SUGAR AND ACID IN GRAPES DURING RIPENING. 27 



In Tabic 6 it will bo seen that the water-extract sample was used 

 for a partial ash analysis as well as for the organic work. The pur- 

 pose in view was to ascertain whether the thorough extraction in 

 boiling water to which the fruit was subjected would yield an ash 

 which gave alkalinities like or different from the whole fruit when 

 burned. Several analyses were made to ascertain the comparative 

 content of phosphoric acid in the extract and in the whole fruit. 

 The results differ so widely, both for alkalinities and phosphoric acid, 

 that they do not support each other; that is, if the organic salts were 

 calculated from the alkalinities of the whole fruit ashed, this would 

 give results differing so widely as to be impossible of explanation, 

 thus raising the question of correct methods of treating the sample. 

 From careful checks made of our methods, however, by use of syn- 

 thetic solutions the authors are convinced of the reliability of the 

 results given by the water-extraction sample. It is possible that 

 in ashing the whole fruit it was heated in such manner as to lose a 

 portion of the alkali carbonates. The discrepancy is more marked 

 as the fruit matures. 



The fact that the attempt to determine chlorin in the water- 

 extract sample gave results entirely too high has been noted in 

 another section. The results for chlorin in the ashed samples are 

 reasonably constant and have an important bearing on the occurrence 

 of this element in supposedly sophisticated grape products, which 

 will be discussed in a report on the experimental wines. 



The results for potassium, sodium, calcium, and magnesium oxids 

 are presented simply as data on the ash composition of pure and 

 adulterated grape products, the application of which must await 

 further investigation. 



COMPARISON OF RESULTS ON JUICE AND WHOLE-FRUIT SAMPLES. 



The results for the organic elements and the acid salts in the whole 

 fruit samples are more readily compared from Table 7. 



The figures given in this table are percentage results for weighed 

 samples of whole fruit and percentage results for the 1912 juice 

 samples calculated from Table 1. It will be noted that the results 

 for sugar as a soluble constituent are noticeably less on the whole 

 fruit samples. This is explained by the fact that the seeds, skins, 

 and woody fiber of the fruit is a part of the whole-fruit sample, and 

 results in lowering the percentage content of sugar because the juice 

 extracted by pressure always carries a greater percentage of sugar 

 than is found in the residue left as marc or pomace. 



