70 



Ashman — Radio- Activity of Thori 



iu?n. 



the accompanying curve, which represents a film of sample 

 " D." The activities are in terms of the U 3 8 standard, which 

 had an activity of 35*0 units. This correction was necessary 

 as the time intervening between the last precipitation of the 

 thorium and the first activity measurement was usually one to 

 two hours. 



Fig. 1. 



.55 



10 12 14 16 



Time in Hours. 



18 



20 



24 



Table I gives the results obtained from the four samples of 

 oxide. 



Table I. 









Date 



of Measurement 







Date of 



Minimum 





of 



Maximum 



Sample 



preparation* 



activity 



maximum activity 



activity 



"A" 



Aug. 28 



167 





Oct. 1 



400 



«B" 



Oct. 19 



167 





Nov. 21 



380 



"C" 



Aug. 29 



286 





Oct. 4 



921 



"D" 



Oct. 23 



292 





Nov. 23 



948 



"D" 



Oct. 23 









Nov. 23 



948 



All dates refer to the year 1901 



