100 NICCOLITE. 



filtered off, washed, and digested with concentrated 

 caustic ammonia until they are dissolved. 



The blue solution is then set aside in an open vessel 

 until all the free ammonia has evaporated (under a 

 bell-jar over sulphuric acid, so that the ammonia may 

 not all be lost), during which time the nickel separates 

 in the form of green oxalate of protoxide of nickel 

 and ammonia, whilst the cobalt remains in the solution 

 to which it imparts a red color. 



The nickel-salt is filtered off, washed, and ignited in 

 a closed crucible or in a glass tube, when pure metallic 

 nickel remains behind. 



The cobalt may be obtained from the solution by 

 evaporation and ignition of the residue, or by boiling 

 it with caustic potassa until no farther disengagement 

 of ammonia takes place ; or when smaller quantities 

 are operated upon, by an alkaline sulphide, and subse- 

 quent addition of dilute sulphuric acid in order to 

 separate the sulphide of cobalt. It however still con- 

 tains nickel. 



The pure metal may be easily prepared from com- 

 mercial nickel by dissolving it in hydrochloric acid 

 with the addition of some nitric acid, purifying the 

 solution by sulphuretted hydrogen, and then precipi- 

 tating nickel and cobalt by the addition of a boiling 

 saturated solution of binoxalate of potassa. The 

 washed precipitate is then ignited, the metal dissolved 

 in hydrochloric with nitric acid and cobalt and nickel 

 separated by nitrite of potassa. 



For the purpose of separating the iron, the solution, 

 after being again oxidized, may also be mixed with 

 chloride of ammonium, and then with ammonia in 

 excess, when sesquioxide of iron (with a little nickel 

 and cobalt) is precipitated, whilst nickel and cobalt 

 remain in solution. 



II. QUANTITATIVE ANALYSIS. The very finely- 

 powdered arsenide of nickel is fused with 2 parts of 



