8 BULLETIN 335,, U. S- DEPARTMENT OF AGRICULTURE. 
methods have been carefully checked in this laboratory and at the 
Bureau of Chemistry and found to give more reliable results than 
the methods given in Bureau of Chemistry Bulletin 107, Revised. 
For the items reported as " Fixed acid other than tartaric," the fol- 
lowing formula was used: Total acid as tartaric — [(total alkalinity 
X 0.0075) +free tartaric acid] = fixed acid other than tartaric expressed 
as tartaric. This result is practically the same as the "Sauerrest" 
of the German chemists. 1 
This formula gives those acids present other than tartaric, but as 
it is known that almost the total quantity of these acids in the grape 
consists of malic acid, 2 the result may be interpreted as this acid for 
the considerations involved in this report. To actually convert this 
result to malic acid, multiply the figures given in the table by 0.8934. 
It was not possible, with the conditions under which this work was 
done, to determine the minute quantities of other acids present, such 
as succinic and glycolic acids. 
The total acid percentage is practically the same in the green fruit of 
Concord in both juice and whole-fruit samples, and this relation con- 
tinues so nearly throughout the entire period that either result may 
be taken as fairly expressing the content. The total acid is decid- 
edly higher in the juice sample of green Catawba than in the whole 
fruit for the first three samples taken; then the acid content of both 
samples becomes about what may be expected of check samples. 
The results for total tartaric acid in the juice and whole fruit are 
not so uniform as for total acid. Yet for the Concord samples, both 
at Sandusky and Charlottesville, there is a degree of uniformity 
which is striking, considering the difficulty of sampling which has 
been mentioned. The Catawba samples show much difference in 
the green fruit, but the later samples approach uniformity. 
There is a striking dissimilarity in the percentage of tartaric acid 
for the Concord samples at Sandusky and Charlottesville through- 
out the period of investigation. Those taken at Sandusky show 
much less variation than the Charlottesville samples and the former 
show approximately the same amount at the close of the season as 
for the partly colored samples first taken, while the Charlottesville 
samples show a very marked decline in tartaric acid for both the 
juice and fruit samples. Further investigation of this point is neces- 
sary before offering any critical discussion. 
It would appear that the crushed fruit invariably yields decidedly 
the greater part of the free tartaric acid content when pressed. The 
rapid diminution of the percentage of this acid as the fruit ripens is 
shown for both the juice and fruit samples. These results support 
i Babo and Mach, Kellenvirtschaft, 4th ed., 1910, 2: 629. 
2 Babo and Mach, Weinbau and Kellerwirtschaft. loc. cit. 
