TANTALITE. 177 



The acids are now digested with sulphide of ammo- 

 nium, which dissolves the two latter and converts the 

 sesquioxide of iron into sulphide, which imparts a 

 black color to the acids. This may be effected upon 

 the filter itself, if the stem of the funnel be passed air- 

 tight into a flask ; the funnel should be kept as closely 

 covered as possible after the mass upon the filter has 

 been carefully mixed with sulphide of ammonium.* 



After washing, very dilute hydrochloric acid is 

 allowed to flow over the mass upon the filter, when 

 the sulphide of iron is dissolved, and the acids again 

 become white. They are then washed, dried, and 

 ignited, when the sulphuric acid with which they are 

 combined is volatilized, which may be effected with 

 greater rapidity and certainty if a fragment of car- 

 bonate of ammonia be held in the closed crucible 

 during ignition. 



The stannic and tungstic acids may be separated 

 with more certainty by fusing the columbic and tanta- 

 lie acids with three times their weight of alkaline car- 

 bonates and sulphur, leached, washed with sulphide of 

 ammonium, and treated as above. 



95. TANTALITE. 

 (FeO, MnO) TaO 5 . 



The analysis is made in the same manner as that of 

 columbite. 



The tanlalic acid, Ta0 5 , is white, even at a red heat, 

 sp. gr. 7.9. Heated to redness it becomes insoluble 

 in concentrated hydrochloric and sulphuric acids. 

 Fused with caustic potassa or soda, it behaves like 

 niobic acid. The soda-salt may be crystallized. In a 



* Tin and tungsten may be precipitated by dilute sulphuric acid 

 as sulphides, which are converted in oxides by roasting. If the 

 mass is ignited in hydrogen, the reduced zinc maybe extracted by 

 concentrated hydrochloric acid. 



