on the specific Gravities, &c. of Saline Subfiances, 209 
. The only queftion that remains then is, whence the phlo- 
gifticated air proceeded which Dr. priestley mentions to have 
found ? The circumftance of his experiment would furnifh a 
platifible anfwer ; but the dodfcor has lately informed me, tliat 
he believes the air was really inflammable, but being a 
fmall quantity efcaped before the flame could be applied. 
It feems, thetefore, fufficiently proved, that inflammable 
air purified from the acids or other fubftances that expel it from 
its bafis, and alfo from all particles of the body to which it 
was originally united, fuch as inflammable air from metals ie- 
ceived on mercury, and well wafhed in lime-water, is one and 
the fame fubftance with phlogifton, differing only in quantity of 
fire, inflammable air containing nearly the fame quantity of 
this element as the fame bulk of atmofpheric air, as Dr. craw- 
ford has found by fome late experiments, an account of which 
will foon be laid before the public. This does not contradict 
that moft important difcovery of this ingenious philofopher, 
that fire and phlogifton repel each other : the meaning of this 
being only, that the addition of phlogifton to any fubftance, 
as to refpirable air, dephlogifticated acids, metallic calces, ex- 
pels part of the fire already contained in fuch fubftance ; and r 
on the contrary, by the removal of phlogifton from any fub- 
ftance, the quantity of fire abforbed by fuch fubftance is 
increafed. . . 
It may appear extraordinary, fuppofing inflammable air and 
phlogifton to be the fame fubftance, that inflammable air fhould 
mix fo eafily with water, whereas phlogifton conftantly repels 
and is repelled by it ; but this intirely depends on the ftate of 
this fame fubftance, which, when fixed and concrete, is called 
fhlogijhn , and, when ratified and aeriform, inflammable air. In 
this latter ftate it mixes with water in proportion to its rare- 
Vol. LXXII. E e faaion? 
