Manganese(II) oxide
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Manganese(II) oxide is an inorganic compound with chemical formula MnO.[2] It forms green crystals. The compound is produced on a large scale as a component of fertilizers and food additives.
Structure, stoichiometry, reactivity
Like many metal monoxides, MnO adopts the rock salt structure, where cations and anions are both octahedrally coordinated. Also like many metal oxides, manganese(II) oxide is often nonstoichiometric: its composition can vary from MnO to MnO1.045.[3]
Below 118 K, MnO is antiferromagnetic.[3] MnO has the distinction of being one of the first compounds[4] to have its magnetic structure determined by neutron diffraction, the report appearing in 1951.[5] This study showed that the Mn2+ ions form a face centered cubic magnetic sub-lattice where there are ferromagnetically coupled sheets that are anti-parallel with adjacent sheets.
Manganese(II) oxide undergoes the chemical reactions typical of an ionic oxide. Upon treatment with acids, it converts to the corresponding manganese(II) salt.[3] Oxidation of manganese(II) oxide gives manganese(III) oxide.
Preparation and occurrence
MnO occurs in nature as the rare mineral manganosite.
It is prepared commercially by reduction of MnO2 with hydrogen, carbon monoxide or methane, e.g.:[2]
- MnO2 + H2 → MnO + H2O
- MnO2 + CO → MnO + CO2
Upon heating to 450Script error: No such module "String".°C, manganese(II) nitrate gives a mixture of oxides, denoted MnO2−x, which can be reduced to the monoxide with hydrogen at ≥750Script error: No such module "String".°C.[6] MnO is particularly stable and resists further reduction.[7] MnO can also be prepared by heating the carbonate:[8]
- MnCO3 → MnO + CO2
This calcining process is conducted anaerobically, lest Mn2O3 form.
An alternative route, most interest for demonstration purposes, is the "oxalate method". Also applicable to the synthesis of ferrous oxide and stannous oxide, it entails heating in an oxygen-free atmosphere (often CO2), hydrated manganese(II) oxalate:[9]
- MnC2O4·2H2O → MnO + CO2 + CO + 2 H2O
Applications
Together with manganese sulfate, MnO is a component of fertilizers and food additives. Many thousands of tons are consumed annually for this purpose. Other uses include: a catalyst in the manufacture of allyl alcohol, ceramics, paints, colored glass, bleaching tallow and textile printing.[2]
References
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- ↑ a b Script error: No such module "citation/CS1".
- ↑ a b c Arno H. Reidies "Manganese Compounds" Ullmann's Encyclopedia of Chemical Technology 2007; Wiley-VCH, Weinheim. Script error: No such module "CS1 identifiers".
- ↑ a b c Script error: No such module "citation/CS1".
- ↑ J.E Greedon, (1994), Magnetic oxides in Encyclopedia of Inorganic chemistry Ed. R. Bruce King, John Wiley & Sons Template:ISBN
- ↑ Script error: No such module "Citation/CS1".
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- ↑ W.H. McCarroll (1994) Oxides- Solid State Chemistry, Encyclopedia of Inorganic Chemistry Ed. R. Bruce King, John Wiley & Sons Template:ISBN
- ↑ Arthur Sutcliffe (1930) Practical Chemistry for Advanced Students (1949 Ed.), John Murray - London.
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