The mineral is the source of manganese and all its Compounds; largely used in manufacture of manganese steel; oxidizer; in alkaline batteries (dry cells); for making amethyst glass, decolorizing glass; painting on porcelain, faience and majolica. The ppt is used in electrotechnics, pigments, browning gun barrels, drier for paints and varnishes, printing and dyeing textiles.
Black tetragonal crystals; density 5.08 g/cm3; Moh’s hardness 6.3; decomposes at 535°C; insoluble in water.
Manganese dioxide, mainly used as a depolarizer in dry cell batteries, is the most important non-metallic form of manganese. In either traditional alkaline and rechargeable battery cells, Manganese dioxide takes in electrons through a redox reaction, becoming Manganese III oxide. It also has applications in lithium-ion technologies.
It is also the primary precursor to ferromanganese, an alloy of iron used for its lower melting point and low cost.
It is black in appearance and used to color glass and ceramics, as well as for cave art and possibly body paint in prehistorical eras. Further uses include the purification of drinking water, and production of pure oxygen and chlorine.
Manganese(IV) oxide is the most important ore of manganese from which the metal is mostly manufactured. The oxide occurs in nature as the mineral pyrolusite as heavy gray lumps, or black when powdered.
The mineral is used to produce manganese metal, most manganese salts, and also manganese steel and other alloys. The metallurgical applications of manganese(IV) oxide mainly involve making ferromanganese and special manganese alloys. Another important application of manganese(IV) oxide is in manufacturing dry-cell batteries and alkaline cells. The oxide also is a colorant in brick, tile, porcelain and glass; a drier for paints and varnishes; a 552 MANGANESE(IV) OXIDEpreparation for printing and dyeing textiles; a curing agent for polysulfide rubbers; an adsorbent for hydrogen sulfide and sulfur dioxide; an oxidizing agent in many organic syntheses such as quinone and hydroquinone; and a catalyst in laboratory preparation of oxygen from potassium chlorate. Manganese(IV) oxide also is used to make welding rods and fluxes, and ceramic magnets (ferrites); and is an additive to fertilizers.
Pure manganese(IV) oxide (precipitate form) may be prepared by reducing permanganate ion with a manganous salt:
2KMnO4 + 3MnSO4 + 2H2O → 5MnO2 + K2SO4 + 2H2SO4
Manganese(IV) oxide can also be precipitated by oxidation of a manganese(II) salt using an oxidizing agent such as hypochlorite or peroxydisulphate:
Mn2+ + S2O82– + 2H2O → MnO2 + 2SO42– + 4H+
Manganese(IV) oxide may also be made by thermal decomposition of manganese(II) nitrate; or from roasting manganese(II) carbonate in air: Mn(NO3)2 → MnO2 + 2NO2
MnCO3 + ½ O2 → MnO2 + CO2
A highly active gamma-MnO2 can be produced by treating manganese(III) oxide with hot sulfuric acid:
Mn2O3 + H2SO4 → MnO2 + MnSO4 + H2O
Mn2O3 is derived from pyrolusite by heating the mineral at 600–800°C or reducing with powdered coal at 300°C.