FERMENTED AND DISTILLED LIQUORS. 85 



conveniently employed for this purpose. Fill a flask graduated at 50 and 55 cc to 

 the 50-cc mark with the filtrate, add 5 cc of concentrated hydrochloric acid, invert; 

 polarize in a 220-mrn tube, and increase the reading one-tenth to allow for dilution. 



(3) After fermentat ion . 



In the case of wines polarizing between +2.3 and +0.9 the use of glucose in 

 their preparation can be proved or disproved after fermentation by the presence or 

 absence of certain unfermentable constituents. 



Dealcoholize 200 cc of wine by evaporating to about one-fourth its volume, and 

 add enough water to the residue to make its sugar content less than 15 per cent. 

 For the purpose of this operation the sugar content of the wine may be assumed to 

 be 2 per cent less than the extract. Add 2 or 3 grams of compressed yeast, let stand 

 at about 25 C. for four or five days, when fermentation will be complete. 



Evaporate the fermented liquid in a porcelain dish to a thin sirup after the addi- 

 tion of a little sand and a few drops of a 20 per cent solution of potassium acetate. 

 To the residue add 200 cc of 90 per cent alcohol with constant stirring. Separate the 

 alcoholic solution by filtration and evaporate until about 5 cc remain. Mix the 

 residue with washed boneblack, filter into a graduated cylinder, and wash until the 

 filtrate (cooled to 15 C. ) amounts to 30 cc. When the filtrate shows a dextrorota- 

 tion of more than 1.5 it indicates the presence of the unfermentable constituents of 

 commercial glucose. Results by this method are not reliable with wines that are 

 heavily preserved. 



(c) REDUCING SUGARS. 



Dilute a portion of the solution prepared as directed under (a) until it does not 

 contain more than 1 per ceftt of sugar. In making this dilution the sugar-free 

 extract of a wine may be taken as 2 per cent. The number of volumes of water to 

 be added to the filtrate is thus determined by deducting 2 from the total extract. 

 If the wine is not to be polarized, or for any reason a separate portion is to be pre- 

 pared for the reduction, the dilution may be conveniently made prior to the clarifi- 

 cation. Use Allihn's method, expressing the results as dextrose (see p. 49). 



(d) CANE SUGAR. 



( 1 ) By reduction. 



Invert a portion of the filtrate obtained in (a) as directed under (b) (2) ; determine 

 reducing sugars according to (c) ; deduct from the figure thus obtained the reducing 

 sugars originally present, and multiply the result by 0.95 for conversion into cane 

 sugar. 



(2) By polarization. 



Calculate from the direct and invert polarizations by the Clerget formula: 

 Per cent sucrose 



144- - 



(e) COMMERCIAL GLUCOSE.* 



(1) Wine with not more than 0.1 per cent of reducing sugar, and which polarizes 

 to the left or not more than 0.9 to the right, has not been treated with glucose. 



(2) Wine with not more than 0.1 per cent of reducing sugar, and which polarizes 

 0.9 or more to the right, may contain dextrin and the unfermentable constituents 

 of commercial glucose. In such a case, examine according to 10 (3) and 11. 



(3) If the reducing sugar exceeds 0.1 per cent, examine according to 10 (3) for the 

 unfermentable constituents of commercial glucose. 



Borgmann, Analyse des Weines, 2d ed., p. 77. 



