relating to P bio gift on, &c. Part III. \ ? 
i ** 
difficulty, which I acknowledged, p. 128. in finding different 
rel alts from feemuigly fimilar circumflances ; whereas I now 
fin H that both the circumflances and the refults are different,, 
Beiides, the poftive evidence of actually finding a fubflance is 
always more conclufive than the negative one, of not finding 
it- ' > 
I do not know that any objection can be made to the inflam- 
mable air from tin 9 as this metal has not been proved to con- 
tain plumbago. I wiflied, however, to repeat this experi- 
ment with inflammable air from fulphur . But though, when 
fleam isffent over melted fulphur, a fmall quantity of inflam- 
mable air is procured, as I obferved in my laft volume of expe- 
riments ; yet, as fulphur cannot part with much phlogiflon 9 
except in proportion as it imbibes pure air, to form oil of vitriol,, 
I could not in this manner eafily procure enough for my 
purpofe. 
In order to fupply the fulphur with pure air, I mixed with 
it a quantity of turbith mineral ; but this made it yield vitriolic 
acid air, though in great abundance,, there not being, I ima- 
gine, water enough to form inflammable air : for when iron is 
difiolved in concentrated acid of vitriol, yitriolic acid air is pro- 
duced; but in diluted vitriolic acid, the produce is inflammable .* 
air. With a view to fupply thefe materials with water, I 
fent fleam over them; but it did not combine with the air, 
which was ftill only vitriolic acid air* 
Since, however, vitriolic acid air unqueflionably contains 
the fame principle which forms the inflammability of inflam* 
mable air, this experiment proves, that fulphur is not that 
Ample fubflance which the antiphlogiftians fuppofe it to be; 
but that it contains phlogiflon. Had it been nothing more 
than a fubflance which had a flrong affinity to pure air, it would 
have; 
