phthalic acid[t̸hal′ik, ft̸hal′-]
any of three isomeric acids, CH(COOH), esp. one (ortho-phthalic acid) obtained by oxidation of naphthalene or xylene and used in the manufacture of dyes, medicines, etc.
Origin of phthalic acid(na)phthal(ene) + -ic
The colorless crystalline ortho-isomer of benzene dicarboxylic acid, C8H6O2, used in the synthesis of dyes, perfumes, and other organic compounds.