18 FRUITS AND FRUIT PRODUCTS. 



Where occasional determinations of alcohol are made it is found 

 convenient to use an alembic saleron. This apparatus is made of 

 copper and can be readily taken apart and placed in a small box. No 

 rubber connections are necessary, so that the setting up requires only 

 a few minutes. 



POLARIZATION. 



Dissolve half the normal weight of jelly or other fruit product, or 

 the normal weight of juices or fresh fruits, in a sufficient quantity of 

 water in a 100 cc sugar flask, add an excess of lead subacetate a (from 

 5 to 10 cc), make up to 100 cc, filter, and polarize in a 200 mm tube, 

 observing- the temperature of the solution. Invert 50 cc of this solu- 

 tion, using 5 cc of hydrochloric acid by heating to 68 in fifteen 

 minutes. Polarize in a 220 mm tube at the same temperature as was 

 employed in making the direct reading. 



On account of the large amounts of invert sugar usually found in 

 these products, it is necessary that the direct and invert readings 

 should be made at the same temperature. 



DETERMINATION OF CANE SUGAR. 



BY CALCULATION FROM CLERGET's FORMULA. 



The cane-sugar results given in this bulletin were calculated from 

 the direct and the invert readings according to Clerget's formula: 



_(a-b) 100 

 



This method is as accurate as any for the examination of glucose 

 goods. In the absence of glucose much greater accuracy may be 

 secured by using a modified formula, which will correct for the change 

 in optical power of the invert sugar present at the time of the direct 

 polarization, caused by the addition of hydrochloric acid used in mak- 

 ing the inversion. This formula, which is based on the effect of hydro- 

 chloric acid on solutions of invert sugar containing citric acid and on 

 solutions containing no acid at all, is as follows: 



S - ~ ~ - 100 



141.79 -4- 



2 



S = cane sugar. 

 A = direct reading at t. 

 B = invert reading at t. 

 t = temperature. 



a 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. 



