I 3*5 } 



\T[. On the d'lffersnt Kinds of Cadmta, and particularly thofe 

 of Zinc and Cobalt. By I. I. BiNDHElM of Mojcoiu, 



[Concluded from Page 255.] 



Of Cobalt. 



T 



XT is fcarcely a centun- and a half fince people kne\v 

 how to make ufe of cobalt ore. Brand, counfellor of the 

 mines in Sweden, firft proved that cobalt was a femi-meial, 

 and that it poflelled peculiar properties different from thofe 

 of other metals. He defended his opinion againft various 

 olijeclions that were made to it; but it is ftill believed by 

 fome, that it is a mixture of copper, iron, and arfenic : and 

 this feenis the more probable, as a fixed blue colour, fit for 

 being employed in the arts and manufaftures, is prepared 

 vith advantage at Vienna from iron and arfcntc. This, 

 however, does not place the circumftance beyond all doubt, 

 for it Hill remains to be examined whether the arfenic and 

 ifon employed for that purpofe be free from cobalt ; and, 

 until that be afcertained, the fatl muft be involved in un- 

 certainty ; for both, or at leafl one of them, may be mixed 

 uith cobalt. 



Lehmann was of opinion, that the colouring matter of 

 cobalt confided of a fine alcaline earth combined with fomc 

 particles of copper and iron ; and he made experiments on 

 this fubjeft, by which he obtairjed blue glafs. But from 

 the defcriptiou he gives of his experiments it does not appear 

 fufficiently proved that ingredients free from Qobalt were ufcd 

 for the mixture . 



The reafon why fome may have been inclined not to 

 afcribe the principle which colours fmalt to a metallic fub- 

 j^ance may have becri, that thev employed for their experi- 

 ments a cobalt ore free from arfenic, and did not apply a 

 fufficiently llrong heat, without which the regulus of cobalt 

 i« difficult to i)e fufcd, and not fo eafily feparated : the prin- 

 -ciple which givw tlie blue colour to glafs is, however, to be 



afcribcd 



