through in several places. That which had been put into the air
when just dead was quite firm; and the flesh of the other, which had
been putrid and soft, was still soft, but perfectly sweet.

In order to compare the antiseptic power of this kind of air with that
of fixed air, I examined a mouse which I had inclosed in a phial full of
fixed air, as pure as I could make it, and which I had corked very
close; but upon opening this phial in water about a month after, I
perceived that a large quantity of putrid effluvium had been generated;
for it rushed with violence out of the phial; and the smell that came
from it, the moment the cork was taken out, was insufferably offensive.
Indeed Dr. Macbride says, that he could only restore very thin pieces
of putrid flesh by means of fixed air. Perhaps the antiseptic power of
these kinds of air may be in proportion to their acidity.

If a little pains were taken with this subject, this remarkable
antiseptic power of nitrous air might possibly be applied to various
uses, perhaps to the preservation of the more delicate birds, fishes,
fruits, &c. mixing it in different proportions with common or fixed air.
Of this property of nitrous air anatomists may perhaps avail themselves,
as animal substances may by this means be preserved in their natural
soft state; but how long it will answer for this purpose, experience
only can shew.

I calcined lead and tin in the manner hereafter described in a quantity
of nitrous air, but with very little sensible effect; which rather
surprized me; as, from the result of the experiment with the iron
filings and brimstone, I had expected a very great diminution of the
nitrous air by this process; the mixture of iron filings and brimstone,
and the calcination of metals, having the same effect upon common air,
both of them diminishing it in nearly the same proportion. But though I
made the metals _fume_ copiously in nitrous air, there might be no real
_calcination_, the phlogiston not being separated, and the proper
calcination prevented by there being no _fixed_ _air_, which is
necessary to the formation of the calx, to unite with it.

Nitrous air is procured from all the proper metals by spirit of nitre,
except lead, and from all the semi-metals that I have tried, except
zinc. For this purpose I have used bismuth and nickel, with spirit of
nitre only, and regulus of antimony and platina, with _aqua regia_.

I got little or no air from lead by spirit