Argon in the Vapour rising from Liquid Air. 679 



the comparison may be made by means of Mr. Baly's 

 observations (Phil. Mag. xlix. p. 517, 1900). It will appear, 

 for example, that when the vapour contains 30 per cent, of 

 oxygen, the liquid will contain about 60 per cent., and that 

 when the vapour contains 90 per cent, the liquid will be of 

 95 or 96 per cent. At every stage the liquid will be the 

 stronger in the less volatile constituents ; so that the 

 proportion of argon to nitrogen, or to nitrogen + argon, 

 will be higher in the liquid than in the vapour. 



The constancy of the proportion of argon to the whole 

 over a considerable range may be explained to a certain 

 extent, for it will appear that the proportion must rise to 

 a maximum and thence decrease to zero. To understand 

 this, we must remember that "liquid air" is something of a 

 misnomer. In the usual process the whole of the air 

 concerned is not condensed, but only a part ; and the part 

 that is condensed is of course not a sample of the whole. As 

 compared with the atmosphere the liquid contains the less 

 volatile ingredients in increased proportion, and the part not 

 condensed and rejected contains the more volatile ingredients 

 in increased proportion. The vapour coining away from the 

 liquid as first collected has the same composition as the gas 

 rejected in the process of condensation. At the beginning 

 of our table, a point, however, which it would be difficult to 

 reach in actual experiment, we should have an oxygen 

 content much below 20 per cent., a ratio of argon to nitrogen 

 + argon below 1 per cent., and in all probability a ratio of 

 argon to the whole also below 1 per cent. 



The object which I had in view was principally to obtain 

 information as to the most advantageous procedure for the 

 preparation of argon. So many laboratories are now provided 

 with apparatus for liquifying air, that it will usually be 

 convenient to start in this way if a sufficient advantage can 

 be gained. The above results show clearly that the advantage 

 that may be gained is great. Something depends upon the 

 procedure to be adopted for eliminating the nitrogen. Upon 

 a moderate scale and where there is a supply of alternating 

 current, the method of oxidation, as in the analyses, is 

 probably the most convenient. In this case it may be an 

 advantage to retain the oxygen. If the oxygen content be 

 about 60 per cent., as in the third experiment, the proportion 

 is about sufficient to oxidize the nitrogen. We may compare 

 tins with the mixture of atmospheric air and oxygen which 

 behaves in the same manner. In the latter case the proportion 

 of argon would be reduced from 2*0 per cent, to about '4 per 

 cent., so that the advantage of using the liquid air amounts 

 to about five times. In the arrangement that I described for 



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