440 Mr. S. Ratner on the Distribution of the Active 



remains fairly constant during several successive expe- 

 riments, even when the foil is exposed for a long time to a 

 large quantity of emanation. This coefficient being constant, 

 the quantity of radium B collected on the plate can be taken 

 as a measure of the amount of radium A present on the 

 electrode. 



The electrode covered with aluminium foil was exposed to 

 the emanation of Wertenstein's exposure vessel for different 

 intervals of time varying from 10 seconds to 3 hours. Care 

 had been taken to remove the gas activity from the emanation 

 before each exposure (see sec. 10). The accumulation on the 

 plate of the recoil atoms of radium B began 2 minutes after 

 the removal of the electrode from the emanation, and lasted 

 for 6 minutes. 



In curve I (fig. 4) the quantities of radium B given up by 



Fig. 4. 















n 























— — 















i 







/ 















i 























15 45 75 105 



Duration of exposure /n min. 



135 



165. 



recoil from the aluminium surface of the electrode are plotted 

 against the duration of exposure of the electrode, while 

 II represents the growth of radium A from emanation as 

 given by theory. The curves are divided into two parts 

 drawn on different scales in order to show distinctly the 

 comparatively short period of rapid growth of radium A. 

 Curve I shows a very distinct departure from the theoretical 

 curve in a way which might have been expected from the 

 results given above. Since the quantity of radium A received 

 by the electrode per unit time diminishes with the increase 

 of the active matter accumulated on it, the total amount of 

 radium A present on the electrode decreases slightly after 



