■ HISTORY OP COBALT AND NICKEL. 49 



If the ammonia be merely saturated with carbonic acid, This a solutioh 

 the liquid will be a solution of oxide of cobalt in carbonat oftheoxide » 

 of ammonia : but if we continue to pass corbonic acid into 

 this solution, we obtain a solution of carbonat of cobalt in or of carbonat. 

 carbonat of ammonia. This solution, kept in a full bottle 

 corked, deosits crystals of metallic carbonate ; it likewise 

 lets fall a part on the addition of water j but an excess of 

 ammonia redissolves this precipitate. 



This solution may be made very quickly, by throwing car- Made directly, 

 bonat of cobalt into carbonat of ammonia. 



If pure ammonia be poured on carbonat of cobalt with Ammonia with 

 excess of acid, what occurs is very different. The carbonat cobalt 

 of cobalt separates into two parts ; one gives out its acid to 

 the ammonia, and becomes a hidrat, which falls to the bot- 

 tom of the vessel ; while the portion not decomposed dis- 

 solves in the carbonat of ammonia. 



Thus we have two kinds of ammoniacal solutions of co- 

 balt ; and there is a third, which Taffaret observed, but 

 which has been hitherto little noticed. This is obtained by 

 putting well washed hidrat, or blue oxide, into a phial full and with hidtat, 

 Of ammonia, and closely stopped. A solution will take place 01 " blue 0Xlde ' 

 in the course of four and twenty hours. This is red, iikc 

 the preceding ; but differs from them in this, that, if it 

 be poured in a very slender stream into boiling water, blue 

 oxide wll immediately be precipitated j if into cold water, 

 green oxide will be obtained. If ammonia dissolve hidrat of 

 cobalt, or blue oxide fresh made, more readily than the gray 

 oxide, it is because they are in a state of extreme division. 



Distillation of ammoniacal solutions. 



When carbonated solution of cobalt are distilled, carbonate The carbonated 

 ©f ammonia passes over, and at length the liquor lets fall an JSiedleave'the 

 oxide, which is at first of a dirty green, but which afterwards cobalt more 

 becomes black. This is a mixture of the gray and black oxided - 

 oxides. 



How is this superoxidation effected ? The author reports 

 the facts, but does not endeavour to explain them, when 

 data are wanting. 



Vol, XVIL— Jvne, 1807> £ Hidrat 



