Tetrachlorophthalic anhydride, chemical formula C?Cl?O?, CAS number 117-08-8, is a white crystalline or colorless prismatic needle-like crystal with a melting point of 254-256℃, a boiling point of 371℃, a vapor pressure of 0.16 mmHg (145℃), and a solubility of 0.8 mg/L at 21℃. It is soluble in dioxane, sparingly soluble in ether, and decomposes in hot water to tetrachlorophthalic acid.

Tetrachlorophthalic anhydride is mainly used as a flame retardant for polyesters and epoxy resins, and can also be used as a synthetic intermediate for the pesticide thiocyanate, phthalocyanine pigments, and thallium-based dyes. In organic synthesis, tetrachlorophthalic anhydride reacts with 1,1-bis[4-(N,N-disubstituted amino)phenyl]ethylene in acetic anhydride solution to produce 3,3-bis{2,2-bis[4-(N,N-disubstituted amino)phenyl]vinyl}-4,5,6,7-tetrachloro-2-benzo[c]furanone, with a yield of 89%–93%. Product packaging includes 25kg and 40kg paper-plastic composite bags and 750kg bulk bags.