Webster’s Revised Unabridged Dictionary · 1913
Fraxin
Frax′in (frăks′ĭn), n. [From Fraxinus.] (Chem.) A colorless crystalline substance, regarded as a glucoside, and found in the bark of the ash (Fraxinus) and along with esculin in the bark of the horse-chestnut. It shows a delicate fluorescence in alkaline solutions; — called also paviin.