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, 3MnCO_{3} + 2KMnO_{4} + H_{2}O = 2KHCO_{3} + 5MnO_{2} + CO_{2}