igos.] 



HALL AND SMITH— COLUMBIUM. 179 



solution allowed to evaporate, when large characteristic crystals of 

 uranium nitrate separated. The solution decanted from the original 

 ammonium hydroxide precipitate, which contained manganese and 

 allied elements, was treated with an excess of sodium carbonate. 

 The precipitate produced was allowed to settle, the supernatant 

 liquid decanted into other jars, and hydrogen sulphide passed 

 through it. A small amount of a black sulphide was obtained. It 

 consisted of zinc, iron, copper and nickel (from the crucible tongs). 

 The precipitate produced by sodium carbonate contained manga- 

 nese, zinc and iron. Ten grams of it were dissolved in hydrochloric 

 acid and the iron removed by the basic acetate method. The zinc 

 was then precipitated as sulphide. The latter was changed to 

 chloride and tested for gallium. Not a trace of the latter was 

 found. Zinc lines alone were shown in the spectrum. 



Tin and tungsten were contained in part II. Part III was not 

 further examined. It may be concluded, therefore, that the 

 columbite from South Dakota contains as acids : tantalum, colum- 

 bium, titanium, silicon, zirconium, tin and tungsten ; as bases : 

 iron, maganese, zinc, uranium, copper (?) and nickel (?). 



The moist metallic acids, after having been washed with dilute 

 sulphuric acid, were brought into a large platinum dish and dis- 

 solved in fairly concentrated hydrofluoric acid. This solution was 

 then filtered, through a hot water funnel, from undecomposed 

 mineral and from potassium silicofluoride (due to the presence of 

 some potassium sulphate in the moist oxides). The hydrofluoric 

 acid solutions were collected in large rubber dishes and sufficient 

 potassium hydroxide was introduced to convert the tantalum into 

 potassium tantalum fluoride, most of which separated out and was 

 removed by filtration. This precipitate was dried as far as pos- 

 sible by suction. It was washed once and then allowed to dry in 

 the air. It weighed n kilograms. The mother-liquor from the 

 potassium tantalum fluoride was evaporated in stages, potassium 

 hydrate being added. The columbium separated usually in hexag- 

 onal, hard, short crystals, such as separate from a strongly acid 

 solution containing an insufficient amount of potassium fluoride. 

 The total residue obtained in this way amounted to about 8 to 10 

 kilograms. These residues were decomposed by treating them with 

 twice their own weight of sulphuric acid, heating gently until the 

 bulk of the hydrofluoric acid was expelled, and then evaporating 



