H. L. Bronson — Decay of Deposit from Radium. 63 



time. Fig. 2 shows the result of two experiments of this 

 kind. 1 A, 1 B and 1 C are three sections of the same curve, 

 obtained after heating the active deposit to about 650° C. 1 A 

 was taken immediately after heating, 1 B after about two hours, 

 and 1 C after about four hours. The respective values of 6 

 were 22*4, 23*6, and 25'5. In the case of curve 2,'the tem- 

 perature used was about 800°C. 2 A was taken immediately 

 after heating, 2 B after about one hour, and 2 C after about 



'•B 



3 



A 





















^3 







^ 









*^fe 



^vL 













s 













100 



125 



150 175 



Time in minutes. 



200 



225 



two and one-half hours, and the values obtained for were, 

 respectively, 20*1, 21*3, and 22.8. 



The above results furnished very strong evidence in favor 

 of the supposition that the heating did not actually alter the 

 rate of decay of the active deposit. In order to make this 

 conclusive, the wire on which the active matter had been 

 deposited was sealed, before heating, in a piece of glass com- 

 bustion tubing. This prevented the escape of any volatile 

 products, which in the previous experiments had evidently 

 been the uncertain factor. By exhausting the glass before 

 sealing, it was found that it would stand temperatures high 

 enough to melt the copper wires, which were used in this case. 



