168 TRIPHYLITE. 



a boiling saturated solution of sulphate of potassa. 

 In this way all the thoria, like the oxides of the cerium- 

 class, is precipitated as a white pulverulent double 

 salt. After cooling, this is filtered off', and washed 

 with a saturated solution of sulphate of potassa. There 

 remains in the solution the unessential elements of the 

 mineral, iron, manganese, lirne, magnesia, alumina, and 

 the alkalies. It is then dissolved in boiling water and 

 the alumina precipitated by caustic potassa. 



After ignition, thoria is white, and has a spec. grav. 

 of 9.4. It can only be dissolved in hot concentrated 

 sulphuric acid. The hydrate of thoria is insoluble in 

 potassa. 



Chloride of thorium is fusible, and may be sublimed. 



Sulphate of thoria dissolves but slowly in water. 

 When the solution is heated, a tissue of fine crystalline 

 needles separates, consisting of salt containing less 

 water, which is very sparingly soluble. 



90. TRIPHYLITE. 

 3 (FeO, MnO, MgO, LiO) PO 5 . 



Besides the principal constituents this mineral con- 

 tains small quantities of silicic acid, lime, potassa, and 

 soda. For analysis it is dissolved in hot nitric acid, 

 the silicic acid filtered off, a few grains of mercury 

 dissolved in the filtrate, evaporated to dry ness on the 

 water-bath, moistened with water, and again evaporated 

 to drive off all the free acid. The mass is then lixiviated 

 with hot water, which dissolves all the bases, the phos- 

 phoric acid remaining in the residue. This is fused 

 with carbonate of soda and potash, as in the case of 

 apatite. The alkaline phosphate is dissolved in water, 

 the oxide of iron filtered off, and the phosphoric acid 

 precipitates as a double salt of magnesia. 



