Z1ECON. 157 



which immediately dissolves the sulphide of iron 

 leaving the zirconia colorless. For quantitative anal- 

 ysis the solution containing zirconia and iron, after 

 neutralization, is mixed with hyposulphite of soda, 

 and heated until all the zirconia is precipitated free 

 from iron. It is then ignited. 



For the preparation of zirconia in large quantities, 

 the zirconia which has been heated to redness and 

 cooled suddenly by cold water is broken up in an iron 

 mortar, sifted and freed from iron by hydrochloric 

 acid and the residuum fused with two or three times its 

 weight of the fluorhydride of the fluoride of po- 

 tassium. It is gently heated at first to drive off the 

 water and afterwards when dry and hard, the 

 temperature is raised until the mass is completely 

 fused. It is then poured out, coarsely pulverized, 

 and heated to boiling with a little water mixed 

 with hydrofluoric acid. The solution of fluozirconate 

 of potassium, which is very soluble in hot water 

 filtered off from the fluosilicate of potassium, the 

 latter being washed with hot water. On cooling 

 the salt crystallizes in fine prisms. It may be purified 

 by recrystallization. Heated with sulphuric acid, it 

 is converted into a double sulphate, which leaves 

 after strong ignition pure zirconia mixed with sul- 

 phate of potassa. 



The ignited zirconia is again rendered soluble 

 by heating for a long time with concentrated sul- 

 phuric acid, or with acid fluoride of ammonium. 

 It is completely precipitated from a neutral solution, by 

 a boiling saturated solution of sulphate of potassa, as a 

 white pulverulent double salt. After boiling this 

 precipitate is scarcely soluble in water or even in 

 acids. 



The chloride of zirconium, Zr C1 Q , can be prepared 

 directly from zircon, as a white sublimate soluble 

 in water, if the very finely levigated mineral with 

 14 



