MANGANESII OXIDUM NIGRUM - BLACK OXIDE OF MANGANESE, MnO2, = 87.

Characters And Tests

Occurs in brilliant needle-shaped crystals, or in compact masses, but is usually met with in the shops as a dull, earthy, dark-brown or black powder, which contains iron and other impurities. Treated with hydrochloric acid it causes evolution of chlorine, thusMnO2 + 4HCl = MnCl2 + 2H1O + Cl2

When heated to redness, it gives off oxygen and leaves a residue of red oxide of manganese 3MnO2(heated) = Mn3O4 + O2 Sulphuretted hydrogen causes in manganic solutions a flesh-colored precipitate of sulphide.