Moss—On the State in which Helium Exists in Pitchblende. 155 
The connections attached to the syphon tube, by which the gas had been 
admitted, were so arranged that by lowering a mercury reservoir a certain amount 
of gas would flow from the Pliicker tube to the other parts of the apparatus, and 
on raising the reservoir the opposite effect was produced. By circulating the gas 
in this way while the discharge was passing in the Pliicker tube, all the nitrogen 
was quickly absorbed. ‘The tap communicating with the Sprengel pump was 
now opened, and the gas pumped off and measured. Its volume was found to be 
0:0454 c.c., and I conclude from the appearance of its spectrum that it was 
practically pure helium. ‘The results of the various measurements corrected for 
temperature and pressure were as follows :— 
Original volume of gas, Kos _ 0-094 
After action of KHO, ae 0-077 
After removal from the Pliicker tube, ce 0:045 
The composition of the gas is accordingly :— 
Per Cent. 
CORE. ws eh oo — OLY 18°35 
He, a a ae 0-045 48°27 
N, &e., sis ee 0-032 33°38 
0-094 100-00 
In the second grinding, which it will be observed yielded almost exactly the 
same volume of gas as the first grinding, the quantity of water obtained was 
0:1020 gramme. ‘This is about five times as much as was obtained in the first case. 
I believe this marked difference is due, in part at any rate, to absorption of 
moisture by the powder from the air. The first determination of water was probably 
correct; but the conditions under which the second determination was made did 
not admit of the necessary accuracy. 
The helium obtained in the first grinding was unfortunately lost; but, con- 
sidering the similarity in composition of the two lots of gas, so far as they were 
examined, it is perhaps admissible to conclude that the quantity of helium in 
the first lot was about the same as in the second lot. This would give a total of 
0:09 c.c. of helium, or 0:00125 ¢.c. of helium per gramme of pitchblende, while 
the carbon dioxide liberated in the two grindings corresponds to 0:0004 c.c.° per 
gramme of the mineral. 
I found that the second grinding had reduced about half the pitchblende to a 
powder, 62 per cent. of which passed through a sieve having meshes measuring about 
0-17 mm. between the wires (100 meshes to the inch), 36 per cent. passed through 
a 0'4 mm. mesh, and the remaining 2 per cent. passed through a 0°8 mm. mesh. 
2H 2 
