\Phthal"i*mide\, n. [Phthalic + imide.] (Chem.)
An imido derivative of phthalic acid, obtained as a white
crystalline substance, {C6H4.(CO)2NH}, which has itself (like
succinimide) acid properties, and forms a series of salts.
Cf. {Imido acid}, under {Imido}.