MANGANESE AND COBALT, OR NICKEL. 107 



be effected by neutralizing the solution with ammonia, 

 precipitating both metals by sulphide of ammonium, 

 and then adding a slight excess of dilute hydrochloric 

 acid, when sulphide of iron is dissolved and sulphide 

 of cobalt is left undissolved. 



Or both oxides are precipitated by caustic potassa, 

 the precipitate washed, removed from, the filter, and 

 the latter carefully cleansed with water from the wash- 

 ing-bottle ; the mass is then mixed with a slight excess 

 of powdered oxalic acid, when the oxide of cobalt is 

 converted into rose-colored, insoluble oxalate, whilst 

 the sesquioxide of iron is dissolved. After twenty-four 

 hours the former is collected on a weighed filter, washed 

 with cold water, dried at 100, and a weighed portion 

 of it ignited in a glass tube, one end of which is sealed, 

 whilst the other is drawn out into a point; by this pro- 

 cess the oxalate of cobalt is reduced to metal. Whilst 

 the tube is still red-hot the point is sealed with the 

 blow-pipe, and the tube weighed when cold. 



68. MANGANESE AND COBALT, OR NICKEL.* 



For the merely approximate separation, the oxides 

 are precipitated by carbonate of soda, the precipitate 

 dissolved in an excess of acetic acid and the cobalt or 

 nickel precipitated from the solution by sulphuretted 

 hydrogen, when manganese remains dissolved. The 

 solution of the chlorides or of the sulphates may also 

 be mixed with acetate of soda, and the nickel or cobalt 

 precipitated by sulphuretted hydrogen. 



Or the solution is mixed with considerable chloride 



* Black cobalt-ore (earthy ore of cobalt) is a compound of prot- 

 oxide of cobalt with binoxide of manganese. Moreover, almost 

 every variety of manganese-ore contains small quantities of cobalt 

 for the detection of which the residues of the preparation of chlo- 

 rine may be used. 



