lOi COBALTITE. 



acetate of soda, and the pale rose-red oxide of cobalt 

 precipitated by a hot saturated solution of oxalic acid. 

 The yellow salt may also be changed directly to an 

 oxalate by boiling with oxalic acid. After it is 

 washed and dried, it is placed in an unglazed porcelain 

 crucible, standing in a Hessian crucible, pressed in 

 firmly, both crucibles covered and luted, and then 

 placed in a strong blast or furnace fire. 



The cobalt may also be separated from the nickel, 

 if the solution mixed with hydrochloric acid is con- 

 siderably concentrated by evaporation, mixed with 

 sal-ammoniac and ammonia in excess, and the brown 

 solution allowed to stand exposed to the air until it 

 has acquired a fine purple tint. If it be now saturated 

 with hydrochloric acid and heated to boiling, the 

 greater portion of the cobalt separates in the form of 

 a carmine crystalline powder, which appears to be 

 5NH 3 -f CojjCly and when ignited leaves protochloride 

 of cobalt. 



If dissolved in boiling dilute hydrochloric acid, this 

 compound crystallizes in dark red octahedral crystals. 

 Heated alone blue chloride of cobalt is formed, in 

 hydrogen gas, metallic cobalt. 



67. COBALTITE. 

 CoS 2 +CoAs 2 . 



I. The finely-powered mineral is decomposed by 

 heating it in a current of dry chlorine-gas, as in the 

 analysis of tetrahedrite, when the cobalt remains be- 

 hind in the form of protochloride, whilst arsenic and 

 sulphur are obtained as acids, dissolved in the water 

 of the receiver. The protochloride of cobalt can then 

 immediately be reduced to metal, in the same tube, by 

 heating it in hydrogen, and weighed, if the determina- 



