[KENNEDY] 



ACTIVE DEPOSIT FROM ACTINIUM 



61 



VTII. Comparison of the Active Deposits in Air, Carbon Dioxide, 



AND Hydrogen. 



For purposes of comparison the active deposits obtained under the 

 various circumstances are collected in Table VI. From this table it will 

 be seen, that the pressure at which the maximum cathode deposits were 

 obtained for the different gases are : carbon dioxide, 60 mms. ; air, 80 

 mms. ; hydrogen, 250 mms. These pressures are approximately in the 

 ratio 1 : 1.33 : 4.3. Now, since the coefficient of diffusion of a gas is 

 inversely proportional to the molecular weight of a gas into which it is 

 diffused, and since, further, the coefficient of diffusion is inversely pro- 

 portional to the total pressure of the two diffusing gases, it follows, since 

 in this case the diffusing transmutation product must be exceedingly 

 minute, that the coefficient of diffusion for the product will be inversely 

 proportional to the pressure of the gas into which it is passing. 



TABLE VI 



Further, since the maximum activities on the cathode for the dif- 

 ferent gases are approximately the same, i.e. 82, 93, and 108, we may 

 look upon the results as due to the diffusion of a maximum distribution 

 of activity in the three gases, and consequently for the critical pressures 



