106 COBALTITE. 



acetate of soda added and heated to boiling, which pre- 

 cipitates the iron free from cobalt.* 



The protoxide of cobalt is precipitated from the fil- 

 tered solution at a boiling heat by means of caustic 

 soda, washed with hot water, ignited, and reduced in 

 a current of hydrogen at as high a temperature as 

 possible. When moistened with water after being 

 weighed, the metal must not exhibit an alkaline reac- 

 tion. Any nickel present may be determined as in 

 No. 65. 



III. The mineral is fused with carbonate of soda 

 and saltpetre as in the analysis of copper-nickel, No. 

 65. The mass is then treated with warm water, and 

 the black oxide of cobalt filtered off. The solution is 

 slightly acidified with hydrochloric acid and the sul- 

 phuric acid precipitated by chloride of barium. After 

 the excess of baryta has been removed by sulphuric 

 acid, the solution is concentrated by evaporation, mixed 

 with sal-ammoniac and sulphate of magnesia, and the 

 arsenic acid precipitated by ammonia. 



The oxide of cobalt is dried, the filter incinerated, 

 the ash added to the oxide, and the whole dissolved in 

 concentrated hydrochloric acid. The sesquioxide of 

 iron is then precipitated, by means of succinate of soda, 

 from the dilute solution, after carefully neutralizing 

 with carbonate o soda ; and the cobalt and nickel 

 separated as above. 



The sesquioxide of iron cannot be precipitated, in 

 this case, by carbonate of baryta, because some oxide 

 of cobalt is precipitated at the same time ; neither does 

 the precipitation by an excess of ammonia lead to 

 exact results, on account of some oxide of cobalt remain- 

 ing combined with the sesquioxide of iron. 



An approximate separation of both oxides may also 



* From a solution of nickel, iron thus precipitated always con- 

 tains some of the nickel. 



