Mannitol (C 6 H 14 O 6 ) is the most common of the naturally occurring hexahydric alcohols. It is a curious fact that while glucose is the most commonly occurring hexose, the corresponding alcohol, sorbitol, is of relatively uncommon occurrence, while mannose and fructose, which are structurally related to mannitol, are not of such common occurrence as glucose. Mannitol is a common constituent of many plants, but occurs principally in the curious plant exudation known as “ manna,” and is at present produced technically by two methods, both of which are open to obvious disadvantages. (a) From “manna” (b) By the bacterial fermentation of fructose.