160 Moss— On the State in which Helium Exists in Pitehblende. 
On removing the tube of phosphorus pentoxide through which the gases from 
the grinding apparatus had passed to the pump, it was found to have gained 0-100 
grammes in weight, so that in this case, as in previous experiments, by far the most 
abundant substance liberated by grinding the mineral 7 vacuo is water vapour. 
The total quantity of the helium obtained in the above experiment is 
0-181 + 0-008 = 0184 ¢.c., or in the proportion of -00092 c.c. for each gramme of 
the mineral. 
The total quantity of helium in the mineral was determined as before by 
fusing with potassium hydrogen sulphate. Hach gramme of the mineral gave 
0-082 ¢.c. The helium liberated by grinding mm vacuo is therefore 1:11 per cent. 
of the total quantity present—a very close approximation to the 1:17 per cent. 
obtained with the other specimen of pitchblende. 
The occurrence of hydrogen in this case is noteworthy. When the gas, mixed 
with oxygen, was sparked in the eudiometer, there was an unmistakable explosion, 
and a contraction which was appreciable before the gas was transferred to the 
measuring apparatus. There was no change in volume when the gas was exposed 
to the action of moist caustic potash. There can be little doubt, therefore, that 
the gas was hydrogen. I did not detect hydrogen in the other specimen of 
pitchblende. A small quantity might have escaped detection. In a radium- 
bearing mineral the presence of hydrogen in cavities containing water might be 
anticipated. 
I hope to submit a further communication on other minerals in which helium 
has been found. 
THe Laporarory, Royan Dusiin Society, 
Lemnster Hovusr, Dustin. 
