Antimony(III) Oxide
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Antimony(III) oxide is the
inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...
with the
formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
Sb2O3. It is the most important commercial compound of
antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
. It is found in nature as the minerals
valentinite Valentinite is an Antimony trioxide, antimony oxide mineral with formula antimony, Sb2oxygen, O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorl ...
and senarmontite. Like most polymeric
oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...
s, Sb2O3 dissolves in aqueous solutions with
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...
. A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite.


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%). 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

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: :2 Sb2S3 + 9 O2 → 2 Sb2O3 + 6 SO2 Step 2) The crude antimony(III) oxide is 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 Sb + 3 O2 → 2 Sb2O3


Properties

Antimony(III) oxide is an
amphoteric oxide In chemistry, an amphoteric chemical compound, compound () is a molecule or ion that can react both as an acid and as a base (chemistry), base. What exactly this can mean depends on acid–base reaction, which definitions of acids and bases are ...
. It dissolves in aqueous
sodium hydroxide Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions . Sodium hydroxide is a highly corrosive base (chemistry), ...
solution to give the meta-antimonite NaSbO2, which can be isolated as the trihydrate. Antimony(III) oxide also dissolves in concentrated
mineral acids A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, as opposed to organic acids which are acidic, organic compounds. All mineral acids form hydrogen ions and the conjugate base when dissolved in water. Cha ...
to give the corresponding salts, which hydrolyzes upon dilution with water. With
nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...
, the trioxide is oxidized to
antimony(V) oxide Antimony pentoxide (molecular formula: Sb2O5) is a chemical compound of antimony and oxygen. It contains antimony in the +5 oxidation state. Structure Antimony pentoxide has the same structure as the ''B'' form of niobium pentoxide and can be deri ...
. When heated with
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
, the oxide is reduced to
antimony Antimony is a chemical element; it has chemical symbol, symbol Sb () and atomic number 51. A lustrous grey metal or metalloid, it is found in nature mainly as the sulfide mineral stibnite (). Antimony compounds have been known since ancient t ...
metal. With other reducing agents such as
sodium borohydride Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula (sometimes written as ). It is a white crystalline solid, usually encountered as an aqueous basic solution. Sodi ...
or
lithium aluminium hydride Lithium aluminium hydride, commonly abbreviated to LAH, is an inorganic compound with the chemical formula or . It is a white solid, discovered by Finholt, Bond and Schlesinger in 1947. This compound is used as a reducing agent in organic synthe ...
, the unstable and very toxic gas
stibine Stibine (IUPAC name: stibane) is a chemical compound with the formula Sb H3. A pnictogen hydride, this colourless, highly toxic gas is the principal covalent hydride of antimony, and a heavy analogue of ammonia. The molecule is pyramidal with H ...
is produced. When heated with
potassium bitartrate Potassium bitartrate, also known as potassium hydrogen tartrate, with formula K C4 H5 O6, is the potassium acid salt of tartaric acid (a carboxylic acid)—specifically, l-( + )-tartaric acid. Especially in cooking, it is also known as cream o ...
, a complex salt potassium antimony tartrate, KSb(OH)2·C4H2O6, is formed.


Structure

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 Phosphorus trioxide is the chemical compound with the molecular formula P4O6. Although the molecular formula suggests the name tetraphosphorus hexoxide, the name phosphorus trioxide preceded the knowledge of the compound's molecular structure, a ...
. 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 In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
senarmontite. Above 606 °C, the more stable form is
orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, res ...
, 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 Valentinite is an Antimony trioxide, antimony oxide mineral with formula antimony, Sb2oxygen, O3. Valentinite crystallizes in the orthorhombic system and typically forms as radiating clusters of euhedral crystals or as fibrous masses. It is colorl ...
.


Uses

The annual consumption of antimony(III) oxide in the United States and Europe is approximately 10,000 and 25,000
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...
s, respectively. The main application is as
flame retardant Flame retardants are a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an combustion, ignition source and pr ...
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. Other applications: *Antimony(III) oxide is an opacifying agent for
glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
es,
ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...
s and enamels. *Some specialty
pigments A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
contain antimony. *Antimony(III) oxide is a useful
catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
in the production of
polyethylene terephthalate Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in synthetic fibre, fibres for clothing, packaging, conta ...
(PET plastic) and the
vulcanization Vulcanization (British English: vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to ...
of rubber.


Safety

Antimony(III) oxide has suspected carcinogenic potential for humans. Its TLV is 0.5 mg/m3, as for most antimony compounds. 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 The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the US federal government created to protect the health of the US people and providing essential human services. Its motto is ...
categorised antimony(III) oxide as carcinogenic.


References


Further reading

* Institut national de recherche et de sécurité (INRS), ''Fiche toxicologique nº 198 : Trioxyde de diantimoine'', 1992. * The Oxide Handbook, G.V. Samsonov, 1981, 2nd ed. IFI/Plenum,


External links


International Antimony Association



Antimony Market And Price

Société industrielle et chimique de l'Aisne
{{DEFAULTSORT:Antimony Trioxide Antimony(III) compounds Oxides Inorganic pigments IARC Group 2B carcinogens Sesquioxides Adamantane-like molecules Flame retardants