CHAPTEE XV. 







GLUCIC ACID. 



THE experiments tried by Graham, Hoffmann, and 

 Eedwood, show that, besides carbonic acid and alcohol, 

 another substance is formed during the fermentation 

 of sugar which is no longer capable of fermenting, 

 and is compared by them to glucic acid.* By adding 

 1^, 2, and 3 per cent., by volume, of wet yeast, 

 to a solution of sugar, they obtained 4*4, 3'72, 3 f 7 per 

 cent, of this substance, and more might have been 

 procured, had a larger quantity of yeast been em- 

 ployed. By filtering and evaporating the liquid this 

 substance was obtained as a dark brown matter, of the 

 nature of extract, which had a bitter taste, and owing 

 to the lactic acid contained in it, was acid. More than 

 one substance was discovered in it, but no sugar, 

 although it was able to reduce oxide of copper to a 

 sub-oxide. 



Thenard has already recognised this substance, and 

 says, that when he allows sugar to ferment with a 

 large quantity of yeast, he always obtained 4 per cent, 

 of the sugar thus employed as an extractive matter. 



* Liebig u. Kopp, Jahresber, 1852, s. 801. 



