Separation of the most Volatile Gases from Air. 127 



A repetition of the same process with the 23 per cent, of oxygen would 

 bave raised the percentage about 60 per cent., or a stronger concentra- 

 tion could have been reached by fractionating the gas as it slowly 

 leaves the charcoal on gradually increasing the temperature. 



This preliminary investigation suggests many fields for further 

 inquiry, and some of these I hope to deal with in future papers. 



I have to express my thanks to Mr. Eobert Lennox, F.C.S., for 

 efficient aid in the conduct of the experiments, and Mr. J. W. 

 Heath, F.C.S., has also rendered valuable assistance. 



" The Separation of the most Volatile Gases from Air without 

 Liquefaction." By Sir JAMES DEWAR, M.A., D.Sc., LL.D., 

 F.R.S., Jacksoniau Professor, University of Cambridge, and 

 Fullerian Professor, Royal Institution, London. Received 

 June 15, Read June 16, 1904. 



From the time when liquid air came to be an ordinary laboratory 

 agent, I have continually used it for the purpose of producing high 

 vacua in vessels that had been previously filled with easily condensable 

 gases, like sulphurous acid, carbonic acid, vapour of water or benzol. 



When the liquefaction of hydrogen was effected one of the first 

 scientific uses to which it was put was that described in my paper on 

 the " Application of Liquid Hydrogen to the Production of High 

 Vacua, together with their Spectroscopic Examination."* In that 

 communication it was shown by theory and confirmed by experiment 

 that the condensing power of liquid hydrogen is so great relatively to 

 that of liquid oxygen or nitrogen, that any closed vessel, a part of 

 which is cooled to the boiling point of hydrogen must suddenly become 

 a highly vacuous space. This was proved by the great difficulty of 

 getting electric discharges to pass through specially prepared spectro- 

 scopic tubes when subjected to liquid hydrogen cooling, and from the 

 fact that when the current did pass no lines of oxygen or nitrogen 

 were seen, but only those of hydrogen, helium and neon. In order to 

 separate these latter gases from air it was necessary to liquefy a 

 quantity of air and to distil off the most volatile portion at as low a 

 temperature as possible into a separate receiver placed in liquid 

 hydrogen. In this way many spectroscopic tubes were filled with the 

 uncondensable air gases and the results of their examination is recorded 

 in a paper entitled " On the Spectra of the more Volatile Gases of 

 Atmospheric Air, which are not Condensed at the Temperature of 

 Liquid Hydrogen,"! by Professor Liveing and myself. 



* 'Roy. Soc. Proc.,' vol. 64., 1898. 

 t ' Roy. Soc. Proc.,' vol. 67, 1900. 

 VOL. LXXIV. K 



