56 COMPOSITION OF AMERICAN WINES. 



add about 10 drops of a neutral litmus solution and titrate with deci- 

 normal sodium hydroxid solution. With red wines, add decinormal 

 sodium hydroxid solution until the red color changes to violet. Con- 

 tinue adding a few drops at a time until a drop of the mixture placed 

 on delicate red litmus paper shows an alkaline reaction. The result 

 is expressed in terms of tartaric acid. 



Practically identical results may be obtained by diluting 10 cc of 

 wine with about 400 cc of boiling water and titrating with decinormal 

 sodium hydroxid, using phenol phthalein as indicator. 



One cc of decinormal sodium hydroxid solution = 0. 03 gram tartaric 

 acid per 100 cc (0.075 gram when 10 cc wine are employed). 



ESTIMATION OF VOLATILE ACIDS. 



Fifty cc of wine, to which a little tannin has been added to prevent 

 foaming, are distilled in a current of steam. The flask is heated until 

 the liquid boils, when the lamp under it is turned down, and the steam 

 passed through until 200 cc have been collected in the receiver. The 

 distillate is titrated with decinormal sodium hydroxid solution, using 

 phenol phthalein as indicator, and the result expressed as acetic acid. 



One cc of decinormal sodium hydroxid solution = 0.012 gram acetic 

 acid per 100 cc. 



ESTIMATION OF FIXED ACIDS. 



The amount of fixed acids is ascertained by subtracting 1.25 times 

 the volatile acids from the total acids. 



ESTIMATION OF UNDETERMINED EXTRACT. 



The amount of undetermined extract is ascertained by subtracting 

 the sum of the glycerol, ash, and fixed acids from the weight of the 

 sugar-free extract. 



ESTIMATION OF SUGAR. 



One hundred and sixty cc of wine are transferred to a porcelain dish, 

 exactly neutralized with an approximately normal solution of sodium 

 hydroxid, using litmus paper as an indicator, and evaporated to about 

 one-fourth of the original volume. It is again made up to the volume 

 of 160 cc, 16 cc of basic lead acetate 1 added, shaken and filtered. 



To 88 cc of the filtrate are added 8 cc of a saturated solution of 

 sodium sulphate, the flask is well shaken and the contents are filtered. 

 Part of the filtrate is polarized in a 200 mm tube, in a Schmidt and 

 Haensch polariscope, arid the reading increased by one-fifth for the 

 polariscope reading. 



1 Prepared by boiling for half an hour 430 grams of normal lead acetate, 130 grams 

 of litharge, and 1,000 cc of water. The mixture is allowed to cool and settle, when 

 the supernatant liquid is diluted to 1.25 specific gravity with recently boiled water. 



