Antimony trioxide

{{chembox | Watchedfields = changed | verifiedrevid = 449655175 | Name = Antimony(III) oxide | ImageFile = Antimony trioxide.jpg | ImageSize = 200px | ImageName = Antimony(III) oxide | IUPACName = Antimony(III) oxide | OtherNames = Antimony sesquioxide<br />Antimonous oxide<br />Flowers of Antimony |Section1={{Chembox Identifiers | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID = 25727 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = P217481X5E | InChI = 1/3O.2Sb/rO3Sb2/c1-4-3-5-2 | SMILES = O=[Sb]O[Sb]=O | InChIKey = ADCOVFLJGNWWNZ-VTKDZCJOAA | StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI = 1S/3O.2Sb | StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} | StdInChIKey = ADCOVFLJGNWWNZ-UHFFFAOYSA-N | CASNo_Ref = {{cascite|correct|CAS}} | CASNo = 1309-64-4 | RTECS = CC5650000 | KEGG_Ref = {{keggcite|correct|kegg}} | KEGG = C19192 | PubChem = 14794 | EC_number = 215-474-6 }} |Section2={{Chembox Properties | Formula = Sb₂O₃ | MolarMass = 291.518 g/mol | Appearance = white solid | Odor = odorless | Density = 5.2 g/cm³, α-form <br> 5.67 g/cm³ β-form | Solubility = {{val|370|37}} μg/L between 20.8&nbsp;°C and 22.9&nbsp;°C | SolubleOther = soluble in acid | MeltingPtC = 656 | BoilingPtC = 1425 | BoilingPt_notes = (sublimes) | pKa = | RefractIndex = 2.087, α-form <br> 2.35, β-form | MagSus = {{val|-69.4e-6|u=cm³/mol}} }} |Section3={{Chembox Structure | Coordination = pyramidal | CrystalStruct = cubic (α) <&nbsp;570&nbsp;°C<br />orthorhombic (β) >&nbsp;570&nbsp;°C | Dipole = zero }} |Section7={{Chembox Hazards | ExternalSDS = | NFPA-H = 2 | NFPA-F = 0 | NFPA-R = 0 | GHSPictograms = {{GHS08}}<ref name="GESTIS">{{GESTIS|Name=Antimony trioxide|ZVG=3440|CAS=1309-64-4|Date=23 August 2017}}</ref> | GHSSignalWord = Warning<ref name="GESTIS" /> | HPhrases = {{H-phrases|351}}<ref name="GESTIS" /> | PPhrases = {{P-phrases|281}}<ref name="GESTIS" /> | LD50 = 7000 mg/kg, oral (rat) | REL = TWA 0.5 mg/m³ (as Sb)<ref name=PGCH>{{PGCH|0036}}</ref> | PEL = TWA 0.5 mg/m³ (as Sb)<ref name=PGCH/> }} |Section8={{Chembox Related | OtherAnions = Antimony trisulfide<br>Antimony triselenide<br>Antimony telluride | OtherCations = Dinitrogen trioxide<br>Phosphorus trioxide<br>Arsenic trioxide<br>Bismuth trioxide | OtherCompounds = Diantimony tetraoxide<br />Antimony pentoxide }} }}

'''Antimony(III) oxide''' 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.<ref>Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. {{ISBN|0-7506-3365-4}}.</ref> A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite.<ref>{{Cite web|url=https://www.mindat.org/min-32285.html|title = Stibioclaudetite}}</ref><ref>{{Cite web|url=https://www.ima-mineralogy.org/Minlist.htm|title=List of Minerals|date=21 March 2011}}</ref>

==Production and properties== 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%).<ref>{{cite report|url=http://esis.jrc.ec.europa.eu/doc/risk_assessment/REPORT/datreport415.pdf |title=European Union Risk Assessment Report: DIANTIMONY TRIOXIDE (draft)|date=November 2008|location=Sweden|id=CAS No: 1309-64-4; EINECS No: 215-175-0|url-status=dead |archive-url=https://web.archive.org/web/20140106155610/http://esis.jrc.ec.europa.eu/doc/risk_assessment/REPORT/datreport415.pdf |archive-date=2014-01-06 }}</ref>

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 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(III) oxide <span class="anchor" id="sublimate of antimony"></span>=== Crude stibnite is oxidized to crude antimony(III) oxide using furnaces operating at approximately 500 to 1,000&nbsp;°C. The reaction is the following: :2&nbsp;Sb₂S₃ + 9&nbsp;O₂ → 2&nbsp;Sb₂O₃ + 6&nbsp;SO₂ The crude antimony(III) oxide is then purified by sublimation.

===Oxidation of antimony metal=== 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: :4&nbsp;Sb + 3&nbsp;O₂ → 2&nbsp;Sb₂O₃

===Properties=== Antimony(III) oxide is an amphoteric oxide. It dissolves in aqueous sodium hydroxide solution to give the meta-antimonite NaSbO₂, which can be isolated as the trihydrate.{{citation needed|date=May 2026}} Antimony(III) oxide also dissolves in concentrated mineral acids to give the corresponding salts, which hydrolyzes upon dilution with water.<ref name="InorgChem">{{cite book | title = Inorganic Chemistry | edition = 3rd | chapter = Chapter 15: The group 15 elements | author1 = Housecroft, C. E. | author2 = Sharpe, A. G. | publisher = Pearson | year = 2008 | isbn = 978-0-13-175553-6 | page = 481 }}</ref> With nitric acid, the trioxide is oxidized to antimony(V) oxide.<ref name="Handbook">{{cite book | title = Handbook of Inorganic Chemicals | author = Patnaik, P. | publisher = McGraw-Hill | year = 2002 | isbn = 0-07-049439-8 | page = 56 }}</ref>

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.<ref>{{ cite journal |author1=Bellama, J. M. |author2=MacDiarmid, A. G. | title = Synthesis of the Hydrides of Germanium, Phosphorus, Arsenic, and Antimony by the Solid-Phase Reaction of the Corresponding Oxide with Lithium Aluminum Hydride |journal = Inorganic Chemistry | year = 1968 | volume = 7 | issue = 10 | pages = 2070–2072 | doi = 10.1021/ic50068a024 }}</ref> When heated with potassium bitartrate, a complex salt potassium antimony tartrate, ({{chem2|K2Sb2(C4H2O6)2*3H2O}}) is formed.<ref name="Handbook" />

==Structure== The structure of Sb₂O₃ depends on the temperature of the sample. Dimeric Sb₄O₆ is the high temperature (1560&nbsp;°C<!--seems high-->) gas.<ref name ="Wiberg&Holleman">{{ cite book |author1=Wiberg, E. |author2=Holleman, A. F. | year = 2001 | title = Inorganic Chemistry | publisher = Elsevier | isbn = 0-12-352651-5 }}</ref>{{page needed|date=May 2026}} Sb₄O₆ molecules are bicyclic cages, similar to the related oxide of phosphorus(III), phosphorus trioxide.<ref name = "Wells">{{ cite book | author = Wells, A. F. | year = 1984 | title = Structural Inorganic Chemistry | location = Oxford | publisher = Clarendon Press | isbn = 0-19-855370-6 }}</ref> The cage structure is retained in a solid that crystallizes in a cubic habit. The Sb–O distance is 197.7&nbsp;pm and the O–Sb–O angle of 95.6°.<ref>{{ cite journal | author = Svensson, C. | title = Refinement of the crystal structure of cubic antimony(III) oxide, Sb₂O₃ | journal = Acta Crystallographica B | year = 1975 | volume = 31 | issue = 8 | pages = 2016–2018 | doi = 10.1107/S0567740875006759 | bibcode = 1975AcCrB..31.2016S | doi-access = }}</ref> This form exists in nature as the mineral senarmontite.<ref name = "Wells"/> Above 606&nbsp;°C, the more stable form is orthorhombic, 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 mineral valentinite.<ref name = "Wells"/>

{| class="wikitable" style="margin:1em auto; text-align:center;" |100px||200px||220px |- |Sb₄O₆||senarmontite||valentinite |}

==Uses== The annual consumption of antimony(III) oxide 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 halogens and antimony is key to the flame-retardant action of polymers, helping to form less flammable chars. Such flame retardants are found in electrical apparatuses, textiles, leather, and coatings.<ref name=Ullmann>{{ Ullmann | author = Grund, S. C. |author2=Hanusch, K. |author3=Breunig, H. J. |author4=Wolf, H. U. | title = Antimony and Antimony Compounds | doi = 10.1002/14356007.a03_055.pub2 }}</ref>

Other applications: *Antimony(III) oxide is an opacifying agent for glasses, ceramics and enamels. *Some specialty pigments contain antimony.{{citation needed|date=May 2026}} *Antimony(III) oxide is a useful catalyst in the production of polyethylene terephthalate (PET plastic) and the vulcanization of rubber.

==Safety== Antimony(III) oxide has suspected carcinogenic potential for humans.<ref name=Ullmann/> Its TLV is 0.5&nbsp;mg/m³, as for most antimony compounds.<ref>{{ cite journal |author1=Newton, P. E. |author2=Schroeder, R. E. |author3=Zwick, L. |author4=Serex, T. | title = Inhalation Developmental Toxicity Studies In Rats With Antimony(III) oxide (Sb₂O₃) | journal = Toxicologist | year = 2004 | volume = 78 | issue = 1–S | pages = 38 }}</ref> 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 the US Department of Health and Human Services categorised antimony(III) oxide as carcinogenic.<ref>{{Cite web |title=15th Report on Carcinogens |url=https://ntp.niehs.nih.gov/whatwestudy/assessments/cancer/roc |archive-url=https://web.archive.org/web/20200209202629/https://ntp.niehs.nih.gov/whatwestudy/assessments/cancer/roc/ |url-status=dead |archive-date=February 9, 2020 |access-date=2023-06-15 |website=National Toxicology Program |language=en}}</ref>

==References== {{reflist}}

==Further reading== * Institut national de recherche et de sécurité (INRS), ''Fiche toxicologique nº 198&nbsp;: Trioxyde de diantimoine'', 1992. * The Oxide Handbook, G.V. Samsonov, 1981, 2nd ed. IFI/Plenum, {{ISBN|0-306-65177-7}}

==External links== * [http://www.antimony.com/ International Antimony Association] * [http://www.inchem.org/documents/icsc/icsc/eics0012.htm International Chemical Safety Card 0012] * [https://web.archive.org/web/20160819095940/http://www.manymetal.com/Antimony/ Antimony Market And Price] * [http://www.sica-chauny.com/ Société industrielle et chimique de l'Aisne]

{{Antimony compounds}} {{Oxides}}

{{DEFAULTSORT:Antimony Trioxide}} Category:Antimony(III) compounds Category:Oxides Category:Inorganic pigments Category:IARC Group 2B carcinogens Category:Sesquioxides Category:Adamantane-like molecules Category:Flame retardants