[ 7 ] 
Oil of Vitriol employed unites with the fixed Al- 
kali, fo as to make the true Tartarus e uitriolatas ; 
and leaves the lighter Spirit quite detached and free 
to rife, and come over the Helm in Diflillation : 
So that this volatile Spirit and the fixed Oil of 
Vitriol are by no means the fame Thing ; nor 
fhould the one be ufed for the other, efpecially 
in Phyfic. 
IX. But tho’ the Oil of Vitriol be allowed to differ 
from the volatile Acid of Sulphur, fome may ima- 
gine, that there is no Difference betwixt this vola- 
tile Acid and the volatile Spirit of Vitriol, as it 
comes over in the Re&ification of Oil of Vitriol; 
or betwixt our Spirit and the Gas Sulphuris , which 
is extremely pungent and volatile : But whoever 
attentively examines and compares the volatile 
Spirit of Vitriol, or the Gas Sulphur is, with our 
Spirit, will foon be convinced of a great Differ- 
ence; tho’, indeed, they agree in the Point of 
Gajjy Volatility: For the volatile Spirit of Vitriol 
is only an impure Phlegm of Vitriol, containing 
very little Acid, and is chiefly impregnated with 
the wild Fumes of the Vitriol ; fo as, upon (land- 
ing a while, to quit the Liquor, and leave it nau- 
feous, vapid, and grofs ; whereas the volatile Spi- 
rit of Sulphur long preferves its Volatility, the 
purer Gas being here lodged in a pure acid Liquor, 
lefs clenfe and grofs than Oil of Vitriol ; fo that 
when, by being long unfeopped, this acid Spirit 
lofes of its Volatility (as it will do), yet it never 
lofes of its Acidity ; and even then appears to be 
the mod pure and perfed Mineral Acid we can 
any way procure. And, as to the Gas Sulphur is , 
when 
