MENACCANITE. 173 



and may be extracted by hydrochloric acid ; the 

 reduction, however, requires a very long time and an 

 intense red heat, and, after all, the titanic acid is not 

 free from iron. The following methods are more 

 efficient : 



I. The very finely-powdered mineral is fused in a 

 platinum crucible, placed within an earthen crucible, 

 with 3 parts of carbonate of potassa ; the fused mass 

 is powdered, and dissolved in a platinum capsule, in 

 the requisite quantity of dilute hydrofluoric acid. 

 Titano-fluoride of potassium is thus produced, which is 

 sparingly soluble, and crystallizes readily, while most 

 of the sesquioxide of iron is separated free from 

 titanium. The mixture is heated to boiling, so much 

 water being added as is requisite to dissolve all the 

 salt, and filtered while boiling hot ; glass vessels rnay 

 now be employed, provided an unnecessary excess of 

 hydrofluoric acid has been avoided. On cooling, the 

 greater part of the salt separates in lustrous crystalline 

 scales. It is filtered off, pressed, washed once or twice 

 with cold water, and purified completely by recrystal- 

 lization from boiling water. 



The sesquioxide of iron is washed, the washings 

 mixed with the mother-liquor from the salt, and with 

 the washings from the latter, and the dissolved sesqui- 

 oxide of iron, together with very little titanic acid, 

 precipitated from the mixed solution, in the cold, by 

 dilute ammonia. The precipitate must be filtered off 

 immediately, for otherwise the titanic acid also begins 

 to separate. The filtrate is then heated to ebullition, 

 when all the titanic acid is precipitated as white 

 titanate of ammonia. In the same manner the titanic 

 acid may be obtained from the crystallized titano- 

 fluoride of potassium previously separated. 



The titanate of ammonia is easily soluble in hydro- 

 chloric acid, and, at a red heat, is con verted, with incan- 

 descence, into pure titanic acid. 



