The addition of bromine or chlorine to such a solution determines the
precipitation of a still higher oxide (approximately MnO_{2}). On
treating a compound containing manganese with nitric acid and dioxide of
lead (PbO_{2}), the oxidation is carried still further, a
purple-coloured solution of permanganic acid (HMnO_{4} or
H_{2}O.Mn_{2}O_{7}) being formed. On fusing minerals containing (even
traces of) manganese with sodium carbonate in an open crucible, a green
"melt" is obtained which owes its colour to sodium manganate
(Na_{2}MnO_{4} or Na_{2}O.MnO_{3}). This salt is soluble in water,
forming a green solution; which, when rendered acid, rapidly changes
into the permanganate with the characteristic purple colour.
Permanganate of potash is a salt much used in assaying, with some
properties of which the student will have already become familiar.
Compounds of manganese, on boiling with strong hydrochloric acid, yield
manganous chloride[80] (MnCl_{2}).
The properties given above serve for the detection of manganese; the
higher oxides are distinguished by causing the evolution of chlorine
(with its peculiarly suffocating smell) when acted on with hydrochloric
acid; while the green "melt," with sodium carbonate, can be relied on
for the recognition of manganese itself. There is no dry assay of
manganese ores.
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