Is cobalt oxide dangerous?

May be harmful if swallowed. Inhalation: May cause respiratory tract irritation. May cause chronic airway hyperreactivity and asthma, with changes in pulmonary function. Chronic: Cobalt compounds may cause cancer based upon animal studies.

 Cobalt oxide (Co2O3) is a high-valent oxide of cobalt. The theoretical cobalt content is 71.06%, the oxygen content is 28.94%, and the density is 6.079/cm3. It is a black amorphous powder that generates Co3O4 (Co3O4) when heated. Cobalt oxide is an unstable and impossible to be a free compound. The commonly referred to as cobalt oxide actually still contains a certain amount of cobalt tetroxide. Co2O3 is only stable when it is in a hydrated state, and this hydrate will be dehydrated at 265°C to transform into the intermediate oxide tricobalt tetroxide (Co3O4). Cobalt oxide can be reduced to cobalt tetroxide (Co3O4) by H2 at 125°C, reduced to CoO at 200°C, and reduced to metallic cobalt at 250°C. Cobalt oxide is insoluble in water, but soluble in acid to form the corresponding salt.

The properties of cobalt oxide: There are three types of cobalt oxide: cobalt oxide (CoO), high cobalt oxide (Co2O3) and cobalt tetroxide (Co3O4). Cobalt oxide is the most stable oxide of cobalt. Due to the difference in preparation method and purity, it appears grayish green, brown, pink, and dark gray. The theoretical cobalt content of cobalt oxide is 78.65%, the oxygen content is 21.35%, the melting point is 1935°C, and the density is 5.7-6.79/cm3. The CoO crystal is face-centered cubic, with a lattice constant a=4.24x10-10m. The gray-green CoO powder tends to turn brown in the air, and the pink CoO powder is relatively stable in the air, and will not generate high-priced oxides even if it is left for a long time. Cobalt in cobalt oxide can dissociate with oxygen at high temperatures, and the dissociation pressure is 3.36x10-12 atmospheres at 1000°C. Under heating conditions, cobalt oxide is easily reduced to elemental cobalt by H2, C or Co. Cobalt oxide is soluble in acid and alkali, but insoluble in water, alcohol and ammonia. It turns red after adding water. Cobalt oxide reacts with silicon dioxide, aluminum oxide or zinc oxide at high temperatures to produce a variety of pigments.