Antimony trioxide

Key takeaways

Antimony trioxide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Antimony trioxide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Antimony trioxide from memory before moving on to harder problems.

Reference excerpt

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. 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 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 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 Sb + 3 O2 → 2 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. Antimony(III) oxide 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, (K2Sb2(C4H2O6)2·3H2O) 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. 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 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.

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. Other applications:

Antimony(III) oxide is an opacifying agent for glasses, ceramics and enamels. Some specialty pigments contain antimony. 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. 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 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, ISBN 0-306-65177-7

External links International Antimony Association International Chemical Safety Card 0012 Antimony Market And Price Société industrielle et chimique de l'Aisne

Illustrations

Worked examples

Example 1 — a first encounter with Antimony trioxide

Start with the simplest possible case. Write down what Antimony trioxide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Antimony trioxide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Antimony trioxide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Antimony trioxide

In research: Antimony trioxide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Antimony trioxide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Antimony trioxide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Adamantane-like molecules, Antimony(III) compounds, Flame retardants, so understanding it makes those chapters shorter.
In everyday life: Look for Antimony trioxide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Antimony trioxide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Antimony trioxide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Antimony trioxide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Antimony trioxide in simple terms?

Antimony(III) oxide is the inorganic compound with the formula Sb2O3. It is the most important commercial compound of antimony.

Why does Antimony trioxide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Antimony trioxide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Antimony trioxide.