50 HISTORY OF COBALT AND NICKEL. 



Hidrat of Cobalt. 



Hidrat of Crystals of sulphat or nitrat of cobalt, thrown into a bottle 



cobalt, tilled with a solution of potash, and immediately corked up, 



are decomposed. A blue precipitate is formed, which changes 



to a violet, and afterwards to a rose colour, becoming a 



hidrat. 

 decomposed by If the hidrat of cobalt be boiled with potash, this dissolves 

 potash, some oxide, and acquires a fine blue colour. This solution 



i is decomposed by the addition of water. By exposure to the 



air the oxide becomes black, and falls down, 

 and dissolved Hidrat fresh made dissolves without heat in carbonat of 

 m its carbonat. potash, and tinges it red. The oxide does not dissolve in 



it. 

 Characters of The hidrat of cobalt is of a rosy feuillemorte colour, 

 the hidrat. Acids dissolve it with heat, and without effervescence. 



The hidrat is not decomposed by boiling either in pure 01 



in alkalized water. Heat expels from it 20 or 21 of water, 



and reduces it to very pure gray oxide. 



It does not keep well under water 5 when it is exposed t© 



the contact of air, it grows black. Dry hidrat keeps better, 



but it attacts carbonic acid. 



Dissolves in When crystals of sulphat of cobalt are thrown into a phial 



ammonia as it f u ]j f ammonia, which is immediately closed, they yield a 

 forms from the . , . . , . , , . . , 



sulphat, bl ue precipitate, which does not become rose coloured, as in 



potash. Mr. Proust affirms, that the hidrat is formed, but 



that as fast as it is produced it dissolves in the ammonia j so 



that it is the hidrat that colours the solution, and not the 



simple oxide. 



Kutirnation of the quantity ofoxigen in the oxide at a minimum,. 



■"iray o\iu* A hundred parts of gray oxide, reduced with the requisite 



c«ntams iG\5 precautions in a closed crucible, afforded 83 • 5 of metallic 



per cent, ot r J J 



rtfaen. grains. One hundred parts of the metal therefore appear t© 



absorb nineteen of oxigejvto become oxide at a minimum. 



Oxide at a maximum. 



^Jiack oxid< ; 20 If a nitric solution of cobalt be distilled, black incrustation* 

 #©rt:ent. w i]l 



