Cobalt(III) oxide
Cobalt oxide is the inorganic compound with the formula of Co2O3. Although only two oxides of cobalt are well characterized, CoO and Co3O4, procedures claiming to give Co2O3 have been described. Thus treatment of Co salts such as cobalt nitrate with an aqueous solution of sodium hypochlorite gives a black solid. Some formulations of the catalyst hopcalite contain "Co2O3".
