Lead and the End Product o] Thorium. 



83£ 



used as a source of lead, but Curie states that it was specially 

 chosen as being relatively free from uranium. While the 

 result indicates the possibility of a small proportion of thorium 

 lead being present, it points to the improbability of any 

 additive accumulation of that product during the history of 

 the monazite. Until more determinations from thorium 

 minerals are made, it is, however, impossible to build up a 



conclusive argument. 



Table Y. 





Mineral from which 



Atomic 



Weights. 









Experimenters. 



'• lead " was prepared. 



RaG. 



Th E (?) or 







Common Lead. 



Honigschiuid and 



Pitchblende. 



2067 





St. Herovitz * 



Joaehimstal. 







Honigschmid t. 



Pitchblende. 

 Joaehimstal. 



206-4 





Richards and 



Pitchblende. 



206-57 





Lembert \. 



Joaehimstal. 







n 



Pitchblende. 



206-86 







Cornwall. 







n )i 



Uraninite. 



206-40 







N. Carolina. 







>1 ;' 



Carnotite. 

 Color 



206-59 





)5 1) 



Thorianite§. 



206-4 



207-1 





Ceylon. 



- 







■20 



-v— ■ 



6-82 



1) 



Ordinary Lead. 







20715 



Soddy and 



Thorite. 





208 4 



Hyman ||. 



Cei/lon. 







Curie §§. 



Monazite. 





207-0S 





Galena . 



z..\ 



207-01 





Yttrotantalite. 



206-54 







Carnotite. 



206 36 







Pitchblende. 



200-64 





* Wica. Anzeiger, xiv. 12 June. 1014. 



t Privately communicated to the authors. 



J Fajans, faitzungsb. Heidclbergcr Acad. Wiss. A., 16 May, 1914. 



Richards and Lembert, Journ. Am. Chem. Soc. xxxvi. p. 1329(1914). 



§ Contains 60 p. c. Th, and 20 p. c. U". " Lead" from this source gave ;i 

 value of 20682, which, combined with Richards and Lembert's value of 206 - 4 

 for RaG, gives 207*1 for Th E. on the assumption that the latter is stable 

 and has accumulated in the mineral. 



I! Trans. Chem. Soc. vol. cv. p. 1407 (1914). 



§§ C. R. clviii. p. 1676 (1914). 



For the present we can only sum up the position by saying 

 that atomic weight determinations are consistent with the 

 stability of Ra G and its isotopy with lead, but that the 

 stability of Th E must be regarded as "not proven." 



