360 PROCEEDINGS OF SECTION B, 



due to it as determined in his previous work. Tiie residual activity, 

 whicli he supposes due to thorivim and its products, is very accurately- 

 proportional to the thoria present. Results are given for thorianite 

 (Ceylon), thorite (Norway), monazite (Norway), and monazite (North 

 Carolina). He assumes also that actinium belongs to either the uranium 

 or thorium radio-chain. 



(<?) Dadourian uses the emanation, measuring the excited activity 

 produced by it (which is proportional to the emanation when the two are 

 in equilibrium quantity) after the decay of the excited activity of radium 

 and actinium. The method is very direct, and the results give a con- 



. , . Emanation Activity . ■, . . ,^ , s ■, , . 



stant tor the ratio — : ^ tor thorianite (Ceylon) and thorite 



(Norway). thoria 



(fZ) McCoy and Ross obtain the correct total activity, estimate the 

 uranium analytically, subtract the activity due to it, and assume the 

 remaining activity wholly due to thorium chain products. The constancy 

 of the ratio is proved for thorite (Norway), monazite (Norway), and 

 monazite (North Carolina). The results are conclusive, but as only two 

 localities are determined without any assumptions regarding the actinium 

 present, and as the localities are the sources of commercial thorium salts, 

 it seems worth while publishing the more extended list. The thirteen 

 (13) minerals examined represented twelve (12) quite distinct mineral 

 provinces. 



Analytical Methods. 



Uraninite (Colorado) ... \ 



Broeggerite (Norway) . . . . ; Dissolved in concentrated HNOg 



Thorianite (Ceylon) ) 



Thorite (Norway) \ 



Thorogummite (Texas) . . . . > Dissolved in concentrated HCl 

 Gadolinite (West Australia) ) 



The solutions were evaporated to dryness, and heated to dehydrate 

 silica. They were then moistened with acid, taken up with water, and 

 filtered. Any undecomposed residues were fused with KHSO4, taken 

 up in water acidulated with HCl, and the oxalates precipitated separately 

 from the main solution. Group II. metals were removed by HoS, and 

 the rare earths precipitated as oxalates in about 250c. c. solution by 50c. c. 

 of a cold-saturated solution of oxalic acid. The precipitate was allowed 

 to settle out for 24 hours, then filtered, and washed with very dilute 

 oxalic acid water. 



Mo7iazites. 



The monazite, after being very finely ground in an agate mortar, was 

 treated with concentrated H2SO.1, in a platinum dish, on an asbestos 

 board, over a medium Bunsen flame, for at least six hours. It was kept 

 covered Avith a thin clock glass, and the HoSO^ was replaced as 

 evaporated. The cooled mass was then poured very carefully into 700c. c. 

 water at 0°C, and allowed to stand in its freezing mixture for several 

 hours, with occasional stirring. The monazites were very carefully hand- 

 picked in every instance, and the residue in all cases was very slight. 

 Any residue was filtered off, and Group II., &c., precipitated by HjS in 



(c) Dadourian: American Jourrud of Science, xxi., 126, p. 427. 

 (d) McCoy and Ross : American Journal of Science, xxi., 126, p. 433. 



