the Electrical Conduction produced by it. 



119 



metal was used in the form of powder, and a smaller area of 

 it was used than in the other cases. For the experiments on 

 uranium oxide a thin layer of fine powder was employed, 

 and we see, in that case, that the ft radiation bears a much 

 smaller proportion to the total than for the other compounds. 

 When a thick layer of the oxide was used there was, how- 

 ever, an increase in the ratio, as the following table shows : — 



Number of layers 

 of Aluminium foil. 



Rate of Leak. 



Thin layer of 

 Uranium Oxide. 



Thick layer of 

 Uranium Oxide. 







1 



1 



1 



•42 



5 



2 



•18 





4 



•05 



•12 



8 





•113 



12 



•04 



... 



18 



... 



•11 



The amount of the a radiation depends chiefly on the 

 surface of the uranium compound, while the ft radiation 

 depends also on the thickness of the layer. The increase of 

 the rate of leak due to the ft radiation with the thickness of 

 the layer indicates that the ft radiation can pass through a 

 considerable thickness of the uranium compound. Experi- 

 ments showed that the leak due to the a radiation did not 

 increase much with the thickness of the layer. I did not, 

 however, have enough uranium salt to test the variation of 

 the rate of leak due to the ft radiation for thick layers. 



The rate of leak from a given weight of uranium or 

 uranium compound depends largely on the amount of surface. 

 The greater the surface, the greater the rate of leak. A small 

 crystal of uranium nitrate was dissolved in water, and the 

 water then evaporated so as to deposit a thin layer of the 

 salt over the bottom of the dish. This gave quite a large 

 leakage. The leakage in such a case is due chiefly to the 

 a radiation. 



Since the rate of leak due to any uranium compound 

 depends largely on its amount of surface, it is difficult to 

 compare the quantity of radiation given out by equal amounts 

 of different salts : for the result will depend greatly on the 



