Antimony(III) oxide

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Antimony(III) oxide
IUPAC name
Antimony(III) oxide
Systematic IUPAC name
Antimony trioxide
Other names
Antimony sesquioxide
Antimonous oxide
Flowers of Antimony
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)
0.0033 g/100 ml (at 20 °C)
Safety data sheet Sigma-Aldrich
Lethal dose or concentration (LD, LC):
7,000 mg/kg (rat, oral)
Related compounds
Related compounds
Antimony(V) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Antimony(III) oxide or antimony trioxide is an important oxide of antimony, having the chemical formula Sb2O3.

It is found in nature as the minerals senarmontite and valentinite.



Antimony(III) oxide reacts with acids to form antimony salts, which may hydrolyze if the pH is not low enough.

Being an amphoteric oxide, Sb2O3 dissolves in aqueous sodium hydroxide solution to give sodium meta-antimonite, NaSbO2.


Antimony trioxide is a white solid insoluble in water.


Antimony(III) oxide is sold by various chemical suppliers.

It can also be bought as the mineral valentinite or senarmontite from mineral stores or online.


Can be prepared by roasting antimony in air. Stibnite (antimony(III) sulfide) can also be used.

Dissolving lead-antimony alloys (found in car battery and wheel weights) in acid in the presence of an oxidizer (oxygen or hydrogen peroxide) will give lead salts and antimony oxide/oxyacid, which precipitate as a superfine powder. Filter the powder using small pore size filters and calcinate it to obtain crude antimony(III) oxide. The antimony oxide obtained this way is heavily contaminated with lead oxides and further purification is required to obtain a relative pure compound.


  • Make elemental antimony
  • Catalyst in polyethylene terephthalate (PET) synthesis
  • Glass, ceramic and enamel opacifying agent



Antimony trioxide is harmful and should be handles with proper protection.


In closed bottles, away from acids.


Should be taken to waste disposal centers or recycled.


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