In July of last year Professors Bunge 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 elements. 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, A = 5015-6.^ Subsequently, at the meeting of the British Association at Ipswich, Professor Bunge 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 just 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. MTe observed the same phenomena to take place on several subsequent occasions, but only in the case of tubes with platinum electrodes.*
Row, 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 emploved in these experiments a piece of apparatus figui’cd 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 (‘ Roy. Soc. Proc.,’ 1895, vol. 58, p. 193).
