$28 



Mr. G. N. Antonoff on Radium D 



column A. This is shown in fig. 1, where curve 1 represents 

 the theoretical values, and the points represent the experi- 

 mental values. If the recovery is due to the formation of 

 successive products radium E L and E 2 , which have constants 

 X 1 and X 2 , and of which only the latter emits /3-rays, it can 

 easily be shown that the activity I at any time t is given by 



I 

 Io 



A.]_— " A. 2 



r 



where I is the maximum value. Taking Meyer and 

 v. Schweidler's suggested periods for radium E L and radium 

 E 2 , viz. 4*8 and 6*2 days respectively, the activity at any 

 time is given in column C, and is shown in curve 2 of fig. 1. 

 The difference between this curve and the previous one is so 

 striking that it is impossible to confuse them. It may be 

 remarked that in the first case the activity after 5 days is 

 50 per cent, of the maximum, while in the latter it is only 

 14 per cent. This experiment shows conclusively that only 

 one product exists between radium D and radium F, and 

 that this product emits /3 rays. 



Table I. 





Activities in 



arbitrary units, final value taken = 100. 



A. 



B. 



C. 



Time in Days. 



Experimental. 



Theoretical for one 



Theoretical for two 

 products radium 







product radium E 



E x and E 2 with 

 periods 48 and 







with period 5 days. 









6"2 days resp. 



















1-04 



13-3 



13-4 



2-2 



1-9 



22-4 



23-1 



4-8 



22 



26-4 



26-3 



5-6 



2-8 



31-9 



32-2 



7-0 



3-8 



41-2 



41-3 



101 



4-8 



48 3 



48-6 



14-2 



49 



49-2 



49-3 



149 



51 



50-7 



503 



150 



5-8 



546 



55-2 



18-5 



68 



60-4 



610 



225 



7-8 



657 



66-1 



260 



8-8 



68-6 



70-5 



30-2 



9-9 



74-4 



746 



35-0 



19 



92-5 



92-8 



690 



55 



100 



100 



99 



115 



100 



100 



100 - 



