h
fixed air should be retained in any liquid. Water, at least, we know,
cannot be made to contain much more than its own bulk of fixed air.

After this disappointment, I confined myself to the use of that volatile
spirit of sal ammoniac which is procured by a distillation with slaked
lime, which contains no fixed air; and which seems, in a general state,
to contain about as much alkaline air, as an equal quantity of spirit of
salt contains of the acid air.

Wanting, however, to procure this air in greater quantities, and this
method being rather expensive, it occurred to me, that alkaline air
might, probably, be procured, with the most ease and convenience, from
the original materials, mixed in the same proportions that chemists had
found by experience to answer the best for the production of the
volatile spirit of sal ammoniac. Accordingly I mixed one fourth of
pounded sal ammoniac, with three fourths of slaked lime; and filling a
phial with the mixture, I presently found it completely answered my
purpose. The heat of a candle expelled from this mixture a prodigious
quantity of alkaline air; and the same materials (as much as filled an
ounce phial) would serve me a considerable time, without changing;
especially when, instead of a glass phial, I made use of a small iron
tube, which I find much more convenient for the purpose.

As water soon begins to rise in this process, it is necessary, if the
air is intended to be conveyed perfectly _dry_ into the vessel of
quicksilver, to have a small vessel in which this water (which is the
common volatile spirit of sal ammoniac) may be received. This small
vessel must be interposed between the vessel which contains the
materials for the generation of the air, and that in which it is to be
received, as _d_ fig. 8.

This _alkaline_ air being perfectly analogous to the _acid_ air, I was
naturally led to investigate the properties of it in the same manner,
and nearly in the same order. From this analogy I concluded, as I
presently found to be the fact, that this alkaline air would be readily
imbibed by water, and, by its union with it, would form a volatile
spirit of sal ammoniac. And as the water, when admitted to the air in
this manner, confined by quicksilver, has an opportunity of fully
saturating itself with the alkaline vapour, it is made prodigiously
stronger than any volatile spirit of sal ammoniac that I have ever seen;
and I believe stronger than it can be made in the c