Manganese(II,III)oxide:
Manganese(II,III)
oxide, Mn3O4 is found in black tetragonal crystal form. Additionally,
available in red powder form. Manganese(II, III) oxide, with a molecular
weight of 228.79 and a melting point of 1562 ◦C, occurs naturally as
hausmannite and crystallizes tetragonally (with a density of 4.84 g/cm3).
It can be obtained
by heating other manganese oxides above 950 ◦C in the presence of air. An
alternative method involves producing high-purity Mn3O4 from an aqueous
suspension of finely divided manganese metal through air oxidation at 30 – 100
◦C in the presence of ammonium salts. Black crystals are formed by the
compound, but when finely dispersed, it manifests as a red powder. Highly
purified Mn3O4 is utilized in the manufacture of semiconductors and ceramic
magnets.
Manganese(II,III)
oxide is manufactured by heating manganese(IV) oxide, MnO2, or
manganese(III) oxide, Mn2O3, above 950°C. When Mn2O3 is subjected to heating in
air, the temperature should exceed 940°C; however, if heated in oxygen, it
should surpass 1,090°C.
Furthermore,
by heating manganese(III) oxide at 230°C in hydrogen, Mn3O4 is yielded.
Nevertheless, heating Mn3O4 above 300°C results in the conversion of formed
Mn3O4 to green manganese(II) oxide, MnO. Manganese(II,III) oxide is also
acquired by heating the dioxide, MnO2, with carbon at temperatures ranging from
600 to 700°C.
Dilute
acids react with Manganese(II,III) oxide, Mn3O4, producing the corresponding
manganous salt and manganese(IV) oxide, MnO2.
Mn3O4 + 2H2SO4 ⇀ 2MnSO4 + MnO2 + 2H2O
The oxide,
however, dissolves slowly in cold sulfuric acid forming a red solution that
also contains manganic sulfate, Mn2(SO4)3:
Mn3O4 + 4H2SO4 ⇀ MnSO4 + Mn2(SO4)3 + 4H2O
MANGANESE(IV)
OXIDE
Synonyms
for manganese dioxide, MnO2, include
manganese peroxide and black manganese oxide.
Manganese(IV)
oxide, MnO2, with a molecular weight of 86.937 and
a density of 5.08 g/cm3, is deemed as the primary manganese ore, predominantly
utilized for metal production. The mineral pyrolusite, occurring naturally as
heavy gray lumps or black when in powdered form, represents the source of this
oxide. Its decomposition takes place at 535°C, and it remains insoluble in
water.
The production
of manganese metal, numerous manganese salts, as well as manganese steel
and various alloys, is facilitated through the utilization of this mineral.
Manganese(IV) oxide finds significant application in metallurgy, particularly
in the creation of ferromanganese and specialized manganese alloys. Another
crucial role is observed in the manufacturing of dry-cell batteries and
alkaline cells.
Furthermore,
the oxide functions as a coloring agent in brick, tile, porcelain, and
glass. It serves as a drying agent for paints and varnishes, a textile printing
and dyeing preparation, a curing agent for polysulfide rubbers, an adsorbent
for hydrogen sulfide and sulfur dioxide, and an oxidizing agent in various
organic syntheses such as quinone and hydroquinone. In addition, it acts as a
catalyst in the laboratory preparation of oxygen from potassium chlorate.
Manganese(IV) oxide is also integral in the production of welding rods and
fluxes, ceramic magnets (ferrites), and serves as an additive to fertilizers.
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