OXYD, is the term used in the new chemical
nomenclature to express a very numerous class of bodies
formed by the union of certain bases with a smaller
proportion of oxygen than what is necessary for their
conversion into acids. (See OXYGENE). The most
remarkable of these bodies are what were formerly called
metallic calces, and have for their base some met-
allic substance. It is in this state that metals are con-
tained in their ores, from which they are extracted,
and converted into the reguline or metallic form, by
the process called reduction. Metals are converted in-
to oxyds by combustion, and by solution in acids; and
many of them assume this form from the action of the
atmosphere alone, but more readily when this is as-
sisted by moisture. During their conversion into oxyds,
metals lose their splendor, and, acquiring a consider-
able increase of absolute weight, put on an earthy,
pulverulent appearance. It has of late been supposed
that all earths are metallic oxyds, and that all of them
would be capable of reduction, were we possessed of
any body for which oxygen had a stronger elective
attraction than that by which it is kept in conjunc-
tion with the bases of these supposed oxyds. But this
opinion, being perfectly unsupported by experiment,
cannot be admitted in a science which, like the che-
mistry of the present day, aspires to demonstration.
The term oxyd, however, is not confined to the
combinations of metals with oxygen, but expresses
that first degree of oxygenation in all bodies which,
without converting them into acids, causes them to
approach to the nature of salts; and of these there is a
prodigious variety; as the oxyd of phosphorus, which
is the white concrete substance into which that body
is converted by combustion; the oxyd of azote, or
nitrous air of Dr Priestley; and a great many others.
Most of the oxyds from the vegetable and animal king-
doms have bases compounded of different simple com-
bustible bodies. Thus sugar, all the gums, mucus,
and starch, are vegetable oxyds; the bases of which
are hydrogen and carbon, combined in various pro-
portions. We find accordingly, that all these bodies
are, by farther additions of oxygen, convertible into
acids; and it is probable that these acids differ from
each other only in the proportion of the hydrogen Oxydation,
and carbon in their bases. The bases of the animal Oxygene.
oxyds are still more complicated; all, or most of them,
consisting of various combinations of azote, phos-
phorus, hydrogen, carbon, and sulphur. See
CALX, CHEMISTRY, and TABLE OF CHEMICAL NO-
MENCLATURE.