Some Experiments on Helium. 449 



" Some Experiments on Helium." By MORRIS W. TRAVERS, 

 B.Sc. Communicated by Professor W. RAMSAY, F.R.S. 

 Received December 30, 1896, Read February 4, 1897. 



In July of last year Professors Runge and Paschen (' Phil Mag./ 

 1895, [ii], vol. 40, pp. 297 302) announced their discovery that the 

 spectrum of the gas from cleveite indicated the presence of two ele- 

 ments. They also stated that by means of a single diffusion through 

 an asbestos plug, they had been able to effect a partial separation of 

 the lighter constituent, which was characterised by the green glow 

 which it gave under the influence of the electric discharge in a 

 vacuum-tube, and which was represented in the spectrum by the 

 series containing the green line, X = 5015'6. Subsequently, at the 

 meeting of the British Association at Ipswich, Professor Runge 

 exhibited a tube containing the so-called green constituent; the 

 colour of the glow differed strongly from that of an ordinary helium 

 tube, but the gas contained in it was evidently at very low pressure, 

 as phosphorescence was jusfc commencing. Professor Runge has 

 since acknowledged that the green effect in the helium tube may be 

 produced by a change of pressure alone (' Astrophysical Journal,' 

 January, 1896). 



During an exhibition of the spectrum of helium at -the soiree of 

 the Royal Society on May 9, 1895, it was noticed that one of the 

 Pliicker tubes which had been running for nearly three hours, had 

 become strongly phosphorescent. The tube was fitted with platinum 

 electrodes, and the helium had apparently been absorbed by the 

 platinum sparked on to the walls of the tube. We observed the same 

 phenomena to take place on several subsequent occasions, but only in 

 the case of tubes with platinum electrodes.* 



Now, if helium is not a single gas, it must consist of a mixture of 

 two or more monatomic gases, capable of mechanical separation, and 

 it is possible that one of its constituents might be absorbed by the 

 platinum faster than the other. At the end of September, 1895, I 

 commenced some experimental work on this subject, with the view 

 of separating the two or more possible constituents from one another. 

 The results were negative. 



I employed in these experiments a piece of apparatus figured 

 below (fig. 1). 



A large Pliicker tube, bent into a U -shape, has two side-tubes, A 

 and B. The electrodes are of platinum, and project far into the 

 tube ; the straight parts, which are of thick wire, and about 30 mm. 



* So far as I know, this phenomenon was first recorded by Professor Norman 

 Lockyer (< Eoy. Soc. Proc.,' 1895, vol. 58, p. 193). 



