362 



ORGANIC CHEMISTRY. 



leaves the sugar to form a pure and crystallizable syrup. 

 Another method of increasing the product of sugar has 

 been described in the section on sulphurous acid. 



How is alcohol 



produced from 



ALCOHOL. 

 912. PRODUCTION FROM SUGAR. By 



i - 



the addition of brewers' yeast or some si- 

 milar ferment to sugar, it is gradually con- 

 verted into alcohol. Two molecules of water are sepa- 

 rated in the process. One-third of the carbon and two- 

 thirds of the oxygen which remain, pass off as carbonic 

 acid gas, while alcohol remains. The yeast enters into 

 no combination, and furnishes no material in the pro- 

 cess. It acts merely by its presence to effect the de- 

 composition, as will be hereafter explained. 

 Explain the 913. In this process of conversion, each 



diagram. molecule of sugar makes two of alcohol, and 

 four of the acid. The figure repre- 

 sents a molecule of grape sugar, after 

 the removal of two molecules of 

 water. An arbitrary arrangement is 

 given to the atoms for convenience 

 of illustration. On striking off 

 enough carbon and oxygen from the 

 corners to make the required amount 

 of carbonic acid, the residue may be supposed to fall 

 apart into two molecules of alcohol. Alcohol is also 

 produced from cane sugar by fermentation. The first 

 stage in the process is its conversion, by yeast, into 



