326 VINEGAR, CIDER, AND FRUIT-WINES. 



a determined quantity of acid. To be sure the content of acid is 

 sometimes increased by fermentation, some succinic acid, as pre- 

 viously mentioned, being formed and perhaps also some acetic 

 acid ; sometimes, however, the content of acid decreases, which is 

 very likely partially due to the water used for the dilution of the 

 must containing earthy carbonates (lime, magnesia). It is, there- 

 fore, best not to have too much acid in the must, since, if the 

 finished wine should be lacking in acid, it can be readily reme- 

 died by a suitable addition of tartaric acid, which is, however, 

 not the case when it contains too much free acid. 



The determination of the sugar in must is less difficult and has 

 already been fully described on p. 197, hence there remains only 

 the question how much sugar has to be added to the must in 

 order to obtain a durable wine. 



Numerous analyses have shown that there is scarcely any 

 grape-wine which contains less than 7 per cent, by weight of 

 alcohol, while in more generous wines the content rises to 12 per 

 cent, and more. Fruit-wines in order to possess good keeping 

 properties should never show less than 7 per cent, by weight of 

 alcohol, but there is no reason why they should not contain as 

 much as 10 per cent. The advantage of the latter content is 

 evident, the wines being thereby almost absolutely protected from 

 spoiling while they improve in aroma and taste, the various kinds 

 of ether being only formed in wine rich in alcohol. 



The manner of calculating the quantity of sugar which has to 

 be added to the must to give the wine the desired content of 

 alcohol will be best shown by the following example : Suppose 

 135 liters of must which contains 4 per cent, of sugar are to be 

 changed into must with 15 per cent, of sugar. 



For this purpose deduct from the weight of the must (which 

 for the sake of simplicity we will consider equal to its volume) the 

 weight of the sugar contained therein, multiply by the difference 

 the per cent, of sugar the must is to contain, divide the product 

 by 100 less the per cent, of sugar and deduct from the quotient 

 the per cent, of sugar already present in the must. For instance : 

 135 liters of must with 4 per cent, of sugar are to be changed 

 into must with 15 per cent, of sugar. In 135 liters are contained 

 5.4 kilogrammes of sugar, 1355.4 = 129.6, which multiplied by 



