[Footnote: _From Jernkontorets Annaler_, vol. xxxvi.--_Iron_.]
By C. G. SARNSTROM.
If we dissolve black oxide of manganese, permanganate of potash, or any
other compound of manganese of a higher degree of oxidation than the
protoxide in hydrochloric acid, we obtain, as is well known, a dark
colored solution of perchloride of manganese, which, when heated to
boiling loses color pretty rapidly, chlorine being given off, until
finally only protochloride remains. This decomposition also proceeds at
the common temperature, though much more slowly, and we may therefore
say that manganese when dissolved in hydrochloric acid always tends to
descend to its lowest, and, considered as a base, strongest degree of
oxidation, which is not raised to a higher degree even by chameleon
solution. In slightly acid, neutral, or alkaline solutions on the other
hand, protoxide of manganese absorbs oxygen with great avidity and
forms with it different compounds, according to the means of oxidation
employed. Thus, for example, manganese is slowly deposited from an
ammoniacal solution, when it is permitted to take up oxygen from the
air, as hydrated sesquioxide, and from neutral or alkaline solutions,
as hydrated peroxide on the addition of chlorine, bromine, or chameleon
solution. For if to an acid solution of protochloride of manganese we
add a solution of bicarbonate of soda, as long as carbonic acid escapes
or till the free acid is saturated and the protochloride of manganese
converted into carbonate of protoxide of manganese, which forms with
bicarbonate of soda a soluble double salt, resembling the carbonate of
lime and magnesia, we obtain a solution which is, indeed, acid from free
carbonic acid, but has a slight alkaline reaction with litmus paper, and
with the greatest ease deprives chameleon solution of its color, the
permanganic acid being reduced and the protoxide of manganese being
oxidized to peroxide, which is precipitated as hydrate. This reaction
proceeds according to the formula,