[edwards-elworthy] continuous FLOW APPARATUS 49 



a fact sadly referred to by the author^ of a German aeronautical 

 book published in 1914, after pointing out the great advantage of using 

 helium as a balloon gas. 



On account of the great advances which have now been made in 

 the commercial separation of helium from natural gas, more rapid 

 laboratory methods of purification are required. 



Most of the work on the absorptive power of charcoal has been 

 carried out at low pressures. Dewar,^ however, investigated the 

 volumes of various gases absorbed at atmospheric pressure, the heat 

 evolved during the absorption and the rate of absorption. 



Claude^ published data on the charcoal absorption of nitrogen, 

 hydrogen, neon and helium at pressures varying from a few hundredths 

 of a millimeter to 247 mms. He found that the volumes absorbed 

 increased with pressure although a considerable time was required 

 for the complete establishment of equilibrium at the higher pressures. 



In view of this work it was considered probable that cooled 

 charcoal would be effective in removing nitrogen from impure helium, 

 passing over its surface at atmospheric pressure at a slow rate. 



As a result of successful preliminary experiments the apparatus 

 described in the following paper was constructed. 



It consisted essentially of two sets of charcoal tubes arranged in 

 parallel so that when one set became saturated with impurity the gas 

 flow could be diverted through the second set while the first set of 

 tubes was revivified. 



Description of Apparatus 



The diagrammatic sketch, Fig. 1, indicates the general arrange- 

 ment of the apparatus. The impure gas passed from the gasometer 

 (a) through a Venturi meter to approximately measure the rate of 

 flow (b) through a drying train into (c) either set of charcoal tubes as 

 desired, (d) past the side tubes leading to the exhaust pump, to (e) a 

 Shakespear Hydrogen Purity Meter, which, calibrated for helium*, 

 showed the purity of the treated gas and through it (b) into the re- 

 ceiving bottle and finally into the storage bottles. The purity was 

 also checked by density measurements. 



The appearance of the central portion of the apparatus is shown 

 in Fig. 2, which represents the two sets of charcoal tubes arranged 

 in parallel and the six mercury seals used instead of glass stop cocks 



1 G. Austerweil. Die Angewandte Chemie in der Luftfahrt. 



2 Dewar. Loc. cit. Also Proc. Roy. Inst. 21-240-1914. 



3 Claude. Comptes Rendus. 1914, 158, 861. 

 * V. F. Murray, vide this journal. 



