Manganese(III) oxide Manganese(III) oxide Manganese(III) oxide is a chemical compound with the formula MnO. Heating MnO in air at below 800 °C produces α-MnO (higher temperatures produce MnO). γ-MnO can be produced by oxidation followed by dehydration of manganese(II) hydroxide. Many preparations of nano-crystalline MnO have been reported, for example syntheses involving oxidation of Mn salts or reduction of MnO. Manganese (III) oxide is formed by the redox reaction in an alkaline cell: Manganese (III) oxide MnO must not be confused with MnOOH manganese (III) oxyhydroxide. Contrary to MnO, MnOOH is a compound that decomposes at about 300 °C to form MnO.
Manganese modern times as pyrolusite or manganese dioxide. Neither this mineral nor elemental manganese is magnetic. In the 16th century, manganese dioxide was called "manganesum" (note the two Ns instead of one) by glassmakers, possibly as a corruption and concatenation of two words, since alchemists and glassmakers eventually had to differentiate a "magnesia negra" (the black ore) from "magnesia alba" (a white ore, also from Magnesia, also useful in glassmaking). Michele Mercati called magnesia negra "manganesa", and finally the metal isolated from it became known as "manganese" (German: "Mangan"). The name "magnesia" eventually was then used to refer only to the