826 Mr. G. N. Antonoff on Radium D 



deduced the period of transformation of radium D, which he 

 found to be about 40 years ; while by comparison of the 

 a-ray activity of radium F with that of radium C, Meyer 

 and v. Schweidler* obtained the value 12 years. In the 

 latter experiments a correction was made for the difference 

 in ionizing power of the a particles from radium G and 

 radium F. Data are not yet available for the corresponding- 

 correction due to the difference in speed of the ft particles 

 from radium C and radium E. 



As it is now a matter of importance to know the period 

 of transformation of these products with accuracy, the 

 period of radium D has been determined by a new method, 

 and the question as to whether there are two products 

 between radium D and radium F has been closely examined. 

 From experiments on the initial rise of the /3-ray activity of 

 radium D, Rutherford f found the time period of radium E 

 to be 6 days, while the period of decay of radium E, from 

 which most of the radium D had been driven by heating, was 

 found to be 4"5 days. Meyer and v. Schweidler found that 

 a preparation of radium E lost its /3-ray activity initially 

 according to a period of 4*8 days, but finally decayed more 

 slowly according to a period of 6*2 da}'s. They suggested 

 as an explanation of their own and Rutherford's experiments 

 that there are two products between radium D and radium F, 

 and that the first is rayless, and has a period of 6'2 days, 

 while the second is a /3-ray product, and has a period of 

 4*8 days J. The following experiments were made with the 

 view of settling definitely whether or not there are two 

 products. 



Experiments with Radium E. 



Suppose that radium E is complex and consists of two 

 successive products, E x which is rayless and E 2 which emits 

 ft rays. Then, if radium E x is completely separated from 

 the mixture of radium D and radium E x and E 2 , the /3-ray 

 activity of radium E 2 will decrease exponentially with its 

 characteristic period. Similarly radium D will recover its 

 /3-ray activity according to the same period. If, however, 

 radium E x and radium E 2 are separated together, the /3-ray 



* Wien. Ber. cxyi. Abt. ii a, April 1907. 



t Loc. cit. 



t H. W.Schmidt, Phi/s. Zeit. viii. p. 365 (1907). Also Meyer and 

 v. Schweidler, Phys. Zeit. viii. p. 457 (1907). Also H. Hess, Wien. Ber. 

 cxvi. II. p. 1289 (1907). 





