cf Cobalt and Nickel, '^-'^ ^3§ 



precipitate totally : applied to the other two, they separate 

 black oxide from them. Lastly, the blue oxide does not 

 give any gas with the muriatic acid, while the green does. 



From this we mfcwt coi>clude, that the blue oxtd^id oxy- 

 genated at the expense of tlie air contained in cold Hquids-, 

 and that the grec'n oxide is a mixture of blue oxide and black 

 oxide, M. Proust thinks nevertheless, that there is some- 

 thing more than a simple niixture ; for the blue and black" 

 colours would not give this shade of grass green, which, 

 distinguishes it from every other oxide. Nothing but a 

 true combination can yield a colour foreign to that of 

 its components, and Kirtder the action of the air from 

 elevating to the maximum the portion of blue oxide which 

 forms part of the greeii precipitate. In order to oxidize thi^ 

 precipitate completely, we must dry it by means of heat, as 

 Thenard has shown. 



The reddish gray precipitate, in the third experiment, is a 

 mixture of hydrate'and black oxide. 



It is only the minirmim oxide that can be combined with 

 the 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. — ^The gray oxide put into 

 a well-closed flask, along with ammonia, communicates 

 to it a slight red colour, which does not become higher, 

 however long the flask is kept : this oxide is therefore but 

 very difficultly soluble in ammonia. But if the flas-k remain 

 uncorked the ammonia is very quickly coloured^ because it 

 attracts carbonic acid from the air. We mar operate this 

 solution in a very short time, by placing the flask in a 

 large bason, in which we put a salt of carbonic acid. 



If we only saturate the Ammonia with acid, the solution 

 is that of the oxide in the carbonate of ammonia. If we 

 continue to make the carbonic acid pass, we obtain a solution 

 oi carbonate of cobalt in the carbanate of ammonia* Thiy 

 solution^ when kept in a flask full and corked, deposits cry- 

 stals of metallic carbonate j it abandons a part of them by 

 the addition of water : an excess of volatile alkali redissolves 

 this precipitate. We may make this solution \tiry speedily, 

 by throwing carbonate of cobalt into carbonate of ammonia. 



Y2 If 



