Salicin is a substance belonging to the group of compounds known as glucosides, which is found chiefly in the bark of various species of willow and poplar. It may be extracted from this source by means of water, and by crystallisation is obtained as bright colourless prisms which melt at 198°. It possesses a very bitter taste, and by the action of acids or certain natural ferments - e.g. emulsin - it splits up into glucose and salicylic alcohol. C13H18O7 + OH2 = C7H8O2 + C6H12O6.