phthalic acid

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A colorless crystalline organic acid, C₆H₄(COOH)₂, prepared from naphthalene and used in the synthesis of dyes, perfumes, and other organic compounds.

Wiktionary

1. n. organic chemistry 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.

GNU Webster's 1913

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

WordNet 3.0

1. n. a colorless acid used to make dyes and perfumes