£8 HISTORY OP COBALT AND NICKEL. 



Without heat 2. If cold alkalized water be employed, the blue preci- 

 pe precipitate . tate is f ormed lii ce wise ; but, instead of constituting a 

 is green. ' 7 ° 



hidrat, it passes to green, without the contact of air being 



capable of obscuring its tint, which it retains after it is dried. 

 Changed to a 3 - If this green precipitate^ when fresh made, be boiled 

 grey by boiling. j n W ater alkalized with potash, it becomes of a reddish grey, 



and changes no further. 

 Action of acids Very weak acids, as vinegar for instance, totally dissolve 

 en thepreci- f nc first precipitate. Applied to the other two, they sepa- 

 rate from it black oxide. Lastly, the blue oxide yields no 

 gas with muriatic acid, but the green does. 

 Creenoxidea Hence we must conclude, that the blue oxide oxigenizes 

 compound of itself at the expence of the air contained in cold liquors, 



the blue and , , , .,. . . /.,, ., ,,,, 



Wade, and that the green oxide is a mixture of blue oxide and black 



oxide. Mr Proust however thinks, that something more 

 than simple mixture takes place ; for blue and black would 

 not produce that grass green colour, which distinguishes it 

 from every other oxide. A true combination alone could 

 form a colour different from that of the mixture of its com- 

 ponent parts, and prevent the action of the air from raising 

 to a maximum the portion of blue oxide, which makes a 

 part of the green preripitate. To oxide this precipitate 

 completely, it must be dried with the assistance of heat, as 

 Thenard shewed. 



The reddish grey precipitate of the third experiment is a 

 mixture of hidrat and black oxide. 

 Maximum ox- ' The oxide at a minimum only is capable of combining 

 ide only solu- with acids. The green oxide is never obtained from any so- 

 lution, and cannot become the base of any saline combina- 

 tion. 



Ammonia and Oxide of Cobalt. 

 Dissolves with If the grey oxide be enclosed with ammonia in a Avell 

 ammonia * stopped phial^ it imparts to it a slight rose colour, which 

 docs not become deeper, however long it may be kept. This 

 oxide is consequently very difficultly soluble in ammonia.— 

 readily in its But if the phial be left open, the ammonia becomes coloured 

 very quickly, because it attracts carbonic acid from the air. 

 This solution may be effected in a very little time, by plac- 

 ing the phial in a large jar containing a carbonate. 



If 



carbonate. 



