[johnston'e] 



EMAXATIXG POWER OF MINERALS 



107 



evolved measured, a subsequent heating at the same temperature 

 produced a value which was smaller, the higher the temperature of 

 the first heating. 



140 

 130 

 120 



no 



100 

 90 

 80 

 70 

 60 

 50 

 40 

 30 



ao 



JO 





y / 



/y 



<; • — 



10 2Û 30 40 ^O 60 70 SO 90 lOO NO 120 

 T£MPER/JTURE 



It should be noted here that the emanating powers were calculated 

 on the assumption that the emanation escaped at the same rate for 

 thirty days as it did for the first 20 hours of heating. But, as was 

 pointed out, the rate of escape rapidly decreases with the time of 

 heating and, therefore, the values calculated have only a relative 

 significance. 



The uraninite tubes were examined in the same way and similar 

 results found, which are plotted in curve 2. In the calculation of the 



^Loc. cit. 



