms a brilliant red
solution, similar in colour to that made by putting iodine into
sulphuret of carbon or chloric aether. It does not exert any
further action on iodine at common temperatures.

An electric spark passed through a mixture of the vapour of
the chloride with hydrogen, does not cause any detonation;
but when many are passed, the decomposition is gradually
effected, and muriatic acid is formed. When hydrogen and
the vapour of the protochloride are passed through a red-hot
tube, there is a complete decomposition effected, muriatic acid
gas being formed, and charcoal deposited. The mixed vapour
and gas burn with flame as they arrive in the hot part of the
tube. The vapour of the protochloride detonates readily by
the electric spark with a mixture of oxygen and hydrogen
gases, and a complete decomposition is effected. It will not
detonate with the vapour of water.

Sulphur and phosphorus both dissolve in it, but exert no
decomposing action at temperatures at or below the boiling-
point of the chloride. The hot solution of sulphur becomes a
solid crystalline mass by cooling. Phosphorus decomposes it
at a red heat.

Its action on metals is very similar to that of the perchloride.
When passed over them at a red heat, it forms chlorides, and
liberates charcoal. Potassium does not act on it immediately
at common temperatures ; but, when heated in its vapour,
burns brilliantly, and deposits charcoal.

When passed over heated metallic oxides, chlorides of the
metals are formed, and carbonic oxide or carbonic acid, ac-
cording to the state of oxidation of the metal. When its
vapour is transmitted over heated lime, baryta, or strontia, the
same brilliant combustion is produced as with the perchloride.
While engaged in analysing this chloride of carbon for the
purpose of ascertaining the proportions of its elements, I en-
deavoured at first to find how much chlorine was liberated
from a certain weight of perchloride during its conversion into
protochloride, and for this purpose distilled the perchloride
through red-hot tubes into solution of nitrate of silver, receiving
the gas into tubes filled with and immersed in the same solu-

E



50 On two new Compounds [1820.

tion ; but I could never get accurate results in this way, from
the difficulty of producing a complete decomposition, and also
from the formation of chloric acid. Five grains of perchloride
distilled in this manner gave 4*3 grains of chloride of silver,
which are equivalent to 1'06 grain of chlorine; but some of the
chloride evidently passed undecomposed, and crystallized in
the tube.

2*7 grains of the pure protochloride were passed over red-
hot pure baryta in a glass tube : a very brilliant combustion
with flame took place, chloride of barium and carbonic acid
were produced, and a little charcoal deposited. When the tube
was cold, the barytes was dissolved in nitric acid, and the chlo-
rine precipitated by nitrate of silver. 9*4 grains of dry chlo-
ride of silver were obtained =2'32 grains of chlorine.

Other experiments were made with lime, which gave results
very near to this, the quantity of chloride being rather less.

Three grains of pure protochloride were passed over per-
oxide of copper heated red-hot in an iron tube, and the gas
received over mercury. 3*5 cubic inches of carbonic acid
gas came over, mixed with *1 of a cubic inch of common air.
These 3*5 cubic inches are nearly equal to '449 of a grain of
carbon.

These experiments indicate the composition of the fluid
chloride of carbon to be one proportion of chlorine and one
of carbon, or 33*5 of the former, and 5*7 of the latter. The
difference between these theoretical numbers, and the results
of the experiments, is not too great to have arisen from errors
in working on such small quantities of the substance.

A mixture of equal volumes of oxygen and hydrogen was
made, and two volumes of it detonated with the vapour of the
protochloride in excess over mercury by the electric spark.
The expansion was very nearly to four volumes ; of these, two
were muriatic acid, and the rest pure carbonic oxide : and
calomel had been formed, its presence being ascertained by
potash. Hence it appears, that one volume of hydrogen and
half a volume of oxygen had decomposed one proportion of the
protochloride, forming the two volumes of muriatic acid gas
and one volume of carbonic oxide ; and that at the intense
temperature produced within the tube by the inflammation, the
rest of the oxygen and the mercury had decomposed a further



1820.] of Chlorine and Carbon, $c. 51

portion of the substance, giving rise to the second volume of
the carbonic oxide, and to the calomel.

A mixture of two volumes of hydrogen and one volume of
oxygen was made, and three volumes of it detonated with the
vapour, as before. After cooling, the expansion was to six
volumes, four of which were muriatic acid, and two carbonic
oxide. There was no action on the mercury in this experiment.
Again, five volumes of the same mixture being detonated with
the vapour of the substance expanded to 9*75 volumes, of
which 6'25 were absorbed by water and were muriatic acid, and
3*5 were carbonic oxide mixed with a very small portion of air
introduced along with the fluid chloride. These experiments,
I think, establish the composition of the protochloride of car-
bon, and prove that it contains one proportion of each of its
elements.

From a consideration of the proportions of these two chlorides
of carbon, it seems extremely probable that another may exist,
composed of two proportions of chlorine combined with one of
carbon. I have searched assiduously for such a compound,
but am undecided respecting its production. When the fluid
protochloride was exposed with chlorine to solar light, crystals
were formed, as before described. The greater number of
these were certainly the perchloride first mentioned in this
paper ; but when the retort was examined by a microscope,
some rhomboidal crystals were observed here and there among
those of the usual dendritic and square forms. These may
perhaps be the real perchloride ; but I had not time, before the
season of bright sunshine passed away, to examine minutely
what happens in these circumstances ; and must defer this, with
many other points, till the next year brings more favourable
weather.

Compound of Iodine, Carbon, and Hydrogen. The analogy
which exists between chlorine and iodine, naturally suggested
the possible existence of an iodide of carbon, and the means
which had succeeded with the one element offered the best
promise of success with the other.

Iodine and olefiant gas were put in various proportions into
retorts, and exposed to the sun's rays. After awhile, colour-
less crystals formed in the vessels, and a partial vacuum was
produced. The gas in the vessels being then examined, was



52 On two new Compounds of Chlorine and Carbon. [1820.

found to contain no hydriodic acid, but only pure olefiant gas.
Hence the effect had been simply to produce a compound of
the iodine with the olefiant gas.

O

The new body formed was obtained pure by introducing a
solution of potash into the retort, which dissolved all the free
iodine ; the substance was then collected together and dried.
It is a solid white crystalline body, having a sweet taste and
aromatic smell. It sinks readily in sulphuric acid of specific
gravity 1 '85. It is friable ; is not a conductor of electricity.
When heated, it first fuses, and then sublimes without any
change. Its vapour condenses into crystals, which are either
prismatic or in plates. On becoming solid after fusion, it also
crystallizes in needles. The crystals are transparent. When
highly heated it is decomposed, and iodine evolved. It is not
readily combustible; but when held in the flame of a spirit-lamp,
burns, diminishing the flame, and giving off abundance of
iodine and some fumes of hydriodic acid. It is insoluble in
water, or in acid and alkaline solutions. It is soluble in alco-
hol and aether, and may be obtained in crystals from these so-
lutions. The alcoholic solution is of a very sweet taste, but
leaves a peculiarly sharp biting sensation on the tongue.

Sulphuric acid does not dissolve it. When heated in the
acid to between 300 and 400, the compound is decomposed,
apparently by the heat alone ; and iodine and a gas, probably
olefiant gas, are liberated. Solution of potash acts on it very
slowly, even at the boiling-point, but does gradually decom-
pose it.

This substance is evidently analogous to the compound of
olefiant gas and chlorine, and remarkably resembles it in the
sweetness of its taste, though it differs from it in form, &c. It
will, with that body, form a new class of compounds, and they
will require names to distinguish them. The term chloric aether,
applied to the compound of olefiant gas and chlorine, did not



Online LibraryMichael FaradayExperimental researches in chemistry and physics → online text (page 5 of 49)