Cobalt(III) oxide

Cobalt(III) oxide is the inorganic compound with the formula of Co₂O₃. 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]

2CoSO₄ + 4NaOH + NaOCl → Co₂O₃ + 2Na₂SO₄ + NaCl

Cobalt(III) oxide^[1]

Names
IUPAC name cobalt(III) oxide, dicobalt trioxide
Other names cobaltic oxide, cobalt sesquioxide
Identifiers
CAS Number	1308-04-9 Y
3D model (JSmol)	Interactive image
ChemSpider	3324433
ECHA InfoCard	100.013.779
EC Number	215-156-7
PubChem CID	4110762
RTECS number	GG2900000
CompTox Dashboard (EPA)	DTXSID20893870
InChI InChI=1S/2Co.3O Key: UPWOEMHINGJHOB-UHFFFAOYSA-N
SMILES O=[Co]O[Co]=O
Properties
Chemical formula	Co2O3
Molar mass	165.8646 g/mol
Appearance	red powder
Density	5.18 g/cm3 [2]
Melting point	895[3] °C (1,643 °F; 1,168 K)
Solubility in water	negligible
Magnetic susceptibility (χ)	+4560.0·10−6 cm3/mol
Structure
Crystal structure	Corundum, hR30
Space group	R3c, No. 167
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−577 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	toxic
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H317, H351, H410
Precautionary statements	P280
NFPA 704 (fire diamond)	3 0 0 OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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.

Co₂O₃ + 3H₂SO₄ → Co₂[SO₄]₃ + 3H₂O

Cobalt(III) ion is a strong oxidizer in acidic solution, its standard electrode potential is +1.84V in this situation.^[8]

See also

• Cobalt oxide nanoparticles