of nitre, and have not yet
made any experiments to ascertain the nature of this solution. With zinc
I have taken a little pains.

Four penny-weights and seventeen grains of zinc dissolved in spirit of
nitre, to which as much water was added, yielded about twelve ounce
measures of air, which had, in some degree, the properties of nitrous
air, making a slight effervescence with common air, and diminishing it
about as much as nitrous air, which had been itself diminished one half
by washing in water. The smell of them both was also the same; so that I
concluded it to be the same thing, that part of the nitrous air, which
is imbibed by water, being retained in this solution.

In order to discover whether this was the case, I made the solution boil
in a sand-heat. Some air came from it in this state, which seemed to be
the same thing, with nitrous air diminished about one sixth, or one
eighth, by washing in water. When the fluid part was evaporated, there
remained a brown fixed substance, which was observed by Mr. Hellot, who
describes it, Ac. Par. 1735, M. p. 35. A part of this I threw into a
small red-hot crucible; and covering it immediately with a receiver,
standing in water, I observed that very dense red fumes rose from it,
and filled the receiver. This redness continued about as long as that
which is occasioned by a mixture of nitrous and common air; the air was
also considerably diminished within the receiver. This substance,
therefore, must certainly have contained within it the very same thing,
or principle, on which the peculiar properties of nitrous air depend.

It is remarkable, however, that though the air within the receiver was
diminished about one fifth by this process, it was itself as much
affected with a mixture of nitrous air, as common air is, and a candle
burned in it very well. This may perhaps be attributed to some effect of
the spirit of nitre, in the composition of that brown substance.

Nitrous air, I find, will be considerably diminished in its bulk by
standing a long time in water, about as much as inflammable air is
diminished in the same circumstances. For this purpose I kept for some
months a quart-bottle full of each of these kinds of air; but as
different quantities of inflammable air vary very much in this respect,
it is not improbable but that nitrous air may vary also.

From one trial that I made, I conclude that nitrous air may be kept in a
bladder much better than most other kinds