296 Analyfis of the Air. 
fccms to make up a conftderable part of its 
compofition 5 which air, when by the adion 
of fire it is more firmly united with the 
earth, and acid fulphureous particles, requires 
a more intenfe degree of heat, to extricate 
it from thofe adhering fubftances, as we find 
in the diftillation of Sal Tartar , Expel*. 74. 
which Air and volatile Salt are molt readi- 
ly feparated by fermentation. 
And by Experiment 72, plenty of air arifes 
alfo from Nitre , at the fame time that the 
acid fpirit is feparated from it by, the adion 
of fire. 
We find alfo by Experiment 71, that 
fome air is by the fame means obtained 
from common fea Salt, the not in fo great 
plenty, nor fo eafily, as from Tartar and Ni- 
tre , it being a more fixt body, by rcafon of 
the fulphur which abounds in it 5 neither 
is it fo eafily changed in animal bodies, as 
other Salts arc, yet fince it fertilizes ground, 
it muft needs be changed by vegetables. 
There is good reafon alfo to fufped, that 
thefe acid fpirits are not wholly free from 
air particles, notwithftanding there were no 
elaft'ick ones produced, when they were put 
into a brisk motion, by the action of fire in 
Experiment 75, which might be occafioned 
1 by 
