274 Lord Rayleigh and Prof, Ramsay. [Jan. 31, 



VI. Proof of the Presence' of Argon in Air by means of Atmolysis. 



It has already ( II) been suggested that if " atmospheric nitrogen" 

 contains two gases of different densities, it should be possible to 

 obtain direct evidence of the fact by the method of atmolysis. The 

 present section contains an account of carefully conducted experi- 

 ments directed to this end. 



The atmolyser was prepared (after Graham) by combining a num- 

 ber of " churchwarden " tobacco pipes. At first twelve pipes were 

 used in three groups, each group including four pipes connected in 

 series. The three groups were then connected in parallel, and placed 

 in a large glass tube closed in such a way that a partial vacuum 

 could be maintained in the space outside the pipes by a water 

 pump. One end of the combination of pipes was open to the 

 atmosphere ; the other end was connected to a bottle aspirator, in- 

 itially full of water, and so arranged as to draw about 2 per cent, 

 of the air which entered the other end of the pipes. The gas col- 

 lected was thus a very small proportion of that which leaked 

 through the pores of the pipes, and should be relatively rich in 

 the heavier constituents of the atmosphere. The flow of water 

 from the aspirator could not be maintained very constant, but the 

 rate of 2 per cent, was nevr much exceeded. 



The air thus obtained was treated exactly as ordinary air had 

 been treated in determinations of the density o.f atmospheric nitro- 

 gen. Oxygen was removed by red-hot copper, followed by cupric 

 oxide, ammonia by sulphuric acid, moisture and carbonic acid by 

 potash and phosphoric anhydride. 



In a total weight of approximately 2*3 grams the excess of weight 

 of the diffused nitrogen over ordinary atmospheric nitrogen was in 

 four experiments, O0049, O'OOU, O0027, O0015. 



The mean excess of the four determinations is 0'00262 gram, or, 

 if we omit the first, which depended upon a vacuum weighing of two 

 months old, O00187 gram. 



The gas from prepared air was thus in every case denser than 

 from unprepared air, and to an extent much beyond the possible 

 errors of experiment. The excess was, however, less than had been 

 expected, and it was thought that the arrangement of the pipes 

 could be improved. The final delivery of gas from each of the 

 groups in parallel being so small in comparison with the whole 

 streams concerned, it seemed possible that each group was not con- 

 tributing its proper share, and even that there might be a flow in 

 the wrong direction at the delivery end of one or two of them. To 

 meet this objection, the arrangement in parallel had to be abandoned, 

 and for the remaining experiments eight pipes were connected in 

 simple series. The porous surface in operation was thus reduced, 



