H. L. Bronson — Decay of Deposit from Radium. 61 



Timme of Berlin, and were then placed in the testing vessel. 

 A calibration curve for the furnace had previously been made 

 by the use of a platinum-rhodium thermo- junction. 



A large number of experiments were made using several 

 temperatures between 700° and 1100° C. An example of 

 the kind of results obtained is given in fig. 1. A, B, C 

 and Gr are four decay curves of the active deposit, which 

 had been previously heated to about 800° C. In the case 

 of D, E and F the temperature used was about 900° C. 

 The time is reckoned from the removal of the wire from the 



100 

 Time in minutes. 



175 



emanation. The first points on curves F and G should be at 

 about 200 and 300 minutes respectively, as in these cases the 

 wires were not placed in the furnace until several hours after 

 their removal from the emanation. These curves are apparently 

 exponential, as was found by Curie and Danne, but does not 

 at all seem to be a function of the temperature, for its value 

 seems just as liable to change when the temperature is kept 

 the same as when a different temperature is used. In fact 6 

 was found liable to take on any value between nineteen and 

 twenty-seven minutes, and this was true for all temperatures 

 between 700° and 1100°. Among these values of there 

 were, however, a large number between nineteen and twenty- 

 one minutes. This was nearly always the case when the wire 

 was not heated until several hours after removal from the 

 emanation. 



Now Rutherford* has shown that, neglecting the first half 

 * Philosophical Transactions. 204, p. 196. 



