26 BULLETIN 656, U. S. DEPARTMENT OE 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 nialic acid of a grape juice, figured 
approximately from the acidity of the juice, free tartaric acid, and 
the total alkalinities 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. 
