.Boltivood — Thorium Minerals and Salts. 417 



cipitate all of the rare earths as oxalates were measured out. 

 These portions of the ammonium oxalate solution were heated 

 to boiling and the dilute, boiling solutions of the neutral 

 nitrates of the rare earths were poured into them with constant 

 stirring. The mixed solutions were diluted with water to 

 twice their initial volume and were allowed to stand in the 

 cold for 48 hours, when the precipitates formed were removed, 

 converted into neutral nitrates and again subjected to the 

 treatment with an excess of ammonium oxalate. The second 

 precipitate of rare earths free from thorium was filtered off, 

 and the two ammonium oxalate solutions were combined, 

 heated to boiling and an excess of hydrochloric acid was 

 added. The solutions were then allowed to stand at ordinary 

 temperatures for 48 hours, the precipitated thorium oxalate 

 was collected on a filter and was ignited to convert the oxalate 

 into oxide. 



The finely pulverized monazite was treated with sulphuric 

 acid in a platinum dish. The resulting product was treated 

 with ice water, and the insoluble portion was again treated 

 with sulphuric acid. After removing the part soluble in ice- 

 cold water, the insoluble material remaining was a third time 

 treated with hot sulphuric acid, and a residue amounting to 

 3'0 per cent of the original mineral remained, which was not 

 further attacked by sulphuric acid. The combined aqueous 

 solutions were made strongly alkaline with ammonia, and the 

 precipitate of phosphates was removed, washed free from sul- 

 phates and dissolved in nitric acid. The dilute, nitric acid 

 solution was heated to boiling and poured into a boiling solu- 

 tion containing an excess of oxalic acid. After 24 hours the 

 precipitate of oxalates was removed, the oxalates were con- 

 verted into chlorides, and the precipitation of the rare earths 

 as oxalates was repeated. The second precipitate of oxalates 

 was converted into chlorides, and to the dilute, boiling solution 

 of the chlorides was added an excess of sodium thiosulphate. 

 The solution was boiled for about 20 minutes until the odor 

 of sulphurous acid could no longer be detected in the steam. 

 The precipitate was then separated from the solution, was 

 treated with hot, dilute hydrochloric acid, the residue of sul- 

 phur was removed, and, after the excess of hydrochloric acid 

 present had been largely neutralized with ammonia, the treat- 

 ment with sodium thiosulphate was repeated. The second 

 precipitate was treated with hot, dilute hydrochloric acid, the 

 chlorides obtained were converted into the neutral nitrates, 

 and the solution of the nitrates was twice treated with an 

 excess of ammonium oxalate in the manner described for 

 thorite and thorianite. The thorium w r as finally weighed in 

 the form of the oxide. The rare earths were all recovered 



