152 Thornton, Jr. — Separation of Thorium front Iron. 



and also to accomplish the indirect separation of thorium from 

 iron. 



A standard solution of thorium sulphate was employed for 

 these experiments. This was prepared hy dissolving the 

 Welsbach Light Company's thorium nitrate in boiling water 

 and precipitating the thorium with a boiling solution of sebacic 

 acid according to the method of Smith and James.* The 

 thoroughly washed precipitate was dried and ignited to thorium 

 oxide in a platinum dish. The residue was then subjected 

 to a prolonged digestion with hot sulphuric acid. After cool- 

 ing, the semi-solid mass was poured into cold water and the 

 solution filtered from an insoluble residue of unattacked 

 thorium oxide. The filtrate was made nearly neutral With 

 redistilled ammonium hydroxide and the thorium precipitated 

 with recrystallized oxalic acid. The thorium oxalate, after 

 complete washing, was dried at 110° C. and the sample pre- 

 served. Of the oxalate thus obtained 8*5 grams was digested 

 with 50 cm s of sulphuric acid (made by diluting acid of sp. 

 g. = 1*84 with an equal volume of water), adding a little nitric 

 acid to oxidize traces of organic matter which discolored the 

 liquid, and warming until nitric acid could no longer be detected 

 by its odor. On pouring the residue into cold water the 

 thorium sulphate dissolved completely and the solution wa9 

 made up to a volume of one liter. Two experiments were 

 made in order to set the standard of this solution. Weighed 

 portions were treated with redistilled ammonium hydroxide at 

 the boiling temperature, the resulting thorium hydroxide was 

 ignited to the oxide, and the latter was brought to constant 

 weight over the blast lamp. Duplicate determinations gave 

 the following result : — 



Thorium sulphate solution Thorium oxide 



(a) 25 cm 3 25 740 grm. 00922 grm. 0-3582^ 



(b) 25 cm 3 25-757 grm. . 0-0925 grm. 0'3592^ 



The mean of these two values was taken as correct. 



Preliminary experiments soon revealed the fact that even 

 with small concentrations of free sulphuric acid the precipi- 

 tation of thorium by the "cupferron" reagent is incomplete. 

 The author, therefore, resorted to the expedient of throwing 

 out the thorium from a medium containing acetic as the 

 only free acid. Accordingly weighed portions of 25 cm 5 of 

 the standard thorium sulphate containing also about 1*25 cm 3 

 of sulphuric acid (1 : 1) were taken and treated with 15 grm. 

 of ammonium acetate in the form of a strong solution and the 

 volume made up with water to 500 cm 3 . A 5 per cent "cup- 



*Jour. Am. Chem. Soc, xxxiv, 281, 1912. 



