Transformation of llwrium and Actinium Emanation. 729 



were then selected for initial and final values and substituted 



*693l£ 

 in the equation P = , — -r^ x , t being the time in seconds, I 

 log, J /I 



and I the initial and final activities, and P the half-value 



period. 



Fig. 4 shows the log. curve from data given in Table II., 



as well as one for an experiment with thorium emanation, 





Fig. 4. 



15 30 45 Time in Seconds (Actinium Em ) 







-5 













3 

 Si 





\ 



"\ 



"v. 









V 



\ 



\ 



\Act.Em. 



\ 



"''v.Zy Em 









\ 



N 



\ 



'\ 



*\ 

















Time in Minutes (Thorium Em ) 



giving a calculated half -value period of 54*6 seconds as the 

 mean of three separate determinations. 



Table III. contains the results from a number of experi- 

 ments with actinium and thorium emanation. These give 

 mean values for the half-value periods of 3*92 and 54*53 

 seconds respectively, corresponding to \ = *1768 and '01271 

 respectively. 



Resume. 



By successively inserting suitable capacities in parallel 

 with the leaf of a Wilson-Kaye electroscope as decay pro- 

 gressed, the half-value periods of thorium and actinium 

 emanation were found to be 54*53 + '041 and 3'92 + , 004 

 respectively. 



