fart'iCiilarlv ihop of Zhic and Coh.iU. ^S 



proportion of the iron be coufiderably lels^ that eflcA is not 

 produced. 



The fpecific gravity of a regnlus of cobalt, purified a9 

 much as poffible by the above method, is 7700*; its colour 

 is a pale grcvifli blue, but it becomes fomewhat darker when 

 expofed to the atmofphere : it is finely granulated on the 

 frafture, and requires a ftrong degree of heat to be fufcd, 

 cfpeclally when no arfcnic is prefent ; and therefore it hap- 

 pens that it is fo difficult to extraa the regulus by fufion 

 from cobalt ore which contains no arfenic. It is not, how- 

 ever, volatile, like the greater part of the femi-metals; and 

 docs not inflame and evaporate, but when calcined becomes 

 a blackidi oxyde. 



When cobalt is pure, it diflblves in acids with a red colour ; 

 when it docs not diiVolve, it is a fign that it is prevented by 

 fome foreign mixture : if the folution be green, it commonly 

 implies the prefence of nickel. 



With the vitriolic acid cobalt affords brownifh red cryf- 

 tals ; the nitrous acid diffolves it alfo of a red colour : by the 

 muriatic acid regulus of cobalt is dlflblved with difficulty, 

 but its calx eafily diifolves. This folution is red when cold, 

 but when expofcd to a heat of 80 degrees becomes green ; it 

 flioots into red cryftals inclining to blue : if thefe cryftals are 

 (iilTolved in water, and a little of the muriatic acid be added, tt 

 produces that kind of fvmpathciic ink which becomes green 

 when heated, and invifible when cold. The acetous acid 

 diflblves the calx of cobalt alfo of a red colour. If fuch folu- 

 tions are precipitated by volatile lixivious falts (ammonia), 

 and the quantity neceflury for faturation be added, it is re- 

 diffolved of a dark red colour. 



In the wet way the oxalic acid, and in the dry way iron, 

 have the greatcft affinity with cobalt. It combines with aU 

 raetals except filver, lead, and bifmuth. Regulus of cobalt 

 unites only weakly with fulphur, but is fully dilVolvcd by 

 fulphat of pol-aHi. 



* Bergmann Sciagr., but in hr- Dlflcrution on Nickel he makes it 3- 1 <. 

 6 VII. Svi- 



