Quantity of Radium in Rocks and Minerals, fyc. 143 



28 grams carbonates. As the entire melt weighed 28' 28 

 grams and contained 0*72 mgm. uraninite, this represented 

 16*62 x 10~ 12 gram radium. From this, making the proper 

 allowance for the weight o£ granite introduced along with 

 the uraninite, the constant can be derived as before. De- 

 ducting for the leak due to the basic rock present, the 

 constant was 0*67 x 10~ 12 . It appeared as if the added 

 melt had the effect of increasing the fluidity or the 

 ebullition. 



The results on basic rocks by the fusion method show a great 

 increase on those by solution : — 





Wt. of Rock, 

 grms. 



Wt. of Carbs., 



grms. 



Result by Eesult by 

 Solution. Fusion. 



Andesitic tuff ... 



Same 

 Andesitic laya ... 



10 



5 



10 



25 

 20 

 25 



12 



111 X 10 



036 „ 



3-8xl0" 12 

 3-8 „ 

 20 





Means 



074 „ 2-9 



It does not seem possible to question the very great increase 

 obtained by the new method. The constant upon which the 

 above results are based is 0*77 x 10" 12 . This was used 

 because the experiments were made without adding boracic 

 acid. But even if the lowest value of the constant was used 

 the increase on the solution method is remarkable. I would 

 call attention to the exact agreement between the first 

 and second results where a very considerable difference 

 in the amount of rock and proportion of carbonates 

 obtained. 



An experiment on a Vesuvian lava from Colle Umbeito, 

 for which I had previously obtained 14'6 x 10" 12 (Phil. Mag. 

 Oct. 1909), gave with the new method 25 XlO" 12 , or, if the 

 lower constant is used, 19'5 X 10~ 12 . 



Against the above consistently increased results has to be 

 set some which I next carried out on the traps of the Deccan, 

 using the same materials formerly dealt with. (British Assoc. 

 Address Sec. C, 1908, and ' Radioactivity and Geology/ p. 42.) 

 The result in this case was to lower the values originally 

 found : — 



