246 ESSAYS anv OBSERVATIONS 
pens in the precipitation of a calcarious 
earth from an acid, by means of the com- 
mon or mild volatile alkali, 
I remember likewife a parallel inftance 
with regard to quick-filver. This metal 
has an attraction for the vitriolic acid, 
and when joined to it appears under the 
form of turbith mineral: But this attra@ti- 
on is weaker than that of the fixed alkali 
for the fame acid; for if we mixa diflolved 
falt of tartar with turbith mineral, the tur- 
bith is converted into a brown powder, and 
the alkali into vitriolated tartar ; which 
change happens the fooner, ifthe pure or 
cauftic alkali is ufed. Yet, if to a com- 
pound of quick filver and the nitrous a- 
cid, we add a compound of the fixed al- 
kali and the vitriolic acid, or a vitriolated 
tartar, and digeft the mixture with a 
ftrong heat, the vitriolic acid does not re- 
main with the alkali, but is joined to the 
quick-filver which it attracts more weakly, 
compofing with it a turbith mineral; 
while the alkali is joined to the nitrous 
acid, which it likeways attracts more 
weakly 
