The anodic oxidation of bivalent manganese to tetravalent manganese.

Natural manganese dioxide pyrolusite has been known since the time of Pliny as an agent for decolorizing glass. Pyrolusite is usually found mixed with ferric oxide, since both are deposited by atmospheric oxidation of their bicarbonates. It contains about 63 per cent manganese. Minerals of manganese are listed in Table I. The different ores of manganese may also be classified according to the fields in which they are used. This classification can be seen in Table II