178 WOLFRAMITE. 



solution of this salt it may be precipitated by ackls; 

 for example, sulphuric. If precipitated by hydro- 

 chloric acid, it is soluble in an excess, although not 

 wholly. With zinc it gives a pale blue color, which 

 becomes very bright if the solution of the bichloride 

 of tantalum in sulphuric acid is mixed with a little 

 water and zinc placed in it. The blue color does not 

 change to brown. Fused with salt of phosphorus it 

 remains colorless in the inner flame, and also when 

 ignited in hydrogen gas. 



The chloride of tantalum, prepared in the same 

 manner as chloride of columbium, is pure yellow, 

 easily fused, volatile, forms a crystalline sublimate. 

 Water transforms it into hydrated tantalic acid and 

 hydrochloric acid, which does not retain it in so- 

 lution. 



If the tantalic acid contains titanic acid, by convert- 

 ing it into the chloride, a very fuming liquid bichloride 

 of titanium is formed. By fusion with bisulphate of 

 potassa the separation is incomplete. 



96. WOLFRAMITE. 

 (MnO, FeO), WO 3 . 



I. In order to effect merely a qualitative separation, 

 for obtaining tungstic acid, the very finely-powdered 

 mineral is digested with a mixture of concentrated 

 hydrochloric acid and about J of nitric acid, until it is 

 converted into yellow, pulverulent tungstic acid. This 

 is filtered oftj washed, dissolved in ammonia,* the solu- 



* By this treatment, there is left undissolved, besides the unde- 

 composed particles of mineral which have not been finely powered, 

 a white substance, consisting of silica and niobic acid, of which 

 latter the wolfram contains about 2 per cent. In order to remove 

 the silica, it is repeatedly evaporated with hydrofluoric and sul- 

 phuric acids, then fused with bisulphate of potassa and farther 

 treated as directed for columbite. 



