130 A SYSTEM OF 



who deny arfenic to be a femi-metal, that it may 

 as well be a fait of a peculiar nature ♦, as, for in- 

 fiance, the vitriolic acid •, and that it may, like ful- 

 phur, difTplve the metals in form of a kind of re-r 

 gulus •, and farther, that its affuming a metallic 

 appearance, when it is united with an inflamma- 

 ble fubflance, is of no confequence, fmce there 

 are fiih and infects who have a mining metallic co- 

 lour: But all this does not deferve an anfwer, 

 fmce it has been already agreed, that fyftems mutt 

 not be too feverely criticifed. 



SECT. CCXLVI. 



£>. Cobalt, Cobahum. 



This femi-metal is, 



a. Of a whitifh grey colour, nearly as fine 

 tempered fteel. 



£. Is hard and brittle, and of a fine grained 

 texture -, hence it is of a dufky, or not (lim- 

 ing appearance. 



C Its fpecific gravity to water is 6000 : : 1000, 



$. It is fixt in the fire, and becomes black by 

 calcination -, it then gives to glaffes a blue 

 colour, inclining a little to violet, which 

 colour, of all others, is the mod fixed in 

 fire, 



f. The concentrated oil of vitriol, aquafortis., 

 and aqua regia, difTclve it ; and the folu- 

 tions become red. The cobalt calx is like- 

 wife diffolved by the fame menflrua, and 

 alio by the volatile alcali, and the fpirit of 

 lea- fait. 



/". When united with the calx of arfenic in a 

 flow (not a brisk) calcining heat, it aiTumes 

 a red colour : The fame colour is naturally 

 produced by way of efHorefcence, and is 



then 



