﻿of the a. Rays of Radiothorium. 85 



are present. The divergence between theory and experiment 

 indicates that at least half of the emanation produced in the 

 preparation escapes into the air. 



The absence of any well-marked breaks in the curve 

 renders it impossible to determine with certainty by this 

 method the ranges of the various sets of a. particles emitted 

 by the products. 



Fi?. l. 

 10 



'43 G 





I 









: la 



\ 



V 











\ 



V 



i 





i 



i i 





l°^"~ 



^H^ 





'-P — IQ— 











. is 





T «: 











' 



3 4 



Ionization. 



For comparison fig. 1 b shows a curve obtained from a 

 radiothorium preparation in a thick layer. From the results 

 obtained by Bragg and Kleeman with a thick layer of radium, 

 one should expect to observe fairly abrupt changes in the 

 slope of the ionization curve at points where a new set of 

 a particles enters the ionization-chamber. The part of the 

 curve due to thorium C is well-defined as in the case of a 

 thin laver. A change of slope begins below 6 centims., but 

 the rest of the curve does not give any detinite information 

 in regard to the ranges of the other products. 



An examination of the ionization curves of radiothorium 

 in equilibrium, whether in the form of a thin or of a thick 

 layer, thus did not give any information of value in regard 

 to the ranges of the a-ray products. 



It was, consequently, necessary to obtain as far as possible 

 each product free from mixture of the others, and to separately 



