Transformation Products of Radium. 



299 



The a, ray activity at any time is proportional to q, and a 

 maximum value is reached at a time T, when 



Since D is half transformed in 40 years, A^'0173 (year)" 1 , 

 and since radium F is half transformed in 143 days, 

 X = l-77 (year)" 1 . 



Activity • 





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2 



A maximum will be reached after a period of about 2*7 

 years. The activity will then diminish exponentially with 

 the time according to the period of radium D, that is, it will 



