EXAMINATION OF WINE. 57 



For reducing sugar, 25 cc of the filtrate are reduced according to 

 Allihu's method for the determination of dextrose. The reagents em- 

 ployed in this method are: 



34.639 grams of CuSO 4 .5H 2 O, dissolved in water and diluted to 500 cc. 



1 73 grams of Rochelle salt ~i , 



io~ , . -. , . , > dissolved in water and diluted to 500 cc. 



12o grams of potassium hydroxid J 



Place 30 cc of the copper solution, 30 cc of the alkaline tartrate 

 solution, and 60 cc of water in a beaker, and heat to boiling. Add 

 25 cc of the filtrate mentioned above and boil for two minutes. Filter 

 immediately through a Gooch crucible and wash with hot water. The 

 crucible and precipitate are dried and ignited to bright redness in the 

 absence of reducing gases. The weight of black oxid is multiplied 

 by 0.799 for the weight of copper, and the corresponding amount of 

 reducing sugar (calculated as dextrose) is determined by Table IV. 

 The weight of sugar thus obtained, expressed in grams, multiplied by 

 4.8 gives grams reducing sugar per 100 cc. 



If the filtrate is found to contain more than 1 per cent of reducing 

 sugar (0.571 grams of CuO per 100 cc), more accurate results may be 

 obtained by treating the first determination as approximate, and repeat- 

 ing the determination with such an amount of the filtrate as, diluted 

 to 25 cc, will contain less than 1 per cent of reducing sugar. 



ESTIMATION OF SODIUM CHLORID. 



Sodium chlorid is obtained b} r dissolving the ash in water, slightly 

 acidifying with nitric acid, neutralizing with calcium carbonate, 

 and titrating with silver nitrate, using normal potassium chromate as 

 indicator. 



ESTIMATION OF POTASSIUM SULPHATE. 



The sulphuric acid is precipitated directly, in 50 cc of wine, by 

 means of barium chlorid, and the resulting barium sulphate determined 

 by the ordinary method. The result is expressed in grams of potas- 

 sium sulphate per 100 cc. In all cases this determination should be 

 made in the original wine, as results obtained with the ash are always 

 low. 



ESTIMATION OF SULPHUROUS ACID. 



One hundred cc of the wine are distilled in a current of carbon 

 dioxid, after the addition of 5 cc of a 20 per cent solution of glacial 

 phosphoric acid, until 50 cc have passed over. The distillate is col- 

 lected in a decinormal iodin solution in a flask closed with a stopper 

 perforated with two holes, through one of which the end of the con- 

 denser passes and through the other a U-tube containing a portion of 

 the standardized iodin solution. Twenty-five cc of n / 10 iodin solution 

 may be employed, diluted with water to give the desired volume. 



