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| Names | |
|---|---|
| IUPAC name Antimony(III) oxide | |
| Other names | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.013.796 |
| EC Number |
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| KEGG |
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| RTECS number |
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| UNII | |
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| Properties | |
| 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) |
| 370±37 μg/L between 20.8 °C and 22.9 °C | |
| Solubility | soluble in acid |
| −69.4×10−6 cm3/mol | |
Refractive index (nD) | 2.087, α-form 2.35, β-form |
| Structure | |
| cubic (α) < 570 °C orthorhombic (β) > 570 °C | |
| pyramidal | |
| zero | |
| Hazards | |
| GHS labelling: | |
 [1] | |
| Warning[1] | |
| H351[1] | |
| P281[1] | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 7000 mg/kg, oral (rat) |
| 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 | |
Otheranions | Antimony trisulfide Antimony triselenide Antimony telluride |
Othercations | Dinitrogen trioxide Phosphorus trioxide Arsenic trioxide Bismuth trioxide |
Related compounds | Diantimony tetraoxide Antimony pentoxide |
| Supplementary data page | |
| Antimony trioxide (data page) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Antimony(III) oxide is theinorganic compound with theformula Sb2O3. It is the most important commercial compound ofantimony. It is found in nature as the mineralsvalentinite and senarmontite.[3] Like most polymericoxides, Sb2O3 dissolves in aqueous solutions withhydrolysis. A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite.[4][5]
Global production of antimony(III) oxide 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%).[6]
As of 2010, antimony(III) oxide was produced at four sites in the EU. It is produced via two routes, re-volatilizing of crude antimony(III) oxide and by oxidation of antimony metal.Oxidation of antimony metal dominates in Europe. Several processes for the production of crude antimony(III) oxide 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 byfroth 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.
Step 1) Crude stibnite is oxidized to crude antimony(III) oxide using furnaces operating at approximately 500 to 1,000 °C. The reaction is the following:
Step 2) The crude antimony(III) oxide is purified bysublimation.
Antimony metal is oxidized to antimony(III) oxide in furnaces. The reaction is exothermic. Antimony(III) oxide is formed through sublimation and recovered in bag filters. The size of the formed particles is controlled by process conditions in furnace and gas flow. The reaction can be schematically described by:
Antimony(III) oxide is anamphoteric oxide. It dissolves in aqueoussodium hydroxide solution to give the meta-antimonite NaSbO2, which can be isolated as the trihydrate. Antimony(III) oxide also dissolves in concentratedmineral acids to give the corresponding salts, which hydrolyzes upon dilution with water.[7] Withnitric acid, the trioxide is oxidized toantimony(V) oxide.[8]
When heated withcarbon, the oxide is reduced toantimony metal. With other reducing agents such assodium borohydride orlithium aluminium hydride, the unstable and very toxic gasstibine is produced.[9] When heated withpotassium bitartrate, a complex saltpotassium antimony tartrate, KSb(OH)2·C4H2O6, is formed.[8]
The structure of Sb2O3 depends on the temperature of the sample. Dimeric Sb4O6 is the high temperature (1560 °C) gas.[10] Sb4O6 molecules are bicyclic cages, similar to the related oxide of phosphorus(III),phosphorus trioxide.[11] 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°.[12] This form exists in nature as themineralsenarmontite.[11] Above 606 °C, the more stable form isorthorhombic, consisting of pairs of -Sb-O-Sb-O- chains that are linked by oxide bridges between the Sb centers. This form exists in nature as the mineralvalentinite.[11]
 | -oxide-senarmontite-xtal-2004-3D-balls.png) | -oxide-valentinite-xtal-2004-3D-balls.png) |
| Sb4O6 | senarmontite | valentinite |
The annual consumption of antimony(III) oxide in the United States and Europe is approximately 10,000 and 25,000tonnes, respectively. The main application is asflame retardant synergist in combination with halogenated materials. The combination of the halides and the antimony is key to the flame-retardant action for polymers, helping to form less flammable chars. Such flame retardants are found in electrical apparatuses, textiles, leather, and coatings.[13]
Other applications:
Antimony(III) oxide has suspected carcinogenic potential for humans.[13] ItsTLV is 0.5 mg/m3, as for most antimony compounds.[14] Before 2021, no other human health hazards were identified for antimony(III) oxide, and no risks to human health and the environment were identified from the production and use of antimony trioxide in daily life. However, the 15th Report on Carcinogens released on December 21, 2021, by theUS Department of Health and Human Services categorised antimony(III) oxide as carcinogenic.[15]
