﻿182 Dr. M. Levin on the Origin of the /3 Rays 



maximum about a month later. The lowest value of the 

 a ray activity obtained in this way was about 23 per cent, of 

 the maximum. This value lies between the lowest values 

 observed by Rutherford and Soddy. For the minimum 

 /3 ray activity, two separate experiments gave 4*0 and 2*8 

 per cent. It is thus clear that neither thorium nor radio- 

 thorium emits /3 rays. The small value obtained is un- 

 doubtedly due to the presence of some of the active deposit, 

 which was not volatilized at the highest temperatures em- 

 ployed. 



It might be thought possible to remove the active deposit 

 from the thorium in equilibrium by heating, without first 

 separating the thorium X. An experiment in this direction 

 was tried but was unsuccessful ; it is impossible to volatilize 

 all the active deposit when it is distributed throughout the 

 mass of the thorium. 



Actinium X. 



From a study of the actinium products it is known that 

 the actinium-emanation emits a rays, and it will be seen later 

 that it emits no /3 rays. The active deposit consists of two 

 products, actinium A and actinium B*; the former is a ray- 

 less product, whilst the latter emits a, /3, and <y rays. Grod- 

 lewskif, in his work on actinium, pointed out that actinium 

 X probably emitted /3 as well as a rays. We have seen that 

 the product thorium X in thorium, which corresponds to the 

 product actinium X in the actinium, emits only a rays. The 

 close analogy between thorium and actinium both in the 

 character and number of their products and the radiations 

 emitted by them, suggested a closer examination to see 

 whether actinium X emitted /3 rays. 



In these experiments, the emanating substance of Giesel 

 was used. The actinium X was separated by ammonia. 

 Since the active deposit of actinium is more readily volati- 

 lized % than that of thorium, the method of heating was em- 

 ployed to get rid of the active deposit, which is separated 

 with actinium X. But the elimination of the active deposit 

 by this method was more difficult than in the case of thorium, 

 since the residues remaining in the filtrate with ammonia 

 prevent the complete escape of the volatile products. It was 



* Miss Brooks, Phil. Mag. Sept. 1904. 



+ Godlewski, Phil. Mag. July 1905. 



X According to measurements of the writer, which will be published 

 later, the temperatures at which actinium A and actinium B commence 

 to volatilize are 400° C. and 700° C. respectively. 



