60 II L. Br onson — Decay of Deposit from Badium. 



Art. IX. — The Effect of High Temperatures on the Bate 

 of Decay of the Active Deposit from. Badium; by Howard 

 L. Bronson. 



In the course of a careful investigation of the decay of the 

 active deposit from radium, some experiments of Curie and 

 Danne* were repeated. These consisted in determining the 

 change which high temperatures produce on the rate of decay 

 of this active deposit. As a result of the following experi- 

 ments, a different conclusion from that offered by Curie and 

 Danne has been arrived at. 



Miss Gatesf showed that high temperatures produced at least 

 a partial separation of the components of the active deposit 

 from radium, owing to the fact that they are not all equally 

 volatile. Curie and Danne verified this, and also found that 

 the rate of decay of the active deposit apparently was perma- 

 nently altered by exposure to temperatures between 650° and 

 1300° C. The following table gives some of their results : 



t e 



6 30° 29-3 



8 30 24-6 



10 00 2T0 



11 00 20-3 



12 50 24-1 



13 00 25-4 



Here t is the temperature in degrees centigrade to which the 

 active deposit was raised, and 6 is the " period," that is the 

 time in minutes required for the activity to fall to half value. 

 From this table it is seen that the rate of decay increased as 

 the temperature was raised from 650° to 1100°, but decreased 

 again at still higher temperatures. Curie and Danne also 

 stated that the decay curves were exponential, and they there- 

 fore concluded that the rate of decay had been permanently 

 altered. 



In the following experiments the measurements were all 

 made with an electrometer, and the "constant deflection 

 method " described by the writer:): was employed. The active 

 deposit was collected on platinum wires by connecting them to 

 the negative pole of a battery of 400 volts, and exposing them 

 for several hours in the emanation from radium. After 

 removal the wires were kept for a few minutes at the desired 

 temperature in a small electric furnace, made by Dr. C. A. 



* Comptes Rendus, cxxxviii, p. 748, 1904. 

 f Physical Review, May, 1903. 

 X This Journal, Feb., 1905. 



