vf Cobalt and Nickel. 343 



The red efflorescences which we find upon minerals con- 

 taining cobalt arc formed of arseniate. IM. Proust found 

 llie arsenite in the heart of some pieces only. 



Hydro svlphnret ted Oxide. Siilpkiiret oj Cobalt. — The gray 

 oxide, the hydrate, and carbonate, take from water the sul- 

 phuretted liydrogen, and become hydro-sulphuretted oxide* 

 The latter is not dissolved in ammonia; it give? water and sul- 

 phnrous acid upon distillation. The remainder is sulphiiret. 



The oxides when heated with sulphur become sulphuret. 

 Cobalt absorbs 40 per cent, of sulphur. The authoj h^s still 

 some doubts upon this subject. 



Facts respeciiug the History of Nickel, 



Nitrate, — 100 parts of metal dissolved in the nitric acid, 

 and distilled until perfectly decomposed, leave from 123 to 

 126 of greenish gray oxide at the viinimum. The nitric 

 acid cannot make this oxide pass to the muximum. 



In order to ascertain the purity of the oxide of nickel, 

 we must dissolve it in the muriatic a<:id and heat it. If it 

 contains a littJe oxide of cobalt, ther« will be an extrication 

 of oxygenated muriatic gas : if it be pure, none will be dis- 

 engaged. 



The gray oxide is dissolved in all the acids, and gives the 

 same solutions as the metals. 



Nitrate at the min'minm. — By (tistilling the nitrate of 

 nickel with the same precautions as the nitrate of copper, 

 we obtain, as with the latter, a nitrate with excess of base, 

 which is insoluble in water, 100 parts of nickel give 142 

 of this nitrate : on deducting the 25 parts of oxygen ab- 

 sorbed by the aaetalj we have 1 7 parts of acid .fixed upon 

 this oxide- 



100 parts of iry nitrate of nickel gave upon distillation 

 5^0 of water, and 25 of oxide : therefore 53 of acid. These 

 proportioniJ are not rigorously exact, because the last^ por-f: 

 tions of water are a little acid. • 



Muriate of Nickel, — ^This is a gramilous crystallization of 

 an apple green, and very deliquescent. 



The traces of this salt, when dried upon paper, are yellow. 



Y 4 This 



