Phthalic anhydride, also known as o-phthalic anhydride, is abbreviated as PA in English. It appears as white flaky solid or powder, or white needle-like crystals, with a slight odor, specific gravity of 1.527 (4°C), melting point of 130.8°C, boiling point of 284.5°C, and is easily sublimable. It is slightly soluble in cold water, easily soluble in hot water and hydrolyzes to phthalic acid, and soluble in ethanol, benzene, and pyridine.

Phthalic anhydride is currently widely used in industrial sectors such as chemical industry, pharmaceuticals, electronics, agriculture, coatings, and fine chemicals. In China, phthalic anhydride is mainly used to produce o-xylene ester plasticizers, accounting for about 60% of the total consumption of phthalic anhydride, dyes and paints account for 25%, and unsaturated resins and other products account for about 15%. Phthalic anhydride is an important organic chemical raw material, mainly used in the production of plastic plasticizers, alkyd resins, dyes, unsaturated resins, as well as certain pharmaceuticals and pesticides.