Manganese

Manganese is a gray/white metal, which is oxidized easily. It is slowly attacked by water. By dilute acids, it is attacked more quickly.

The metal can be purchased from several vendors on eBay in all kinds of quantities. For the home chemist, however, it is more convenient to have a water-soluble compound of this metal at hand.

The most stable oxidation states of manganese in its compounds are +2, +4 and +7. It, however, also is possible quite well to prepare aqueous solutions, containing manganese in its +3 and +6 oxidation states. The +5 oxidation state can only be obtained in aqueous solutions in a transient state.

For the general public a few manganese compounds are accessible:

• manganese (II) sulfate, MnSO₄·H₂O
• manganese (II) carbonate, MnCO₃
• manganese (VI) oxide, MnO₂
• potassium permanganate, KMnO₄

Manganese (II) sulfate is a light pink powder, which dissolves in water easily. Solutions of manganese (II) are almost colorless. The pink color hardly is visible in solution. Manganese (II) ions only have limited coordination chemistry. However, there is an interesting redox chemistry. Manganese (II) sulfate is an interesting compound for the home lab. It can be ordered from chemical supply houses. When one also has access to potassium permanganate, then there is less need for manganese (II) sulfate. Solutions of manganese (II) salts can easily be prepared from potassium permanganate.

Manganese (II) carbonate is available at pottery and ceramics shops. The pure compound is pale pink, the commercial product usually is light brown, due to some manganese (IV) impurities. Manganese (II) carbonate easily dissolves in dilute acids, forming colorless solutions. The commercial product also can be dissolved cleanly, by adding a minute quantity of a sulfite, which reduces the brown manganese (IV) compounds.

Manganese (IV) oxide is available as a dark brown or black crystalline powder at pottery and ceramics shops. The product, which can be obtained there, usually contains some silicate impurity. Manganese (IV) oxide slowly dissolves in dilute acid, to which some sulfite is added, forming a manganese (II) solution. The silicate impurity remains as a white solid, which can easily be separated from the clear liquid. Manganese (IV) oxide in the solid state also can be interesting in some pyrotechnic experiments.

Potassium permanganate is the most interesting manganese compound, which is available for the public. It is available at photography raw chemical suppliers, in shops for textile processing chemicals and also in some shops, which sell equipment and chemicals for aquarium/water conditioning. Potassium permanganate is a strong and powerful oxidizer, which is dark purple in the solid state and which dissolves moderately well, forming extremely dark solutions. Potassium permanganate can be used as a source for manganese in other oxidation states (+2, +4 and +6 and to a lesser extent also +3) in aqueous solutions. It also can be used in dry-chemical and pyrotechnic experiments. In dry chemical experiments, reactions of potassium permanganate can be very violent and very hot, so care must be taken when these experiments are performed.

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