The liquefaction of gases

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LIQUEFACTION OF GASES

PAPERS

BY

MICHAEL FARAD - '
(1823-1845).

WITH \PPKN!H

Biembie €iub IReptint0f

No. 12.

REESE LIBRARY

UNIVERSITY OF. CALIFORNIA

ClaxsNo. ,

(gfemfitc Cfufi (Reprints— (Uo. 12,
THE

LIQUEFACTION OF GASES

PAPERS

BY

MICHAEL FARADAY, F.R.S.

(1823-1845.)

WITH AN APPENDIX

CONSISTING OF

PAPERS BY THOMAS NORTHMORE

ON THE COMPRESSION OF GASES.

(1805-1806).

EDINBURGH :
WILLIAM F. CLAY, 18 TEVIOT PLACE.

LONDON :

SIMPKIN, MARSHALL, HAMILTON, KENT, & CO. LTD.
1896.

PREFACE.

THE papers by Faraday on the Liquefaction of Gases,
here reprinted, give an account of the earliest
work carried out at the Royal Institution on that most
interesting and important subject, with which the Insti-
tution has been more or less intimately associated for
three-quarters of a century. The extreme beauty and
simplicity of Faraday's experiments, as well as the
peculiarly felicitous manner in which his various experi-
ments are described, render these papers especially
instructive, and suitable for reproduction in the series to
which this little volume belongs.

It was considered advisable to reprint Faraday's
Historical Statement respecting the Liquefaction of
Gases, and, for the sake of greater completeness, to
include, in the form of an Appendix, the papers of Mr
Northmore which are particularly referred to in that

Statement.

L. D.

95769

I. ON FLUID CHLORINE*

Read March 13, 1823.

IT is well known that before the year 1810, the solid
substance obtained by exposing chlorine, as usually
procured, to a low temperature, was considered as the
gas itself reduced into that form ; and that Sir HUMPHRY
DAVY first showed it to be a hydrate, the pure dry gas
not being condensible even at a temperature of -40° F.f

I took advantage of the late cold weather to procure
crystals of this substance for the purpose of analysis. The
results are contained in a short paper in the Quarterly
Journal of Science, Vol. XV. Its composition is very
nearly 27.7 chlorine, 72.3 water, or i proportional of
chlorine, and 10 of water.

The President of the Royal Society having honoured
me by looking at these conclusions, suggested, that an
exposure of the substance to heat under pressure, would
probably lead to interesting results ; the following experi-
ments were commenced at his request. Some hydrate of
chlorine was prepared, and being dried as well as could
be by pressure in bibulous paper, was introduced into a
sealed glass tube, the upper end of which was then
hermetically closed. Being placed in water at 60°, it
underwent no change; but when put into water at 100°,
the substance fused, the tube became filled with a bright
yellow atmosphere, and, on examination, was found to
contain two fluid substances : the one, about three-fourths
of the whole, was of a faint yellow colour, having very

* [From Philosophical Transactions for 1823, Vol. 113, pp.
160-165.]
t [See Alembic Club Reprints, No. 9, p. 58.]

6 Faraday,

much the appearance of water ; the remaining fourth was
a heavy bright yellow fluid, lying at the bottom of the
former, without any apparent tendency to mix with it.
As the tube cooled, the yellow atmosphere condensed
into more of the yellow fluid, which floated in a film on
the pale fluid, looking very like chloride of nitrogen ; and
at 70° the pale portion congealed, although even at 32°
the yellow portion did not solidify. Heated up to 100°
the yellow fluid appeared to boil, and again produced the
bright coloured atmosphere.

By putting the hydrate into a bent tube, afterwards
hermetically sealed, I found it easy, after decomposing it
by a heat of 100°, to distil the yellow fluid to one end of
the tube, and so separate it from the remaining portion.
In this way a more complete decomposition of the hydrate
was effected, and, when the whole was allowed to cool,
neither of the fluids solidified at temperatures above 34°,
and the yellow portion not even at o°. When the two
were mixed together they gradually combined at tempera-
tures below 60°, and formed the same solid substance as
that first introduced. If, when the fluids were separated,
the tube was cut in the middle, the parts flew asunder as
if with an explosion, the whole of the yellow portion dis-
appeared, and there was a powerful atmosphere of chlorine
produced ; the pale portion on the contrary remained,
and when examined, proved to be a weak solution of
chlorine in water, with a little muriatic acid, probably
from the impurity of the hydrate used. When that end
of the tube in which the yellow fluid lay was broken
under a jar of water, there was an immediate production
of chlorine gas.

I at first thought that muriatic acid and euchlorine had
been formed ; then, that two hew hydrates of chlorine had
been produced ; but at last I suspected that the chlorine
had been entirely separated from the water by the heat,

Liquefaction of Gases. 7

and condensed into a dry fluid by the mere pressure of
its own abundant vapour. If that were true, it followed,
that chlorine gas, when compressed, should be condensed
into the same fluid, and, as the atmosphere in the<tube
in which the fluid lay was not very yellow at 50° or 60°,
it seemed probable that the pressure required was not
beyond what could readily be obtained by a condensing
syringe. A long tube was therefore furnished with a
cap and stop-cock, then exhausted of air and filled with
chlorine, and being held vertically with the syringe up-
wards, air was forced in, which thrust the chlorine to the •
bottom of the tube, and gave a pressure of about 4
atmospheres. Being now cooled, there was an immediate
deposit in films, which appeared' to be hydrate, formed
by water contained in the gas and vessels, but some of
the yellow fluid was also produced. As this however
might also contain a portion of the water present, a
perfectly dry tube and apparatus were taken, and the
chlorine left for some time over a bath of sulphuric acid
before it was introduced. Upon throwing- in air and
giving pressure, there was now no solid film formed, but
the clear yellow fluid was deposited, and more abundantly
still upon cooling.. After remaining some time it dis-
appeared, having gradually mixed with the atmosphere
above it, but every repetition of the experiment produced
the same results.

Presuming that I had now a right to consider the
yellow fluid as pure chlorine in the liquid state, I pro-
ceeded to examine its properties, as well as I could when
obtained by heat from the hydrate. However obtained,
it always appears very limpid and fluid, and excessively
volatile at common pressure. A portion was cooled in
its tube to o° : it remained fluid. The tube was then
opened, when a part immediately flew off, leaving the
rest so cooled by the evaporation as to remain a fluid

8 Faraday.

under the atmospheric pressure. The temperature could
not have been higher than -40° in this case; as Sir
HUMPHRY DAVY has shown that dry chlorine does not
condense at that temperature under common pressure.
Another tube was opened at a temperature of 50°; a
part of the chlorine volatilised, and cooled the tube so
much as to condense the atmospheric vapour on it as
ice.

A tube having the water at one end and the chlorine
at the other was weighed, and then cut in two; the
chlorine immediately flew off, and the loss being ascer-
tained was found to be 1.6 grains : the water left was
examined and found to contain some chlorine : its weight
was ascertained to be 5.4 grains. These proportions,
however, must not be considered as indicative of the
true composition of hydrate of chlorine ; for, from the
mildness of the weather during the time when these
experiments were made, it was impossible to collect the
crystals of hydrate, press, and transfer them, without
losing much chlorine ; and it is also impossible to
separate the chlorine and water in the tube perfectly, or
keep them separate, as the atmosphere within will com-
bine with the water, and gradually reform the hydrate.

Before cutting the tube, another tube had been pre-
pared exactly like it in form and size, and a portion of
water introduced into it, as near as the eye could judge,
of the same bulk as the fluid chlorine : this water was
found to weigh 1.2 grains; a result, which, if it may be
trusted, would give the specific gravity of fluid chlorine
as 1.33 ; and from its appearance in, and on water, this
cannot be far wrong.

Liquefaction of Gases. 9

Note on the Condensation of Muriatic Acid Gas
into the liquid form. By Sir H. DAVY,
Bart., Pres. R.S.

IN desiring Mr. FARADAY to expose the hydrate of
chlorine to heat in a closed glass tube, it occurred
to me, that one of three things would happen ; that it
would become fluid as a hydrate ; or that a decomposi-
tion of water would occur, and euchlorine or muriatic acid
be formed; or that the chlorine would separate in a
condensed state. This last result having been obtained,
it evidently led to other researches of the same kind. I
shall hope, on a future occasion, to detail some general
views on the subject of these researches. I shall now
merely mention, that by sealing the muriate of ammonia
and sulphuric acid in a strong glass tube, and causing
them to act upon each other, I have procured liquid
muriatic acid : and by substituting carbonate for muriate
of ammonia, I have no doubt that carbonic acid may be
obtained, though in the only trial I have made the tube
burst. I have requested Mr. FARADAY to pursue these
experiments, and to extend them to all the gases which
are of considerable density, or to any extent soluble in
water ; and I hope soon to be able to lay an account of
his results, with some applications of them that I propose
to make, before the Society.

I cannot conclude this note without observing, that
the generation of elastic substances in close vessels,
either with or without heat, offers much more powerful
means of approximating their molecules than those de-
pendent upon the application of cold, whether natural or
artificial : for, as gases diminish only about -±\-§ in volume
for every — degree of FAHRENHEIT'S scale, beginning at
ordinary temperatures, a very slight condensation only

IO Faraday.

can be produced by the most powerful freezing mixtures,
not half as much as would result from the application of
a strong flame to one part of a glass tube, the other part
being of ordinary temperature : and when attempts are
made to condense gases into fluids by sudden mechanical
compression, the heat, instantly generated, presents a
formidable obstacle to the success of the experiment ;
whereas, in the compression resulting from their slow
generation in close vessels, if the process be conducted
with common precautions, there is no source of difficulty
or danger ; and it may be easily assisted by artificial cold
in cases when gases approach near to that point of com-
pression and temperature at which they become vapours.

II. ON THE CONDENSATION OF SEVERAL
GASES INTO LIQUIDS*

Read April i o, 1823.

I HAD the honour, a few weeks since, of submitting
to the Royal Society a paper on the reduction of
chlorine to the liquid state. An important note was
added to the paper by the President, on the general
application of the means used in this case to the reduc-
tion of other gaseous bodies to the liquid state ; and
in illustration of the process, the production of liquid
muriatic acid was described. Sir HUMPHRY DAVY did
me the honour to request I would continue the experi-
ments, which I have done under his general direction,
and the following are some of the results already
obtained :

Sulphurous Acid.
Mercury and concentrated sulphuric acid were sealed

* [From Philosophical Transactions for 18,23, Vol. 113, pp. 189-198.]

Liquefaction of Gases. 1 1

up in a bent tube, and, being brought to one end, heat
was carefully applied, whilst the other end was preserved
cool by wet bibulous paper. Sulphurous acid gas was
produced where the heat acted, and was condensed by the
sulphuric acid above ; but, when the latter had become
saturated, the sulphurous acid passed to the cold end of
the tube, and was condensed into a liquid. When the
whole tube was cold, if the sulphurous acid were returned
on to the mixture of sulphuric acid and sulphate of mer-
cury, a portion was re-absorbed, but the rest remained on
it without mixing.

Liquid sulphurous acid is very limpid and colourless,
and highly fluid. Its refractive power, obtained by com-
paring it in water and other media, with water contained
in a similar tube, appeared to be nearly equal to that oi
water. It does not solidify or become adhesive at a
temperature of o° F. When a tube containing it was
opened, the contents did not rush out as with explosion,
but a portion of the liquid evaporated rapidly, cooling
another portion so much as to leave it in the fluid state
at common barometric pressure. It was however rapidly
dissipated, not producing visible fumes, but producing
the odour of pure sulphurous acid, and leaving the tube
quite dry. A portion of the vapour of the fluid received
over a mercurial bath, and examined, proved to be sul-
phurous acid gas. A piece of ice dropped into the fluid
instantly made it boil, from the heat communicated by it.

To prove in an unexceptionable manner that the fluid
was pure sulphurous acid, some sulphurous acid gas was
carefully prepared over mercury, and a long tube perfectly
dry, and closed at one end, being exhausted, was filled
with it ; more sulphurous acid was then thrown in by a
condensing syringe, till there were three or four atmo-
spheres ; the tube remained perfectly clear and dry, but
on cooling one end to o°, the fluid sulphurous acid con-

1 2 Faraday.

densed, and in all its characters was like that prepared
by the former process.

A small gage was attached to a tube in which sul-
phurous acid was afterwards formed, and at a temperature
of 45° F. the pressure within the tube was equal to three
atmospheres, there being a portion of liquid sulphurous
acid present : but as the common air had not been ex-
cluded when the tube was sealed, nearly one atmosphere
must be due to its presence, so that sulphurous acid
vapour exerts a pressure of about two atmospheres at
45° F. Its specific gravity was nearly 1.42.*

Sulphuretted hydrogen.

A tube being bent, and sealed at the shorter end,
strong muriatic acid was poured in through a small
funnel, so as nearly to fill the short leg without soiling
the long one. A piece of platinum foil was then crumpled
up and pushed in, and upon that were put fragments of

* I am indebted to Mr. DAVIES GILBERT, who examined with much
attention the results of these experiments, for the suggestion of the
means adopted to obtain the specific gravity of some of these fluids.
A number of small glass bulbs were blown and hermetically sealed ;
they were then thrown into alcohol, water, sulphuric acid, or mix-
tures of these, and when any one was found of the same specific
gravity as the fluid in which it was immersed, the specific gravity of
the fluid was taken : thus a number of hydrometrical bulbs were
obtained ; these were introduced into the tubes in which the sub-
stances were to be liberated ; and ultimately, the dry liquids ob-
tained, in contact with them. It was then observed whether they
floated or not, and a second set of experiments were made with
bulbs lighter or heavier as required, until a near approximation was
obtained. Many of the tubes burst in the experiments, and in others
difficulties occurred from the accidental fouling of the bulb by the
contents of the tube. One source of error may be mentioned in
addition to those which are obvious, namely, the alteration of the
bulk of the bulb by its submission to the pressure required to keep
the substance in the fluid state.

Liquefaction of Gases. 13

sulphuret of iron, until the tube was nearly full. In this
way action was prevented until the tube was sealed. If
it once commences, it is almost impossible to close the
tube in a manner sufficiently strong, because of the
pressing out of the gas. When closed, the muriatic acid
was made to run on to the sulphuret of iron, and then
left for a day or two. At the end of that time, much
proto-muriate of iron had formed, and on placing the
clean end of the tube in a mixture of ice and salt, warming
the other end if necessary by a little water, sulphuretted
hydrogen in the liquid state distilled over.

The liquid sulphuretted hydrogen was colourless,
limpid, and excessively fluid. Ether, when compared
with it in similar tubes, appeared tenacious and oily. It
did not mix with the rest of the fluid in the tube, which
was no doubt saturated, but remained standing on it.
When a tube containing it was opened, the liquid im-
mediately rushed into vapour ; and this being done under
water, and the vapour collected and examined, it proved
to be sulphuretted hydrogen gas. As the temperature of
a tube containing some of it rose from o° to 45°, part of
the fluid rose in vapour, and its bulk diminished; but
there was no other change : it did not seem more adhesive
at o° than at 45°. Its refractive power appeared to be
rather greater than that of water ; it decidedly surpassed
that of sulphurous acid. A small gage being introduced
into a tube in which liquid sulphuretted hydrogen was
afterwards produced, it was found that the pressure of
its vapour was nearly equal to 17 atmospheres at the
temperature of 50°.

The gages used were made by drawing out some tubes
at the blow-pipe table until they were capillary, and of a
trumpet form ; they were graduated by bringing a small
portion of mercury successively into their different parts ;
they were then sealed at the fine end, and a portion of

14 Faraday.

mercury placed in the broad end ; and in this state they
were placed in the tubes, so that none of the substances
used, or produced, could get to the mercury, or pass by
it to the inside of the gage. In estimating the number
of atmospheres, one has always been subtracted for the
air left in the tube.

The specific gravity of sulphuretted hydrogen appeared
to be 0.9.

Carbonic acid.

The materials used in the production of carbonic acid,
were carbonate of ammonia and concentrated sulphuric
acid ; the manipulation was like that described for sul-
phuretted hydrogen. Much stronger tubes are however
required for carbonic acid than for any of the former
substances, and there is none which has produced so
many or more powerful explosions. Tubes which have
held fluid carbonic acid well for two or three weeks
together, have, upon some increase in the warmth of the
weather, spontaneously exploded with great violence ;
and the precautions of glass masks, goggles, &c. which
are at all times necessary in pursuing these experiments,
are particularly so with carbonic acid.

Carbonic acid is a limpid colourless body, extremely
fluid, and floating upon the other contents of the tube.
It distils readily and rapidly at the difference of tempera-
ture between 32° and o°. Its refractive power is much
less than that of water. No diminution of temperature
to which I have been able to submit it, has altered its
appearance. In endeavouring to open the tubes at one
end, they have uniformly burst into fragments, with
powerful explosions. By inclosing a gage in a tube in
which fluid carbonic acid was afterwards produced, it
was found that its vapour exerted a pressure of 36
atmospheres at a temperature of 32°,

Liquefaction of Gases. 15

It may be questioned, perhaps, whether this and other
similar fluids obtained from materials containing water,
do not contain a portion of that fluid ; in as much as its
absence has not been proved, as it may be with chlorine,
sulphurous acid, cyanogen, and ammonia. But besides
the analogy which exists between the latter and the
former, it may also be observed in favour of their dryness,
that any diminution of temperature causes the deposition
of a fluid from the atmosphere, precisely like that pre-
viously obtained ; and there is no reason for supposing
that these various atmospheres, remaining as they do in
contact with concentrated sulphuric acid, are not as dry
as atmospheres of the same kind would be over sulphuric
acid at common pressure.

Euchlorine.

Fluid euchlorine was obtained by inclosing chlorate of
potash and sulphuric acid in a tube, and leaving them to
act on each other for 24 hours. In that time there had
been much action, the mixture was of a dark reddish
brown, and the atmosphere of a bright yellow colour.
The mixture was then heated up to 100°, and the un-
occupied end of the tube cooled to o° ; by degrees the
mixture lost its dark colour, and a very fluid ethereal
looking substance condensed. It was not miscible with
a small portion of the sulphuric acid which lay beneath
it ; but when returned on to the mass of salt and acid, it
was gradually absorbed, rendering the mixture of a much
deeper colour even than itself.

Euchlorine thus obtained is a very fluid transparent
substance, of a deep yellow colour. A tube containing a
portion of it in the clean end, was opened at the opposite
extremity ; there was a rush of euchlorine vapour, but
the salt plugged up the aperture : whilst clearing this

1 6 Faraday.

away, the whole tube burst with a violent explosion,
except the small end in a cloth in my hand, where
the euchlorine previously lay, but the fluid had all dis-
appeared.

Nitrous oxide.

Some nitrate of ammonia, previously made as dry as
could be by partial decomposition, by heat in the air,
was sealed up in a bent tube, and then heated in one
end, the other being preserved cool. By repeating the
distillation once or twice in this way, it was found, on
after-examination, that very little of the salt remained
undecomposed. The process requires care. I have had
many explosions occur with very strong tubes, and at
considerable risk.

When the tube is cooled, it is found to contain two
fluids, and a very compressed atmosphere. The heavier
fluid on examination proved to be water, with a little
acid and nitrous oxide in solution ; the other was nitrous
oxide. It appears in a very liquid, limpid, colourless
state; and so volatile that the warmth of the hand
generally makes it disappear in vapour. The application
of ice and salt condenses abundance of it into the liquid
state again. It boils readily by the difference of tempera-
ture between 50° and o°. It does not appear to have
any tendency to solidify at - 10°. Its refractive power is
very much less than that of water, and less than any fluid
that has yet been obtained in these experiments, or than
any known fluid. A tube being opened in the air, the
nitrous oxide immediately burst into vapour. Another
tube opened under water, and the vapour collected and
examined, it proved to be nitrous oxide gas. A gage
being introduced into a tube, in which liquid nitrous
oxide was afterwards produced, gave the pressure of its
vapour as equal to above 50 atmospheres at 45°,

Liquefaction of Gases. 17

Cyanogen.

Some pure cyanuret of mercury was heated until per-
fectly dry. A portion was then inclosed in a green glass
tube, in the same manner as in former instances, and
being collected to one end, was decomposed by heat,
whilst the other end was cooled. The cyanogen soon
appeared as a liquid : it was limpid,/colourless, and very
fluid ; not altering its state at the temperature of o°. Its
refractive power is rather less, perhaps, than that of water.
A tube containing it being opened in the air, the expan-
sion within did not appear to be very great ; and the
liquid passed with comparative slowness into the state
of vapour, producing great cold. The vapour, being
collected over mercury, proved to be pure cyanogen.

A tube was sealed up with cyanuret of mercury at one
end, and a drop of water at the other ; the fluid cyanogen
was then produced in contact with the water. It did not
mix, at least in any considerable quantity, with that fluid,
but flouted on it, being lighter, though apparently not so
much so as ether would be. In the course of some days,
action had taken place, the water had become black, and
changes, probably such as are known to take place in an
aqueous solution of cyanogen, occurred. The pressure
of the vapour of cyanogen appeared by the gage to be
3.6 or 3.7 atmospheres at 45° F. Its specific gravity was
nearly 0.9.

Ammonia.

In searching after liquid ammonia, it became necessary,
though difficult, to find some dry source of that substance;
and I at last resorted to a compound of it, which I had
occasion to notice some years since with chloride of silver.*
When dry chloride of silver is put into ammoniacal gas,

* Quarterly Journal of Science, Vol. V. p. 74.
B

1 8 Faraday.

as dry as it can be made, it absorbs a large quantity of
it; 100 grains condensing above 130 cubical inches of
the gas : but the compound thus formed is decomposed
by a temperature of 100° F. or upwards. A portion of
this compound was sealed up in a bent tube and heated
in one leg, whilst the other was cooled by ice or water.
The compound thus heated under pressure fused at a
comparatively low temperature, and boiled up, giving off
ammoniacal gas, which condensed at the opposite end
into a liquid.

Liquid ammonia thus obtained was colourless, trans-
parent, and very fluid. Its refractive power surpassed
that of any other of the fluids described, and that also of
watef itself. From the way in which it was obtained, it
was evidently as free from water as ammonia in any state
could be. When the chloride of silver is allowed to cool,
the ammonia immediately returns to it, combining with
it, and producing the original compound. During this
action a curious combination of effects takes place : as
the chloride absorbs the ammonia, heat is produced, the
temperature rising up nearly to 100°; whilst a few inches
off, at the opposite end of the tube, considerable cold is
produced by the evaporation of the fluid. When the
whole is retained at the temperature of 60°, the ammonia
boils till it is dissipated and re-combined. The pressure
of the vapour of ammonia is equal to about 6.5 atmo-
spheres at 50°. Its specific gravity was 0.76.

Muriatic add.

When made from pure muriate of ammonia and sul-
phuric acid, liquid muriatic acid is obtained colourless,
as Sir HUMPHRY DAVY had anticipated. Its refractive
power is greater than that of nitrous oxide, but less than
that of water ; it is nearly equal to that of carbonic acid.

Liquefaction of Gases. 19

The pressure of its vapour at the temperature of 50°, is
equal to about 40 atmospheres.

Chlorine.

The refractive power of fluid chlorine is rather less
than that of water. The pressure of its vapour at 60° is
nearly equal to 4 atmospheres.

Attempts have been made to obtain hydrogen, oxygen,
fluoboracic, fluosilicic, and phosphuretted hydrogen gases
in the liquid state; but though all of them have been
subjected to great 'pressure, they have as yet resisted
condensation. The difficulty with regard to fluoboric
gas consists, probably, in its affinity for sulphuric acid,
which, as Dr. DAVY has shown, is so great as to raise the
sulphuric acid with it in vapour. The experiments will
however be continued on these and other gases, in the
hopes that some of them, at least, will ultimately con-
dense.

III. HISTORICAL STATEMENT RESPECT-
ING THE LIQUEFACTION OF GASES*.

1WAS not aware at the time when I first observed the
liquefaction of chlorine gasf, nor until very lately,
that any of the class of bodies called gases, had been
reduced into the fluid form ; but, having during the last
few weeks sought for instances where such results might
have been afforded without the knowledge of the experi-
menter, I was surprised to find several recorded cases.
I have thought it right therefore to bring these cases

* [From The Quarterly Journal of Science, vol. xvi. (January
1824), pp. 229-240.]
t Phil. Transactions, 1823, pp. 160, 189.

2O Faraday.

together, and only justice to endeavour to secure for
them a more general attention, than they appear as yet
to have gained. I shall notice in chronological order,
the fruitless, as well as the successful, attempts, and
those which probably occurred without being observed,
as well as those which were remarked and described
as such.

Carbonic Acid, &c. — The Philosophical Transactions
for 1797, contain, p. 222, an account of experiments made
by Count Rumford, to determine the force of fired gun-
powder. Dissatisfied both with the deductions drawn, and
the means used previously, that philosopher proceeded to
fire gunpowder in cylinders of a known diameter and
capacity, and closed by a valve loaded with a weight that
could be varied at pleasure. By making the vessel strong
enough and the weight sufficiently heavy, he succeeded
in confining the products within the space previously
occupied by the powder. The Count's object induced
him to vary the quantity of gunpowder in different ex-
periments, and to estimate the force exerted only at the
moment of ignition, when it was at its maximum. This
force which he found to be prodigious, he attributes to
aqueous vapour intensely heated, and makes no reference
to the force of the gaseous bodies evolved. Without
considering the phenomena which it is the Count's object
to investigate, it may be remarked, that in many of the
experiments made by him, some of the gases, and especi-
ally carbonic acid gas, were probably reduced to the
liquid state. The Count says,

" When the force of the generated elastic vapour was
sufficient to raise the weight, the explosion was attended
by a very sharp and surprisingly loud report ; but when
the weight was not raised, as also when it was only a
little moved, but not sufficiently to permit the leather
stopper to be driven quite out of the bore, and the

Liquefaction of Gases. 21

elastic fluid to make its escape, the report was scarcely
audible at the distance of a few paces, and did not at
all resemble the report which commonly attends the
explosion of gunpowder. It was more like the noise
which attends the breaking of a small glass tube, than
any thing else to which it could be compared. In many
of the experiments, in which the elastic vapour was
confined, this feeble report attending the explosion of
the powder, was immediately followed by another noise
totally different from it, which appeared to be occasioned
by the falling back of the weight upon the end of the
barrel, after it had been a little raised, but not sufficiently
to permit the leather stopper to be driven quite out of the
bore. In some of these experiments a very small part
only of the generated elastic fluid made its escape, in
these cases the report was of a peculiar kind, and though
perfectly audible at some considerable distance, yet not
at all resembling the report of a musket. It was rather
a very strong sudden hissing, than a clear distinct and
sharp report."

In another place it is said, " What was very remark-
able in all these experiments, in which the generated
elastic vapour was completely confined, was the small
degree of expansive force which this vapour appeared to
possess, after it had been suffered to remain a few minutes,
or even only a few seconds, confined in the barrel ; for
upon raising the weight, by means of its lever, and suffer-
ing this vapour to escape, instead of escaping with a loud
report it rushed out with a hissing noise, hardly so loud
or so sharp as the report of a common air-gun, and its
effects against the leather stopper, by which it assisted
in raising the weight, were so very feeble as not to be
sensible." This the Count attributes to the formation of
a hard mass, like a stone, within the cylinder, occasioned
by the condensation of what was, at the moment of igni-

22 Faraday.

tion, an elastic fluid. Such a substance was always found
in these cases ; but when the explosion raised the weight
and blew out the stopper, nothing of this kind remained.

The effects here described both of elastic force and its
cessation on cooling, may evidently be referred as much
to carbonic acid and perhaps other gases as to water.
The strong sudden hissing observed as occurring when
only a little of the products escaped, may have been due
to the passage of the gases into the air, with comparatively
but little water, the circumstances being such as were not
sufficient to confine the former, though they might the
latter ; for it cannot be doubted but that in similar cir-
cumstances, the elastic force of carbonic acid would far
surpass that of water. Count Rumford says, that the
gunpowder made use of, when well shaken together,
occupied rather less space than an equal weight of water.
The quantity of residuum before referred to, left by a
given weight of gunpowder, is not mentioned, so that the
actual space occupied by the vapour of water, carbonic
acid, &c., at the moment of ignition, cannot be inferred ;
there can, however, be but little doubt that when perfectly
confined they were in the state of the substances, in M.
Cagniard de la Tour's experiments*.

When allowed to remain a few minutes, or even
seconds, the expansive force at first observed, diminished
exceedingly, so as scarcely to surpass that of the air in
a charged air-gun. Of course all that was due to the
vaporization of water and some of the other products
would cease, as soon as the mass of metal had absorbed
the heat, and they would concrete into the hard substance
found in the cylinder : but it does not seem too much to
suppose, that so much carbonic acid was generated in the
combustion, as would, if confined, on the cooling of the

* See vol. xv* p. 145, of this Journal.

Liquefaction of Gases. 23

apparatus, have been equal to many atmospheres, but that
being condensible, a part became liquid, and thus assisted
in reducing the force within, to what it was found to be.

Ammonia. — I find the condensation of ammoniacal gas
referred to in Thomson's System, first edition, i. 405,
and other editions; Henry's Chemistry, i. 237; Accum's
Chemistry, i. 310; Murray's Chemistry, ii. 73; and
Thenard' s Traite de Chimie, ii. 133. Mr. Accum refers
to the experiments of Fourcroy and Vauquelin, Ann.
de Chimie, xxix. 289, but has mistaken their object.
Those chemists used highly saturated solution of am-
monia, see pp. 281, 286, and not the gas; and their
experiments on gases, namely, sulphurous acid gas, muri-
atic acid gas, and sulphuretted hydrogen gas, they state
were fruitless, p. 287. "All we can say is, that the con-
densation of most of these gases was above three fourths
of their volume."

Thomson, Henry, Murray, and, I suppose, Thenard,
refer to the experiments of Guyton de Morveau, Ann.
de Chimie, xxix. 291, 297. Thomson states the result
of liquefaction at a temperature of- 45°, without referring
to the doubt, that Morveau himself raises, respecting the
presence of water in the gas ; but Murray, Henry, and
Thenard, in their statements notice its probable presence.
Morveau's experiment was made in the following manner :
a glass retort was charged with the usual mixture of
muriate of ammonia, and quick lime, the former material
being sublimed, and the latter carefully made from white
marble, so as to exclude water as much as possible. The
beak of the retort was then adapted to an apparatus con-
sisting of two balloons, and two flasks successively con-
nected together, and luted by fat lute. The balloons were
empty, the first flask contained mercury, the second,
water. Heat was then applied to the retort, and the first
globe cooled to - 21. 25°C., aqueous vapours soon rose,

24 Faraday.

which condensed as water in the neck of the retort, and
as ice in the first balloon. Continuing the heat, ammoni-
acal gas was disengaged, and it escaped by the last flask
containing water, without anything being perceived in the
second balloon. This balloon was then cooled to - 43.25°
C., and then drops of a fluid lined its interior, and ulti-
mately united at the bottom of the vessel. When the
thermometer in the cooling mixture stood at - 36.25°C.,
the fluid already deposited preserved its state, but no
further portions were added to it ; reducing the tempera-
ture again to -4i°C., and hastening the disengagement
of ammoniacal gas, the liquid in the second balloon
augmented in volume. Very little gas escaped from the
last flask, and the pressure inwards was such as to force
the oil of the lute into the balloon where it congealed.
Finally, the apparatus was left to regain the temperature
of the atmosphere, and as it approached to it, the liquid
of the second balloon became gaseous. The fluid in the
first balloon became liquid, as soon as the temperature
had reached - 2i.25°C.

M. Morveau remarks on this experiment, that it ap-
pears certain that ammoniacal gas made as dry as it can
be, by passing into a vessel in which water would be
frozen, and reduced to a temperature of -2i°C., con-
denses into a liquid at the temperature of -48°C, and
resumes its elastic form again as the temperature is
raised; but he proposes to repeat the experiment and
examine whether a portion of the gas so dried, when
received over mercury would not yield water to well
calcined potash, "for as it is seen that water charged
with a little of the gas, remained liquid in the first
balloon, at a temperature of -21°, it is possible that a
much smaller quantity of water united to a much larger
quantity of the gas, would become capable of resisting a
temperature of - 48°C.

Liquefaction of Gases. 25

Sir H. Davy, who refers to this experiment in his
Elements of Chemical Philosophy, p. 267, urges the un-
certainty attending it, on the same grounds that Morveau
himself had done; and now that the strength of the
vapour of dry liquid ammonia is known, it cannot be
doubted that M. Morveau had obtained in his second
balloon only a very concentrated solution of ammonia in
water. I find that the strength of the vapour of ammonia
dried by potash, is equal to about that of 6.5 atmospheres
at 50° F*. and according to all analogy it would require
a very intense degree of cold, and one at present beyond
our means, to compensate this power and act as an
equivalent to it.

Sulphurous Acid Gas. — It is said that sulphurous acid
gas has been condensed into a fluid by Monge and
Clouet, but I have not been able to find the description
of their process. It is referred to by Thomson, in his
System, first edition, ii. 24, and in subsequent editions ;
by Henry, in his Elements, i. 341 ; by Accum, in his
Chemistry, i. 319 ; by Aikin, Chemical Dictionary, ii. 391 ;
by Nicholson, Chemical Dictionary, article, gas (Sulphur-
ous acid) ; and by Murray, in his System, ii. 405. All
these authors mention the simultaneous application of
cold and pressure, but Thomson alone refers to any
authority, and that is Fourcroy, ii. 74.

It is curious that Fourcroy does not, however, mention
condensation as one of the means employed by Monge
and Clouet, but merely says the gas is capable of lique-
faction at 28° of cold. "This latter property," he adds,
" discovered by citizens Monge and Clouet, and by which
it is distinguished from all the other gases, appears to be
owing to the water which it holds in solution, and to
which it adheres so strongly as to prevent an accurate

* Philosophical Transactions, 1823, p. 197.

26 Faraday.

estimate of the proportions of its radical and acidifying
principles."

Notwithstanding Fourcroy's objection, there can be
but little reason to doubt that Monge and Clouet did
actually condense the gas, for I have since found that
from the small elastic force of its vapour at common
temperatures (being equal to that of about two atmo-
spheres only *) a comparatively moderate diminution of
temperature is sufficient to retain it fluid at common
pressure, or a moderate additional pressure to retain it so
at common temperature ; so that whether these philoso-
phers applied cold only as Fourcroy mentions, or cold
and pressure, as stated by the other chemists, they would
succeed in obtaining it in the liquid form.

Chlorine. — M. de Morveau, whilst engaged on the appli-
cation of the means best adapted to destroy putrid effluvia
and contagious miasmata, was led to the introduction of
chlorine as the one most excellent for this purpose ; and
he proposed the use of phials, containing the requisite
materials, as sources of the substance. One described
in his Trait'e des Moyens de d'esinfecter Pair (1801),
was of the capacity of two cubical inches nearly ; about
62 grains of black oxide of manganese in coarse powder
was introduced, and then the bottle two-thirds filled with
nitro-muriatic acid ; it was shaken, and in a short time
chlorine was abundantly disengaged. M. Morveau re-
marks upon the facility with which the chlorine is retained
in these bottles ; one, thus prepared, and forgotten, when
opened at the end of eight years, gave an abundant odour
of chlorine.

I had an impression on my mind that M. de Morveau
had proposed the use of phials similarly charged, but
made strong, well stoppered, and confined by a screw in

* Philosophical Transaction 's, 1823, p. 192.

Liquefaction of Gases. 27

a frame, so that no gas should escape, except when the
screw and stopper were loosened ; but I have searched for
an account of such phials without being able to find any.
If such have been made, it is very probable that in some
circumstances, liquid chlorine has existed in them, for
as its vapour at 6o°F. has only a force of about four
atmospheres*, a charge of materials might be expected
frequently to yield much more chlorine than enough to
fill the space, and saturate the fluid present ; and the
excess would of course take the liquid form. If such
vessels have not been made, our present knowledge of
the strength of the vapour of chlorine will enable us to
construct them of a much more convenient and portable
form than has yet been given to them.

Arseniuretted Hydrogen. — This is a gas which it is said
has been condensed so long since as 1805. The experi-
ment was made by Stromeyer, and was communicated,
with many other results relating to the same gas, to the
Gottingen Society, Oct. 12, 1805. See Nicholson's Journal \
xix. 382; also, Thenard Traite de Chimie, i. 373 ; Brande's
Manual, ii. 212; and A?males de Chimie, Ixiv. 303.
None of these contain the original experiment ; but
the following quotation is from Nicholson's Journal.
The gas was obtained over the pneumatic apparatus,
by digesting an alloy of fifteen parts tin and one part
arsenic, in strong muriatic acid. "Though the arseni-
cated hydrogen gas retains its aeriform state under every
known degree of atmospheric temperature and pressure,
Professor Stromeyer condensed it so far as to reduce it
in part to a liquid, by immersing it in a mixture of snow
and muriate of lime, in which several pounds of quick-
silver had been frozen in the course of a few minutes."
From the circumstance of its being reduced only in part

* Ibid. p. 198,

28 Faraday.

to a liquid, we may be led to suspect that it was rather
the moisture of the gas that was condensed than the gas
itself; a conjecture which is strengthened in my mind
from finding that a pressure of three atmospheres was
insufficient to liquefy the gas at a temperature of o°F.

Chlorine. — The most remarkable and direct experiments
I have yet met with in the course of my search after such
as were connected with the condensation of gases into
liquids, are a series made by Mr. Northmore, in the
years 1805-6. It was expected by this gentleman "that
the various affinities which take place among the gases
under the common pressure of the atmosphere, would
undergo considerable alteration by the influence of-
condensation ; " and it was with this in view that the
experiments were made and described. The results of
liquefaction were therefore incidental, but at present it
is only of them I wish to take notice. Mr. Northmore's
papers may be found in Nicholson's Jotirnal, xii. 368,
xiii. 233. In the first is described his apparatus,
namely, a brass condensing pump ; pear-shaped glass
receivers, containing from three and a half to five cubic
inches, and a quarter of an inch thick ; and occasionally
a syphon gauge. Sometimes as many as eighteen atmo-
spheres were supposed to have been compressed into the
vessel, but it is added, that the quantity cannot be de-
pended on, as the tendency to escape even by the side
of the piston, rendered its confinement very difficult.

Now that we know the pressure of the vapour of
chlorine, there can be no doubt that the following
passage describes a true liquefaction of that gas. "Upon
the compression of nearly two pints of oxygenated muri-
atic acid gas in a receiver, two and a quarter cubic inches
capacity, it speedily became converted into a yellowy?///^,
of such extreme volatility, under the common pressure of
the atmosphere, that it instantly evaporated upon open-

Liquefaction of Gases. 29

ing the screw of the receiver ; I need not add, that this
fluid, so highly concentrated, is of a most insupportable
pungency." " There was a trifling residue of a yellowish
substance left after the evaporation, which probably arose
from a small portion of the oil and grease used in the
machine," &c. xiii. 234.

Muriatic Acid. — Operating upon muriatic acid, Mr.
Northmore obtained such results as induced him to
state he could liquefy it in any quantity, but as the
pressure of its vapour at 5o°F. is equal to about
40 atmospheres*, he must have been mistaken. The
following is his account : "I now proceeded to the
muriatic acid gas, and upon the condensation of
a small quantity of it, a beautiful green-coloured sub-
stance adhered to the side of the receiver, which had all
the qualities of muriatic acid ; but upon a large quantity,
four pints, being condensed, the result was a yellowish
green glutinous substance, which does not evaporate, but
is instantly absorbed by a few drops of water ; it is of a
highly pungent quality, being the essence of muriatic
acid. As this gas easily becomes fluid, there is little or no
elasticity, so that any quantity may be condensed without
danger. My method of collecting this and other gases,
which are absorbable by water, is by means of an ex-
hausted Florence flask, (and in some cases an empty
bladder) connected by a stop cock with the extremity of
the retort." xiii. 235. It seems probable that the facility
of condensation, and even combination, possessed by
muriatic acid gas in contact with oil of turpentine, may
belong to it under a little pressure, in contact with
common oil, and thus have occasioned the results Mr.
Northmore describes.

Sulphurous Acid Gas. — With regard to this gas, Mr.

Philosophical Transactions, 1823, p. 198.

OF THE

I UNIVERSITY

OF

^LIFOR^

3O Faraday.

Northmore says, " having collected about a pint and
a half of sulphurous acid gas, I proceeded to con-
dense it in the three cubic inch receiver, but after
a very few pumps the forcing piston became im-
moveable, being completely choked by the operation
of the gas. A sufficient quantity had, however, been
compressed to form vapour, and a thick slimy fluid, of a
dark yellow colour, began to trickle down the sides of the
receiver, which immediately evaporated with the most
suffocating odour upon the removal of the pressure."
xiii. 236. This experiment, Mr. Northmore remarks,
corroborates the assertion of Monge and Clouet, that by
cold and pressure they had condensed this gas. The
fluid above described was evidently contaminated with
oil, but from its evaporation on removing the pressure,
and from the now ascertained low pressure of the vapour
of sulphurous acid, there can be no hesitation in ad-
mitting that it was sulphurous acid liquefied.

The results obtained by Mr. Northmore, with chlorine
gas and sulphurous acid gas, are referred to by Nicholson,
in his Chemical Dictionary, 8vo. Articles, Gas (muriatic
acid oxygenized) and Gas (sulphurous acid) ; and that of
chlorine is referred to by Murray, in his System, ii.
550; although at page 405 of the same volume, he says
that, only sulphurous acid " and ammonia of these gases
that are at natural temperatures permanently elastic, have
been found capable of this reduction."

Carbonic Acid. — Another experiment in which it is very
probable that liquid carbonic acid has been produced, is
one made by Mr. Babbage, about the year 1813^ The
object Mr. Babbage had in view, was to ascertain whether
pressure would prevent decomposition, and it was expected
that either that would be the case, or that decomposition
would go on, and the rock be split by the expansive
force of carbonic acid gas. The place was Chudley

Liquefaction of Gases. 31

rocks, Devonshire, where the limestone is dark and of a
compact texture. A hole, about 30 inches deep and two
inches in diameter, was made by the workmen in the
usual way, it penetrated directly downwards into the
rock; a quantity of strong muriatic acid, equal to perhaps
a pint and a half, was then poured in, and immediately a
conical wooden plug, that had previously been soaked in
tallow, was driven hard into the mouth of the hole. The
persons about then retired to a distance to watch the
result, but nothing apparent happened, and, after waiting
some time, they left the place. The plug was not loosened
at the time, nor was any further examination of the state
of things made : but it is very probable that if the rock
were sufficiently compact in that part, the plug tight, and
the muriatic acid in sufficient quantity, that a part of the
carbonic acid had condensed into a liquid, and thus,
though it permitted the decomposition, prevented that
development of power which Mr. Babbage expected would
have torn the rock asunder.

Oil Gas Vapour. — An attempt has been made by
Mr Gordon, within the last few years, and is still con-
tinued, to introduce condensed gas into use in the
construction of portable, elegant, and economical gas
lamps. Oil gas has been made use of, and, I be-
lieve, as many as thirty atmospheres have been thrown
into vessels, which, furnished with a stop cock and
jet, have afterwards allowed of its gradual expansion
and combustion. During the condensation of the
gas in this manner, a liquid has been observed to
deposit from it. It is not, however, a result of the
liquefaction of the gas, but the deposition of a vapour
(using the terms gas and vapour in their common
acceptation) from it, and when taken out of the vessel it
remains a liquid at common temperatures and pressures ;
may be purified by distillation, in the ordinary way, and

32 baraday.

will even bear a temperature of i7o°F. before it boils, at
ordinary pressure. It is the substance referred to by Dr
Henry, in the Philosophical Transactions, 1821, p. 159.

There is no reason for believing that oil gas, or olefiant
gas, has, as yet, been condensed into a liquid, or that it
will take that form at common temperatures under a
pressure of five, or ten, or even twenty atmospheres. If
it were possible, a small, safe, and portable gas lamp
would immediately offer itself to us, which might be
filled with liquid without being subject to any greater
force than the strength of its vapour, and would afford
an abundant supply of gas as long as any of the liquid
remained. Immediately upon the condensation of cyan-
ogen, which takes place at 5o°F. at a pressure under
four atmospheres, I made such a lamp with it. It suc-
ceeded perfectly, but, of course, either the expense of the
gas, the faint light of its flame, or its poisonous qualities,
would preclude its application. But we may, perhaps,
without being considered extravagant, be allowed to
search in the products of oil, resins, coal, &c., distilled,
or otherwise treated, with this object in view, for a sub-
stance, which being a gas at common temperatures and
pressure, shall condense into a liquid, by a pressure of
from two to six or eight atmospheres, and which being
combustible, shall afford a lamp of the kind described*.

Atmospheric Air. — As my object is to draw attention
to the results obtained in the liquefaction of gases before
the date of those described in the Philosophical Trans-
actions for 1823, I need not, perhaps, refer to the notice
given in the Annals of Philosophy ', N.S. vi. 66, of the
supposed liquefaction of atmospheric air, by Mr. Perkins,
under a pressure of about noo atmospheres, but as such

* In reference to the probability of such results, see a paper " On
Olefiant Gas." Annals of Philosophy, N.S. iii. 37.

Liquefaction of Gases. 33

a result would be highly interesting, and is the only
additional one on the subject I am acquainted with, I
am desirous of doing so, as well also to point out the
remarkable difference between that result and those
which are the subject of this and the other papers re-
ferred to. Mr. Perkins informed me that the air upon
compression disappeared, and in its place was a small
quantity of a fluid, which remained so when the pressure
was removed, which had little or no taste, and which did
not act on the skin. As far as I could by inquiry make
out its nature, it resembled water, but if upon repetition
it be found really to be the product of compressed
common air, then its fixed nature shews it to be a result
of a very different kind to those mentioned above, and
necessarily attended by far more important consequences.

IV. ON THE LIQUEFACTION AND SOLID-
IFICATION OF BODIES GENERALLY
EXISTING AS GASES*

Received December 19, 1844, — Read January 9, 1845.

THE experiments formerly made on the liquefaction
of gases, t and the results which from time to
time have been added to this branch of knowledge,
especially by M. THILORIER,| have left a constant desire
on my mind to renew the investigation. This, with con-
siderations arising out of the apparent simplicity and
unity of the molecular constitution of all bodies when in

* [From Philosophical Transactions for 1845, Vol. 135, pp. 155-
I77-]

t Philosophical Transactions, 1823, pp. 160, 189.
Annales cle Chimie, 1835, Ix. 427, 432.
C

34 Faraday.

the gaseous or vaporous state, which may be expected,
according to the indications given by the experiments of
M. CAGNIARD ^DE LA TOUR, to pass by some simple law
into their liquid state, and also the hope of seeing
nitrogen, oxygen, and hydrogen, either as liquid or solid
bodies, and the latter probably as a metal, have lately
induced me to make many experiments on the subject ;
and though my success has not been equal to my desire,
still I hope some of the results obtained, and the means
of obtaining them, may have an interest for the Royal
Society ; more especially as the application of the latter
may be carried much further than I as yet have had
opportunity of applying them. My object, like that of
some others, was to subject the gases to considerable pres-
sure with considerable depression of temperature. To
obtain the pressure, I used mechanical force, applied by
two air-pumps fixed to a (table. The first pump had a
piston of an inch in diameter, and the second a piston of
only half an inch in diameter ; and these were so asso-
ciated by a connecting pipe, that the first pump forced
the gas into and through the valves of the second, and
then the second could be employed to throw forward this
gas, already condensed to ten, fifteen, or twenty atmo-
spheres, into its final recipient at a much higher pressure.
The gases to be experimented with were either pre-
pared and retained in gas holders or gas jars, or else,
when the pumps were dispensed with, were evolved in
strong glass vessels, and sent under pressure into the
condensing tubes. When the gases were over water, or
likely to contain water, they passed, in their way from the
air-holder to the pump, through a coil of thin glass tube
retained in a vessel filled with a good mixture of ice and
salt, and therefore at the temperature of o° FAHR. ; the
water that was condensed here was all deposited in the
first two inches of the coil.

Liquefaction of Gases.

35

Fig. 1.

The condensing tubes were of green bottle glass,
being from ^th to Jth of an inch external diameter, and
from T\d to ^Vtn °f an mcn m thickness. They were
chiefly of two kinds, about eleven and nine
inches in length ; the one, when horizontal,
having a curve downward near one end to
dip into a cold bath, and the other, being in
form like an inverted siphon, could have the
bend cooled also in the same manner when
necessary. Into the straight part of the hori-
zontal tube, and the longest leg of the siphon
tube, pressure gauges were introduced when
required.

Caps, stop-cocks and connecting pieces
were employed to attach the glass tubes to
the pumps, and these, being of brass, were
of the usual character of those employed
for operations with gas, except that they were
small and carefully made. The caps were of such size
that the ends of the glass tubes entered freely into them,
and had rings or a female screw worm cut in the interior,

Fig. 2.

against which the cement was to adhere. The ends of
the glass tubes were roughened by a file, and when a cap
was to be fastened on, both it and the end of the tube
were made so warm that the cement*, when applied, was
thoroughly melted in contact with these parts, before the
tube and cap were brought together and finally adjusted

* Five parts of resin, one part of yellow bees'-wax, and one part
of red ochre, by weight, melted together.

36 Faraday.

to each other. These junctions bore a pressure of
thirty, forty, and fifty atmospheres, with only one failure,
in above one hundred instances ; and that produced no
complete separation of parts, but simply a small leak.

The caps, stop-cocks, and connectors, screwed one
into the other, having one common screw thread, so as
to be combined in any necessary manner. There were
also screw plugs, some solid, with a male screw to close
the openings or ends of caps, &c., others with a female
screw to cover and close the ends of stop-cocks. All
these screw joints were made tight by leaden washers ;
and by having these of different thickness, equal to from
fth to yth of the distance between one turn of the
screw thread and the next, it was easy at once to select
the washer which should allow a sufficient compression
in screwing up to make all air-tight, and also bring every
part of the apparatus into its right position.

I have often put a pressure of fifty atmospheres into
these tubes, and have had no accident or failure (except
the one mentioned). With the assistance of Mr. ADDAMS
I have tried their strength by a hydrostatic press, and
obtained the following results : — A tube having an ex-
ternal diameter of 0.24 of an inch and a thickness of
0.0175 of an inch, burst with a pressure of sixty-seven
atmospheres, reckoning one atmosphere as 15 Ib. on the
square inch. A tube which had been used, of the shape
of fig, i, its external diameter being 0.225 °f an inch,
and its thickness about 0.03 of an inch, sustained a
pressure of 118 atmospheres without breaking, or any
failure of the caps or cement, and was then removed for
further use.

A tube such as I have employed for generating gases
under pressure, having an external diameter of 0.6 of an
inch, and a thickness of 0.035 °f an inch, burst at
twenty-five atmospheres.

Liquefaction of Gases. 37

Having these data, it was easy to select tubes abun-
dantly sufficient in strength to sustain any force which
was likely to be exerted within them in any given ex-
periment.

The gauge used to estimate the degree of pressure to
which the gas within the condensing tube was subjected
was of the same kind as those formerly described,* being
a small tube of glass closed at one end with a cylinder
of mercury moving in it. So the expression of ten or
twenty atmospheres, means a force which is able to com-
press a given portion of air into y^tti or ^Vtn °f ^ts Du^
at the pressure of one atmosphere of thirty inches of
mercury. These gauges had their graduation marked on
them with a black varnish, and also with Indian ink : —
there are several of the gases which, when condensed,
cause the varnish to liquefy, but then the Indian ink stood.
For further precaution, an exact copy of the gauge was
taken on paper, to be applied on the outside of the con-
densing tube. In most cases, when the experiment was
over, the pressure was removed from the interior of the
apparatus, to ascertain whether the mercury in the gauge
would return back to its first or starting-place.

For the application of cold to these tubes a bath of
THILORIER'S mixture of solid carbonic acid and ether was
used. An earthenware dish of the capacity of four cubic
inches or more was fitted into a similar dish somewhat
larger, with three or four folds of dry flannel intervening,
and then the bath mixture was made in the inner dish.
Such a bath will easily continue for twenty or thirty
minutes, retaining solid carbonic acid the whole time ;
and the glass tubes used would sustain sudden immersion
in it without breaking.

But as my hopes of any success beyond that heretofore

i

* Philosophical Transactions, 1823, p. 192,

38 Far fid ay.

obtained depended more upon depression of temperature
than on the pressure which I could employ in these
tubes, I endeavoured to obtain a still greater degree of
cold. There are, in fact, some results producible by cold
which no pressure may be able to effect. Thus, solidi-
fication has not as yet been conferred on a fluid by
any degree of pressure. Again, that beautiful condition
which CAGNIARD DE LA TOUR has made known, and
which comes on with liquids at a certain heat, may have
its point of temperature for some of the bodies to be
experimented with, as oxygen, hydrogen, nitrogen, &c.,
below that belonging to the bath of carbonic acid and
ether ; and, in that case, no pressure which any apparatus
could bear would be able to bring them into the liquid
or solid state.

To procure this lower degree of cold, the bath of
carbonic acid and ether was put into an air-pump, and
the air and gaseous carbonic acid rapidly removed. In
this way the temperature fell so low, that the vapour of
carbonic acid given off by the bath, instead of having a
pressure of one atmosphere, had only a pressure of ^j-th
of an atmosphere, or 1.2 inch of mercury; for the air-
pump barometer could be kept at 28.2 inches when the
ordinary barometer was at 29.4. At this low temperature
the carbonic acid mixed with the ether was not more
volatile than water at the temperature of 86°, or alcohol
at ordinary temperatures.

In order to obtain some idea of this temperature, I
had an alcohol thermometer made, of which the gradua-
tion was carried below 32° FAHR., by degrees equal in
capacity to those between 32° and 212°. When this
thermometer was put into the bath of carbonic acid and
ether surrounded by the air, but covered over with paper,
it gave the temperature of 106° below o°. When it was
introduced into the bath under the air-pump, it sank to the

Liquefaction of Gases.

39

when the mercury in
pump barometer

the air-
was i
10

20

22

24
26

...

27
28
28.2

temperature of 166° below o° ; or 60° below the tempera-
ture of the same bath at the pressure of one atmosphere,
i.e. in the air. In this state the ether was very fluid, and
the bath could be kept in good order for a quarter of an
hour at a time.

As the exhaustion proceeded I observed the tempera-
ture of the bath and the corresponding pressure, at certain
other points, of which the following may be recorded : —
The external barometer was 29.4 inches :

inch. FAHR.

the bath temperature was — 106,

... —121,"'
... —125,

••• —139!
... —146,
— 160,
... —i 66,

but as the thermometer takes some time to acquire the
temperature of the bath, and the latter was continually
falling in degree ; as also the alcohol thickens consider-
ably at the lower temperature, there is no doubt that the
degrees expressed are not so low as they ought to be,
perhaps even by 5° or 6° in most cases.

With dry carbonic acid under the air-pump receiver
I could raise the pump barometer to twenty-nine inches
when the external barometer was at thirty inches.

The arrangement by which this cooling power was
combined in its effect on gases with the pressure of the
pumps, was very simple in principle. An air-pump re-
ceiver open at the top was employed ; the brass plate
which closed the aperture had a small brass tube about
six inches long, passing through it air-tight by means of
a stuffing-box, so as to move easily up and down in a
vertical direction. One of the glass condensing siphon
tubes, already described, fig. i, was screwed on to the
lower end of the sliding tube, and the upper end of the

4O Faraday.

latter was connected with a communicating tube in two
lengths, reaching from it to the condensing pumps ; this
tube was small, of brass, and 9 J feet in length ; it passed
six inches horizontally from the condensing pumps, then
rose vertically for two feet, afterwards proceeded horizon-
tally for seven feet, and finally turned down and was
immediately connected with the sliding tube. By this
means the latter could be raised and lowered vertically,
without any strain upon the connections, and the con-
densing tube lowered into the cold bath in vacuo^ or
raised to have its contents examined at~pleasure. The
capacity of the connecting tubes beyond the last con-
densing pump was only two cubic inches.

When experimenting with any particular gas, the
apparatus was put together fast and tight, except the
solid terminal screw-plug at the short end of the con-
densing tube, which being the very extremity of the
apparatus, was left a little loose. Then, by the con-
densing pumps, abundance of gas was passed through
the apparatus to sweep out every portion of air, after
which the terminal plug was screwed up, the cold bath
arranged, and the combined effects of cold and pressure
brought to unite upon the gas.

There are many gases which condense at less than
the pressure of one atmosphere when submitted to the
cold of a carbonic acid bath in air (which latter can upon
occasions be brought considerably below — 106° FAHR.).
These it was easy, therefore, to reduce, by sending them
through small conducting tubes into tubular receivers
placed in the cold bath. When the receivers had pre-
viously been softened in a spirit lamp flame, and narrow
necks formed on them, it was not difficult by a little
further management, hermetically to seal up these sub-
stances in their condensed state. In this manner chlorine,
cyanogen, ammonia, sulphuretted hydrogen, arseniuretted

Liquefaction of Gases. 41

hydrogen, hydriodic acid, hydrobromic acid, and even
carbonic acid, were obtained, sealed up in tubes in the
liquid state ; and euchlorine was also secured in a tube
receiver with a cap and screw-plug. By using a carbonic
acid bath, first cooled in vacuo, there is no doubt other
condensed gases could be secured in the same way.

The fluid carbonic acid was supplied to me by Mr.
ADDAMS, in his perfect apparatus/ in portions of about
220 cubic inches each. The solid carbonic acid, when
produced from it, was preserved in a glass ; itself retained
in the middle of three concentric glass jars, separated
from each other by dry jackets of woollen cloth. So
effectual was this arrangement, that I have frequently
worked for a whole day of twelve and fourteen, hours,
having solid carbonic acid in the reservoir, and enough
for all the baths I required during the whole time, pro-
duced by one supply of 220 cubic inches.*

By the apparatus, and in the manner, now described,
all the gases before condensed were very easily reduced,
and some new results were obtained. When a gas was
liquefied, it was easy to close the stop-cock, and then
remove the condensing tube with the fluid from the rest
of the apparatus. But in order to preserve the liquid
from escaping as gas, a further precaution was necessary ;
namely, to cover over the exposed end of the stop-cock
by a blank female screw-cap and leaden washer, and also

* On one occasion the solid carbonic acid was exceedingly
electric, but I could not produce the effect again : it was probably
connected with the presence of oil which was in the carbonic acid
box ; neither it nor the filaments of ice which formed on it in the
air conducted, for when touched it preserved its electric state.
Believing as yet that the account I have given of the cause of the
electric state of an issuing jet of steam and water (Phil. Trans. 1843,
p. 17) is the true one, I conclude that this also was a case of the
production of electricity simply by friction, and unconnected with
vaporization.

42 Faraday.

to tighten perfectly the screw of the stop-cock plug.
With these precautions I have kept carbonic acid, nitrous
oxide, fluosilicon, &c., for several days.

Even with gases which could be condensed by the
carbonic acid bath in air, this apparatus in the air-pump
had, in one respect, the advantage ; for when the con-
densing tube was lifted out of the bath into the air, it
immediately became covered with hoar frost, obscuring
the view of that which was within ; but in vacua this was
not the case, and the contents of the tube could be very
well examined by the eye.

Olefiant gas. — This gas condensed into a clear, colour-
less, transparent fluid, but did not become solid even in
the carbonic acid bath in vacuo; whether this was because
the temperature was not low enough, or for other reasons
referred to in the account of euchlorine, is uncertain.

The pressure of the vapour of this substance at the
temperature of the carbonic acid bath in air (-103°
FAHR.) appeared singularly uncertain, being on different
occasions, and with different specimens, 3.7, 8.7, 5 and 6
atmospheres. The Table below shows the tension of
vapour for certain degrees below o° FAHR., with two
different specimens obtained at different times, and it
will illustrate this point.

FAHR. Atmospheres. Atmospheres.

— loo . . 4.60 . . 9.30

- 90 . . 5.68 . . 10.26

- 80 . . 6.92 . . 11.33

- 70 . . 8.32 . . 12.52

- 60 . . 9.88 . . 13.86

- 50 . . 11.72 . . 15.36

- 40 . . 13.94 . . 17.05

— 30 . . 16.56 . . 18.98

- 20 . . 19.58 . . 21.23

- 10 23.89

o 27.18

10 31-70

20 36.80

30 ...... 42.50

Liquefaction of Gases. 43

I have not yet resolved this irregularity, but believe
there are two or more substances, physically, and perhaps
occasionally chemically different, in olefiant gas ; and
varying in proportion with the circumstances of heat,
proportions of ingredients, &c., attending the prepara-
tion.

The fluid affected the resin of the gauge graduation,
and probably also the resin of the cap cement, though
slowly.

Hydriodic add. — This substance was prepared from
the iodide of phosphorus by heating it with a very little
water. It is easily condensable by the temperature of a
carbonic acid bath ; it was redistilled, and thus obtained
perfectly pure.

The acid may be obtained either in the solid or
liquid, or (of course) in the gaseous state. As a solid
it is perfectly clear, transparent, and colourless ; having
fissures or cracks in it resembling those that run through
ice. Its solidifying temperature is nearly — 60° FAHR.,
and then its vapour has not the pressure of one atmo-
sphere ; at a point a little higher it becomes a clear
liquid, and this point is close upon that which corre-
sponds to a vaporous pressure of one atmosphere. The
acid dissolves the cap cement and the bitumen of the
gauge graduation ; and appears also to dissolve and act
on fat, for it leaked by the plug of the stop-cock with
remarkable facility. It acts on the brass of the apparatus,
and also on the mercury in the gauge. Hence the
following results as to pressures and temperatures are not
to be considered more than approximations : —

At o° FAHR. pressure was 2.9 atmospheres.
At 32° FAHR. pressure was 3.97 atmospheres.
At 60° FAHR. pressure was 5-86 atmospheres.

Hydrobromic acid. — This acid was prepared by adding

44 Faraday.

to perbromide of phosphorus* about one-third of its bulk
of water in a proper distillatory apparatus formed of glass
tube, and then applying heat to distil off the gaseous
acid. This being sent into a very cold receiver, was
condensed into a liquid, which being rectified by a
second distillation, was then experimented with.

Hydrobromic acid condenses into a clear colourless
liquid at 100° below o°, or lower, and has not the
pressure of one atmosphere at the temperature of the
carbonic acid bath in air. It soon obstructs and
renders the motion of the mercury in the air-gauge
irregular, so that I did not obtain a measure of its elastic
force ; but it is less than that of muriatic acid. At and
below the temperature of — 124° FAHR. it is a solid, trans-
parent, crystalline body. It does not freeze until reduced
much lower than this temperature ; but being frozen by
the carbonic acid bath in vacuo, it remains a solid until
the temperature in rising attains to — 124°.

Fluosilicon. — I found that this substance in the gas-
eous state might be brought in contact with the oil
and metal of the pumps, without causing injury to them,
for a time sufficiently long to apply the joint process of
condensation already described. The substance liquefied
under a pressure of about nine atmospheres at the lowest
temperature, or at 160° below o° ; and was then clear,
transparent, colourless, and very fluid like hot ether. It
did not solidify at any temperature to which I could
submit it. I was able to preserve it in the tube until the

* The bromides of phosphorus are easily made without risk of
explosion. If a glass tube be bent so as to have two depressions,
phosphorus placed in one and bromine in the other ; then by in-
clining the tube, the vapour of bromine can be made to flow gradually
on to, and combine with, the phosphorus. The fluid protobromide
is first formed, and this is afterwards converted into solid per-
bromide. The excess of bromine may be dissipated by the careful
application of heat.

Liquefaction of Gases. 45

next day. Some leakage had then taken place (for it
ultimately acted on the lubricating fat of the stop-cock),
and there was no liquid in the tube at common tempera-
tures ; but when the bend of the tube was cooled to 32°
by a little ice, fluid appeared : a bath of ice and salt
caused a still more abundant condensation. The pres-
sure appeared then to be above thirty atmospheres, but
the motion of the mercury in the gauge had become
obstructed through the action of the fluosilicon, and no
confidence could be reposed in its indications.

Phosphuretted hydrogen. — This gas was prepared by
boiling phosphorus in a strong pure solution of caustic
potassa, and the gas was preserved over water in a dark
room for several days to cause the deposition of any
mere vapour of phosphorus which it might contain. It
was then subjected to high pressure in a tube cooled by
a carbonic acid bath, which had itself been cooled under
the receiver of the air-pump. The gas in its way to the
pumps passed through a long spiral of thin narrow glass
tube immersed in a mixture of ice and salt at o°, to re-
move as much water from it as possible.

By these means the phosphuretted hydrogen was
liquefied; for a pure, clear, colourless, transparent and
very limpid fluid appeared, which could not be solidified
by any temperature applied, and which when the pressure
was taken off immediately rose again in the form of gas.
Still the whole of the gas was not condensable into this
fluid. By working the pumps the pressure would rise up
to twenty-five atmospheres at this very low temperature,
and yet at the pressure of two or three atmospheres and
the same temperature, liquid would remain. There can
be no doubt that phosphuretted hydrogen condensed, but
neither can there be a doubt that some other gas, not so
condensable, was also present, which perhaps may be
either another phosphuretted hydrogen or hydrogen itself.

Faraday.

Fluoboron. — -This substance was prepared from fluor
spar, fused boracic acid and strong sulphuric acid, in a
tube generator such as that already described, and con-
ducted into a condensing tube under the generating
pressure. The ordinary carbonic acid bath did not con-
dense it, but the application of one cooled under the air-
pump caused its liquefaction, and fluoboron then appeared
as a very limpid, colourless, clear fluid, showing no signs
of solidification, but when at the lowest temperature
mobile as hot ether. When the pressure was taken off,
or the temperature raised, it returned into the state of
gas.

The following are some results of pressure, all that I
could obtain with the liquid in my possession ; for, as
the liquid is light and the gas heavy, the former rapidly
disappears in producing the latter. They make no pre-
tensions to accuracy, and are given only for general
information.

FAHK. Atmospheres.

— 100

— 82

4.6l

7-5

FAHR. Atmospheres.

-72
—66

9-23
10.00

FAHR. Atmosphen
— 62 . .11.54

The preceding are, as far as I am aware, new results
of the liquefaction and solidification of gases. I will
now briefly add such other information respecting solidi-
fication, pressure, &c., as I have obtained with gaseous
bodies previously condensed. As to pressure, consider-
able irregularity often occurred, which I cannot always
refer to its true cause ; sometimes a little of the com-
pressed gas would creep by the mercury in the gauge,
and increase the volume of inclosed air ; and this varied
with different substances, probably by some tendency
which the glass had to favour the condensation of one (by

Liquefaction of Gases.

47

something analogous to hygrometric action) more than
another. But even when the mercury returned to its
place in the gauge, there were anomalies which seemed
to imply, that a substance, supposed to be one, might be
a mixture of two or more. It is, of course, essential that
the gauge be preserved at the same temperature through-
out the observations.

Muriatic acid. — This substance did not freeze at the
lowest temperature to which I could attain. Liquid
muriatic acid dissolves bitumen ; the solution, liberated
from pressure, boils, giving off muriatic acid vapour, and
the bitumen is left in a solid frothy state, and probably
altered, in some degree, chemically. The acid unites
with and softens the resinous cap cement, but leaves it
when the pressure is diminished. The following are
certain pressures and temperatures which, I believe, are
not very far from truth ; the marked numbers are from
experiment.

FAHR. Atmospheres.! FAHR. Atmospheres.

FAHR. Atmospheres.

^—loo . i. 80 ; ^—53 5.83

«- 5 13-88

^ — 92

. 2.28 i — 50

6.30

^ o

15.04

— 90

. 2.38

-—42

7.40

10

17.74

-- 83

. 2.90

—40

7.68

20

21.09

— 80

. 3.12

w— 33

8.53

0 25

23.08

w_ 77

• 3-37

-30

9.22

30

25-32

- 7o

. 4.02 ; ^—22

10.66

~ 32

26.20

--67

. 4.26 — 20

10.92

40

30.67

— 60

. 5.08 —io

12.82

The result formerly obtained* was forty atmospheres at
the temperature of 50° FAHR.

Sulphurous acid. — When liquid, it dissolves bitumen.
It becomes a crystalline, transparent, colourless, solid
body, at — 105° FAHR.; when partly frozen the crystals
are well-formed. The solid sulphurous acid is heavier
than the liquid, and sinks freely in it. The following is

* Philosophical Transactions, 1823, p. 198.

48

Faraday.

a table of pressures in atmospheres of 30 inches mercury,
of which the marked results are from many observations,
the others are interpolated. They differ considerably
from the results obtained by BUNSEN,* but agree with my
first and only result.

FAHK. Atmospheres. I FAHK.

O .

10 ,

°H -
-19

-23 .

^26 .

31-5-

°32 .
^33

40 .
46.5.

^48 .
^56

58 .

^64 .
68 .

^73-5-

spheres.

FAHK

Atmosphere

0

1.78

76-8

• 3-50

2.00

85

. 4.00

2.O6

^90

• 4-35

2.42

93

• 4-50

2.50

98

. 5.00

2.76

^100 .

. 5-16

3-00

104 .

• 5-50

3-28

no .

. 6.00

0.725 !
0.92

.00
.12

.23

•33
.50

•53
•57

Sulphuretted hydrogen. — This substance solidifies at
122° FAHR. below o°, and is then a white crystalline
translucent substance, not remaining clear and trans-
parent in the solid state like water, carbonic acid, nitrous
oxide, &c., but forming a mass of confused crystals like
common salt or nitrate of ammonia, solidified from the
melted state. As it fuses at temperatures above — 122°,
the solid part sinks freely in the fluid, indicating that it is
considerably heavier. At this temperature the pressure
of its vapour is less than one atmosphere, not more, pro-
bably, than 0.8 of an atmosphere, so that the liquid
allowed to evaporate in the air would not solidify as
carbonic acid does.

The following is a table of the tension of its vapour,
the marked numbers being close to experimental results,
and the rest interpolated. The curve resulting from
these numbers, though coming out nearly identical in
different series of experiments, is apparently so different
in its character from that of water or carbonic acid, as to
leave doubts on my mind respecting it, or else of the

* Bibliotheque Universelle, 1839, xxiii. p. 185.

Liquefaction of Gases.

49

identity of every portion of the fluid obtained, yet the
crystallization and other characters of the latter seemed to
show that it was a pure substance.

FAHR.

Atmospheres.

FAHR.

Atmospheres.

FAHR.

Atmospher

— IOO

.02

— 50

• • 2.35

O .

. 6. 10

- 94

. . .09

--45

• • 2.59

10 .

. 7.21

— 90

• • -IS

^—40

. . 2.86

2O .

. 8.44

-83

. . .27

—30

• 3-49

-26 .

• 9-36

— 80

• • -33

-—24

• • 3-95

30 •

. 9.94

— 74

.50

^ — 20

. 4.24

40 .

. 11.84

— 7o

• • -59

"— 16

. 4.60

-48 .

• I3-70

— 68

. . .67

— 10

. . 5.11

50 -

. 14.14

- 60

• • -93

v — 2

. . 5.90

-52 •

. 14.60

— 58

. 2.OO

Carbonic acid. — The solidification of carbonic acid by
M. THILORIER is one of the most beautiful experimental
results of modern times. He obtained the substance, as
is well known, in the form of a concrete white mass like
fine snow, aggregated. When it is melted and resolidified
by a bath of low temperature, it then appears as a clear,
transparent,- crystalline, colourless body, like ice; so clear,
indeed, that at times it was doubtful to the eye whether
anything was in the tube, yet at the same time the part
was filled with solid carbonic acid. It melts at the tem-
perature of — 70° or — 72° FAHR., and the solid carbonic
acid is heavier than the fluid bathing it. The solid or
liquid carbonic acid at this temperature has a pressure of
5.33 atmospheres nearly. Hence it is easy to understand
the readiness with which liquid carbonic acid, when
allowed to escape into the air, exerting only a pressure of
one atmosphere, freezes a part of itself by the evaporation
of another part.

THILORIER gives — 100° C. or —148° FAHR. as the
temperature at which carbonic acid becomes solid. This
however is rather the temperature to which solid carbonic
acid can sink by further evaporation in the air, and is a
temperature belonging to a pressure, not only lower than

/ .

5O Faraday.

that of 5.33 atmospheres, but even much below that of
one atmosphere. This cooling effect to temperatures
below the boiling-point often appears. A bath of car-
bonic acid and ether exposed to the air will cool a tube
containing condensed solid carbonic acid, until the pres-
sure within the tube is less than one atmosphere ; yet, if
the same bath be covered up so as to have the pressure
of one atmosphere of carbonic acid vapour over it, then
the temperature is such as to produce a pressure of 2.5
atmospheres by the vapour of the solid carbonic acid
within the tube.

The estimates of the pressure of carbonic acid vapour
are sadly at variance ; thus, THILORIER* says it has a
pressure of 26 atmospheres at — 4° FAHR., whilst
ADDAMS f says that for that pressure it requires a tem-
perature of 30°. ADDAMS gives the pressure about 27 J
atmospheres at 32°, but THILORIER and myself \ give it
as 36 atmospheres at the same temperature. At 50°
BRUNEL§ estimates the pressure as 60 atmospheres,
whilst ADDAMS makes it only 34.67 atmospheres. At 86°
THILORIER finds the pressure to be 73 atmospheres; at
4° more, or 90°, BRUNEL makes it 120 atmospheres; and
at 10° more, or 100°, ADDAMS makes it less than
THILORIER at 86°, and only 62.32 atmospheres; even at
150° the pressure with him is not quite 100 atmospheres.

I am inclined to think that at about 90° CAGNIARD
DE LA TOUR'S state comes on with carbonic acid. From
THILORIER'S data we may obtain the specific gravity of
the liquid and the vapour over it at the temperature of
86° FAHR., and the former is little more than twice that
of the latter ; hence a few degrees more of temperature

* Annales de Chimie, 1835, Ix. 427, 432.
t Report of British Association, 1838, p. 70.
J Philosophical Transactions, 1823, p. 193.
§ Royal Institution Journal, xxi. 132,

Liquefaction of Gases.

5

would bring them together, and BRUNEL'S result seems
to imply that the state was then on, but in that case
ADDAMS'S results could only be accounted for by sup-
posing that there was a deficiency of carbonic acid. The
following are the pressures which I have recently ob-
tained : —

FAHR.

Atmospheres.

FAHR.

Atmospheres.

FAHR.

Atmospheres.

0

o

o

— Ill

. . 1.14

-60

. . 6.97

^ 4 •

. 21.48

— no

. . I.i;

— 56

. . 7.70

o .

. 22.84

-—107

1 . 36

-50

. . 8.88

^ 5 •

• 24.75

— IOO

1.85

—40

. 11.07

^ 10 .

. 26.82

'— 95

. . 2.28

w— 34

. 12.50

~ IS •

. 29.09

— 90

• • 2.77

—30

• • 13-54

20 .

• 30.65

'— 83

. 3.60

--23

• • 15-45

^ 23 .

• 33-15

— 80

• • 3-93

—20

. 16.30 30 .

• 37-19

-— 75

. 4.60

w— 15

. . 17.80 j - 32 .

- 38.50

- 7o

• • 5-33

— 10

. . 19.38

Carbonic acid is remarkable amongst bodies for the
high tension of the vapour which it gives off whilst in the
solid or glacial state. There is no other substance which
at all comes near it in this respect, and it causes an
inversion of what in all other cases is the natural order of
events. Thus, if, as is the case with water, ether, mercury
or any other fluid, that temperature at which carbonic
acid gives off vapour equal in elastic force to one atmo-
sphere, be called its boiling-point ; or, if (to produce the
actual effect of ebullition) the carbonic acid be plunged
below the surface of alcohol or ether, then we shall per-
ceive that the freezing and boiling-points are inverted, i.e.
that the freezing-point is the hotter, and the boiling-point
the colder of the two, the latter being about 50° below
the former.

Etichlorine. — This substance was easily converted
from the gaseous state into a solid crystalline body,
which, by a little increase of temperature, melted into an
orange-red fluid, and by diminution of temperature again
congealed ; the solid euchlorine had the colour and

5 2 Faraday.

general appearance of bichromate of potassa ; it was
moderately hard, brittle and translucent ; and the crystals
were perfectly clear. It melted at the temperature of 75°
below o°, and the solid portion was heavier than the
liquid.

When in the solid state it gives off so little vapour
that the eye is not sensible of its presence by any degree
of colour in the air over it when looking down a tube
four inches in length, at the bottom of which is the sub-
stance. Hence the pressure of its vapour at that tem-
perature must be very small.

Some hours after, wishing to solidify the same portion
of euchlorine which was then in a liquid state, I placed
the tube in a bath at — 110°, but could not succeed
either by continuance of the tube in the bath, or shaking
the fluid in the tube, or opening the tube to allow the
full pressure of the atmosphere ; but when the liquid
euchlorine was touched by a platinum wire it instantly
became solid, and exhibited all the properties before
described. There are many similar instances amongst
ordinary substances, but the effect in this case makes me
hesitate in concluding that all the gases which as yet have
refused to solidify at temperatures as low as 166° below
o°, cannot acquire the solid state at such a temperature.

Nitrous oxide. — This substance was obtained solid by
the temperature of the carbonic acid bath in vacuo, and
appeared as a beautiful clear crystalline colourless body.
The temperature required for this effect must have been
very nearly the lowest, perhaps about 150° below o°.
The pressure of the vapour rising from the solid nitrous
oxide was less than one atmosphere.

Hence it was concluded that liquid nitrous oxide
could not freeze itself by evaporation at one atmosphere,
as carbonic acid does ; and this was found to be true, for
when a tube containing much liquid was freely opened,

Liquefaction of Gases. 53

so as to allow evaporation down to one atmosphere, the
liquid boiled and cooled itself, but remained a liquid.
The cold produced by the evaporation was very great,
and this was shown by putting the part of the tube con-
taining the liquid nitrous oxide, into a cold bath of
carbonic acid, for the latter was like a hot bath to the
former, and instantly made it boil rapidly.

I kept this substance for some weeks in a tube closed
by stop-cocks and cemented caps. In that time there
was no action on the bitumen of the graduation, nor on
the cement of the caps ; these bodies remained perfectly
unaltered.

Hence it is probable that this substance may be used
in certain cases, instead of carbonic acid, to produce
degrees of cold far below those which the latter body can
supply. Down to a certain temperature, that of its solidi-
fication, it would not even require ether to give contact,
and below that temperature it could easily be used
mingled with ether; its vapour would do no harm to
an air-pump, and there is no doubt that the substance
placed in vacua would acquire a temperature lower than
any as yet known, perhaps as far below the carbonic acid
bath in vacuo as that is below the same bath in air.

This substance, like olefiant gas, gave very uncertain
results at different times as to the pressure of its vapour ;
results which can only be accounted for by supposing
that there are two different bodies present, soluble in
each other, but differing in the elasticity of their vapour.
Four different portions gave at the same temperature,
namely, — 106° FAHR., the following great differences in
pressure, 1.66; 4.4; 5.0; and 6.3 atmospheres, and this
after the elastic atmosphere left in the tubes at the con-
clusion of the condensation had been allowed to escape,
and be replaced by a portion of the respective liquids
which then rose in vapour. The following Table gives

54 Faraday.

certain results with a portion of liquid which exerted a
pressure of six atmospheres at — 106° FAHR.

FAHR. Atmospheres. Atmospheres.

o

— 4O . . IO.2O

—35 • • 10.95
—30 . . 11.80
—25 . . 12.75

— 20 . . 13.80

— 15 . . 14.95
— 10 . . 16.20

- 5 • • 17-55

o . . 19.05 . . 24.40

5 . . 20.70 . . 26.08

10 . . 22.50 . . 27.84

15 . . 24.45 - - 29.68

20 . . 26.55 ' • 31.62
25 . . 28.85 • • 33.66
30 .. - 35.82

35 • • • 38-10

The second column expresses the pressures given as
the fluid was raised from low to higher temperatures.
The third column shows the pressures given the next day
with the same tube after it had attained to and continued
at the atmospheric temperature for some hours. There
is a difference of four or five atmospheres between the
two, showing that in the first instance the previous low
temperature had caused the solution of a more volatile
part in the less volatile and liquid portion, and that the
prolonged application of a higher temperature during the
night had gradually raised it again in vapour. This result
occurred again and again with the same specimen.*
Cyanogen. — This substance becomes a solid trans-

* This substance is one of those which I liquefied in 1823 (see
Philosophical Transactions). Since writing the above I perceive
that M. NATTERER has condensed it into the liquid state by the use
of pumps only (see Comptes Rendus, 1844, iSth Nov. p. mi), and
obtained the liquid in considerable quantities. The non-solidifi-
cation of it by exposure to the air perfectly accords with my own
results.

Liquefaction of Gases. 55

parent crystalline body, as BUNSEN has already stated,*
which raised to the temperature of — 30° FAHR. then lique-
fies. The solid and liquid appear to be nearly of the
same specific gravity, but the solid is perhaps the denser
of the two.

The mixed solid and liquid substance yields a vapour
of rather less pressure than one atmosphere. In accord-
ance with this result, if the liquid be exposed to the air,
it does not freeze itself as carbonic acid does.

The liquid tends to distil over and condense on the
cap cement and bitumen of the gauge, but only slightly.
When cyanogen is made from cyanide of mercury sealed
up hermetically in a glass tube, the cyanogen distils back
and condenses in the paracyanic residue of the distillation,
but the pressure of the vapour at common temperatures
is still as great, or very nearly so, as if the cyanogen were
in a clean separate liquid state.

A measured portion of liquid cyanogen was allowed
to escape and expand into gas. In this way one volume
of liquid at the temperature of 63° FAHR. gave 393.9
volumes of gas at the same temperature and the baro-
metric pressure of 30.2 inches. If 100 cubic inches of
the gas be admitted to weigh 55.5 grains, then a cubic
inch of the liquid would weigh 218.6 grains. This gives
its specific gravity as 0.866. When first condensed I
estimated it as nearly 0.9.

Cyanogen is a substance which yielded on different
occasions results of vaporous tension differing much from
each other, though the substance appeared always to be
pure. The following are numbers in which I place some
confidence, the pressures being in atmospheres of 30
inches of mercury, and the marked results experimental.!

* Bibliotheque Universelle, 1839, xxiii. p. 184.
t See BUNSEN'S results, Bibliotheque Universelle, 1839, xxiii.
p. 185-

FAHR. Atmospheres.

O .

8.5.
^10 .

15 .

^20 .
22.8.

-27 .

^32 •

34-5-

.25

5

•53
,72
.89

2.00
2. 2O

2-37
2.50

Faraday.

FAHR.

Atmospheres.

"38.5-

. 2.72

-44.5-

. 3.00

^48 .

• 3-17

-50 .

. 3.28

-52 .

• 3-36

54-3-

• 3-50

^63

. 4.00

^70 .

• 4-50

^74 •

. 4.79

FAHR. Atmospheres.

77 •

83 '.
88.3.

.4.

-103

5.00
S-l6
5.50

6.00
6.50
6.64
7.00
7-50

Ammonia. — This body may be obtained as a solid,
white, translucent, crystalline substance, melting at the
temperature of 103° below o° ; at which point the solid
substance is heavier than the liquid. In that state the
pressure of its vapour must be very small.

Liquid ammonia at 60° was allowed to expand into
ammoniacal gas at the same temperature ; one volume
of the liquid gave 1009.8 volumes of the gas, the baro-
meter being at the pressure of 30.2 inches. If 100 cubic
inches of ammoniacal gas be allowed to weigh 18.28
grains, it will give 184.6 grains a's the weight of a cubic
inch of liquid ammonia at 60°. Hence its specific
gravity at that temperature will be 0.731. In the old
experiments I found by another kind of process that its
specific gravity was 0.76 at 50°.

The following is a table of the pressure of ammonia
vapour, the marked results, as before, being those ob-
tained by experiment : —

FAHR. Atmospheres.' FAHR. Atmospheres. FAHR. Atmospheres.

^ O .

. 2.48

0

• 5-10

^61.3.

. 7.00

0.5.

. 2.50

W44

• 5-36

^65.6.

• 7-50

0 9-3-

. 3.00

^45 •

• 5-45

-67 .

• 7.63

• 3-50

45.8.

• 5-50

69.4.

. 8.00

^21

. 3-72

°49

5.83

73 •

. 8.50

25.8.

^26 .

. 4.00
. 4.04

-52 .

. 6.00
. 6.10

76.8.
80 .

. 9.00
. 9.50

W32

• 4-44

^55 •

• 6.38

-85 .

. IO.OO

°33 •

• 4-5°

• 6.50

85 .

. 10.30

39-5-

. 5.00

^60' '.

. 6.90

Liquefaction of Gases.

57

Arseniuretted Hydrogen. — This body, liquefied by
DUMAS and SOUBEIRAN, did not solidify at the lowest
temperature to which I could submit it, i.e. not at 166°
below o° FAHR. In the following table of the elasticity
of its vapour the marked results are experimental, and
the others interpolated : —

FAHR. Atmospheres.

FAHR. Atmospheres.

FAHR. Atmosphen

^-75

0.94

—30

2.84

°IO

6.24

—70

.08

--23

3-32

^20

7-39

— 64

.26

, —20

3-5i

30

8.66

—60

.40

— IO

X4-3Q

-32

8.95

w-52

•73

\j . C

4-74

-40

10.05

—So

.80

w O

5.21 | -50

11.56

—40

2,28

— 3

,. 5.56 ! ^60

I3-I9

--36

2.50 i

The following bodies would not freeze at the very
low temperature of the carbonic acid bath in vaaw
( — 1 66° FAHR.) : — Chlorine, ether, alcohol, sulphuret of
carbon, caoutchoucine, camphine or rectified oil of tur-
pentine. The alcohol, caoutchoucine, and camphine lost
fluidity and thickened somewhat at — 106°, and still more
at the lower temperature of — 166°. The alcohol then
poured from side to side like an oil.

Dry yellow fluid nitrous acid when cooled below o°
loses the greater part of its colour, and then fuses into a
white, crystalline, brittle and but slightly translucent sub-
stance, which fuses a little above o° FAHR. The green
and probably hydrated acid required a much lower
temperature for its solidification, and then became a pale
bluish solid. There were then evidently two bodies, the
dry acid which froze out first, and then the hydrate,
which requires at least — 30° below o° before it will
solidify.

The following gases showed no signs of liquefaction

5 8 Faraday.

when copied by the carbonic acid bath in vacua, even at
the pressures expressed : —

Atmospheres.

-Hydrogen at ...... 27

Oxygen at ...... 27

Nitrogen at ...... 50

Nitric oxide at ..... 50

Carbonic oxide at ..... 40

Coal gas ....... 32

The difference in the facility of leakage was one
reason of the difference in the pressure applied. I found
it impossible, from this cause, to raise the pressure of
hydrogen higher than twenty-seven atmospheres by an
apparatus that was quite tight enough to confine nitrogen
up to double that pressure.

M. CAGNIARD TJE LA TOUR has shown that at a
certain temperature, a liquid, under sufficient pressure,
becomes clear transparent vapour or gas, having the same
bulk as the liquid. At this temperature, or one a little
higher, it is not likely that any increase of pressure,
except perhaps one exceedingly great, would convert the
gas into a liquid. Now the temperature of 166° below o°,
low as it is, is probably above this point of temperature
for hydrogen, and perhaps for nitrogen and oxygen, and
then no compression without the conjoint application of
a degree of cold below that we have as yet obtained, can
be expected to take from them their gaseous state.
^Further, as ether assumes this state before the pressure of
its vapour has acquired thirty-eight atmospheres, it is
more than probable that gases which can resist the pres-
sure of from twenty-seven to fifty atmospheres at a tem-
perature of 1 66° below o° could never appear as liquids,
or be made to lose their gaseous state at common
temperatures. They may probably be brought into the
state of very condensed gases, but not liquefied.

Some very interesting experiments on the compression

Liquefaction of Gases. , • 59

of gases have been made by M. G. AIME,* in which
oxygen, olefiant, nitric oxide, carbonic oxide, fluosilicon,
hydrogen, and nitrogen gases were submitted to pressures,
rising up to 220 atmospheres in the case of the two last ;
but this was in the depths of the sea where the results
under pressure could not be examined. Several of them
were diminished in bulk in a ratio far greater than the
pressure put upon them ; but both M. CAGNIARD DE LA
TOUR and M. THILORIER have shown that this is often
the case whilst the substance retains the gaseous form.
It is possible that olefiant gas and fluosilicon may have
liquefied down below, but they have not yet been seen in
the liquid state except in my own experiments, and in
them not at temperatures above 40° FAHR. The results
with oxygen are so unsteady and contradictory as to
cause doubt in regard to those obtained with the other
gases by the same process.

Thus, though as yet I have not condensed oxygen,
hydrogen, or nitrogen, the original objects of my pursuit,
I have added six substances, usually gaseous, to the list
of those that could previously be shown in the liquid
state, and have reduced seven, including ammonia,
nitrous oxide, and sulphuretted hydrogen, into the solid
form. And though the numbers expressing tension of
vapour cannot (because of the difficulties respecting the
use of thermometers and the apparatus generally) be con-
sidered as exact, I am in hopes they will assist in develop-
ing some general law governing the vaporization of all
bodies, and also in illustrating the physical state of
gaseous bodies as they are presented to us under ordinary
temperature and pressure.

Royal Institution ,

Nov. 15, 1844.

* Annales de Chimie, 1843, v"i- 275-

6o

Faraday.

NOTE. — Additional remarks respecting the Condensation

of Gases.
Received February 20, — Read February 20, 1845.

Nitrous oxide. — Suspecting the presence on former
occasions of nitrogen in the nitrous oxide, and mainly
because of muriate in the nitrate of ammonia used, I pre-
pared that salt in a pure state from nitric acid and car-
bonate of ammonia previously proved, by nitrate of silver,
to be free from muriatic acid. After the nitrous oxide
prepared from this salt had remained for some days in
well-closed bottles in contact with a little water, I con-
densed it in the manner already described, and when
condensed I allowed half the fluid to escape in vapour,
that as much as possible of the less condensable portion
might be carried off. In this way as much gas as would
fill the capacity of the vessels twenty or thirty times or
more was allowed to escape. Afterwards the following
series of pressures was obtained : —

FAHR.

Atmospheres.

FAHR.

Atmospheres.

FAHR.

Atmospher

0

0

0

—125 .

.OO

-70 .

. 4.II

-15 •

. 14.69

— I2O .

. IO

-65 .

• 4-70

— 10 .

. 16.15

— US •

.22

—60 .

• 5.36

- 5 •

• 17.70

— 110 .

• .37

-55 •

. 6.09

o .

• 19-34

-105 .

• -55

-50 .

. 6.89

5 •

. 2I.O7

— 100 .

• -77

-45 •

. 7-76

IO .

. 22.89

- 95 •

. 2.03

—40 .

. 8.71

15 •

. 24.80

- 90 .

. 2.34

—35 •

• 9-74

20 .

. 26.80

-85 .

. 2.70

—30 •

. 10.85

25 •

. 28.90

— 80 .

. 3.11

—25 .

. 12.04

30 •

. 31.10

- 75 •

• 3-5*

— 20 .

• J3-32

35 •

• 33-40

These numbers may all be taken as the results of ex-
periments. Where the temperatures are not those actually
observed, they are in almost all cases within a degree of
it, and proportionate to the effects really observed. The
departure of the real observations from the numbers
given is very small. This table I consider as far more

Liquefaction of Gases. 6 1

worthy of confidence than the former, and yet it is mani-
fest that the curve is not consistent with the idea of a pure
single substance, for the pressures at the lowest tempera-
ture are too high. I believe that there are still two
bodies present, and that the more volatile, as before
said, is condensable in the liquid of the less volatile ; but
I think there is a far smaller proportion of the more
volatile (nitrogen, or whatever it may be) than in the
former case.

Olefiant gas. — The olefiant gas condensed in the
former experiment was prepared in the ordinary way,
using excellent alcohol and sulphuric acid ; then washed
by agitation with about half its bulk of water, and finally
left for three days over a thick mixture of lime and water
with occasional agitation. In this way all the sulphurous
and carbonic acids were removed, and I believe all the
ether, except such minute portions as could not interfere
with my results. In respect of the ether, I have since
found that the process is satisfactory; for when I pur-
posely added ether vapour to air, so as to increase its
bulk by one-third, treatment like that above removed it, so
as to leave the air of its original volume. There was yet
a slight odour of ether left, but not so much as that con-
ferred by adding one volume of the vapour of ether to
1200 or 1500 volumes of air. I find that when air is ex-
panded Jth or Jrd more by the addition of the vapour of
ether, washing first of all with about TVn °f its volume of
water, then again with about as much water, and lastly
with its volume of water, removes the ether to such a
degree, that though a little smell may remain, the air is
of its original volume.

As already stated, it is the presence of other and
more volatile hydrocarbons than olefiant gas, which the
tensions obtained seemed to indicate, both in the gas
and the liquid resulting from its condensation. In a

62 Faraday.

further search after these I discovered a property of
olefiant gas which I am not aware is known (since I do
not find it referred to in books), namely its ready solu-
bility in strong alcohol, ether, oil of turpentine, and such
like bodies.* Alcohol will take up two volumes of this
gas ; ether can absorb two volumes ; oil of turpentine two
volumes and a half; and olive oil one volume by agitation
at common temperatures and pressure ; consequently,
when a vessel of olefiant gas is transferred to a bath of any
of these liquids and agitated, absorption quickly takes
place.

Examined in this way, I have found no specimen of
olefiant gas that is entirely absorbed ; a residue always
remains, which, though I have not yet had time to
examine it accurately, appears to be light carburetted
hydrogen ; and I have no doubt that this is the substance
which has mainly interfered in my former results. This
substance appears to be produced in every stage of the
preparation of olefiant gas. On taking six different por-
tions of gas at different equal intervals, from first to last,
during one process of preparation, after removing the
sulphurous and carbonic acid and the ether as before
described, then the following was the proportion per cent,
of insoluble gas in the remainder when agitated with
oil of turpentine, 10.5; 10; 10.1 ; 13.1; 28.3; 61.8.
Whether carbonic oxide was present in any of these
undissolved portions I cannot at present say.

In reference to the part dissolved, I wish as yet to
guard myself from being supposed to assume that it is
one uniform substance ; there is indeed little doubt that
the contrary is true ; for whilst a volume of oil of turpen
tine introduced into twenty times its volume of olefiant

* Water, as BERZELIUS and others have pointed out, dissolves
about £th its volume of olefiant gas, but I find that it also leaves an
insoluble residue, which burns like light carburetted hydrogen.

Liquefaction of Gases,

gas cleared from ether and the acids, absorbs 2\ volumes
of the gas, the same volume of fresh oil of turpentine
brought into similar contact with abundance of the gas
which remains when one-half has been removed by solu-
tion only dissolved 1.54 part, yet there was an abundant
surplus of gas which would dissolve in fresh oil of tur-
pentine at this latter rate. When two-thirds of a portion
of fresh olefiant gas were removed by solution, the most
soluble portion of that which remained required its bulk
of fresh oil of turpentine to dissolve it. Hence at first
one volume of camphine dissolved 2.50, but when the
richer portion of the gas was removed, one volume dis-
solved 1.54 part ; and when still more of the gas was
taken away by solution, one volume of camphine dissolved
only one volume of the gas. This can only be accounted
for by the presence of various compounds in the soluble
portion of the gas.

A portion of good olefiant gas was prepared, well-
agitated with its bulk of water in close vessels, left over
lime and water for three days, and then condensed as
before. When much liquid was condensed, a consider-
able proportion was allowed to escape to sweep out the
uncondensed atmosphere and the more condensable
vapours; and then the following pressures were ob-
served : — -

Atmospheres.

. 16.22

• 17-75

. 19.38

. 21. II

. 22.94

. 24.87

. 26.90

On examining the form of the curve given by these
pressures, it is very evident that, as on former occasions,

FAHR.

Atmospheres.

FAHR.

Atmospheres.

FAHR.

-105 .

. 4.60

-65 .

. 8.30

—3°

— 100 .

. 4.82

—60 .

• 9-H

-25

- 95 •

. 5.10

-55 •

. 10.07

— 20

— 90 .

• 5i4

-5o •

. II. IO

-15

- 85 •

• 5-84

-45 •

. 12.23

— IO

— 80 .

. 6.32

—40 .

. 13.46

- 5

- 75 •

. 6.89

—35 •

. 14.79

o

- 7o .

• 7-55

64 Faraday.

the pressures at low temperatures are too great to allow
the condensed liquid to be considered as one uniform
body, and the form of the curve at the higher pressures is
quite enough to prove that no ether was present either in
this or the former fluids. On permitting the liquid in
the tube to expand into gas, and treating 100 parts of
that gas with oil of turpentine, eighty-nine parts were dis-
solved, and eleven parts remained insoluble. There can
be no doubt that the presence of this latter substance,
soluble as it is under pressure in the more condensable
portions, is the cause of the irregularity of the curve, and
the too high pressure at the lower temperatures.

The ethereal solution of olefiant gas being mixed
with eight or nine times its volume of water, dissolved
and gradually minute bubbles of gas appeared, the sepa-
ration of which was hastened by a little heat. In this
way about half the gas dissolved was re-obtained, and
burnt like very rich olefiant gas. One volume of the
alcoholic solution, with two volumes of water, gave very
little appearance of separating gas. Even the application
of heat did not at first cause the separation, but gradually
about half the dissolved olefiant gas was liberated.

The separation of the dissolved gas by water, heat, or
change of pressure from its solutions, will evidently supply
means of procuring olefiant gas in a greater state of
purity than heretofore ; the power of forming these solu-
tions will also very much assist in the correct analysis of
mixtures of hydrocarbons. I find that light carburetted
hydrogen is hardly sensibly soluble in alcohol or ether,
and in oil of turpentine the proportion dissolved is not
probably -jjth the volume of the fluid employed ; but
the further development of these points I must leave for
the present.

Carbonic acid. — This liquid may be retained in glass
tubes furnished with cemented caps, and closed by plugs

Liquefaction of Gases. 65

or stop-cocks, as described, but it is important to re-
member the softening action on the cement which, being
continued, at last reduces its strength below the necessary
point. A tube of this kind was arranged on the loth of
January and left; an the i5th of February it exploded,
not by any fracture of the tube, for that remained un-
broken, but simply by throwing off the cap through a
failure of the cement. Hence the cement joints should
not be used for long experiments, but only for those en-
during for a few days.

Oxygen. — Chlorate of potassa was melted and pul-
verized. Oxide of manganese was pulverized, heated
red-hot for half an hour, mixed whilst hot with the
chlorate, and the mixture put into a long strong glass
generating tube with a cap cemented on, and this tube
then attached to another with a gauge for condensation.
The heat of a spirit lamp carefully applied produced the
evolution of oxygen without any appearance of water, and
the tubes, both hot and cold, sustained the force gene-
rated. In this manner the pressure of oxygen within the
apparatus was raised as high as 58.5 atmospheres, whilst
the temperature at the condensing place was reduced as
low as — 140° FAHR., but no condensation appeared. A
little above this pressure the cement of two of the caps
began to leak, and I could carry the observation no
further with this apparatus.

From the former scanty and imperfect expressions of
the elasticity of the vapour of the condensed gases, DOVE
was led to put forth a suggestion,* whether it might not
ultimately appear that the same addition of heat (ex-
pressed in degrees of the thermometer) caused the same

* POGGENDORFF'S Annalen, xxiii. 290 ; or THOMSON on Heat
and Electricity, p. 9.

E

66 Faraday.

additional increase of expansive force for all gases or
vapours in contact with their liquids, provided the obser-
vation began with the same pressure in all. Thus to
obtain the difference between forty-four and fifty atmo-
spheres of pressure, either with steam or nitrous oxide,
nearly the same number of degrees of heat were required;
to obtain the difference between twenty and twenty-five
atmospheres, either with steam or muriatic acid, the
same number were required. Such a law would of course
make the rate of increasing expansive force the same for
all bodies, and the curve laid down for steam would
apply -to every other vapour. This, however, does not
appear to be the case. That the force of the vapour in-
creases in a geometrical ratio for equal increments of
heat is true for all bodies, but the ratio is not the same
for all. As far as observations upon the following sub-
stances, namely, water, sulphurous acid, cyanogen, am-
monia, arseniuretted hydrogen, sulphuretted hydrogen,
muriatic acid, carbonic acid, olefiant gas, &c., justify any
conclusion respecting a general law, it would appear that
the more volatile a body is, the more rapidly does the
force of its vapour increase by further addition of heat,
commencing at a given point of pressure for all ; thus for
an increase of pressure from two to six atmospheres, the
following number of degrees require to be added for the
different bodies named : water 69°, sulphurous acid 63°,
cyanogen 64°. 5, ammonia 60°, arseniuretted hydrogen
54°, sulphuretted hydrogen 5 6°. 5, muriatic acid 43°, car-
bonic acid 32°. 5, nitrous oxide 30° ; and though some of
these numbers are not in the exact order, and in other
cases, as of olefiant gas and nitrous oxide, the curves
sometimes even cross each other, these circumstances
are easily accounted for by the facts already stated of
irregular composition and the inevitable errors of first
results. There seems every reason therefore to expect

Liquefaction of Gases. 67

that the increasing elasticity is directly .as the volatility of
the substance, and that by further and more correct ob-
servation of the forces, a general law may be deduced,
by the aid of which, and only a single observation of the
force of any vapour in contact with its fluid, its elasticity
at any other temperature may be obtained.

Whether the same law may be expected to continue
when the bodies approach near to the CAGNIARD DE LA
TOUR state is doubtful. That state comes on sooner
in reference to the pressure required, according as the
liquid is lighter and more expansible by heat and its
vapour heavier, hence indeed the great reason for its
facile assumption by ether. But though with ether,
alcohol and water, that substance which is most volatile
takes up this state with the lowest pressure, it does not
follow that it should always be so ; and in fact we know
that ether takes up this state at a pressure between
thirty-seven and thirty-eight atmospheres, whereas muria-
tic acid, nitrous oxide, carbonic acid and olefiant gas,
which are far more volatile, sustain a higher pressure
than this without assuming that peculiar state, and
whilst their vapours and liquids are still considerably
different from each other. Now whether the curve which
expresses the elastic force of the vapour of a given fluid
for increasing temperatures continues undisturbed after
that fluid has passed the CAGNIARD DE LA TOUR point or
not is not known, and therefore it cannot well be anti-
cipated whether the coming on of that state sooner or
later with particular bodies will influence them in relation
to the more general law referred to above.

The law already suggested gives great encouragement
to the continuance of those efforts which are directed to
the condensation of oxygen, hydrogen and nitrogen, by
the attainment and application of lower temperatures
than those yet applied. If to reduce carbonic acid from

68 Faraday.

the pressure of two atmospheres to that of one, we require
to abstract only about half the number of degrees that is
necessary to produce the same effect with sulphurous
acid, it is to be expected that a far less abstraction will
suffice to produce the same effect with nitrogen or
hydrogen, so that further diminution of temperature and
improved apparatus for pressure, may very well be ex-
pected to give us these bodies in the liquid or solid state.

Royal Institution*

Feb. 19, 1845.

Northmore on Compressed Gases. 69

APPENDIX.

MR. NORTHMORE'S PAPERS ON THE
COMPRESSION OF GASES.

(Referred to at p. 28.)

I.

Experiments on the remarkable Effects which take place in
the Gases, by Change in their Habitudes, or elective
Attractions, when mechanically compressed. By
THOMAS NORTHMORE, Esq. In a Letter
from the Author*

To Mr. NICHOLSON.

Devonshire Street, Portland Place
SIR, Dec. 17, 1805.

IT was my intention to have postponed troubling you
with the following experiments upon the condensa-
tion of the gases, until I had brought them to a greater
degree of perfection ; but being informed that several of
them have already, by means of which I am ignorant,
and probably in a mutilated state, found their way to
the press, any further delay seems improper. If then you
deem the present communication worthy a place in your
interesting Journal, it is entirely at your service.

It had long ago occurred to me, that the various affini-
ties which take place among the gases under the common
pressure of the atmosphere, would undergo considerable

* [From Nicholson's Journal, vol. 12 (1805), pp. 368-373.]

70 Northmore.

alteration by the influence of condensation ; and the suc-
cess attending the violent method adopted by the French
chemists, which violence did not appear to me requisite,
afforded additional encouragement to my undertaking
some experiments upon the subject.

I communicated this to the late chemical operator in
the Royal Institution, a gentleman eminently conversant
in the science, and with whom I was then engaged in a
series of experiments : he not only approved of my de-
sign, but seemed to think it not improbable that an
extensive field might thus be opened to future discoveries.
Whether these opinions are justly founded, is now left for
you, Sir, and the public to judge.

In entering upon a field entirely new, obstacles were of
course to be expected : nor without reason ; for though I
had applied to one of the most eminent philosophical
instrument-makers in London, Mr. Cuthbertson, yet I
began to fear, even at the outset, that his skill would be
•set at defiance. The first instruments which he made for
the present purpose were, a brass condensing-pump, with
a lateral spring for the admission of the gas by means of
stop-cock and bladder ; two pear-shaped receivers, one of
metal of the capacity of seven cubic inches, and another
of glass of about three and a half : these were connected
by a brass stop-cock, having a screw at each end. The
metallic receiver was soon found to be of little or no
utility, as well on account of its liability to be acted
upon by the generated acids ; its being too capacious,
and thus consuming too large a quantity of gas : as
because, though the result of an experiment might thus
be known, yet the changes which the subjects might
undergo would necessarily escape observation. The glass
receiver obviated all these difficulties, and one or two
imperfect experiments were performed with it : but the
stop-cock speedily failed in its effect. For the power of

Compressed Gases. 71

the compressed gases was so great, partly from their
elasticity, and partly (where affinities had operated) from
their corrosive quality, as absolutely to wear a channel in
the metal of which the plug was made, and thus to effect
their escape. But not to trouble you any further with
the obstacles that occurred, and which are mentioned
only to prevent unnecessary expence to others, I have at
last, by Mr. Cuthbertson's assistance, procured a connect-
ing-tube, to which a spring-valve is adapted that has
hitherto answered every purpose.

The instruments which I now use, are, ist. An ex
hausting syringe ; 2d. A condensing-pump, with two
lateral springs for .different gases ; 3d. The connecting
spring-valve ; and lastly, glass receivers, which should
have been of various sizes, but the one mentioned above
having burst, that which I have principally used in the
following experiments, is of about five cubic inches and
a quarter in capacity, and made of glass well annealed
and a quarter of an inch in thickness. Besides these
instruments, I have occasionally applied Mr. Cuthbert-
son's double syphon-gage, by which the number of
atmospheres condensed in the receiver, or rather the
elastic power of the gases, may be measured ; but this is
rendered of less service, because a stop-cock must then
be placed between the receiver and spring-valve, which
frequently impairs the whole experiment ; and also
because, after a certain degree of condensation, and
more particularly upon the admixture of the gases, new
affinities usually take place, which tend to diminish
the elasticity : the greatest number of atmospheres my
gage has yet measured, is eighteen. These, Sir, with
some bladders and stop-cocks, various iron screw-keys,
and a wooden guard for the legs in case of bursting, con-
stitute the principal part of the requisite apparatus.

I now proceed to the experiments, premising that the

72 Northmore.

first four were made with the imperfect apparatus, when
the gas was continually making its escape through the
stop-cock.

Experiment I.

Into the glass receiver, of three cubic inches and a half
capacity, were compressed in the following order : Hidro-
gen, two (wine) pints ; oxigen, two pints ; nitrogen, two
pints. The result was, water which bedewed the inside
of the receiver; white floating vapours (probably the
gaseous oxide of nitrogen) ; and an acid which reddened
litmus paper. Mr. Accum was present at this experi-
ment, and from his opinion, as well as from succeeding
experiments, I have reason to think that this acid is the
nitric.

Experiment II.

As a difference of arrangement in the order of the gases
tends considerably to vary the result, I repeated the
former experiment (having first poured a little lime-water
into the receiver) by injecting first the oxigen, about
three pints, then equal quantities of hidrogen and nitro-
gen. Much of this gas escaped, owing to the imperfec-
tion of the instrument ; but upon the affusion of the
nitrogen, the white vapours again appeared in the re-
ceiver ; water seemed likewise to be formed ; and some
yellow particles were seen floating upon the lime-water.
These particles probably arose from the resinous sub-
stance, used in fastening on the cap of the receiver,
being dissolved by the nitrous gas formed during con-
densation.

I would just observe, that the magnet seemed to be
affected during this experiment ; but as there is iron used
in the machine, this may be otherwise accounted for.

Experiment III.
Two pints of carbonic acid, and two of hidrogen, were

Compressed Gases. 73

subjected to condensation. The result was, a watery
vapour, and a gas of rather offensive smell.

Experiment IV.

Trying to inflame phosphorus by the condensation of
atmospheric air, the bottom of the machine (where it
had been repaired) burst out with an explosion. This
happened when I had immersed the apparatus in water
to discover where the air escaped. The receiver was full
of the fumes of the phosphorus, which was itself dispersed
in the vessel of water. I afterwards repeated this experi-
ment with the more perfect apparatus, but I could not
inflame the phosphorus, and the fumes which arose at
first soon disappeared. There was just enough acid
(probably phosphoric) formed in the inside of the receiver
to tinge litmus.

Experiment V.

Having now the spring-valve, and new receiver of five
cubic inches and a half capacity, I poured in two scruples
of solution of potash, and then injected two pints of
hidrogen, two of nitrogen, and three of oxigen. This
quantity was hardly sufficient for the capacity of the re-
ceiver, and the result was only a smell of the gaseous
oxide of nitrogen, a few yellowish fumes, and scarce
enough acidity to tinge the edge of the test paper : of
course, I could not effect the formation of nitrate of
potash.

Experiment VI.

I now determined to begin with the nitrogen, which
always appeared to me to undergo the most important
chemical changes, and therefore injected two pints of
nitrogen, three of oxigen, and two of hidrogen. Upon
the condensation of the nitrogen, it speedily assumed an
orange-red colour, which upon the accession of the oxi-
gen, gradually diminished, and at length disappeared,

74 Northmore.

though at first it seemed rather deeper. A moist vapour,
coating the inside of the receiver, arose upon the com-
pression of the hydrogen, which moisture was strongly
acid to the taste, coloured litmus, and, when very much
diluted with water, acted upon silver.

Experiment VII.

Nearly the same as the last, but with different arrange-
ment. The nitrogen, three pints and a half, was first
introduced ; then the hidrogen,* two pints \ and next the
oxigen, three and a half. The nitrogen formed the
orange-red colour as before ; the hidrogen produced
white clouds at first (quczre ammonia ?) which afterwards
disappeared, and the orange-red colour became lighter ;
but upon the affusion of the oxigen, the colour did not
disappear as in the last experiment, but, if any thing,
became darker. I then injected two pints more of hidro-
gen, but this had little or no effect upon the colour.
Some vapour was generated, which was, as usual, strongly
acid.

Experiment VIII.

Previous to the bursting of the small receiver, I had
put in it a scruple of lime, and condensed upon it three
pints of nitrogen. The result was, a little reddish colour
at first, which soon vanished. Upon repeating this ex-
periment in the large receiver, I could produce no colour
at all. In my present state of knowledge I am unable to
account for this circumstance ; but as soon as I get my
new receivers of a smaller capacity, I mean to repeat the
experiment.

Besides the above, I have made various other experi-
ments with different gases, but I think it right to repeat
them with greater accuracy before I submit them to the

* [Oxigen in the original.]

Condensed Gases. 75

eye of the public : if upon that repetition they appear to
me to be attended with results of sufficient importance to
occupy a place in your Journal, I will take the liberty of
communicating them to you, and am, Sir,
Your most obedient servant,

THO. NORTHMORE.

P. S. I think it necessary to add, that during the
course of the above-mentioned experiments, there was a
great variation of temperature in the atmosphere, from
the heat of 70 degrees of Fahrenheit to the cold of 33.

II.

Experiments on condensed Gases. By^. NORTHMORE.*

To Mr. NICHOLSON.
SIR,

1NOW take the liberty of presenting you with a con-
tinuation of my experiments upon the condensation
of the gases, but first beg leave to make one observation,
viz. that the quantity of gas said to be injected in each
experiment, cannot (particularly in the preceding article)
always be depended upon ; for its tendency to escape is
so constant and powerful, as frequently to elude every
effort of mine to prevent it, and if it can find no other
exit, it will sometimes escape by the side of the piston
of the forcing pump. In the preceding experiments I
have endeavoured as much as possible to obviate this
evil, but not always with the success that I could wish.

Repeating the eighth experiment mentioned in my
former letter, (see Vol. XII. p. 372-3) viz. the conden-

* [From Nicholson's Journal, vol. 13 (1806), pp. 233-236.]

?6 . Northmore.

sation of nitrogen upon lime, in order to discover the
cause of the loss of colour in the nitrogen, I perceived
that this arose from its fixation, and a nitrate of lime was
the result. This experiment, on account of the elasticity
of nitrogen previous to its change of habitude, requires
some caution ; for one of my best receivers, three-eighths
of an inch thick, was shivered in pieces with a violent
explosion, after I had set it aside to see the effect of time
upon the compressed gas.

Experiment 9. Upwards of a pint of nitrogen was
condensed, and upon this I pumped one pint of gaseous
oxide of carbon. The colour of the nitrogen was de-
stroyed ; nitrous acid was formed ; and upon collecting
the liberated gaseous oxide, it burnt not unlike alcohol.
The two gases together were at first highly elastic.

From the facility with which nitrogen becomes united
and fixed in various bodies, and from its expansive force
when liberated from that state, I know not whether I am
sufficiently warranted in suggesting an opinion, that the
explosive force of various compounds may in a great
measure be attributed to the sudden liberation of this
fixed gas. To this cause I partly attribute the fulminat-
ing silver of Berthollet ; the fulminating gold, and various
nitrates ; and the detonation which accompanies the de-
composition of ammoniac by oxigenated muriatic acid
gas.

Exp. 10. Having been unsuccessful in my endeavours
to inflame phosphorus by the compression of atmospheric
air, (see Exp. 4.) I now tried oxigen, but with little better
effect. The phosphorus appeared to be somewhat dis-
coloured, and I thought had a tendency to liquify, as it
does when put upon a heated plate of iron. Indeed I
have no doubt that some heat is generated by the con-
densation of air, since the thermometer rises upon exter-
nal application to the receiver.

Condensed Gases. 77

Exp. ii. Upon the compression of nearly two pints
of oxigenated muriatic acid gas in a receiver two and a
quarter cubic inches capacity, it speedily became con-
verted into a yellow fluid, of such extreme volatility
under the common pressure of the atmosphere, that it
instantly evaporates upon opening the screw of the re-
ceiver. I need not add, that this fluid, so highly concen-
trated, is of a most insupportable pungency. When
atmospheric air was pumped into the empty receiver, it
was speedily filled with dense white fumes. There was a
trifling residue of a yellowish substance left after the eva-
poration, which probably arose from a small portion of
the oil and grease used in the machine, mixed with some
of the concentrated gas ; it yielded to sulphuric ether, and
destroyed vegetable colours.

This gas is very injurious to the machine, and on that
account difficult to work.

Exp. 12. Upon half a pint of oxigen was injected one
pint of oxigenated muriatic acid gas. The result was a
thicker substance, which did not so soon evaporate, and
a yellowish mass was left behind.

Exp. 13. Upon half a pint of nitrogen was injected
one pint of oxy-muriatic gas. The result was a still
thicker substance, and the yellow colour deeper, nor did
it appear to act so powerfully upon vegetable colours.
Much of the grease of the machine was carried down in
both these last experiments, which formed part of the
yellow residue, and yielded only to ether.

Exp. 14. Having condensed about a pint of carbonic
acid, the receiver very unexpectedly burst with violence.
This circumstance I attribute to the vicinity of the fur-
nace, and I mention it to guard others against standing
too near a fire in these experiments ; nor perhaps may
it be useless to add another precaution, that of using

78 Northmore.

goggles, or at least a thick plate of glass when examining
the results.

I now took a new receiver of three cubic inches of
capacity, and pumped in one pint of carbonic acid, and
upon this rather more than a pint of oxigenated muriatic
acid gas.

The union produced a light sap-green colour, but no
fluid, though as usual the oil of the machine had retained
enough efficacy to destroy vegetable colours.

Exp. 15. Upon rather more than a pint of hidrogen,
which was highly elastic, were compressed two pints of
the oxigenated muriatic gas. The result was a light
yellow-green colour, and no fluid. Some smoke or
vapour seemed to issue out of the receiver upon turning
the screw, and the gas was highly destructive of colouring
matter.

Exp. 1 6. I now proceeded to the muriatic acid gas,
and upon the condensation of a small quantity of it, a
beautiful green coloured substance adhered to the side of
the receiver, which had all the qualities of muriatic acid ;
but upon a large quantity, four pints, being condensed,
the result was a yellowish-green glutinous substance,
which does not evaporate, but is instantly absorbed by a
few drops of water ; it is of a highly pungent quality,
being the essence of muriatic acid. As this gas easily
becomes fluid, there is little or no elasticity, so that any
quantity may be condensed without danger. My method
of collecting this, and other gases which are absorbable
by water, is by means of an exhausted florence flask (and
in some cases an empty bladder) connected by a stop-
cock with the extremity of the retort.

An idea here occurs to me, that the facility of fixa-
tion which is the property of the compressed muriatic,
oxy-muriatic, and some other gases, may be made of
some utility to the arts, since by previously pouring in

Condensed Gases. 79

a little water, or other fluid into the receiver, an acid
may be obtained of almost any degree of concentration.

Exp. 17. Having collected about a pint and a half of
sulphureous acid gas, I proceeded to condense it in the
three cubic inch receiver, but after a very few pumps
the forcing piston became immoveable, being completely
choked by the operation of the gas. A sufficient quan-
tity however had been compressed to form vapour, and a
thick slimy fluid of a dark yellow colour began to trickle
down the sides of the receiver, which immediately eva-
porated with the most suffocating odour upon the removal
of the pressure. This experiment corroborates the affir-
mation of Monge and Clouet, mentioned in Accum's
chemistry, vol. I. p. 319. viz, that "by extreme artificial
cold, and a strong pressure exerted at the same time,
they rendered sulphureous acid gas fluid. From the
injury which this gas does to the machine, it will be
very difficult to perform any experiments upon its elective
attractions with the other gases.
I remain, Sir,

Your obedient humble Servant,
T. NORTHMORE.

Devonshire Street, Portland Place,
Feb. 15, 1806.

THE DARIEN PRESS, BRISTO PLACE, EDINBURGH.

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