541 



considerable depressions of temperature. The first object was ob- 

 tained by tiie successive action of two air-pumps; the first having a 

 piston of one inch in diameter, by which the gas to be condensed 

 was forced into the cylinder of the isecoud pump, the diameter of 

 whose piston was only half an inch. The tubes into which the air, 

 thus further condensed, was made to pass, were of green bottle 

 glass, from one-sixth to one-quarter of an inch in external diameter, 

 and had a curvature at one portion of their length adapted to im- 

 mersion in a cooling mixture : they were provided with suitable 

 stop-cocks, screws, connecting pieces, and terminal caps, all very 

 carefully made, and rendered sufficiently air-tight to retain their 

 gaseous contents under the circumstances of the experiments, and 

 when they were sustaining a pressure of fifty atmospheres, as ascer- 

 tained by mercurial gauges connected with the apparatus. Cold was 

 applied to the curved portions of the tube by their immersion in a 

 bath of Thilorier's mixture of solid carbonic acid and ether. The 

 degree of cold thus produced, when the mixture was surrounded by 

 the air, estimated by an alcohol thermometer, was a temperature of 

 — 106° Fahr. But on placing the mixture under an air-pump, and 

 removing the atmospheric pressure, leaving only that of the vapour 

 of carbonic acid, which amounted only to l-24rth of the former, (that 

 is to the pressure of a column of 1'2 inch of mercury,) the ther- 

 mometer indicated a temperature of 166° below zero of Fahrenheit's 

 scale. 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. 



The author found that there were many gases which, on being sub- 

 jected to cold of this extreme intensity, condensed into liquids, even 

 without a greater condensation than that arising from the ordinary at- 

 mospheric pressure, and that they could then be preserved, sealed up 

 in glass tubes, in this liquid state. Such was the case with chlorine, 

 cyanogen, ammonia, sulphuretted liydrogen, arseniuretted hydrogen, 

 hydroiodic acid, hydrobromic acid, carbonic acid, and euchlorine. 

 With respect to some other gases, such as nitric oxide, fluosilicon, 

 and olefiant gas, it was difficult to retain them for any length of 

 time in the tubes, in consequence of the chemical action they exerted 

 on the cements used in the joinings of caps and other parts of the 

 apparatus. Hydroiodic arid hydrobromic acids could be obtained 

 either in the solid or liquid state. Muriatic acid gas did not freeze 

 at the lovN-est temperature to which it could be subjected. Sulphu- 

 rous acid froze into transparent and colourless crystals, of greater 

 specific gravity than the liquid out of which they were formed. 

 Sulphuretted hydrogen solidified in masses of confused crystals of a 

 Avhite colour, at a temperature of —122° Fahr. Euchlorine w^as 

 easily converted from the gaseous state into a solid crystalline body, 

 which, by a slight increase of temperature, melted into an orange- 

 red fluid. Nitrous oxide was obtained solid at the temperature of 

 the carbonic acid bath in xacuo, and then appeared as a beautifully 

 clear and colourless crystalline body. The author conceives that in 

 this state it might, in certain cases, be substituted with advantage 

 for carbonic acid in frigorific processes, for arriving at degrees of 



