Antimony tetroxide

Antimony tetroxide is an inorganic compound with the formula Sb₂O₄. This material, which exists as the mineral cervantite,^[3] is white but reversibly yellows upon heating. The material, with empirical formula SbO₂, is called antimony tetroxide to signify the presence of two kinds of Sb centers.^[4]

Antimony tetroxide

α-Sb2O4
β-Sb2O4   Sb   O
Names
IUPAC name antimony(III,V) oxide
Identifiers
CAS Number	1332-81-6 Y
ChemSpider	66628
ECHA InfoCard	100.014.161
EC Number	215-576-0
PubChem CID	74002
UNII	XB7RVZ5DN5 Y
CompTox Dashboard (EPA)	DTXSID9061677
Properties
Chemical formula	SbO2; Sb2O4
Molar mass	153.7588; 307.5176 g/mol
Appearance	white solid
Density	6.64 g/cm3 (orthorhombic form) [1]
Melting point	> 930 °C (1,710 °F; 1,200 K) (decomposes)
Boiling point	decomposes
Solubility in water	insoluble
Refractive index (nD)	2.0
Structure
Crystal structure	orthorhombic
Hazards
NFPA 704 (fire diamond)	2 1 0
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 0.5 mg/m3 (as Sb)[2]
REL (Recommended)	TWA 0.5 mg/m3 (as Sb)[2]
Related compounds
Related compounds	Antimony trioxide Antimony pentoxide
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

Formation and structure

The material forms when Sb₂O₃ is heated in air:^[5]

Sb₂O₃ + 0.5 O₂ → Sb₂O₄ ΔH = −187 kJ/mol

At 800 °C, antimony(V) oxide loses oxygen to give the same material:

Sb₂O₅ → Sb₂O₄ + 0.5 O₂ ΔH = −64 kJ/mol

The material is mixed valence, containing both Sb(V) and Sb(III) centers. Two polymorphs are known, one orthorhombic (shown in the infobox) and one monoclinic.^[1] Both forms feature octahedral Sb(V) centers arranged in sheets with distorted Sb(III) centers bound to four oxides.