Active Deposit of Radium in Electric Fieldi 



541 



Valuation of Anode and Cathode Activities with Field 



Strength. 



(Long exposures.) 



It will conduce to simplicity in describing the experi- 

 mental observations if we anticipate one of the results of the 

 investigation, namely, that the anode activity is due to the 

 diffusion to it of unchanged active deposit, and that no 

 negatively charged recoil atoms exist. On this assumption 

 the difference between the activity collected by the cathode 

 and that on the anode gives a lower limit to the amount of 

 positively charged active deposit collected by the cathode ; 

 and the anode activity gives an upper limit to the amount of 

 electrically neutral deposit collected by the cathode. Hence 

 the percentage of positively charged deposit atoms collected 

 by the cathode cannot be less than the ratio 



cathode activity— anode activity 

 cathode activity 



Within the limits of experimental error this quantity, for 

 a given potential difference between the wire and the 

 cylinder, was found to be independent of the amount of 

 emanation employed, even though this varied from 10~ 3 m.g. 

 to 10 _6 in.g. 



Hence it is possible to represent the experimental results 

 graphically. This has been done in fig. 2. Most of the 



Fig. 



100 



$ % 



60 



r 







- — 



B- 







< 

































































100 





300 



500 



600 



700 800 



l/OL T/ICE - 



• 



points on the curve represent the mean of several separate 

 observations at the given potential. It is seen that the 

 percentage of positively charged active deposit collected by 

 the cathode increases with the applied potential to a maxi- 

 mum, but that there is always collected a certain amount of 

 activity on the anode which is independent of the applied 

 potential, and in this particular apparatus represents about 



