Dr. 0. Huhn on Radioactinium. 



17 3 



The above theory depends on the assumption that all of 

 the radioactive products are completely retained in the radio- 

 active matter. In practice, however, the preparations always 

 lose a portion of their emanation dy diffusing into the air. 

 In consequence o£ this, the activity due to the succeeding 

 product actinium B is less than the theoretical value if no 

 emanation escaped., For a thin film of radioactinium we 

 should consequently expect a value of k less than 3*72, and 

 this value will be variable within limits depending upon the 

 emanating power of the compound. 



10 20 



T/ME //V DAYS 



SO 



60 



70 



80 



90 



(00 



15 



25 



35 



4-5 



55 



65 



The theoretical curve is drawn in fig. 1, Curve I., the 

 initial activity due to radioactinium being taken as 100. 

 The shape of the curve agrees fairly closely with the experi- 

 mental curve (Curve II.) plotted in the same way. The 

 maximum ordinate of the theoretical curve is slightly less 

 than the experimental value, showing that the value of A: is 

 slightly greater than 3*5. / ^ao 



The theoretical curve can be simply analysed into its com- 

 ponents. The exponential curve A shows the activity at 

 any time due to radioactinium itself. The difference curve B 

 shows the activity at any time due to actinium X and its 

 succeeding products. 



Curve III. is another example of an experimental curve, 

 which was obtained under conditions where the radioactinium 

 probably contained some actinium and actinium X. 



The maximum of the theoretical curve (Curve I.) is reached 



