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Cobalt(II,III) oxide

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Title: Cobalt(II,III) oxide  
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Subject: Cobalt, Cobalt(II) bromide, Cobalt(II) hydroxide, Oxides, Carbon trioxide
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Cobalt(II,III) oxide

Cobalt(II,III) oxide[1]
Cobalt(II,III) oxide
Ball-and-stick model of the unit cell of Co3O4
CAS number  YesY
ChemSpider  YesY
RTECS number GG2500000
Jmol-3D images Image 1
Molecular formula Co3O4


Molar mass 240.80 g/mol
Appearance black solid
Density 6.11 g/cm3
Melting point 895 °C (1,643 °F; 1,168 K)
Boiling point 900 °C (1,650 °F; 1,170 K) (decomposes)
Solubility in water Insoluble
Solubility soluble in acids and alkalis
Crystal structure cubic
R-phrases R40 R41 R42 R43
S-phrases S36/37
NFPA 704
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY   YesY/N?)

Cobalt(II,III) oxide is formula Co3O4. It is one of two well characterized cobalt oxides. It is a black antiferromagnetic solid. As a mixed valence compound, its formula is sometimes written as CoIICoIII2O4 and sometimes as CoO•Co2O3.[2]


Co3O4 adopts the normal spinel structure, with Co2+ ions in tetrahedral interstices and Co3+ ions in the octahedral interstices of the cubic close-packed lattice of oxide anions.[2]

tetrahedral coordination geometry of Co(II) distorted octahedral coordination geometry of Co(III) distorted tetrahedral coordination geometry of O


Cobalt(II) oxide, CoO, converts to Co3O4 if heated to around 600-700 °C in air. Above 900 °C, CoO is stable.[3] These reaction are described by the following equilibrium:

2 Co3O4 \overrightarrow{\leftarrow} 6 CoO + O2


This inorganic compound is currently utilized in the process of artificial photosynthesis.


Cobalt compounds are potentially poisonous in large amounts.[4]


  1. ^ Sigma-Aldrich product page
  2. ^ a b  
  3. ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. p. 1520.
  4. ^ MSDS
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