OF COBALT, &c. 



precipitation, all but a few pounds of the nickel 

 originally employed, may be feparated. 



Fromthefc facls it plainly appears, that zinc 

 does not precipitate the nickel iticlf (from the fo- 

 lution. For, whatever weight of zinc be put in* 

 to the faturated folution of nickeJ, the green co- 

 lour dill remains unchanged. If, then, there be 

 any portion of nickel in the precipitated pow- 

 der, its precipitation fcems to me to be owing 

 merely to the mutual attraclion of the metallic 

 calces; finceit appears in the precipitate diver- 

 ted of its metallic form, which could not be the 

 cafe, if nickel were, like other metals, precipi- 

 tated by a double affinity. But there are vari- 

 ous inilanccs of metallic calces being connected 

 by mutual attraction : gold combines with tin, 

 copper with zinc, in the form of calces. 



5 iv. Precipitates cfCfbult* 



IF a hundred pounds of regulus of cobalt be 

 diflblvcd in common nitron* acid, and u quanti- 

 ty of aerated mineral alkali be added to the fo- 

 lution thus prepared; a yellowifh dark green 

 precipitate, 1 60 pounds in weight, will inflantly 

 be produced. On the other hand, if cauttic mine- 

 ral alkali be poured into the fame folution, the 

 precipitate will weigh only 140 pound*, and will 

 be indeed of the fame appearance as the forniei 

 precipitate,, only darker in colour. PhbgiiVitat- 



cd 



