the heavy inflammable Ain„ ' 69 
the compound forms of vegetable, animal, and bituminous 
iubftances, all of which yield phlogifticated air and volatile 
alkali in great abundance ; yet when the more fimple modifica- 
tions of the heavy inflammable air, as charcoal, vinegar, and, 
if Dr. Priestley is not miftaken, fixed air, give out phlo- 
gifiicated air, when decompofed in clofe veffels, 1 cannot but 
infer, that phlogifticated air is an effential part of that peculiar 
fubftance which exifts in all thefe ftates, whether that fub- 
ftance be called charcoal,, or the gravitating matter of heavy 
inflammable air. 
Hence it appears, that the phlogifticated and heavy inflam- 
mable airs combined, conftitute charcoal ; and that the mere 
application of heat always relolves charcoal into thefe two fub- 
ftance s. But the heavy inflammable air is itielf a compound 
of the lighter inflammable and phlogifticated airs. If phlo- 
gifticated air be combined with the heavy inflammable, or^, 
which is the fame thing, if light inflammable air be taken 
from it, charcoal is re-produced; therefore, when fulphur is 
melted in the heavy inflammable air,, and hepatic air formed 
in it, the remaining parts of the heavy inflammable air return 
to the ftate of charcoal. And laftly, when fulphur is melted 
in contadt with charcoal, the decompofition is complete ; and 
the charcoal is refolved into its ultimate particles, the phlogifti- 
cated and light inflammable airs, with a fmall admixture of 
volatile alkali. 
Thus far I have proceeded in the decompofition of the heavy 
inflammable air. The formation of this air, on many occa- 
fions, confirms what has been faid concerning its analyfis. In 
the refolution of compound bodies into their conftituent parts, 
it may always be fufpefled, that the whole is not accounted 
for, that fome part may have eluded obfervation, till the very 
4 . parts - 
