[MCLENNAN & shrum] LIQUEFACTION OF HYDROGEN 189 



closed until the pressure reaches 200 atmospheres. Some of the cold 

 hydrogen is used to pre-cool the valves B and Bi and various other 

 parts of the apparatus. As liquid is drawn off it is necessary to 

 introduce fresh hydrogen into the gasometer. The liquéfier will 

 deliver 10 to 15 litres of liquid hydrogen per hour. The pre-cooling 

 of the coils requires about 10 litres of liquid air per hour. Thus a 

 very moderate supply of liquid air is quite sufîfîcient for the production 

 of a large quantity of liquid hydrogen. 



VI. The Helium and its Purification 



The helium was obtained by Professor McLennan from the 

 natural gas of the Bow Island district, near Calgary, Alberta, in the 

 year 1919-20, and has been kept since then safely stored in steel 

 cylinders at about 150 atmospheres pressure. An analysis by means 

 of absorption with cocoanut charcoal showed that it was about 

 90 per cent. pure. The impurity consisted chiefly of nitrogen with 

 a varying percentage of methane. A Shakspear katharometer, such 

 as is ordinarily used for hydrogen has been properly calibrated and 

 is mounted for testing the purity of the gas during the operation of 

 the cycle. 



It is proposed to eliminate a large percentage of the impurity 

 in the helium by means of the condensation produced as it is cooled 

 by liquid air boiling under reduced pressure. In this manner, when 

 the pressure of the helium is 150 atmospheres, the percentage of 

 nitrogen may be reduced to less than . 5 per cent. The remainder 

 of the impurity other than hydrogen it is proposed to absorb by 

 means of cocoanut charcoal at the temperature of liquid air. Traces 

 of hydrogen are removed by absorption with Cu O, or burning with 

 oxygen in the presence of palladiumized asbestos. 



Fig. 5 shows the apparatus diagrammatically while Plate II, 3 is a 

 photograph of the actual installation. The impure gas enters the 

 outer tube of a spiral generator of the Linde type and passes thence 

 through a spiral coil immersed in liquid air boiling at a pressure of 

 5 cms. of mercury. Any impurity that is condensed collects in the 

 trap T while the purified gas passes through the central tube of the 

 spiral regenerator to the valve Vi. The impurity from the trap is 

 drawn off and collected through the micrometer valve F3. An analysis 

 of the gas that is collected serves to determine the quantity that 

 should be drawn off. The level of the liquid air is shown by the 

 indicator B of the cork float Bi. The valve M controls the supply of 

 liquid air that is drawn over into the apparatus from the store bottles. 

 Insulation for the apparatus is provided by a silvered vacuum flask F 



