[¦tü ¦fȯr dī¦nī·trō‚fen·əl′hī·drə‚zēn] (organic chemistry) (NO2)2C6H3-NHNH2 A red, crystalline powder with a melting point of approximately 200°C; soluble in dilute inorganic acids; used as a reagent for determination of ketones and aldehydes.AcronymsSeeDNPH