Slips of linen cloth dipped in very rancid oil, had their rancidity
much diminished by exposure to a stream of fixed air from an
effervescent mixture of chalk and spirit of vitriol. But a pint bottle
of the same oil being saturated with this vapour, was equally offensive
as before the air was thrown into it, though the oil appeared to absorb
a considerable quantity of air.
Dr. Macbride exposed a piece of rag dipped in lixivium tartari, and
another tinged blue by the scrapings of raddishes, to the vapour
arising from a large vat of melasses wash in high fermentation, without
any change being effected in either, which could be supposed to
proceed from an acid vapour. But as water impregnated with fixed air
has evidently an acidulous taste, and it seemed probable that some of
the vitriolic acid might be volatilized during the effervescence which
proceeds from its admixture with the alkaline body, when the air is
procured from these substances, it was apprehended that the antiseptic
and sweetening powers of air thus obtained, might depend on the acid
contained in it. In order to evince how far this conjecture was just,
Doctor Percival was so obliging to assist me in suggesting and making
the following experiments.