What is "phthalic acid"

Phthalic \Phthal"ic\, a. [Naphthalene + -ic.] (Chem.) Pertaining to, or designating, a dibasic acid obtained by the oxidation of naphthalene and allied substances.

Phthalic acid (Chem.), a white crystalline substance, C6H4.(CO2H)2, analogous to benzoic acid, and employed in the brilliant dyestuffs called the phthaleins.

n. (context organic compound English) Any of three isomeric aromatic organic dicarboxylic acids, C₆H₄(COOH)₂; especially the ortho- isomer manufactured from naphthalene, used in the synthesis of dyes, perfumes and other compounds.

n. a colorless acid used to make dyes and perfumes

Phthalic acid is an aromatic dicarboxylic acid, with formula CH(COH). It is an isomer of isophthalic acid and terephthalic acid. Although phthalic acid is of modest commercial importance, the closely related derivative phthalic anhydride is a commodity chemical produced on a large scale.