|Jmol-3D images||Image 1|
|Molar mass||291.518 g/mol|
|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||1.21 mg/100 mL (0 °C)
1.80 mg/100 mL (20 °C)
8.20 mg/100 mL (100 °C), with hydrolysis
|Solubility||soluble in acid|
|Refractive index (nD)||2.087, α-form
|Crystal structure||cubic (α)<570 °C
orthorhombic (β) >570 °C
|EU classification||Harmful (Xn)
Carc. Cat. 3
|S-phrases||(S2), S22, S36/37|
|LD50||7000 mg/kg, oral (rat)|
|Other anions||Antimony trisulfide|
|Other cations||Arsenic trioxide
|Related compounds||Diantimony tetraoxide
|Supplementary data page|
|n, εr, etc.|
Solid, liquid, gas
|Spectral data||UV, IR, NMR, MS|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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. Like most polymeric oxides, Sb2O3 dissolves in aqueous solutions only with hydrolysis.
Production and properties
Global production of antimony trioxide in 2005 was 120,000 tonnes, an increase from 112,600 tonnes in 2002. China produces the largest share (47%) followed by US/Mexico (22%), Europe (17%), Japan (10%) and South Africa (2%) and other countries (2%).
Antimony trioxide is mainly produced via the smelting of stibnite ore, which is oxidised to crude Sb2O3 using furnaces operating at approximately 850 to 1,000 °C. The transformation is described as follows:
- 2 Sb2S3 + 9 O2 → 2 Sb2O3 + 6 SO2
Crude Sb2O3 is purified by sublimation, which allows it to be separated from the more volatile arsenic trioxide. This step is relevant because antimony ores commonly contain significant amounts of arsenic.
Antimony oxide is also obtained via antimony trichloride, which can be obtained from stibnite.
- 2 Sb2S3 + 3 CaCl2 + 6 O2 → 4 SbCl3 + 3 CaSO4
After fractional distillation to separate it from arsenic trichloride, SbCl3 can be hydrolyzed to the oxide:
- 2 SbCl3 + 3 H2O → Sb2O3 + 6 HCl
Intermediates in the hydrolysis include the oxychlorides SbOCl and Sb4O5Cl2.
Although impractical for commercial purposes, Sb2O3 can be prepared by burning elemental antimony in air:
- 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. With nitric acid, the trioxide is oxidized to antimony(V) oxide.
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. When heated with potassium bitartrate, a complex salt potassium antimony tartrate, KSb(OH)2•C4H2O6 is formed.
The structure of Sb2O3 depends on the temperature of the sample. Dimeric Sb4O6 is the high temperature (1560 °C) gas. Sb4O6 molecules are bicyclic cages, similar to the related oxide of phosphorus(III), phosphorus trioxide. 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°. This form exists in nature as the mineral senarmontite. 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.
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 for flame retardants 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.
- Antimony trioxide is an opacifying agent for glasses, ceramics and enamels.
- Some specialty pigments contain antimony.
- Antimony trioxide is a useful catalyst in the production of polyethylene terephthalate (PET plastic) and the vulcanization of rubber.
- Flame retardant for textiles, leather, polymers, and coatings.
The toxicity of Sb2O3 is topical because it is a likely byproduct of the combustion of some materials "fireproofed" with antimony compounds. The oxides of arsenic, antimony, and bismuth are comparable in their toxicity, but their volatilities differ widely. Antimony trioxide has suspected carcinogenic potential for humans. Its TLV is 0.5 mg/m3, as for most antimony compounds.
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- 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.
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- The Oxide Handbook, G.V. Samsonov, 1981, 2nd ed. IFI/Plenum, ISBN 0-306-65177-7
- Antimony trioxide Risk Assessment Report
- International Antimony Association
- International Chemical Safety Card 0012
- ESIS: European chemical Substances Information System
- Antimony Market And Price
- Société industrielle et chimique de l'Aisne