Cobalt(III) oxide

Although only two oxides of cobalt are well characterized, CoO and Co3O4,[4] procedures claiming to give Co2O3 have been described.

Thus treatment of Co(II) salts such as cobalt(II) sulfate with an aqueous solution of sodium hypochlorite (also known as bleach) gives a black solid:[5][6] Some formulations of the catalyst hopcalite contain "Co2O3".

Some studies have been unable to synthesize the compound, and report that it is theoretically unstable.

[7] It is soluble in cold diluted sulfuric acid and produces Co2[SO4]3, which is blue in aqueous solution.

Cobalt(III) ion is a strong oxidizer in acidic solution, its standard electrode potential is +1.84V in this situation.

NFPA 704 four-colored diamond Health 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gas Flammability 0: Will not burn. E.g. water Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen Special hazard OX: Oxidizer. E.g. potassium perchlorate