McCoy and Ross — Thorium Compounds. 



439 



fourth column contains the values of the ratio, x, of the activity 

 of any film to that of a thick film of maximum activity, x = 



a 

 56-9 * 



2-303 s 



w 



log 



1 



1 —X 



~k 2 is the absorption coefficient* and s is the area of each film, 

 39'8 SC1 om . 





Table III. 



Thorium 



Dioxide — A. 





w 



Cti 



a 



X 



&2 



•0546 



12-27 



12-26 



•216 



177 



•1026 



20-70 



20-66 



•363 



175 



•2020 



33-80 



33-66 



•592 



177 



•2798 



41-3G 



41-0 



•721 



182 



•9182 



55-6 



54-7 











•8893- 



58-8 



56-9 



--- 



•■-- 



Mean 



178 



The specific activity, k y , of the sample can now be calculated 

 from the absorption coefficient. 



&,= 



Ikjb __ 2X178X56-9 

 s ~ ~39-8 



= 509 



The mean value of k u for the two methods, is 513. 



Thorium dioxide contains 87'9 per cent of thorium. There- 

 fore the activity of unit weight of thorium, together with its 



5 1 3 

 active products in sample A, is — — = 584. The activities of 



several thorium minerals have been determined by the extrapo- 

 lation method as worked out for sample A of pure thorium 

 dioxide. The locality of origin and the composition are shown 

 in Table IV. 



Table IV. 



No. 



Name. 



Orangite 



Thorite 



Monazite 



Langesundsf jorcl, Norway 



Per cent 



Per cent 



Th. 



U. 



43-1 



7-76 



46-6 



6-26 



5-27 



•33 



15-18 



•46 



2-72 



•12 



McDowell Co., N". Carolina 

 Roade, Norway 

 Commercial sample 



The analyses for thorium were made by the method of Neishf 

 and for uranium by reduction with zinc in sulphuric acid 



* McCoy, J. Chem. Soc, xxvii, 395, 1905. 

 f Loc. cit. 



