k a quantity of common air, which had been diminished and
made noxious by phlogistic processes; and when it had been agitated in
water, I found that it was diminished by nitrous air, though not so much
as it would have been at the first. After cleansing it a second time, it
was diminished again by the same means; and, after that, a third time;
and thus there can be no doubt but that, in time, the whole quantity
would have disappeared. For I have never found that agitation in water,
deprived of its own air, made any addition to a quantity of noxious air;
though, _a priori_, it might have been imagined that, as a saturation
with phlogiston diminishes air, the extraction of phlogiston would
increase the bulk of it. On the contrary, agitation in water always
diminished noxious air a little; indeed, if water be deprived of all its
own air, it is impossible to agitate any kind of air in it without some
loss. Also, when noxious air has been restored by plants, I never
perceived that it gained any addition to its bulk by that means. There
was no incrustation of the lime-water in the above-mentioned experiment.

It is not a little remarkable, that those kinds of air which never had
been common air, as inflammable air, phlogisticated nitrous air, and
nitrous air itself, when rendered wholesome by agitation in water,
should be more diminished by fresh nitrous air, than common air which
had been made noxious, and restored by the same process; and yet, from
the few trials that I have made, I could not help concluding that this
is the case.

In this course of experiments I was very near deceiving myself, in
consequence of transferring the nitrous air which I made use of in a
bladder, in the manner described, p. 15. fig. 9. so as to conclude that
there was a precipitation of lime in all the above-mentioned cases, and
that even nitrous air itself produced that effect. But after repeated
trials, I found that there was no precipitation of lime, except, in the
first diminution of common air, when the nitrous air was transferred in
a glass vessel.

That the calces of metals contain air, of some kind or other, and that
this air contributes to the additional weight of the calces, above that
of the metals from which they are made, had been observed by Dr. Hales;
and Mr. Hartley had informed me, that when red-lead is boiled in linseed
oil, there is a prodigious discharge of air before they incorporate. I
had likewise found, that no weight is