116 On the Liquefaction and Solidification [1844. 



evidently two bodies, the dry acid which froze out first, and 

 then the hydrate, which requires at least 30 below before 

 it will solidify. 



The following gases showed no signs of liquefaction when 

 cooled by the carbonic acid bath in vacuo, even at the pressures 



expressed : 



Atmospheres. 



Hydrogen at ... . . . 27 



Oxygen ........ 7 



Nitrogen . 50 



Nitric oxide ... . . . 50 



Carbonic oxide . " . . . 40 



Coal-gas . ; V-; J . . . 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 de la Tour has shown that at a certain tempe- 

 rature, a liquid, under sufficient pressure, becomes clear trans- 

 parent 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 0, low as it is, is probably above this point of 

 temperature for hydrogen, and perhaps for nitrogen and oxy- 

 gen, 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 pressure of from twenty-seven 

 to fifty atmospheres at a temperature of 166 below 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 of 

 gases have been made by M. G. Aime*, in which oxygen, 



* Annales de Chimie, 1843, viii. 275. 



