oxygenation of lead, tin, and most of the metals, takes place vastly
slower, and consequently the disengagement of caloric, and more
especially of light, is hardly sensible.
Some substances have so strong an affinity with oxygen, and combine with
it in such low degrees of temperature, that we cannot procure them in
their unoxygenated state; such is the muriatic acid, which has not
hitherto been decomposed by art, perhaps even not by nature, and which
consequently has only been found in the state of acid. It is probable
that many other substances of the mineral kingdom are necessarily
oxygenated in the common temperature of the atmosphere, and that being
already saturated with oxygen, prevents their farther action upon that
element.
There are other means of oxygenating simple substances besides exposure
to air in a certain degree of temperature, such as by placing them in
contact with metals combined with oxygen, and which have little affinity
with that element. The red oxyd of mercury is one of the best substances
for this purpose, especially with bodies which do not combine with that
metal. In this oxyd the oxygen is united with very little force to the
metal, and can be driven out by a degree of heat only sufficient to make
glass red hot; wherefore such bodies as are capable of uniting with
oxygen are readily oxygenated, by means of being mixed with red oxyd of
mercury, and moderately heated. The same effect may be, to a certain
degree, produced by means of the black oxyd of manganese, the red oxyd
of lead, the oxyds of silver, and by most of the metallic oxyds, if we
only take care to choose such as have less affinity with oxygen than the
bodies they are meant to oxygenate. All the metallic reductions and
revivifications belong to this class of operations, being nothing more
than oxygenations of charcoal, by means of the several metallic oxyds.
The charcoal combines with the oxygen and with caloric, and escapes in
form of carbonic acid gas, while the metal remains pure and revivified,
or deprived of the oxygen which before combined with it in the form of
oxyd.
All combustible substances may likewise be oxygenated by means of mixing
them with nitrat of potash or of soda, or with oxygenated muriat of
potash, and subjecting the mixture to a certain degree of heat; the
oxygen, in this case, quits the nitrat or the muriat, and combines with
the combustible body. This species of oxygenation requires to be
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