22& Continuation of the Experiments and Obfervations' 
particular circumftances, where a large quantity of phlogiflon 
is fuddenly heated and transferred all at once upon the dephlo- 
giflicated part of common air, phlogiflicated air may be formed 
as fulphur and volatile acid is formed, when a large quantity of 
hot phlogiflon is united all at once to the vitriolic acid. 
Analogous to this is another experiment of Mr. cAvalAo's, 
where he found, that, by the explofion of gunpowder, a largo 
quantity of phlogiflicated air is produced * ; and alfo another 
of Dr. Priestley’s, wherein he found, that by firing a mix- 
ture of equal parts, fulphur and nitre, only one-twelfth of the 
air produced was fixed air, the remainder being phlogiflicated 
air. But I own the circumflancesof the former experiment arc 
not as yet well known to me, not having been able to repeat it in 
luch a manner as to remove all doubt either of the elcape of 
the aii thiough the cement which fixes the wire that conducts 
the elearic fire, during combufHon ; or that the frnall quan- 
tity of inflammable air ufed prevents the fixed from being fen- 
iible. It may alfo happen, that to the produtfion of fixed air 
it is neeeflary that the phlogiflon be condenfed to a certain de- 
gree, as it is in common cafes; and perhaps, when exceedingly 
larified, ns it is in inflammable air from metals, it forms fome 
other, as yet unknown, compound. Thus much is certain, 
that all other inflammable air, fired with the elearic fpark’ 
produces fixed air ; and all other inflammable air is fpecifically 
heavier than the metallic, and before inflammation evidently 
contains no fixed aif. Mr. warltire, after burning metallic 
inflammable air, found a white powdery fubjiance (probably a 
calx) which may have abfofbed the fixed air. 
However, in the common procefs of combuflion of animal 
and vegetable fubflances it is certain, that fixed air is feparated 
* cavallo on Air, p. Si 2 . 
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