n, and the produce was nitrous air; but a less degree of
spirit of nitre in the mixture produced air that was inflammable, and
which burned with a green flame. It also tinged common air a little red,
and diminished it, though not much.

The diminution of common air by a mixture of nitrous air, is not so
extraordinary as the diminution which nitrous air itself is subject to
from a mixture of iron filings and brimstone, made into a paste with
water. This mixture, as I have already observed, diminishes common air
between one fifth and one fourth, but has no such effect upon any kind
of air that has been diminished, and rendered noxious by any other
process; but when it is put to a quantity of nitrous air, it diminishes
it so much, that no more than one fourth of the original quantity will
be left.

The effect of this process is generally perceived in five or six hours,
about which time the visible effervesence of the mixture begins; and in
a very short time it advances so rapidly, that in about an hour almost
the whole effect will have taken place. If it be suffered to stand a day
or two longer, the air will still be diminished farther, but only a very
little farther, in proportion to the first diminution. The glass jar,
in which the air and this mixture have been confined, has generally been
so much heated in this process, that I have not been able to touch it.

Nitrous air thus diminished has not so strong a smell as nitrous air
itself, but smells just like common air in which the same mixture has
stood; and it is not capable of being diminished any farther, by a fresh
mixture of iron and brimstone.

Common air saturated with nitrous air is also no farther diminished by
this mixture of iron filings and brimstone, though the mixture ferments
with great heat, and swells very much in it.

Plants die very soon, both in nitrous air, and also in common air
saturated with nitrous air, but especially in the former.

Neither nitrous air, nor common air saturated with nitrous air, differ
in specific gravity from common air. At least, the difference is so
small, that I could not be sure there was any; sometimes about three
pints of it seeming to be about half a grain heavier, and at other times
as much lighter than common air.

Having, among other kinds of air, exposed a quantity of nitrous air to
water out of which the air had been well boiled, in the experiment to
which I have more than once referred (as having been the oc