186 THE ROYAL SOCIETY OF CANADA 



Liquid hydrogen is siphoned into the apparatus through the 

 insulated tube E to the lower end of the large spiral D. The hydrogen 

 that is to be purified is controlled by a reducing valve, and enters 

 the coils of the two exchangers J and K arranged in parallel. It then 

 passes down over the outside of the spiral D. As the liquid hydrogen 

 is continuously vapourized within this spiral the latter is kept at a 

 very low temperature with the result that the gaseous impurities are 

 condensed out upon the external surface. 



The vapourized hydrogen rises in the spiral and passes out 

 through the regenerator K to the gasometer. The purified hydrogen, 

 upon reaching the bottom of the spiral, passes upward through a 

 fibre tube and the regenerator / to the gasometer, from which it is 

 compressed into cylinders. 



A silvered vacuum flask F insulates the coil while a German silver 

 cylinder A supports the flask and serves to keep the apparatus her- 

 metically sealed. Thermocouples Gi and 6*2 serve to determine the 

 rate of flow of the gas, since they indicate the temperature along the 

 spiral. The arrangement of the connecting pipes is shown clearly in 

 Fig. 3 in which Hi and H^ are mercury safety valves that protect the 

 apparatus at all times. The purifier is entirely wrapped in wool and 

 surrounded with a brass case as shown in Plate II, 1. 



It is capable of purifying approximately 5 cubic metres per hour 

 and requires in this time about 5 litres of liquid hydrogen. It is not 

 suitable for work with hydrogen that has not undergone a preliminary 

 purification, as during the operation all the impurity in the gas remains 

 behind as solid, and is only removed at the close of the operation, 

 when as the temperature rises the nitrogen or other impurities are 

 drawn off by means of a vacuum pump. 



V. The Hydrogen Ligiiefier 



The liquéfier is represented schematically by Fig. 4, while Plate 11,2 

 shows a photograph of the apparatus as it is installed in the Physical 

 Laboratory at Toronto. It will be recognized that the principle of the 

 construction is the same as that of the apparatus described in the first 

 Communication from the Laboratory on this subject. The Joule- 

 Thomson effect and Dewar's ingenious method of placing the re- 

 generator coil in a vacuum flask are utilised. The regenerator coils 

 are similar to those used in Hampson's apparatus for liquefying air. 

 A number of features peculiar to the Leiden installation are also 

 included. 



Pure hydrogen is compressed to 200 atmospheres and cooled to 

 — 205°C. by means of liquid air boiling under reduced pressure. 



