salt, which it really was before calcination, has been changed by fire
into an earthy alkali, by _losing_ half of its weight, with metals
which, by the same means, have joined themselves to a new substance,
whose quantity often _exceeds_ half their weight, and by which they
have been changed almost into the nature of acids. This mode of
classifying substances of so very opposite natures, under the same
generic name, would have been quite contrary to our principles of
nomenclature, especially as, by retaining the above term for this state
of metallic substances, we must have conveyed very false ideas of its
nature. We have, therefore, laid aside the expression _metallic calx_
altogether, and have substituted in its place the term _oxyd_, from the
Greek word [Greek: oxys].
By this may be seen, that the language we have adopted is both copious
and expressive. The first or lowest degree of oxygenation in bodies,
converts them into _oxyds_; a second degree of additional oxygenation
constitutes the class of acids, of which the specific names, drawn from
their particular bases, terminate in _ous_, as the _nitrous_ and
_sulphurous_ acids; the third degree of oxygenation changes these into
the species of acids distinguished by the termination in ic, as the
_nitric_ and _sulphuric_ acids; and, lastly, we can express a fourth, or
highest degree of oxygenation, by adding the word _oxygenated_ to the
name of the acid, as has been already done with the _oxygenated
muriatic_ acid.
We have not confined the term _oxyd_ to expressing the combinations of
metals with oxygen, but have extended it to signify that first degree of
oxygenation in all bodies, which, without converting them into acids,
causes them to approach to the nature of salts. Thus, we give the name
of _oxyd of sulphur_ to that soft substance into which sulphur is
converted by incipient combustion; and we call the yellow matter left by
phosphorus, after combustion, by the name of _oxyd of phosphorus_. In
the same manner, nitrous gas, which is azote in its first degree of
oxygenation, is the _oxyd of azote_. We have likewise oxyds in great
numbers from the vegetable and animal kingdoms; and I shall show, in the
sequel, that this new language throws great light upon all the
operations of art and nature.
We have already observed, that almost all the metallic oxyds have
peculiar and permanent colours. These vary not only in the different
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