Antimony trioxide

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Antimony trioxide
Antimony trioxide
CAS number 1309-64-4 YesY
ChemSpider 25727 YesY
UNII P217481X5E YesY
KEGG C19192 YesY
RTECS number CC5650000
Jmol-3D images Image 1
Molecular formula Sb2O3
Molar mass 291.518 g/mol
Appearance white solid
Odor odorless
Density 5.2 g/cm3, α-form
5.67 g/cm3 β-form
Melting point 656 °C (1,213 °F; 929 K)
Boiling point 1,425 °C (2,597 °F; 1,698 K) (sublimes)
Solubility in water Dissolved concentration of 370 ± 37 µg/L was obtained with a loading of 10 mg/L after 7 days of exposure. Temperature varied between 20.8°C (t=0; start of the test) and 22.9°C
Solubility soluble in acid
2.087, α-form
2.35, β-form
Crystal structure cubic (α)<570 °C
orthorhombic (β) >570 °C
Dipole moment zero
MSDS External MSDS
EU classification Harmful (Xn)
Carc. Cat. 2 (H351)
R-phrases R40
S-phrases (S2), S22, S36/37
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
LD50 7000 mg/kg, oral (rat)
Related compounds
Other anions Antimony trisulfide
Other cations Bismuth trioxide
Related compounds Diantimony tetraoxide
Antimony pentoxide
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Antimony trioxide is the inorganic compound with the formula Sb2O3. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite.[1] Like most polymeric oxides, Sb2O3 dissolves in aqueous solutions with hydrolysis.

Production and properties[edit]

Global production of antimony trioxide in 2012 was 130,000 tonnes, an increase from 112,600 tonnes in 2002. China produces the largest share followed by US/Mexico, Europe, Japan and South Africa and other countries (2%).[2]

As of 2010, antimony trioxide was produced at four sites in EU27. It is produced via two routes, re-volatilizing of crude antimony trioxide and by oxidation of antimony metal. Oxidation of antimony metal dominates in Europe. Several processes for the production of crude antimony trioxide or metallic antimony from virgin material. The choice of process depends on the composition of the ore and other factors. Typical steps include mining, crushing and grinding of ore, sometimes followed by froth flotation and separation of the metal using pyrometallurgical processes (smelting or roasting) or in a few cases (e.g. when the ore is rich in precious metals) by hydrometallurgical processes. These steps do not take place in the EU but closer to the mining location.

Re-volatilizing of crude antimony trioxide[edit]

Step 1) Crude stibnite is oxidised to crude antimony trioxide using furnaces operating at approximately 850 to 1,000 °C. The reaction is the following:

2 Sb2S3 + 9 O2 → 2 Sb2O3 + 6 SO2

Step 2) The crude antimony trioxide is vaporised and condensed

Oxidation of antimony metal[edit]

Antimony metal is oxidized to antimony trioxide in furnaces. The reaction is exothermic. Antimony trioxide is formed through sublimation and recovered in bag filters (bag house). The size of the formed particles is controlled by process conditions in furnace and gas flow. The reaction can be schematically described by:

4 Sb + 3 O2 → 2 Sb2O3


Antimony trioxide is an amphoteric oxide, it dissolves in aqueous sodium hydroxide solution to give the meta-antimonite NaSbO2, which can be isolated as the trihydrate. Antimony trioxide also dissolves in concentrated mineral acids to give the corresponding salts, which hydrolyzes upon dilution with water.[3] With nitric acid, the trioxide is oxidized to antimony(V) oxide.[4]

When heated with carbon, the oxide is reduced to antimony metal. With other reducing agents such as sodium borohydride or lithium aluminium hydride, the unstable and very toxic gas stibine is produced.[5] When heated with potassium bitartrate, a complex salt potassium antimony tartrate, KSb(OH)2•C4H2O6 is formed.[4]


The structure of Sb2O3 depends on the temperature of the sample. Dimeric Sb4O6 is the high temperature (1560 °C) gas.[6] Sb4O6 molecules are bicyclic cages, similar to the related oxide of phosphorus(III), phosphorus trioxide.[7] The cage structure is retained in a solid that crystallizes in a cubic habit. The Sb-O distance is 197.7 pm and the O-Sb-O angle of 95.6°.[8] This form exists in nature as the mineral senarmontite.[7] Above 606 °C, the more stable form is orthorhombic, consisting of pairs -Sb-O-Sb-O- chains that are linked by oxide bridges between the Sb centers. This form exists in nature as the mineral valentinite.[7]



The annual consumption of antimony trioxide in the United States and Europe is approximately 10,000 and 25,000 tonnes, respectively. The main application is as flame retardant synergist in combination with halogenated materials. The combination of the halides and the antimony being key to the flame-retardant action for polymers, helping to form less flammable chars. Such flame retardants are found in electrical apparatus, textiles, leather, and coatings.[9]

Other applications:


Antimony trioxide has suspected carcinogenic potential for humans.[9] Its TLV is 0.5 mg/m3, as for most antimony compounds.[10]
No other human health hazards were identified for antimony trioxide, and no risks to human health and the environment were identified from the production and use of antimony trioxide in daily life.


  1. ^ Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
  2. ^
  3. ^ Housecroft, C. E.; Sharpe, A. G. (2008). "Chapter 15: The group 15 elements". Inorganic Chemistry (3rd ed.). Pearson. p. 481. ISBN 978-0-13-175553-6. 
  4. ^ a b Patnaik, P. (2002). Handbook of Inorganic Chemicals. McGraw-Hill. p. 56. ISBN 0-07-049439-8. 
  5. ^ Bellama, J. M.; MacDiarmid, A. G. (1968). "Synthesis of the Hydrides of Germanium, Phosphorus, Arsenic, and Antimony by the Solid-Phase Reaction of the Corresponding Oxide with Lithium Aluminum Hydride". Inorganic Chemistry 7 (10): 2070–2072. doi:10.1021/ic50068a024. 
  6. ^ Wiberg, E.; Holleman, A. F. (2001). Inorganic Chemistry. Elsevier. ISBN 0-12-352651-5. 
  7. ^ a b c Wells, A. F. (1984). Structural Inorganic Chemistry. Oxford: Clarendon Press. ISBN 0-19-855370-6. 
  8. ^ Svensson, C. (1975). "Refinement of the crystal structure of cubic antimony trioxide, Sb2O3". Acta Crystallographica B 31 (8): 2016–2018. doi:10.1107/S0567740875006759. 
  9. ^ a b Grund, S. C.; Hanusch, K.; Breunig, H. J.; Wolf, H. U. (2005), "Antimony and Antimony Compounds", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a03_055.pub2 
  10. ^ Newton, P. E.; Schroeder, R. E.; Zwick, L.; Serex, T. (2004). "Inhalation Developmental Toxicity Studies In Rats With Antimony Trioxide (Sb2O3)". Toxicologist 78 ((1-S)): 38. 

Further reading[edit]

External links[edit]