38 6 FOOD AND FOOD ADULTERANTS. 



sufficient for the precipitation of 0.05 per cent, of tannin. (New wines are deprived 

 of the carbonic acid held in solution by repeated shaking.) 



Sugar. The sugar should be determined after the addition of carbonate of soda by 

 means of Fehliug's solution, using dilute solutions, and, in wines rich in sugar (;. e. 

 wines containing over .5 gram in lOOcc.), with observance of Soxhlet's modifications, 

 and calculated as grape sugar. Highly colored wines are to be decolorized with ani- 

 mal charcoal if their content of sugar is low, and with acetate of lead and sodium 

 carbonate if it is high. 



If the polarization indicates the presence of cane sugar (compare under polarization) 

 the estimation is to be repeated in the manner indicated after the inversion (heating 

 with hydrochloric acid) of the solution. From the difference the cane sugar can be 

 calculated. 



Polarization. (1) With white wines: GOcc. of wine are treated with 3cc. acetate of 

 lead solution in a graduated cylinder, and the precipitate filtered off. To 30cc. of the 

 filtrate is added 1.5cc. of a saturated solution of sodic carbonate, filtered again, and 

 the filtrate polarized. This gives a dilution of 10: 11 which must be allowed for. 



(2) With red wines: GOcc. wines are treated with 6cc. acetate of lead, and to 30cc. 

 of the filtrate 3cc. of the saturated solution of sodic carbonate added, filtered again, 

 and polarized. In this way a dilution of 5:6 is obtained. 



The above conditions are so arranged (with white and red wines) that the last fil- 

 trate suffices to fill the 220mm. tube of the Wild polaristrobometer of which the ca- 

 pacity is about 28cc. 



In place of the acetate of lead very small quantities of animal charcoal can be used. 

 In this case an addition of sodic carbonate is not necessary, nor is the volume of the 

 wine altered. If a portion of the undiluted wine 220mm. long shows a higher 

 right-handed rotation than 0.3, Wild, the following procedure is necessary . 



Two hundred and ten cubic centimeters of the wine are evaporated on the water 

 bath to a thin sirup, after the addition of a few drops of a 20 per cent, solution of 

 acetate of potash. To the residue is added gradually, with continual stirring, 200cc. 

 of 90 per cent, alcohol. The alcoholic solution, when perfectly clear, is poured on" or 

 filtered into a flask, and the alcohol distilled or evaporated off down to about 5cc. 

 The residue is treated with about 15cc. water and a little boue black, filtered into 

 a graduated cylinder, and washed with water until the filtrate measures 30cc. If 

 this shows on polarization a rotation of more than +0.5, Wild, the wine contains 

 the nufermentable matter of commercial potato sugar (amyliu). If iu the estimation 

 of the sugar by Fehliug's solution more than 0.3 grams sugar iu lOOcc. was found, 

 the original right-rotation caused by the amylin maybe diminished by the h-ft-rotat- 

 iug sugar ; the above precipitation with alcohol is in this case to be undertaken, even 

 when the right-rotation is less than 0.3, Wild. The sugar is, however, first fermented 

 by the addition of pure yeast. With very considerable content in ( Fehling's solution ) 

 reducing sugar and proportionally small left-rotation, the diminishingof the left-rota- 

 tion may be brought about by cane sugar or dextrin or amylin. For the detection 

 of the first the wine js inverted by heating with hydrochloric acid (to 50cc. wine, 5cc. 

 dilute hydrochloric acid of specific gravity 1.10), and again polarized. If the left- 

 rotation has increased, the presence of cane sugar is demonstrated. The presence of 

 dextrin is shown as given in the section on " gum." In case cane sugar is present 

 well washed yeast, as pure as possible, should be added, and the wine polari/ed after 

 fermentation is complete. The conclusions are then I he s.-ime as with the wines poor 

 in sugar. 



For polarization only large, exact instruments are to be used. 



The rotation is to be calculated in degrees Wild according to Landolt (Zeitschr. 

 f. analyt. Chernie, 7. 9): 



1 Wild = 4.6043 Soleil. 

 1 Si.lnl =0.217189 Wild. 

 1 Wild = 2.89005 Vcnt/ke. 

 lVentzke = (>.:; liiulf, Wild. 



