Scheme for the complete utilisation of phtalic anhydride (benzene 1,2 dicarboxylic) in dyestuff manufacture. Drawn by A H Davies in 1920 and modified by R Fraser Thomson in 1926. Phtalic anhydride is also used in the production of plasticizers, paints and polyester resins. It is prepared by air oxidation of napthalene in the presence of a catalyst such as vanadium oxide.
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