1895.] 



Constituent of certain Minerals. 



83 



TO PUMP 



this sample of gas was largely contaminated with atmospheric air. 

 On sparking with oxygen in presence of soda, the nitrogen was, ot 

 course, removed; but it will be seen subsequently that the complete 

 argon spectrum is not visible in the new gas. 



3. Sources of Helium. 



I owe to the kindness of Dr. Hillebrand some grams of the 

 uraninite which served for his experiments. It is a hard, black 

 mineral, containing, according to his account (loc. cit.), the oxides of 

 uranium, lead, thorium, yttrium, and allied metals in smaller amount. 

 It is attacked by acid with great difficulty, and gas is very slowly 

 evolved. A quantitative experiment was made by boiling 2'808 

 grams for 5 hours, when 24 c.c. of gas were evolved. After further 

 boiling for ten hours, an additional 13'5 c.c. were obtained, in all 

 37-5 c.c. 



The first portion of this gas was mixed with oxygen and sparked 

 for a short time. The volume of the mixture was 34'3 c.c., and 

 after sparking it had diminished to 33'9 c.c. This appears to show 

 that very little nitrogen is present if care be taken in collecting 

 the gas. I must reserve to the second part of this paper a further 

 account of this specimen. 



The cleveite which I bought from Mr. Gregory is much more easily 

 decomposed, for in the course of half an hour the mineral is com- 

 pletely disintegrated, and all gas is evolved. Mr. Travers found that 

 3'662 grams of the pure black mineral, free from felspar, yield 26 c.c. 

 of gas. 



This gas when mixed with oxygen and sparked did not contract to 

 any great extent. The actual measurements are : 



