r kills animals as suddenly as fixed air, and, as far as
can be perceived, in the same manner, throwing them into convulsions,
and thereby occasioning present death. I had imagined that, by animals
dying in a quantity of inflammable air, it would in time become less
noxious; but this did not appear to be the case; for I killed great
number of mice in a small quantity of this air; which I kept several
months for this purpose, without its being at all sensibly mended; the
last, as well as the first mouse, dying the moment it was put into it.

I once imagined that, since fixed and inflammable air are the reverse of
one another, in several remarkable properties, a mixture of them would
make common air; and while I made the mixtures in bladders, I imagined
that I had succeeded in my attempt; but I have since found that thin
bladders do not sufficiently prevent the air that is contained in them
from mixing with the external air. Also corks will not sufficiently
confine different kinds of air, unless the phials in which they are
confined be set with their mouths downwards, and a little water lie in
the necks of them, which, indeed, is equivalent to the air standing in
vessels immersed in water. In this manner, however, I have kept
different kinds of air for several years.

Whatever methods I took to promote the mixture of fixed and inflammable
air, they were all ineffectual. I think it my duty, however, to recite
the issue of an experiment or two of this kind, in which equal mixtures
of these two kinds of air had stood near three years, as they seem to
shew that they had in part affected one another, in that long space of
time. These mixtures I examined April 27, 1771. One of them had stood in
quicksilver, and the other in a corked phial, with a little water in it.
On opening the latter in water, the water instantly rushed in, and
filled almost half of the phial, and very little more was absorbed
afterwards. In this case the water in the phial had probably absorbed a
considerable part of the fixed air, so that the inflammable air was
exceedingly rarefied; and yet the whole quantity that must have been
rendered non-elastic was ten times more than the bulk of the water, and
it has not been found that water can contain much more than its own
bulk of fixed air. But in other cases I have found the diminution of a
quantity of air, and especially of fixed air, to be much greater than I
could well account for by any kind of absorption