Euchroic \Eu*chro"ic\, a. [Gr. ? well-colored; ? well + ? color.] (Chem.) Having a fine color. {Euchroic acid} (Chem.), an organic, imide acid, obtained as a colorless crystalline substance, {C12H4N2O8} by heating an ammonium salt of mellitic acid. By reduction it is changed to a dark blue substance (euchrone), -- hence its name.