erature and pressure of our atmosphere, which combines with great
facility, and in great quantity, with water, and whose acidifiable base
adheres so very intimately with oxygen, that no method has hitherto been
devised for separating them. If ever this acidifiable base of the
muriatic acid is discovered to be a known substance, though now unknown
in that capacity, it will be requisite to change its present
denomination for one analogous with that of its base.

In common with sulphuric acid, and several other acids, the muriatic is
capable of different degrees of oxygenation; but the excess of oxygen
produces quite contrary effects upon it from what the same circumstance
produces upon the acid of sulphur. The lower degree of oxygenation
converts sulphur into a volatile gasseous acid, which only mixes in
small proportions with water, whilst a higher oxygenation forms an acid
possessing much stronger acid properties, which is very fixed and cannot
remain in the state of gas but in a very high temperature, which has no
smell, and which mixes in large proportion with water. With muriatic
acid, the direct reverse takes place; an additional saturation with
oxygen renders it more volatile, of a more penetrating odour, less
miscible with water, and diminishes its acid properties. We were at
first inclined to have denominated these two degrees of saturation in
the same manner as we had done with the acid of sulphur, calling the
less oxygenated _muriatous acid_, and that which is more saturated with
oxygen _muriatic acid_: But, as this latter gives very particular
results in its combinations, and as nothing analogous to it is yet known
in chemistry, we have left the name of muriatic acid to the less
saturated, and give the latter the more compounded appellation of
_oxygenated muriatic acid_.

Although the base or radical of the acid which is extracted from nitre
or saltpetre be better known, we have judged proper only to modify its
name in the same manner with that of the muriatic acid. It is drawn from
nitre, by the intervention of sulphuric acid, by a process similar to
that described for extracting the muriatic acid, and by means of the
same apparatus (Pl. IV. Fig. 1.). In proportion as the acid passes over,
it is in part condensed in the baloon or recipient, and the rest is
absorbed by the water contained in the bottles L,L,L,L; the water
becomes first green, then blue, and at last yellow, in proportion to
the concentration o