CHEMICAL COMPOSITION OF GRAPES 445 



in figure 9, ripened more slowly than the Vinifera varieties. For 

 example, during a period of fifty days, the total solids increased only 

 4 per cent. It can not be said from the data at hand whether this 

 slow ripening is due to the conditions under which the grapes were 

 grown or to the variety. 



By reference to figures 1 and 2 it may be seen that the general 

 form of the ripening curves is the same for the first and for second 

 crop. In one case, the Malaga, the curves are almost identical for 

 the period common to both, i.e., from 10.6 Bal. to 26.3 Bal., showing 

 an equal rate of ripening. In the other, the Tokay, the curve of the 

 second crop, from 18.2 Bal. to 24.6 Bal., is much flatter than that of 

 the first, indicating a rate of ripening with the latter of about two 

 and a half times that of the former. This difference can be accounted 

 for by the cooler weather during the time the second crop Tokay was 

 ripening, which was about ten days later than in the case of the second 

 crop Malaga. The slower ripening is probably due both to the direct 

 effect of the cool weather and to the decreased activity of the leaves 

 at lower temperatures. 



(2) Changes in Total Acid, Cream of Tartar, and Free Acid. 

 Owing to the fact that the analyses were started in 1914 and 1915 

 after ripening had commenced, the curves for these years show a 

 decrease in acid throughout the period of the tests. In 1916, however, 

 a rise in total acid occurred during the growing stage, as shown by 

 a rise in the curve during the first thirty days of the experiment. 

 Although this rise is not very large, it is quite definite, and occurs 

 in all three varieties tested. The rise was most positive in the case 

 of the Muscat grape, and amounted to .67 per cent acid as tartaric. 

 From the point of maximum acidity, the total decreases slowly until the 

 period of rapid ripening sets in. The total acid then decreases very 

 rapidly for a time and more or less in proportion to the increase in 

 total solids and sugar. As the grapes near maturity, the rate of de- 

 crease of total acid becomes less and the total remains practically 

 constant after the grapes have reached maturity. 



The cream of tartar in general increases very slightly during the 

 periods of growth and ripening. 



The increase in total acid during the first stages of growth is due 

 to increase in the free acid. Since the cream of tartar remains almost 

 constant throughout the ripening period, the curve of the free acid 

 is practically parallel with that of the total acid. 



As the grapes approach maturity, the cream of tartar calculated as 



[1251 



