oxygen is termed _oxidation_, and the products are termed _oxides_. As
these oxides have qualities differing from those which are
non-oxidized, it therefore frequently becomes necessary to convert
substances into oxides; or, if they are such, of a lower degree, to
convert them into a higher degree of oxidation. These different states
of oxidation frequently present characteristic marks of identity
sufficient to enable us to draw conclusions in relation to the
substance under examination. For instance, the oxidation of manganese,
of arsenic, etc. The conditions necessary for oxidation, are high
temperature and the free admission of air to the substance.

If the oxidation is effected through the addition of a substance
containing oxygen (for instance, the nitrate or chlorate of potash)
and the heating is accompanied by a lively deflagration and crackling
noise, it is termed _detonation_. By this process we frequently
effect the oxidation of a substance, and thus we prove the presence or
the absence of a certain class of substances. For instance, if we
detonate (as it is termed by the German chemists) the sulphide of
antimony, or the sulphide of arsenic with nitrate of potash, we get
the nitrate of antimony, or the nitrate of arsenic. The salts of
nitric or chloric acid are determined by fusing them with the cyanide
of potassium, because the salts of these acids detonate.


(_e._) _Reduction._--If we deprive an oxidized substance of its
oxygen, we term the process _reduction_. This is effected by fusing
the substance under examination with another which possesses a greater
affinity for oxygen. The agents used for reduction are hydrogen,
charcoal, soda, cyanide of potassium, etc. Substances generally, when
in the unoxidized state, have such characteristic qualities, that they