1,3-Isobenzofurandione, 5,5'-carbonylbis- 2421-28-5 3,3',4,4'-Benzophenonetetracarboxylic acid dianhydride 3,3',4,4'-Benzophenonetetracarboxylic dianhydride 3,3',4,4'-Tetracarboxybenzophenone dianhydride 4,4'-Carbonylbis(phthalic anhydride) 4,4'-Carbonyldiphthalic anhydride 4,4'-Diphthalic anhydride ketone Benzophenonetetracarboxylic acid anhydride Benzophenonetetracarboxylic acid dianhydride Benzophenonetetracarboxylic anhydride Benzophenonetetracarboxylic dianhydride NSC78480 Phthalic anhydride, 4,4'-carbonyldi-