A SYSTEM OT 
’^36 
who deny arfenic to be a femi-metal, that it may 
as well be a fait of a peculiar nature y as, for m- 
ftance, the vitriolic acid ^ and that it may, like fub 
phur, diflblve the metals in form of a kind of re- 
gulus *, and farther, that its afluming a metallic 
appearance, when it is united with an inflamma- 
ble fubflance, is of no confequence, fince there 
are fifh and infecfls who have a fhining metallic co- 
lour: But all this does not deferve an anfwer, 
fince it has been already agreed, that fyflieras muft 
not be too feverely criticifed. 
SECT. CCXLVL 
6 , Cobalt, Colaltum, 
This femi-metal is. 
Of a whitifli grey colour, nearly as fine 
tempered Heel. 
Is hard and brittle, and of a fine grained 
texture *, hence it is of a duflcy, or not fhin- 
ing appearance. 
r. Its fpecific gravity to water is 6000 : : 1000, 
It is fixt in the fire, and becomes black by 
calcination •, it then gives to glafles a blue 
colour, inclining a little to violet, which 
colour, of all others, is the moft fixed in 
fire, 
The concentrated oil of vitriol, aqua fortis, 
and aqua regia, diflblve it ; and the folu- 
tions become red, The cobalt calx is like- 
wife diffolved by the fame menftrua, and 
alfo by the volatile alcali, and. the fpirit of 
fea-falt. 
When united with the calx of arfenic in a 
flow (not a brifk) calcining heat, it alTumes 
a red colour : The fame colour h naturally 
produced by way gf efflorefcencev, and is 
then 
