It is one of the most important chemical compounds of antimony. It appears as white or gray in color in cubic crystalline form.

Antimony Trioxide Chemical Formula

The chemical formula of this compound is Sb₂O_3.

Antimony Trioxide Synonyms

It is also known by other names such as

• Antimony White
• Antimony (III) Oxide
• Atox B
• Atox F
• Antimony Bloom 100A
• Bluestar RG
• Flowers of Antimony
• Antimony Sesquioxide
• Bluestar Z
• Diantimony Trioxide
• FireShield H
• Thermoguard B

It has some more trade names.

Antimony Trioxide CAS No

CAS No of this compound is 1309-64-4.

Antimony Trioxide Structure

Its structure depends on the temperature of sample. Under high temperature (1560°C), dimeric Sb₄O₆ is noted. Sb₄O₆ molecules appear as bicyclic cages similar to that of related oxides of phosphorus (III) and phosphorus trioxide. The cage structure is maintained in crystallized solid in a cubic habit. Distance between Sb-O is 197.7 pm with an O-Sb-O angle of 95.6°. Below 606 °C, the more stable type is orthorhombic that includes pairs of Sb-O chains linked by oxide bridges between the Stibium centers.

The compound has a dipole moment of zero.

Picture 1 – Antimony Trioxide
Source – indiamart.com

Density

The density of this compound is 5.7 (g cm^-3).

Vapor Density

Vapor density of this inorganic compound is 10 (air = 1).

Boiling Point

Boiling point of Antimony Trioxide is 1425°C.

Melting Point

Melting point of Antimony Trioxide is 655°C.

Solubility of Antimony Trioxide

It is only with hydrolysis that this substance becomes soluble in aqueous solutions: typical of most other polymeric oxides. It is marginally soluble in water.

Formation by Reaction of Antimony with Air and Water

Antimony reacts with oxygen in air on heating forming Sb₂O₃. The flame is bluish white. The chemical reaction is given as:

4Sb(s) + 3O₂(g) → 2sb₂O₃(s)

Antimony reacts with water at red heat forming Sb₂O₃. This is expressed as:

2Sb(s) + 3H₂O(g) → Sb₂O₃(s) + 3H₂(g)

Antimony Trioxide Availability

It is found in nature as the minerals Valentinite and Senarmontite. Many commercial manufacturers produce Antimony Trioxide using stibnite ores (Antimony Trisulfide) or as a by-product of lead smelting. Antimony Trioxide can also be produced using Antimony Trichloride, which is derived from Stibnite. Although not feasible for commercial purposes, this inorganic compound can also be produced by burning elementary Antimony in air. Countries that produce Antimony Trioxide in the most quantities are:

• China
• South Africa
• Bolivia
• Russia
• Tajikistan
• Kyrgyzstan

Antimony Trioxide Uses

This inorganic compound has a number of industrial uses. They can be summed up as follows:

• It is used as a pigment for other antimony compounds.
• It is used as an ingredient in fire retardant paints. Paint manufacturers use it as a white pigment. It is also with other substances to produce yellow pigments.
• This chemical is used in fire-retardant composition of plastics, paper, textiles and rubbers.
• It is also deployed as a catalyst in the chemical industry
• Glass and ceramic producers use it as an improver. Glass manufacturers use it to remove bubbles (degasser) and as a fining agent.
• It is used as an opacifier in porcelain and enameling products.
• It is used to improve functioning of halogenated flame-retardants by sequentially freeing halogenated radicals to slow down gas phase chain reaction of flames dispersed.
• In Titanium Dioxide preparation, it is used as a flocculant.

Other Properties and Facts

• Its refractive index is 2.087 (n_D).
• Strength of its izod effect and translucency are two chief features that are reduced because of the size of particle and color strength of antimony trioxide. Reduction in translucency restricts choice of accessible color due to high loading needed to counterbalance the pigmentation of Antimony Trioxide.
• Synergy between antimony and halogenated flame-retardants is well exploited in flame-retarding thermoplastics.
• Other related compounds are Diantimony Tetraoxide and Antimony Pentoxide.

Material Safety Data Sheet (MSDS)

This is a stable compound and does not react with strong reducing agents. While dealing with this substance, care should be taken because of its toxic effect.

Toxicology

If inhaled, ingested, or absorbed through skin, this substance can have damaging effects. Exposure to this chemical is suspected of causing cancer, but there is little evidence of its carcinogenic effect. It is non-hazardous for air, sea, or road transportation.

References
1. http://www.aluminahydrate.com/antimony-trioxide.html
2. http://www.amspec.net/products/flame-retardants/antimony-trioxide/
3. http://pubs.acs.org/doi/abs/10.1021/cm9805119
4. http://www.webelements.com/antimony/chemistry.html