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least in any considerable quantity, with that fluid, but floated
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 gauge to be 3*6 or 3'7 atmospheres at 45 F. Its spe-
cific 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, 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 limb, whilst the
other was cooled by ice or water. The compound thus heated
under pressure fused at a comparatively low temperature, and

* Quarterly Journal of Science, v. 74 ; see also page 18.



1823.] of several Gases into Liquids. 95

boiled, giving off ammoniacal gas, which condensed at the
opposite end into a liquid.

Liquid ammonia thus obtained was colourless, transparent,
and very fluid. Its refractive power surpassed that of any
other of the fluids described, and that also of water 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 pro-
duced, 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 atmospheres at 50. Its spe-
cific gravity was 0*76.

Muriatic Acid. When made from pure muriate of ammonia
and sulphuric 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. The pres-
sure 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, fluo-
boracic, 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 hope that some of them, at least, will ultimately
condense.



96 On the Liquefaction and Solidification [1844.

On the Liquefaction and Solidification of Bodies generally
existing as Gases*.

[Received Dec. 19, 1844, Read Jan. 9, 1845.]

THE experiments formerly made on the liquefaction of gases f,
and the results which from time to time have been added to
this branch of knowledge, especially by M. Thilorier J, have
left a constant desire on my mind to renew the investigation.
This, with considerations arising out of the apparent simplicity
and unity of the molecular constitution of all bodies when in
the gaseous or vaporous state, which may be expected, ac-
cording 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 ex-
periments on the subject ; and though my success has not
been equal to my desire, still I hope some of the results ob-
tained, 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 pressure with
considerable depression of temperature. To obtain the pres-
sure, 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 associated 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 atmospheres,
into its final recipient at a much higher pressure.

The gases to be experimented with were either prepared
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,

* Phil. Trans. 1845, p. 155. f Ibid. 1823, pp. 160, 189.

% Annales de Chimie, 1835, 1 X . 427, 432.



1844.] of Bodies generally existing as Gases. 97

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 tempera-
ture of Fahr. ; the water that was condensed here was all
deposited in the first two inches of the coil.

The condensing tubes were of green bottle glass, Fig. 1.
being from ^th to ^th of an inch external diameter,
and from ^nd to y^th of an inch in thickness.
They were chiefly of two kinds, about 11 and 9
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 horizontal tube, and the longest leg of
the siphon tube, pressure-gauges were introduced
when required.

Caps, stopcocks 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

Fig. 2.





of the glass tubes entered freely into them, and had rings or a
female screw worm cut in the interior, 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 to each other. These junctions bore a press-
ure 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, stopcocks, and connectors, screwed one into the

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

H



98 On the Liquefaction and Solidification [1844*

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
stopcocks. All these screw joints were made tight by leaden
washers ; and by having these of different thickness, equal to
from ^ths to ^-ths 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 external 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 Ibs.
on the square inch. A tube which had been used, of the shape
of fig. 1, its external diameter being 0*225 of 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 of an inch, burst at twenty-five atmospheres.

Having these data, it was easy to select tubes abundantly
sufficient in strength to sustain any force which was likely to
be exerted within them in any given experiment.

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 compress a given portion of air into y^th
or ^th of its bulk at the pressure of one atmosphere of 30
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 var-
* Philosophical Transactions, 1823, p. 192; see also p,91,



1844.] of Bodies generally existing as Gases. 99

nish to liquefy, but then the Indian ink stood. For further pre-
caution, an exact copy of the gauge was taken on paper, to be
applied on the outside of the condensing 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 Thilo-
rier's mixture of solid carbonic acid and ether was used. An
earthenware dish of the capacity of 4 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 ob-
tained depended more upon depression of temperature than on
the pressure which I could employ in these tubes, I endea-
voured 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, solidification has not as yet been con-
ferred on a fluid by any degree of pressure. Again, that beau-
tiful 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 tempera-
ture 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 ^th of an atmosphere, or ! inch of mer-
cury ; for the air-pump barometer could be kept at 8'2 inches
when the ordinary barometer was at 29*4. At this low tempe-
rature the carbonic acid mixed with the ether was not more
volatile than water at the temperature of 86, or alcohol at
ordinary temperatures.



100 On the Liquefaction and Solidification [184-4.

In order to obtain some idea of this temperature, I had an
alcohol thermometer made, of which the graduation was carried
below 32 Fahr., by degrees equal in capacity to those between
32 arid 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 0.
When it was introduced into the bath under the air-pump, it sank
to the temperature of 166 below 0; 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 temperature 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 -

when the mercury in the air-"\ , ' the bath tempe-l __JQ^

pump barometer was. . / rature was. . j

33 > 33 33 t) )> 33 ***lj

t3 33 33 33 6\) 33 33 33 I

99

j> 39 39 99 39 "6 33 it it

tt 99 3 i) ^ a 93 39

9(\

J> 33 99 ^ U 99 J) 33

97

t) )> >J 33 33 ~* 33 33 39

9S
J> J> 33 33 33 33

9R'9
i> JJ 33 33 **<3 A ,, ,, ,,

but as the thermometer takes some time to acquire the tempera-
ture of the bath, and the latter was continually falling in degree ;
as also the alcohol thickens considerably at the lower tempera-
ture, 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 29 inches when the external
barometer was at 30 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 receiver open at the top was
employed ; the brass plate which closed the aperture had a
small brass tube about 6 inches long, passing through it air-
tight by means of a stuffing-box, so as to move easily up and



131,



1844'.] of Bodies generally existing as Gases. 101

down in a vertical direction. One of the glass condensing
siphon tubes, already described, fig. 1, was screwed on to the
lower end of the sliding tube, and the upper end of the latter
was connected with a communicating tube in two lengths,
reaching from it to the condensing pumps ; this tube was small,
of brass, and 9J feet in length ; it passed 6 inches horizontally
from the condensing pumps, then rose vertically for 2 feet, after-
wards proceeded horizontally for 7 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 connexions, and the condensing tube low-
ered into the cold bath in vacuo, or raised to have its contents
examined at pleasure. The capacity of the connecting tubes
beyond the last condensing pump was only 2 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 condensing tube, which,
being the very extremity of the apparatus, was left a little
loose. Then, by the condensing 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 press-
ure of one atmosphere when submitted to the cold of a car-
bonic 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 conduct-
ing tubes into tubular receivers placed in the cold bath. When
the receivers had previously 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
substances in their condensed state. In this manner chlorine,
cyanogen, ammonia, sulphuretted hydrogen, arseniuretted hy-
drogen, 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 se-
cured in the same way.



102 On the Liquefaction and Solidification [1844.

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 con-
centric 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, produced 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 stopcock, 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 stopcock by a blank female screw-cap and leaden
washer, and also to tighten perfectly the screw of the stopcock
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 condensing 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 vacuo 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, colourless,
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.

* On one occasion the solid carbonic acid was exceedingly electric, but I
could not produce the effect again : it was probably connected with the pre-
sence 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*



184-4.] of Bodies generally existing as Gases. 103

The pressure of the vapour of this substance at the tempera-
ture 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
Fahr., with two different specimens obtained at different
times, and it will illustrate this point.

Fahr. Atmospheres. Atmospheres.

-100 .... 4-60 .... 9-30

- 90 . .-; V . 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

27-18

10 . . * '.' ,i. ' : * * u . 31-70

20 . . * . * v . 4 . . 36-80

30 . . . - 42-50

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

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

Hydriodic Acid. 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 re-
sembling those that run through ice. Its solidifying tempera-
ture is nearly 60 Fahr., and then its vapour has not the
pressure of one atmosphere ; at a point a little higher it be-



104 On the Liquefaction and Solidification [1844.

comes a clear liquid, and this point is close upon that which
corresponds 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 stopcock 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 approxi-
mations :

At Fahr. pressure was 2*90 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 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 0, or lower, and has not the pressure of one atmo-
sphere 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, transparent,
crystalline body. It does not freeze until reduced much lower
than this temperature ; but being frozen by the carbonic acid
bath in vacua, it remains a solid until the temperature in rising
attains to 124.

Fluosilicon. I found that this substance in the gaseous
state might be brought in contact with the oil and metal of the
pumps, without causing injury to them, for a time sufficiently

* 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 inclining the tube, the vapour of bro-
mine 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 perbromide. The excess of bromine may be dissipated by the careful
application of heat.



1844.] of Bodies generally existing as Gases. 105

long to apply the joint process of condensation already de-
scribed. The substance liquefied under a pressure of about
nine atmospheres at the lowest temperature, or at 160 below
0; 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 next day. Some leakage had then taken place (for it
ultimately acted on the lubricating fat of the stopcock), and



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