FERMENTATION. 383 



whisky. Besides the general wine flavor given by the oenanthic ether, 

 there are other flavors imparted by other substances giving to the various 

 wines individual characteristics. 



541. Acidity of "Wines. The acidity of grape wines is owing to the 

 presence of tartaric acid in combination with potassium, forming the acid 

 tartrate of potassium, or cream of tartar. As this gradually separates from 

 the wine, and collects as a crust on the sides of the casks and bottles, the 

 longer wines are kept the less acid they become, and hence in part the val- 

 ue which age gives to them. The acid which is present in small amount 

 in malt beer is acetic acid, the acid of vinegar ; and that which we have in 

 cider is lactic acid, the acid which is present in soiir milk ; so that wine, 

 malt beer, and cider each has a different acid. When, however, the fer- 

 mentation goes in either of these beyond the production of alcohol, acetic 

 acid results, for then we have the acetous fermentation. 



542. Amount of Alcohol in Wines. The proportion of alcohol 

 varies very much in different wines. Even in the strongest wines more 

 than three fourths of the liquid is water. The proportion, by measure, of 

 alcohol in the most prominent wines is as follows : 



Per Cent. 



Port 21 to 23 



Sherry 15 to 25 



Madeira 18 to 22 



Marsala 14 to 21 



Malmsey 16 



Per Cent . 



Tokay 9 



Khenish 8 to 13 



Moselle 8 to 9 



Champagne 5 to 15 



Burgundy 7 to 13 



Claret 9 to 15 



543. Production of Alcohol from Starchy Substances. In 

 the production of alcoholic liquors from barley, rye, pota- 

 toes, etc., in which starch is the chief ingredient, and sugar 

 is only present in very small amount, a preliminary process 

 is necessary in order to change the starch into sugar. In 

 making beer from barley this is done in the following man- 

 ner : The grain is first moistened in heaps, and spread upon 

 a floor in a dark room. It sprouts, and in doing this some 

 of the starch in it is turned into sugar by the action of the 

 diastase ( 472), so that the barley has quite a sweet taste. 

 The process is arrested by drying in the kiln just as the 

 germs are about to burst from the seed, for if it be left to 



