Source : Webster's Revised Unabridged Dictionary (1913)

Murexan \Mu*rex"an\, n. [From {Murexide}.] (Chem.)
   A complex nitrogenous substance obtained from murexide,
   alloxantin, and other ureids, as a white, or yellowish,
   crystalline which turns red on exposure to the air; -- called
   also {uramil}, {dialuramide}, and formerly {purpuric acid}.