52 COMPOSITION OF AMERICAN WINES. 



(2) The wine rotates to the right. 



This may be caused by unfermented cane sugar, commercial glucose, or both, 

 (a) THE WINE is INVERTED. 



(rtj) It rotates to the left after inversion. Unfermented cane sugar is 

 present. 



(a 2 ) It rotates more than 2.3 to the right. Commercial glucose or its unfer- 

 mentable constituents are present. 



( 3 ) It rotates less than 2.3 and more than 0.9 to the right. It is in this 

 case treated as follows: 



Two hundred and ten cc of the wine are evaporated to about one-third 

 its volume to remove the alcohol, cooled, diluted with water to the original 

 volume, and fermented after evaporating alcohol, with 1 or 2 grams of 

 pressed yeast. The fermented liquid is evaporated in a porcelain dish to a 

 thin sirup with a little sand and a few drops of a 20 per cent solution of 

 potassium acetate added. To the residue 200 cc of 90 per cent alcohol are 

 added, with constant stirring. The alcoholic solution is filtered into a 

 flask, and the alcohol removed by distillation until about 5 cc remain. 

 The residue is mixed with washed boneblack, filtered into a graduated 

 cylinder, and washed until the filtrate amounts to 30 cc. When the filtrate 

 shows a dextro rotation of more than 1.5 it indicates the presence of the 

 unfermentable constituents of commercial glucose. 



(3) The wine rotates to the left. 



It contains unfermented levorotatory sugar, derived either from the must or from 

 the inversion of added cane sugar. It may, however, also contain unfermented cane 

 sugar and the unfermentable constituents of commercial glucose. 

 (a) The wine is fermented. 



(%) It polarizes 3 after fermentation. It contains only levorotatory 

 sugar. 



(a 2 ) It rotates to the right. It contained both levorotatory sugar and the 

 unfermentable constituents of commercial dextrose. 

 (6) The wine is inverted. 



(6j) It is more strongly levorotatory after inversion. It contains both 

 levorotatory sugar and unfermented cane sugar. 



REDUCING SUGARS. 



Dry wines are supposed to be almost completely fermented, and 

 their content of reducing sugars should rarely exceed 0.1 gram per 

 100 cc. In many of the analyses given in this bulletin this quantity 

 is largely overreached, although with the perfection of methods of 

 fermentation the percentage of sugar in diy wines is reduced. 



The Municipal Laboratory of Paris calculates the sugar content of 

 the original must from which the wine was made. It has been deter- 

 mined that French musts never contain more than 32.5 grams of sugar 

 per 100 cc. If, therefore, the sum of the sugar and twice the alcohol 

 content of a wine, both expressed in grams per 100 cc, exceed 32.5 

 grams per 100 cc, it is held that French wines have received an addi- 

 tion of either sugar or alcohol. 



POTASSIUM SULPHATE. 



The quantity of sulphuric acid may be increased by sulphuring the 

 casks, by the addition of sodium sulphite as a bleaching agent and 



