190 



THE ROYAL SOCIETY OF CANADA 



To OASOMCTSR ^ 



To VACUUM ptMP 



NfLIUM 



PURIFIER 



Fig 5 



and a swathing of natural wool. After being partially purified in the 

 manner indicated the gas is passed through the reducing valve Fi, 

 and at low pressure through six cocoanut charcoal tubes, Z>i, D<i, etc. 

 From these it is collected in the gasometer and finally compressed 

 into tanks, to be introduced later into the liquefying system. In the 

 construction of the apparatus care was taken to reduce its size to a 

 minimum, so that the co'nsumptio'n of liquid air would not be very 

 great, even although the alternate heating and cooling of the charcoal 

 tubes necessitated our making the process of purification a dis- 

 continuous one. 



VII. The Helium Liquéfier 



As the design of the hydrogen liquéfier proved to be a highly 

 efficient one it was deemed advisable to construct the helium liquéfier 

 on the same general principles, but on a considerably reduced scale. 

 It will be recalled that in the operation of a helium liquéfier, liquid 

 hydrogen must be employed to cool the helium below the temperature 

 at which the Joule-Thomson effect changes sign. When the gas is 



