Antimony Trioxide - Overview

Antimony Trioxide Chemical Formula
Antimony trioxide is an inorganic compound with the formula Sb2O3. It appears white in color and it is an odourless white crystalline powder, sparingly soluble in water. It is the most important compound prepared from antimony. It is found in nature and extracted from the minerals valentinite and senarmontite. Antimony trioxide dissolves in aqueous solutions only with hydrolysis. Antimony trioxide is an amphoteric oxide and it exhibits redox nature, it can be readily oxidized to antimony pentoxide and related antimony (V) compounds, but it is also easily reduced to antimony, sometimes with production of stibine.

Manufacturing Process

Antimony oxide can be prepared by two processes, the direct and the indirect process.

Indirect process

In this process, antimony metal or ores is melted in a furnace to give ATO vapors. The vapors are quenched with air and cooled to convert the vapor to white powder. These powders are further filtered to give antimony trioxide powder.

Direct process

In this process, crude antimony oxide is roasted in the presence of air to give ATO vapors. The vapors are then condensed to convert the vapor to white powder. These powders are further filtered to give antimony trioxide powder.

The Uses of Antimony Trioxide

Flame Retardant

There are several classes of flame retardants, among this Antimony trioxide is the best compound. Antimony Trioxide (ATO) provides unique properties not easily obtained through other products when applied in a variety of industrial processes. Increasing Fire Safety Ensuring high levels of fire safety. ATO greatly increases flame retardant effectiveness. Flame Retardant are substances that can be chemically inserted into the polymer molecule or be phisically blended in polymers after polymerization to suppress, reduce, delay or modify the propagation of a flame through a plastic materials. Antimony trioxide does not react as flame-retardants directly. Antimony Trioxide are used as synergists to enhance the activity of halogenated flame-retardants by stepwise releasing the halogenated radicals to retard gas phase chain reaction of flame spread. Many industries use antimony as a flame retardant synergist including but not limited to the plastics, textiles, rubber, paper, and paint industries. Antimony Trioxide can be used as an appropriate synergist for flame retarding polyvinyl chloride (PVC), polypropylene (PP), high impact polystyrene (HIPS), polyethylene (PE), ethylene propylene diene rubber (EPDM), acrylonitrile butadiene styrene (ABS), epoxies, phenolic, polyurethanes, and many others. Apart from this antimony trioxide and other antimony compounds also used as flame retardant.

Plastic Industry

The Leading Catalyst for Manufacture of polyethylene terephthalate (PET Plastics) ATO is the major catalyst for the production of PET plastic used in the packaging of mineral water and soft drinks. PET is one of the best materials for plastic bottles, with a history of safe use by millions of consumers every day. ATO’s safe use in the production of PET bottles has been confirmed by the World Health Organisation (2003) and the European Food Safety Authority (2004). The use of ATO as a catalyst in PET bottles does NOT impact the safety of the beverages.

Glass Industry

Antimony trioxide can also be used as a fining agent or as degasser in the manufacturing of glass.It is added to the glass melt to remove bubbles from the solution. Many specialty glass companies use antimony trioxide for this purpose.

Other Applications

Antimony trioxide is used as an opacifier for porcelain and enamel and a white pigment for paint. Antimony oxide is a white crystalline powder so as a result it can be used as a white pigment for paint; it is sometimes used with other materials to form yellow pigments. It is also used in vulcanization of rubber. Antimony Trioxide can be used as an additive in glass and ceramic products and as a catalyst in the chemical industry. It is also used as flocculent in Titanium Dioxide production  and ingredient in ZnO varistors


IUPAC NameAntimony(III) oxide
CAS No1309-64-4
Molecular Weight291.518 g mol-1
H.S Code2825.80.00
SynonymsAntimonous oxide


AppearanceWhite powder
Antimony Oxide%99.5 (min)
Antimony%83.3 (min)
Arsenic%0.2 (max)
Lead%0.1 (max)
Seleniumppm50 (max)
Specific Gravity5.2 - 5.6
Residue on 325 mesh%0.5
Average Particle SizeMicrons1.1 - 1.8
Melting Point°C655
Boiling Point°C1425
Solubilityg/ccImmiscible in water