61 H. L. Br on son — Decay of Deposit from Radium. 



A number of experiments were made in this way, using the 

 same temperatures as before, but in no case did 6 fall below 

 twenty-six minutes. 



B, fig. 3, is the logarithmic decay curve, obtained when the 

 active deposit was sealed in a glass tube and heated to 900° C. 

 A is the normal decay curve for the active deposit. These 

 curves are approximately parallel, showing that the rate of 

 decay had not been measurably changed by a temperature of 

 900° C. 



It is thus evident that temperatures between 700° and 1100° C. 

 have very little, if any, effect on the rate of decay of the active 

 deposit from radium. The results obtained by Curie and 

 Danne and those given in the present paper are satisfactorily 

 explained by assuming that radium C has the shorter instead 

 of the longer of the two periods, and that radium B is the 

 more volatile, but that in general a part of it still remains on 

 the wire after heating. 



The measurements made in this investigation also seem to 

 show that both twenty-eight and twenty-one minutes are too 

 large for the decay periods of radium B and C, and that 

 twenty-six and nineteen minutes are nearer right Experi- 

 ments are at present in progress which it is hoped will settle 

 this definitely. 



In conclusion, I desire to thank Professor Rutherford for 

 his many suggestions and kind supervision of this work. 



Macdonald Physics Building, 



McGill University, Montreal, June 5, 1905. 



