and likewise with
their combinations with the alkalies, which form the triple compounds
called NEUTRAL SALTS.

The class of acids is characterised by very distinct properties. They
all change blue vegetable infusions to a red colour: they are all more
or less sour to the taste; and have a general tendency to combine with
the earths, alkalies, and metallic oxyds.

You have, I believe, a clear idea of the nomenclature by which the base
(or radical) of the acid, and the various degrees of acidification, are
expressed?

EMILY.

Yes, I think so; the acid is distinguished by the name of its base, and
its degree of oxydation, that is, the quantity of oxygen it contains, by
the termination of that name in _ous_ or _ic_; thus sulphure_ous_ acid
is that formed by the smallest proportion of oxygen combined with
sulphur; sulphur_ic_ acid that which results from the combination of
sulphur with the greatest quantity of oxygen.

MRS. B.

A still greater latitude may, in many cases, be allowed to the
proportions of oxygen than can be combined with acidifiable radicals;
for several of these radicals are susceptible of uniting with a quantity
of oxygen so small as to be insufficient to give them the properties of
acids; in these cases, therefore, they are converted into oxyds. Such is
sulphur, which by exposure to the atmosphere with a degree of heat
inadequate to produce inflammation, absorbs a small proportion of
oxygen, which colours it red or brown. This, therefore, is the first
degree of oxygenation of sulphur; the 2d converts it into sulphur_ous_
acid; the 3d into the sulphur_ic_ acid; and 4thly, if it was found
capable of combining with a still larger proportion of oxygen, it would
then be termed _super-oxygenated sulphuric acid_.

EMILY.

Are these various degrees of oxygenation common to all the acids?

MRS. B.

No; they vary much in this respect: some are susceptible of only one
degree of oxygenation; others, of two, or three; there are but very few
that will admit of more.

CAROLINE.

The modern nomenclature must be of immense advantage in pointing out so
easily the nature of the acids, and their various degrees of
oxygenation.

MRS. B.

Till lately many of the acids had not been decomposed; but analogy
afforded so strong a proof of their compound nature, that I never could
reconcile myself to classing them with the simple bodies, though this
division has been adopted by several chemical writers. At prese