LIQUEFAC′TION. The assumption of the liquid form. It is usually applied to the conversion of a solid into the liquid state, which may arise from increase of temperature
(fusion), absorption of water from the atmosphere (deliquescence), or the action of a body already fluid (solution).
Liquefaction of Gases. Under the combined influence of pressure and cold, all the gases may be liquefied, and some even solidified. The first satisfactory experiments in this direction were made by Faraday, who succeeded in reducing to the liquid condition eight bodies which had hitherto been regarded as permanent gases, namely, ammonia, carbonic anhydride, chlorine, cyanogen, hydrochloric acid, nitrous oxide, sulphuretted hydrogen, and sulphurous anhydride. His method of proceeding was very simple:—the materials were sealed up in a strong, narrow, glass tube, bent so as to form an obtuse angle, together with a little ‘pressure gauge,’ consisting of a slender tube closed at one end, and having within it, near the open extremity, a globule of mercury. The gas, being disengaged by the application of heat or otherwise, accumulated in the tube, and by its own pressure brought about liquefaction. The force required for this purpose was judged of by the diminution of volume of the air in the pressure gauge. By employing powerful condensing syringes, and an extremely low temperature, Faraday subsequently succeeded in liquefying olefiant gas, hydriodic and hydrobromic acids, phosphuretted hydrogen, and the gaseous fluorides of silicon and boron. He failed, however, with oxygen, hydrogen, nitrogen, nitric oxide, carbonic oxide, and coal-gas, all of which refused to liquefy at the temperature of -166° Fahr., while subjected to pressures varying in different cases from 27 to 58 atmospheres.
Within the last year, however, viz. toward the end of 1877, these hitherto refractory gases have been reduced to the liquid, and, in the case of hydrogen, to the solid state. These results have been accomplished by subjecting the gases to a pressure considerably greater than that employed by Faraday, combined with the expedient of the sudden removal of this pressure, whereby the escaping gas (previously enormously reduced in temperature) in the act of expansion robs the remainder of so much of its heat as to leave it in the fluid condition.
The liquefaction of oxygen was accomplished independently by M. Cailletet, of Paris, and M. Pictet, of Geneva; the French chemist having effected it on December 2nd, 1877, and the Swiss one on the 22nd of the same month.
Simultaneously with Cailletet’s announcement of the liquefaction of oxygen, that of carbonic oxide was made by the same chemist; who, about three weeks after at a meeting in the Paris Academy of Sciences, stated that he had also reduced hydrogen, nitrogen, and atmospheric air to the fluid state.
In the previous November he had been equally successful in converting gaseous nitric oxide into a liquid.
M. Cailletet, in a communication to the Paris Academy of Sciences, read by M. Dumas at a meeting of that body on 24th December, 1877, thus describes the process by which he liquefied the gases oxygen and carbonic oxide.
“If oxygen or pure carbonic oxide be enclosed in a tube such as I have before described, and placed in an apparatus for compression like that which has already been worked before the Academy,[17] and the gas be then lowered in temperature to 29° C., by means of sulphurous acid and at a pressure of about 300 atmospheres, the two gases preserve their gaseous state.
[17] This apparatus, which consists of a hollow steel cylinder, to which is attached a strong glass tube, is described in the ‘Comptes Rendus,’ tome 85, p. 851. The gas is forced into it by means of a hydraulic pump with the intervention of a cushion of mercury.