304 FERMENTATION OF BEER. 



Hence a certain part of the sugar will not be 

 converted into carbonic acid and alcohol, but will 

 yield other products containing less oxygen than 

 sugar itself contains. These products, as has 

 already been mentioned, are the cause of the great 

 difference in the qualities of fermented liquids, 

 and particularly in the quantity of alcohol which 

 they contain. 



Must and wort do not, therefore, in ordinary fer- 

 mentation, yield alcohol in proportion to the quan- 

 tity of sugar which they hold in solution, a part of the 

 sugar being employed in the conversion of gluten 

 into ferment, and not in the formation of alcohol. 

 But in the fermentation of Bavarian beer all the 

 sugar is expended in the production of alcohol ; 

 and this is especially the case whenever the trans- 

 formation of the sugar is not accompanied by the 

 formation of yeast. 



It is quite certain that in the distilleries of 

 brandy from potatoes, where no yeast is formed, or 

 only a quantity corresponding to the malt which 

 has been added, the proportion of alcohol and car- 

 bonic acid obtained during the fermentation of the 

 mash corresponds exactly to that of the carbon 

 contained in the starch. It is also known that the 

 volume of carbonic acid evolved during the fermen- 

 tation of beet-roots gives no exact indication of the 

 proportion of sugar contained in them, for less 

 carbonic acid is obtained than the same quantity of 

 pure sugar would yield. 



