Antimony trioxide (ATO) is used in a wide variety of industrial applications, as a “synergist” with flame retardant chemicals, as a catalyst in the manufacture of polyester (PET), as a clarifying aid in glasses, additive in semi-conductors, as a coating used on certain grades of titanium dioxide pigments, as a component in the manufacturing of complex inorganic colored rutile pigments and, as an opacifier in cast iron bath and sinking enameling.