The Homogeneity of Helium and Argon. 209 



nate, took to diffuse to the same extent was 1719", giving an 



average rate per millimetre of 2T49". 

 (c) Acetylene. The gas was prepared from pure calcium carbide 



by the action of water. It dissolved completely in alcohol. 



The time required for diffusion was 1550", giving a rate per 



millimetre of 19-37". 



Assuming the times for the diffusion of these gases to be pro- 

 portional to the square roots of their densities, we have 



For oxygen _ _ 2 l-39". Found 21-49". 



\/l-0082 



For acetylene 5 ' 37 "* ^ 13 ' 008 = 19-29". Found 19-37". 

 A/I -0082 



This process may therefore be trusted to give fairly accurate 

 results when applied to test the rates of diffusion of gases of known 

 purity. 



The Separation of a Mixture of Gases. 



To ascertain whether a separation could be easily effected, experi- 

 ments were made (a) on a mixture of oxygen and carbon dioxide, 

 and (6) on a mixture of hydrogen and helium. 



(a) Oxygen and Carbon Dioxide. The original mixture contained 

 36 per cent, by volume of carbon dioxide. It was split into two 

 approximately equal portions ; each of these was again split into 

 two. The most diffusible part contained 30'2 per cent, of carbon 

 dioxide, and the least diffusible part 41 '0 per cent. 



(6) Hydrogen and Helium. The original mixture contained 50 per 

 cent, of each gas, and its volume was 38 c.c. 19 c.c. were diffused ; 

 this was again halved, 9*5 c.c. being passed through the pipe ; and 

 finally another diffusion of the 9'5 c.c. yielded 4*12 c.c. of mixed 

 gases. The hydrogen was removed by explosion with oxygen. 

 This mixture now consisted of 67 per cent, of hydrogen and 33 per 

 cent, of helium. 



From these experiments it is seen that a partial separation of such 

 gases is easily carried out. 



The Fractional Diffusion of Argon. 



Four hundred c.c. of argon, newly circulated over red-hot magne- 

 sium until spectroscopic traces of nitrogen were carefully removed, 

 was diffused according to the subjoined scheme : 



