of Radium and Uranium. 7 



than ten milligrams the absorption of the a-radiation 

 was negligible. In all cases where values of importance 

 were to be derived the weight of the films nsed was less 

 than this maximum, so that no correction has to be made 

 in the results for absorption of the radiations. 



The average of the first eight values in the fourth 

 column of table I is 666, which denotes that the average 

 activity of the eight lighter films was 666 divisions per 

 minute per gram of uranium oxide. This corresponds 

 to an activity of 785 (viz. 666/0-848) divisions per minute 

 per gram of uranium. 



Table I. 



Film 



Weight of oxide 



Activity 



Activity 



Number 



in grams 



Div./Mra. 



Weight 



20 



•00187 



1-24 



663 



19 



•00432 



2-91 



673 



15 



•00566 



3-77 



666 



18 



•00653 



4-37 



669 



21 



•00740 



4-95 



668 



22 



•00832 



5-56 



662 



14 



•00898 



5-95 



662 



23 



•00653 



4-38 



670 



25A 



•01405 



8-89 



633 



8 



•01380 



8-94 



648 



25B 



•01440 



9-30 



645 



26 



•02150 



13-45 



624 



24 



•04350 



25-96 



596 



The specific activity of the uraninite was determined 

 by the measurement of four films weighing from approx- 

 imately 2 to 6 milligrams. The results are given in 

 table II. 





Table II. 







Film 



Weight 



Activity 



in divisions per 



Number 



gram 



minute per gram 



27 



0-00387 





2627 



28 



0-00240 





2655 



29 



0-00588 





2627 



30 



0-00170 





2600 



These results give the mean value for the specific 

 activity of the uraninite as 2624 divisions per minute per 

 gram. 



As already stated the mineral contained 0-019 gram of 



