On a Gas showing the Spectrum of Helium. 65 



April 25, 1895. 

 The LORD KELVIN, D.C.L., LL.D., President, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The following Papers were read : 



]. "On a Gas showing the Spectrum of Helium, the reputed 

 cause of D 3 , one of the Lines in the Coronal Spectrum. 

 Preliminary Note." By WILLIAM RAMSAY, F.R.S., Pro- 

 fessor of Chemistry, University College, London. Received 

 March 26, 1895. 



In the course of investigations on argon, some clue was sought for, 

 which would lead to the selection of one out of the almost innumer- 

 able compounds with which chemists are acquainted, with which to 

 attempt to induce argon to combine. A paper by W. F. Hillebrand, 

 " On the Occurrence of Nitrogen in Uraninite, &c." (' Bull, of the 

 U.S. Geological Survey,' No. 78, p. 43), to which Mr. Miers kindly 

 directed my attention, gave the desired clue. In spite of Hillebrand's 

 positive proof that the gas he obtained by boiling various samples of 

 uraninite with weak sulphuric acid was nitrogen (p. 55) such as 

 formation of ammonia on sparking with hydrogen, analysis of the 

 platinichloride, vacuum-tube spectrum, &c. I was sceptical enough 

 to doubt that any compound of nitrogen, when boiled with acid, 

 would yield free nitrogen. The result has justified the scepticism. 



The mineral employed was cleveite, essentially a uranate of lead, 

 containing rare earths. On boiling with weak sulphuric acid, a con- 

 siderable quantity of gas was evolved. It was sparked with oxygen 

 over soda, so as to free it from nitrogen and all known gaseous bodies 

 except argon ; there was but little contraction ; the nitrogen removed 

 may well have been introduced from air during this preliminary 

 experiment. The gas was transferred over mercury, and the oxygen 

 absorbed by potassium pyrogallate ; the gas was removed, washed 

 with a trace of boiled water, and dried by admitting a little sulphuric 

 acid into the tube containing it, which stood over mercury. The 

 total amount was some 20 c.c. 



Several vacuum-tubes were filled with this gas, and the spectrum 

 was examined, the spectrum of argon being thrown simultaneously 

 into the spectroscope. It was at once evident that a new gas was 

 present along with argon. 



Fortunately, the argon-tube was one which had been made to try 



