SMAtTITE. 103 



3 KO, 5N0 3 HO) is filtered, washed with a solution of 

 chloride of potassium, dissolved in hydrochloric acid 

 and the protoxide of cobalt precipitated by caustic 

 potassa. Protoxide of nickel may be precipitated 

 from the filtered solution in the same manner. 



If nickel is to be precipitated from a solution by 

 means of sulphide of ammonium, it is not complete, 

 leaving sulphide of nickel undissolved, giving a brown 

 color, if the sulphide of ammonium does not contain, 

 by means of oxidation, a higher sulphide. 



The best method is to saturate the nickel solution 

 with sulphuretted hydrogen, and drive off so much 

 ammonia that the solution is feebly alkaline. Then 

 filter as quickly as possible, and wash the precipitate 

 with water containing sulphuretted hydrogen. 



66. SMALTITE. 

 Speiss Cobalt.* 

 (Co, Fe, Ni) As 2 . 



The analysis and the preparation of pure cobalt can 

 be effected by the same process as the analysis of cop- 

 per-nickel and the preparation of pure nickel. 



Since the arsenide of cobalt contains upwards of 70 

 per cent, of arsenic, it is advisable to remove a great 

 portion by first fusing it with common salt, and after- 

 wards roasting or fusing it with a mixture of soda and 

 sulphur. 



It may be separated from nickel by nitrite of potassa. 

 For the preparation of fused metallic cobalt, the yellow- 

 precipitate is dissolved in the smallest possible quan- 

 tity of hydrochloric acid, the solution mixed with 



* Arsenide of cobalt, with small quantities of nickel, iron, and 

 copper. 



