SUGAR AND ACID IN GRAPES DURING RIPENING. 9 



our previous determinations and show that the Concord juice loses 

 free tartaric acid more completely than the Catawba. 



The results for cream of tartar show that in every instance save 

 one the juice sample carries a smaller percentage of cream of tartar 

 than the whole fruit. The one exception, No. 3588, is affected by 

 an evident error and is excluded from consideration. The excess, in 

 per cent, of cream of tartar in the whole fruit is sufficient to support 

 a previous statement that this substance exists as crystals and that 

 some of these are retained in the pulp when the fruit is pressed. 



The constant increase of cream of tartar both in the juice and fruit 

 samples follows naturally from the disappearance of free tartaric 

 acid. The results for 1912 are in this respect more logical than those 

 for 1911. 



The data given under fixed acids other than tartaric are considered 

 by the authors to be remarkably interesting. It is shown that the 

 total content of tartaric acid remains nearly constant, especially 

 when the whole fruit samples are compared, but these other acids, 

 which we have considered as mostly malic, show such a steady aad 

 sharp decline that one is forced to accept conclusions derived from 

 the data given in Table 5. The reduction in the percentage of acid 

 under this head reaches two-thirds to three-fourths of the entire 

 amount given for the first samples taken. 



ANALYTICAL RESULTS ON THE JUICE SAMPLES. 



CROP OF 1911. 



. In Table 1 the condition of the fruit on the vines at the time of 

 sampling and the results of the analyses of samples both at the 

 Sandusky and Charlottesville laboratories are given in detail. The 

 period covered by the analyses at Sandusky was carried beyond the 

 wine-ripe condition, except in the case of the Norton, which was 

 destroyed by the berry moth * before it was fully ripe. This con- 

 tinuation of the analyses was for the purpose of following the changes 

 that occur in the fruit even to the natural destruction of the crop. 

 The high temperature of the fall season at Charlottesville is not 

 favorable to holding samples at that point after they are fully ripe, 

 hence the data for that locality cover only the period to full maturity. 



1 Polychrosis viteana Clemens. 

 12253°— Bull. 335— 16 2 



