I 



I July 28, 1923] 



NATURE 



137 



increase of pressure such as might arise from the break- 

 ing of the flask M3. 



In operating with the hydrogen liquefier it was found 

 necessary to remove all gaseous impurities from the 

 gas. The commercial hydrogen used was made 

 electrolytically and was found to contain as much as 

 1-5 per cent, of oxygen and o-i- 0-3 per cent, of nitrogen. 

 To purify this gas it was passed through a high pressure 

 bomb filled with palladiumised asbestos. This bomb 

 was heated electrically to about 400° C, and at this 

 temperature the palladium acted as a strong and 

 robust catalyser. The water produced 

 by the union of hydrogen with the 

 oxygen present was taken up with 

 caustic potash. The hydrogen ob- 

 tained after this preliminary purifica- 

 tion was again purified by passing it 

 through a specially constructed appar- 

 atus provided with coils cooled with 

 liquid hydrogen, but to make the 

 liquid hydrogen for carrying out this 

 purification it was necessary to oper- 

 ate the hydrogen liquefier with the 

 hydrogen subjected to the preliminary 

 purification only. A few litres only 

 could be made in a run before stop- 

 page occurred, and this was used to 

 effect the final purification of a certain 

 quantity of the gas. 



By repeated operations of this char- 

 acter a supply of about 100 cubic 

 metres of highly purified hydrogen 

 was gradually accumulated, and with 

 it long runs of the liquefier were made 

 without any stoppage occurring. To 

 conserve this original supply of pure 

 hydrogen care had to be taken during 

 a run to store up all gas from the 

 vaporised hydrogen and to use resi- 

 dual supplies of liquid hydrogen to 

 purify additional quantities of the 

 gas so as to make up losses. 



In liquefying hydrogen as well as 

 helium, it was necessary in order to 

 avoid losses so far as possible to oper- 

 ate in a closed cycle that included a 

 gasometer, the compressor and the 

 liquefier. In a number of actual runs 

 with the apparatus described above, 

 no difficulty was experienced in mak- 

 ing from 10 to 15 litres of liquid 

 hydrogen an hour, and in one particular run as much 

 as 50 litres of liquid hydrogen was accumulated. 



Liquid Helium Apparatus. 



The helium used in the experiments was obtained 

 from the natural gas of the Bow Island district near 

 Calgary, Alberta, in the year 1919-20, and had been 

 kept since then safely stored in steel cylinders at about 

 150 atmospheres pressure. An analysis by means of 

 absorption with cocoanut charcoal showed the gas in 

 different cylinders to be about 90-95 per cent, helium. 

 The chief impurity was nitrogen, with a varying per- 

 centage of methane and other gases. Tests made by 



NO. 2804, VOL. I I 2] 



chemical absorption and explosion methods gave no 

 indication of hydrogen being present. 



The preliminary purification of the helium was 

 effected by cooling it at a pressure of 150 atmospheres 

 to -205° C. by means of liquid air boiling under reduced 

 pressure. Under these conditions a large percentage 

 of the impurity was condensed and drawn off. This 

 partially purified helium was passed at high pressure 

 first through a bomb filled with copper oxide and 

 palladiumised asbestos maintained at a temperature of 

 400° C, and then through heavy copper tubes filled 



Fig. 3. — Helium liquefier. 



with cocoanut charcoal and immersed in liquid air. 

 This cycle of purification proved to be satisfactory, 

 for during the liquefaction process there was no evidence 

 at any time of any blocking of the expansion valve 

 of the liquefier or of the very small capillary tubes 

 that made up the expansion coil. 



In the design and construction of the helium liquefier, 

 special attention was given to problems connected with 

 the heat capacity and heat insulation of the various 

 parts of the apparatus. The liquefier is shown dia- 

 grammatically in Fig. 3 and the manner in which it was 

 installed in the laboratory is shown in Fig. 4. 



In the operation of the liquefier the manner in which 

 the helium entered the apparatus is shown in the 



