Ellen Gleditsch — Life of Radium. 123 



main precipitate and the solution finally obtained was brought 

 into a glass bulb. 



The results of the measurements will be found in Table 9. 









Table 9. 







Growth of radium 



in test solution from Bro< 



jgerite 2. 







Radium emanation found 







Time from start 





expressed in 



Growth of radium 



Test 



in days 





terms of radium 



per day 



1 



1-83 





0-022 X 10" 9 





2 



138- 





o-o7o x 10- 9 



o-oo 



This solution shows no augmentation of radium and conse- 

 quently contains no ionium. 



For the main solution from broggerite 2 only two results are 

 yet obtained. As average growth of radium I shall give here 

 the mean value between these two results; but I expect to 

 make some more measurements later on. 



The average growth of radium 



per day is: 0-0236 X 10" 9 gram. 

 " year is: 8-614 X 10 -9 gram. 



The amount of radium in 100 grams of mineral has been found 

 to be 2-08 X 10~ s gram. 



The constant of change of radium then is : 



8-614 x 10~ 9 , , , 



=4-14 X 10~ 4 (year)" 1 



2-08 X 10~ 5 u ; 



and the half-value period is 

 0-693 



4-14 X 10-* 



1674 years. 



The results obtained from the first two minerals, uraninite 

 from N". Carolina and cleveite from Norway, indicate clearly 

 that the constant of change of radium has a higher value than 

 the one generally accepted — 3"48 X 10 -4 (year) -1 . Neither of 

 them, however, can claim a very high degree of accuracy for 

 the reasons already given. But so far as I can understand no 

 objection can be raised against the results from the two sam- 

 ples of broggerite. The two solutions have been prepared at 

 different times and in a different manner ; the radium content 

 in one of them is nearly twice as large as in the other. But 

 the rate of change calculated from the radium present and the 

 radium formed has the same value in both cases. 



I have asked myself if any particular objection may be 

 raised against the use of broggerite, but I do not think this 

 possible. The mineral is certainly one of the oldest uraninites 



