The Collaborative International Dictionary
phthalic
Naphthalic \Naph*tha"lic\, a. (Chem.)
Pertaining to, derived from, or related to, naphthalene; -- formerly used to denote any one of a series of acids derived from naphthalene, and called naphthalene acids, now specifically referring to 1,8-naphthalenedicaboxylic acid, C12H8O4.
Formerly, designating an acid probably identical with phthalic acid.
Wiktionary
phthalic
a. (context chemistry English) of, relating to, or derived from naphthalene or phthalic acid