:Cobalt(III) oxide

{{chembox

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 407839996

| ImageFile = Cobalt(III) oxide.JPG

| Name = Cobalt(III) oxide[http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIAL/12926 Sigma-Aldrich product page]

| IUPACName = cobalt(III) oxide, dicobalt trioxide

| OtherNames = cobaltic oxide, cobalt sesquioxide

|Section1={{Chembox Identifiers

| CASNo_Ref = {{cascite|correct|CAS}}

| CASNo = 1308-04-9

| ChemSpiderID = 3324433

| PubChem = 4110762

| InChI = 1S/2Co.3O

| InChIKey = UPWOEMHINGJHOB-UHFFFAOYSA-N

| SMILES = O=[Co]O[Co]=O

| EINECS = 215-156-7

| RTECS = GG2900000

}}

|Section2={{Chembox Properties

| Formula = Co₂O₃

| MolarMass = 165.8646 g/mol

| Appearance = red powder

| Density = 5.18 g/cm³ {{RubberBible87th}}

| MeltingPtC = 895{{Cite web | url=http://www.chemicalbook.com/ChemicalProductProperty_US_CB4291419.aspx | title=1308-04-9 CAS MSDS (COBALT(III) OXIDE BLACK) Melting Point Boiling Point Density CAS Chemical Properties }}

| BoilingPt =

| Solubility = negligible

| MagSus = +4560.0·10⁻⁶ cm³/mol

}}

|Section3={{Chembox Structure

| CrystalStruct = Corundum, hR30

| SpaceGroup = R{{overline|3}}c, No. 167

}}

|Section4={{Chembox Thermochemistry

| DeltaHf = −577 kJ/mol

}}

|Section7={{Chembox Hazards

| MainHazards = toxic

| GHSPictograms = {{GHS07}}{{GHS08}}

| GHSSignalWord = Warning

| HPhrases = {{H-phrases|302|317|351|410}}

| PPhrases = {{P-phrases|280}}

| AutoignitionPt =

| NFPA-H = 3

| NFPA-F = 0

| NFPA-R = 0

| NFPA-S = OX}}

}}

Cobalt(III) oxide is the inorganic compound with the formula of Co₂O₃. Although only two oxides of cobalt are well characterized, CoO and Co₃O₄,{{Greenwood&Earnshaw2nd}} 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:Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. p. 1675.{{cite journal | last=Hüttner | first=Erwin | title=Beiträge zur Kenntnis der Oxyde des Kobalts | journal=Zeitschrift für anorganische Chemie | publisher=Wiley | volume=27 | issue=1 | date=1901-05-02 | issn=0863-1778 | doi=10.1002/zaac.19010270113 | pages=81–124| url=https://zenodo.org/record/2455069 |language=de}}

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

Some formulations of the catalyst hopcalite contain "Co₂O₃".

Some studies have been unable to synthesize the compound, and report that it is theoretically unstable.{{cite journal | last1=Shanbhag | first1=Pavitra N. | last2=Biswas | first2=Raju K. | last3=Pati | first3=Swapan K. | last4=Sundaresan | first4=Athinarayanan | last5=Rao | first5=Chinthamani Nagesa Ramachandra | title=Elusive Co2O3: A Combined Experimental and Theoretical Study | journal=ACS Omega | publisher=American Chemical Society (ACS) | volume=5 | issue=45 | date=2020-11-02 | issn=2470-1343 | doi=10.1021/acsomega.0c03397 | pages=29009–29016| pmid=33225132 | pmc=7675568 }}

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.{{cite book |last1=Guoqing |first1=Wu |title=无机化学 (Inorganic Chemistry) |date=2003 |publisher=高等教育出版社 (Higher Education Press) |location=People's Republic of China |isbn=9787040115833 |page=781 |edition=4th }}