Widely used as a flame retardant synergist, especially in combination with halogenated compounds. It enhances the fire resistance of plastics, textiles, rubber, and coatings by promoting char formation and reducing flammable gas release during combustion. Commonly found in electrical appliances, construction materials, and automotive components for improved fire safety. Also utilized in the production of colored glasses and ceramics as a fining agent to remove bubbles and improve clarity. Plays a role in certain catalyst systems for the manufacture of polyester and other polymers.