i 9 o 5 .] HALL AND SMITH— COLUMBIUM. 177 



[Contribution from the John Harrison Laboratory of Chemistry. J 



SOME OBSERVATIONS ON COLUMBIUM. 



BY ROY D. HALL AND EDGAR F. SMITH. 



( Read May ig, igoj. ) 



The starting-out material in this study was columbite from Law- 

 rence County, South Dakota. Its specific gravity equaled 5.86. 

 It contained 81 per cent, of the mixed oxides of columbium and 

 tantalum. The total quantity of substance decomposed by fusion 

 with acid potassium sulphate (58.5 kilograms) was 21.3 kilograms. 

 Each fusion was made in a platinum dish, using 100 grams of 

 mineral and 275 grams of acid potassium sulphate. While still 

 liquid the mass was poured into a porcelain dish. When cold the 

 fusion separated readily from the dish and was broken into small 

 pieces, which were boiled with water in large No. 11 evaporating 

 dishes until thoroughly disintegrated ; when they were transferred 

 to precipitating jars and the hydrates washed by decantation until 

 the wash water gave no precipitate or only a slight precipitate with 

 ammonium hydroxide. The solution and the washings were evapo- 

 rated to dryness. The residue was designated part I. The moist 

 hydrates of columbium and tantalum were covered with ammonium 

 sulphide and allowed to stand for several days. This ammonium 

 sulphide solution was decanted and designated part II. The re- 

 maining oxides were finally treated with very dilute sulphuric acid 

 and then thoroughly washed with water. The washings and the 

 diluted sulphuric acid solution were also evaporated to dryness and 

 marked part III. The residue labeled part I contained potassium 

 and the bases from the mineral in the form of sulphates. It was 

 dissolved in water, poured into five-gallon jars and there precipi- 

 tated with a slight excess of ammonium hydroxide. Having de- 

 canted the supernatant liquid the precipitate was washed once with 

 water, after which the hydrates were covered with a solution of 

 ammonium carbonate and allowed to stand for several days. The 

 ammonium carbonate solution was then siphoned off, acidulated 

 with dilute hydrochloric acid, and any metal present precipitated 



