20 BULLETIN 656, U. S. DEPARTMENT OF AGRICULTURE. 



SUMMARY. 



Generally speaking, a Concord grape juice properly prepared con- 

 tains small amounts of alcohol. The juice contains more than 0.4 

 per cent by volume only when too much time has been allowed for 

 the pressing period. A pure Concord grape juice has not been found 

 to contain sucrose. The polarization of the inverted solution at 

 87° C. is levorotatory. The free malic acid of a grape juice, figured 

 approximately from the acidity of the juice, free tartaric acid, and 

 the total alkaiinities of the ash, 1 amounts on an average to about 

 0.5 gram per 100 cubic centimeters. The Concord grape juices ex- 

 amined contained free tartaric acid. The cream of tartar of a Concord 

 grape juice amounts to about 0.54 gram per 100 cubic centimeters, 

 ranging between 0.36 and 0.79 grams. 



i U. S. Dept. Agr., Bur. Chem. Bui. 162: 75. 



