common air being put to near
twenty ounce measures of nitrous air, made an addition to it of about
half an ounce measure. This being a much greater proportion than the
diminution of common air, in the former experiment, proves that part of
the diminution in the former case is in the nitrous air. Besides, it
will presently appear, that nitrous air is subject to a most remarkable
diminution; and as common air, in a variety of other cases, suffers a
diminution from one fifth to one fourth, I conclude, that in this case
also it does not exceed that proportion, and therefore that the
remainder of the diminution respects the nitrous air.

In order to judge whether the _water_ contributed to the diminution of
this mixture of nitrous and common air, I made the whole process several
times in quicksilver, using one third of nitrous, and two thirds of
common air, as before. In this case the redness continued a very long
time, and the diminution was not so great as when the mixtures had been
made in water, there remaining one seventh more than the original
quantity of common air.

This mixture stood all night upon the quicksilver; and the next morning
I observed that it was no farther diminished upon the admission of
water to it, nor by pouring it several times through the water, and
letting it stand in water two days.

Another mixture, which had stood about six hours on the quicksilver, was
diminished a little more upon the admission of water, but was never less
than the original quantity of common air. In another case however, in
which the mixture had stood but a very short time in quicksilver, the
farther diminution, which took place upon the admission of water, was
much more considerable; so that the diminution, upon the whole, was very
nearly as great as if the process had been intirely in water.

It is evident from these experiments, that the diminution is in part
owing to the absorption by the water; but that when the mixture is kept
a long time, in a situation in which there is no water to absorb any
part of it, it acquires a constitution, by which it is afterwards
incapable of being absorbed by water, or rather, there is an addition to
the quantity of air by nitrous air produced by the solution of the
quicksilver.

It will be seen, in the second part of this work, that, in the
decomposition of nitrous air by its mixture with common air, there is
nothing at hand when the process is made in quicksilver, with which the