52 THE ROYAL SOCIETY OF CANADA 



The first set of charcoal tubes was given the most complete 

 trial. The following volumes of pure gas were recovered before the 

 charcoal was saturated. 



Run III 23 -6 litres 



« IV 21-3 " 



" VI 25-0 " 



« VII 21-2 " 



Mean 22-8 « 



The impure gas contained 88% "C" gas, therefore 26 litres of 

 impure gas was treated on an average. Ninety grams of cocoanut 

 charcoal was saturated by 3 litres of impurity (in this case nitrogen). 

 The partial pressure of the nitrogen was about 90 mms. From 

 Claude's data 11-2 litres of nitrogen was absorbed at 90 mms. by 100 

 gms. of charcoal, but the gas was left in contact with the charcoal for 

 hours. In these experiments the impure helium was in contact with 

 the charcoal for from one to two minutes only. It is probable that 

 charcoal in a more efficient condition could be prepared, resulting in 

 an even greater volume of gas being passed through before the char- 

 coal becomes saturated. 



Summary 



The results of the tests show: 



1. That helium containing at least 12% impurity can be readily 

 purified bypassing in a continuous stream over charcoal at the tempera- 

 ture of liquid air or oxygen. 



2. The rate of flow can be increased up to at least ten litres an 

 hour without decreasing the efficiency of the process. The maximum 

 possible rate of flow was not determined. 



3. By the use of two or more sets of charcoal tubes, arranged in 

 parallel, the process may be made a continuous one as this form of 

 apparatus permits of revivification of the charcoal without disturbing 

 the flow. 



This work was carried out at the Admiralty Physical Laboratory, 

 South Kensington, under the direction of Professor J. C. McLennan, 

 F.R.S. 



