ˈthalik-, ˈthālik- noun
Etymology: phthalic International Scientific Vocabulary, short for naphthalic (in naphthalic acid )
: any of three isomeric dicarboxylic acids C 6 H 4 (COOH) 2 obtained by oxidation of various benzene derivatives:
a. : a crystalline acid made usually by hydration of phthalic anhydride that regenerates the anhydride on heating and is used chiefly in making esters, benzoic acid, dyes, and intermediates; ortho -benzene-dicarboxylic acid
b. : isophthalic acid
c. : terephthalic acid