On the Companions of Argon. 437 



investigated by means of radiometer mill wheels, recently described 

 in a paper to the Physical Society. 



In any case, it seems clear that in the tubes observed and photo- 

 graphed with the pin-hole camera, the Rontgen rays given off by 

 certain portions of the fluorescent glass are not originated by the 

 impact of an ordinary cathode stream, but apparently by the 

 impact of positively charged streams proceeding from the anti- 

 cathode. 



The writer is greatly indebted to Mr. J. C. M. Stanton and Mr. EL 

 Tyson Wolff, for the construction of the apparatus described, as also 

 for valuable assistance in the carrying out of the experiments. 



" On the Companions of Argon." By WILLIAM RAMSAY, F.R.S., 

 and MORRIS W. TRAVERS. Received June 13, Read June 

 16, 1898. 



For many months pasb we have been engaged in preparing a large 

 quantity of argon from atmospheric air by absorbing the oxygen 

 with red-hot copper, and the nitrogen with magnesium. The amount 

 we have at our disposal is some 18 litres. It will be remembered 

 that one of us, in conjunction with Dr. Norman Collie, attempted to 

 separate argon into light and heavy portions by means of diffusion, 

 and, although there was a slight difference* in density between the 

 light and the heavy portions, yet we thought the difference too slight 

 to warrant the conclusion that argon is a mixture. But our 

 experience with helium taught us that it is a matter of the 

 greatest difficulty to separate a very small portion of a heavy gas 

 from a large admixture of a light gas ; and it therefore appeared 

 advisable to re-investigate argon, with the view of ascertaining 

 whether it is indeed complex. 



In the meantime, Dr. Hampson had placed at our disposal his 

 resources for preparing large quantities of liquid air, and it was a 

 simple matter to liquify the argon which we had obtained by causing 

 the liquid air to boil under reduced pressure. By means of a two- 

 way stopcock the argon was allowed to enter a small bulb, cooled by 

 liquid air, after passing through purifying reagents. The two-way 

 stopcock was connected with mercury gas-holders, as well as with 

 a Topler pump, by means of which any part of the apparatus could 

 be thoroughly exhausted. The argon separated as a liquid, but at 

 the same time a considerable quantity of solid was observed to sepa- 

 rate partially round the sides of the tube, and partially below the 



* Density of lighter portion, 19'93 ; of heavier portion, 20'01, ' Koy. Soc. Proc. r * 

 vol. 60, p. 206. 



