210 Liming and Dewar — Separation of the Least Volatile 



B and the pump. The tube e was partly immersed in liquid 

 air in order to condense vapor of mercury, which would other- 

 wise pass from the pump into the sparking tube. The gas 

 passing into the sparking tube would, of course, have a pres- 

 sure corresponding to the temperature of B, and this was 

 further ensured by making the connecting tube pass through 

 the liquid in which B was immersed. The success of the 

 operation of separating all the gases which occur in air and 

 which boil at different temperatures depends on keeping the 



Inlet-. 



Jbfyutnp 



^ 



temperature of B as low as possible, as will be seen from the 

 following consideration : — 



The pressure j?, of a gas G, above the same material in the 

 liquid state, at temperature 1\ is given approximately by the 

 formula 



log^ = A- — , 



where A and B are constants for the same material, 

 some other gas G' the formula will be 



]ogp 1 = A 



For 



and 



log 



P 



A-A x + 



T ' 

 B-B 



Pl T 



Now for argon, krypton, and xenon respectively the values of 

 A are 6 '782, 6'972, and 6'963, and those of ^'are 339, 496"3, 



