Manganese oxide

Manganese oxide (MnO₂) is a chemical compound also known as manganese dioxide. It has a blackish or brown color. It is the main source for extracing the metal manganese. It can also be used for production of manganates, both MnO₄^2- and MnO₄^-.

A green substance was obtained after melting manganese oxide with an alkaline salt and adding oxidizing agents like saltpeter (sodium nitrate NaNO₃) or potassium perchlorate (KClO₄). This substance dissolves in cold water, giving a dark green color. Potassium manganate (K₂MnO₄), a salt in dark green crystalized rombic prisms (dark green), was formed after vacuum distilling with a metal "finish". Potassium manganate is soulable in lye ONLY, otherwise it will disproportionate into potassium permanganate (KMnO₄^-) and manganese oxide (MnO₂).

Potassium manganate is converted into potassium permaganate in aqueous acidic solution:

3MnO₄^2- + 4H⁺ --> 2MnO₄^- + MnO₂) + 2H₂O

MnO₄(-) has a purple color

MnO₄(2-) has a green color

MnO₂ is used as a catalyst in the laboratory preparation of oxygen from potassium chlorate, one of the classical experiments of elementary chemistry classes. The procedure consists of merely heating potassium chlorate and manganese dioxide together in a hard glass container and collecting the gas over water. See oxygen, manganese and potassium chlorate for precautions.

Eighteenth-century British chemists referred to MnO₂ simply as manganese. Elemental manganese was known as reglus of manganese.

Ancient cave painters sometimes used MnO₂ as black paint