Phthalic Anhydride is a principal commercial form of phthalic acid. It was the first anhydride of a dicarboxylic acid to be used commercially. This white solid is an important industrial chemical, especially for the large-scale production of plasticizers for plastics. Widely used in the production of plasticizers and pigments, and also as an anti-scorching agent, and as a light- and heat-stabilizer of polyolefins. Phthalic Anhydride is a monomer for synthetic resins such as glyptal, the alkyd resins, and the polyester resins intended for contact with food.