Antimony trioxide, with the chemical formula Sb2O3, is a chemical compound composed of two antimony ions (Sb3+) and three oxide ions (O2-). It occurs naturally as the mineral senarmontite, but it is more commonly produced industrially through the processing of antimony ores.

Antimony trioxide is a white, odorless powder that is insoluble in water but can dissolve in certain acids. It is a versatile compound with several key properties and uses, including:

1. Flame Retardant: Antimony trioxide is one of the most important flame retardants used in various materials, including plastics, textiles, and coatings. It acts as a synergist with halogenated flame retardants, enhancing their fire-retardant properties.
2. Catalysis: It is used as a catalyst in some chemical reactions, particularly in the production of polyester resins and polyethylene terephthalate (PET) plastics.
3. Pigment: Antimony trioxide is used as a white pigment in certain applications, such as in paints and ceramics.
4. Glass and Ceramic Industry: It is used as a fining agent and opacifier in the glass and ceramic manufacturing processes.
5. Electrical and Electronic Applications: Antimony trioxide is used as a flame-retardant additive in electrical and electronic products to improve their fire safety.

Antimony trioxide is generally considered safe when used in its intended applications. However, it is important to handle it with care, especially during processing, to prevent potential exposure to fine particles.

As a flame retardant and synergist, antimony trioxide plays a critical role in enhancing the fire resistance of various materials. It is widely used in industries to improve the fire safety of consumer products and industrial materials.