Antimony trioxide

Antimony trioxide is a solid white powder which sinks in water, slowly dissolving.

Antimony trioxide is produced by exposing molten antimony sulphide and/or pure antimony to air at 600-800ºC. 

Antimony trioxide is used mainly as a fire prevention additive and pigment (concentration: 1-13%). The substance comes in various grades, depending on particle size. The breakdown of particle size affects both physical properties and pigment property. The finer fraction is used for pigmentation.

 The flame-retardant property, however, is not affected by particle size. This property is based on antimony trioxide reacting in the event of a fire with the surrounding material, with the result that a protective layer of various antimony compounds covers the combustible materials. Since the formation of these compounds consumes heat and because they are generally difficult to ignite, they protect the underlying material from ignition. The presence of thermally unstable halogen compounds accelerates the protective impact of antimony. Antimony trioxide is therefore nearly always used together with high-halogenated organic compounds such as chloroparaffins.

Antimony trioxide is used as a fire prevention additive in a number and variety of materials, e.g. polystyrene (present, for example, in the casings of computer display screens), in fire-retardant paint for application to wood, and in PVC plastic in cables.

Another use for antimony trioxide is as a trace element additive to phosphorescent light sources such as fluorescent tubes and TV/computer screens. Antimony reinforces the photogenic capacity of phosphorus. 

In glass manufacturing, antimony trioxide is used instead of arsenic as a plaining agent. When the paraison of glass is heated, antimony trioxide is gasified, whereupon bubbles of gas are formed which serve to create a remixture of the molten glass and also to trap other substances in the gas bubbles formed and to remove them from the glass.