This is obtained as an olive-green powder by heating the metal in air or steam or by thermal decomposition of the hydroxide, carbonate or nitrate. It has the sodium chloride lattice and is antiferromagnetic below 292°K. When heated in oxygen above 400° the black oxide Co3O4 is obtained. This oxide is isomorphous with magnetite Fe3O4, and has tetrahedrally surrounded cobalt(II) ions and octahedrally surrounded cobalt(III) ions. Both these oxides are readily reduced to the metal by heating in hydrogen or with carbon. The reactions of CoO with silica, alumina and zinc oxide are used to form pigments in the ceramic industry.
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Melting point
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1785 °C
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density
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6.45
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vapor pressure
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0Pa at 20ºC
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solubility
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insoluble in H2O; soluble in acid solutions
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form
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Powder
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Specific Gravity
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6.45
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color
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Green-brown
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Water Solubility
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insoluble
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Sensitive
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Air Sensitive
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Exposure limits
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ACGIH: TWA 1 mg/m3
OSHA: TWA 15 mg/m3; TWA 5 mg/m3
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Stability:
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Stability Stable, but may be moisture sensitive.
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Mainly used for glass, enamel, ceramic, magnetic materials such as dense agent, azure blue, cobalt blue, cobalt green color colorant, catalyst, livestock nutrition agent. It is also used in the preparation of cobalt salts.
In pigments for ceramics; glass coloring and decolorization; oxidation catalyst for drying oils, fast-drying paints and varnishes; preparation of cobalt-metal catalysts, Co powder for binder in sintered tungsten carbide; in semiconductors.
