Source : Webster's Revised Unabridged Dictionary (1913)

Phthalimide \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}.