dye obtained from coal tar, introduced as an antiseptic in 1912 by the German medical-research worker Paul Ehrlich and used extensively in World War I to kill the parasites that cause sleeping sickness. The hydrochloride and the less irritating base, neutral acriflavine, both are odourless, reddish-brown powders used in dilute aqueous solutions primarily as topical antiseptics or given orally as urinary antiseptics. Once used in the treatment of gonorrhea, acriflavine has been replaced by the antibiotics.