The recent extensive therapeutic use of cocain has naturally aroused great interest with regard to its chemical constitution. As is well known, when heated with dilute mineral acids, it takes up two molecules of water, and becomes decomposed into benzoic acid, methyl alcohol, and another alkaloid ecgonin. When cocain, however, is simply heated in watery solution for some hours, a less complete decomposition ensues, the solution depositing on evaporation a crystalline substance, which is benzoylecgonin.