102 



Boltwood — Ratio of Radium to Uranium. 



for sample No. 1 under these conditions 



gave the 



value of t 



ratio as 263. 















Per cent 



Grams 



Leak 



Eatio 







uranium in 



uranium 



divisions 



leak to 



No. 



Substance. 



mineral. 



taken. 



per min. 



uranium. 



1 



Uraninite 



82-5 



0-1067 



22-5 



211 



2 



Gumraite 



66-1 



0*0982 



20-8 



212 



3 



Uranophane 



46-6 



0-0671 



12-1 



181 



4 



Samarskite 



9-8 



0-0299 



6-4 



214 



5 



Uraninite 

 Carnotite 



83-9 

 18-0 



0-0994 



20-6 

 6-9 



207 



6 



0-0258 



267 



H 

 1 



Uraninite 



54-6 



0-0783 



19*8 



253 



8 



Uraninite 



48-5 



0-0699 



16-5 



231 



The low value of the ratio in the experiment with No. 3 was 

 at first attributed to the fact that this material appeared to give 

 off in the cold a greater proportion of its emanation than the 

 other minerals of the series and that it had, therefore, not 

 reached a state of equilibrium at the time when the emanation 

 was measured. A more careful measurement of the propor- 

 tion of emanation lost by the cold pulverized samples was 

 made and no differences sufficiently great to explain the low 

 value in No. 3 were obtained. Since the solution of the urano- 

 phane had gelatinized on standing in the solution apparatus, 

 owing to the relatively high proportion of silica which the 

 mineral contains, it was thought that this might have been the 

 cause of the low result. Small samples of Nos. 1, 2 and 3 

 were, therefore, completely decomposed with acids and the 

 resulting solutions evaporated to dryness on the water-bath. 

 The residues were treated with dilute hydrochloric acid and 

 the solutions thus obtained were introduced into apparatus 

 similar to the solution tubes (fig. 2) already described, except 

 that the lower part consisted of a single bulb only. The solu- 

 tions were then sealed up and allowed to stand for thirty days. 

 At the end of this period the bulb A was sealed off and the 

 accumulated emanation transferred to the electroscope. The 

 results thus obtained are give 



Per cent 

 uranium in 

 No. Substance. mineral. 



1 Uraninite 82*5 



2 Gummite 66*1 



3 Uranophane 46-6 

 It is therefore probable that the low value obtained in the 



first experiment with the uranophane was due to the forma- 

 tion of gelatinous silica. The value of the ratio stands in 

 no direct relation to that obtained in the other series, since the 

 adjustment of the electroscope was again different. 



n the following table 





Grams 



Leak 





uranium 



divisions 





taken. 



per min. 



Eatio. 



0-1227 



16-6 



135 



0-0964 



13-3 



138 



0-0686" 



9-8 



143 



