SPHENE. 171 



The Triphylite contains more than 7 per cent, of 

 lithium and more than 44 per cent, of phosphoric acid. 



91. TITANITE (SPHENE). 



(CaCM-Ti0 2 )Si0 2 . 



This mineral, even in the state of very fine powder, 

 is only attacked with difficulty, and at best incom- 

 pletely, by hydrochloric 01 sulphuric acid. 



It is better to heat it in a platinum capsule with bi- 

 sulphate of ammonia, gradually raising the temper- 

 ature, with constant stirring, till the salt fuses; the 

 heat is finally increased to ignition. A little dilute 

 sulphuric acid is then added, and heat again applied 

 until the acid begins to volatilize. When the mass is 

 perfectly cold, it is mixed with water, the silicic acid 

 filtered off, and the sulphate of lime thoroughly 

 washed. 



From the solution, the titanic acid is precipitated in 

 the cold, together with the small quantity of sesqui- 

 oxide of iron, by ammonia, the solution filtered rapidly, 

 with as little exposure to air as possible, and the lime 

 precipitated by oxalate of ammonia. 



The titanic acid containing iron is dissolved in hy- 

 drochloric acid, the solution diluted and carefully 

 neutralized as completely as possible, decomposed by 

 hyposulphite of soda, and heated to ebullition. The 

 titanic acid is precipitated and ignited. 



Another method (in which, however, the silicic acid 

 is determined by loss) consists in decomposing the 

 mineral by concentrated hydrofluoric acid. The mass 

 is afterwards mixed with concentrated sulphuric acid, 

 heated until all the tetrafluoride of silicon and most of 

 the sulphuric acid are expelled, mixed once more 

 with concentrated sulphuric acid, and heated until it 



