[C.I. 46005]. 3,6-bis(dimethylamino)acridine hydrochloride; a basic fluorescent dye useful as a metachromatic stain for nucleic acids; also used in screening cervical smears for abnormal and malignant cells, where unusual amounts of DNA and RNA occur during proliferation and in tumors (DNA fluoresces yellow to green; RNA fluoresces orange to red). Syn: tetramethyl acridine.