Manganese(II,III) oxide is made by heating manganese(IV) oxide, MnO 2, or manganese(III) oxide, Mn 2 O 3, above 950°C. When Mn 2 O 3 is heated in air, the temperature should be above 940°C, but if heated in oxygen, the temperature should be above 1,090°C. Also, heating manganese(III) oxide at 230°C in hydrogen yields Mn 3 O 4.
