phthalic anhydrideDefinition of phthalic anhydride noun [mass noun] Chemistry a crystalline compound made by oxidizing naphthalene, used as an intermediate in the manufacture of plastics, resins, and dyes. A bicyclic anhydride; chemical formula: C6H4(CO)2O Origin: mid 19th century: phthalic, shortening of naphthalic (see naphthalene)phthalic anhydride in other Oxford dictionaries Definition of phthalic anhydride in the US English dictionary
