SUGAR AND ACID IN GRAPES DURING RIPENING. 23 



of this whole fruit sample. The physical examinations noted were 

 made in triplicate and the average results used in the table. From 

 these results, in connection with the analyses of the completely 

 extracted fruit samples, some comparisons of definite value in regard 

 to the actual weight content of acid in 100 berries at different periods 

 of maturity may be drawn. 



RELATIVE ACTUAL WEIGHT OF TOTAL ACID IN GREEN AND RIPE FRUIT. 



The volume of the 100 berries was determined by displacement of 

 water, and the specific gravity was determined by weighing first in 

 air and then in water and calculating the gravity. 



It was found necessary to rinse the berries with a weak solution 

 of alcohol (10 to 15 per cent) in order to obviate the formation of 

 air bubbles on the surface, which otherwise markedly interfered with 

 both the volume measurement and the weighing for specific gravity. 



The volume and weight of the Concord berries did not show marked 

 changes in size of the fruit throughout the period of the examina- 

 tions of the samples, but for Catawba there was a decided increase 

 of about 39 per cent in volume and about 44 per cent in weight. 

 It appears that this late-maturing variety for that season shows 

 considerable change in size and weight of berries during the period 

 from coloring to maturity. 



On calculating the actual weight of acid in grams present for each 

 sample of 100 berries examined there is shown in a positive manner, 

 in Table 5, a fairly constant diminution in total weight of this ingre- 

 dient. The percentage of acid in the water-exhausted sample is used 

 for this calculation. There are some apparently abnormal results; 

 that is, during some periods the actual weight of acid increased 

 slightly, yet this is invariably reversed for the subsequent analysis 

 and the comparison of the first samples and the last taken show a 

 positive loss in total weight of acid present in 100 berries for all the 

 crops analyzed. The data appear to establish the fact that there 

 is a very decided loss in total weight of acid as the fruit ripens. 

 The weight loss is in case of Concord, both at Charlottesville and 

 Sandusky, approximately one-half the total acid found in the first 

 sample. For Catawba the proportion falls slightly under one-half 

 the original acid. 



These results are such as should be expected from the analysis 

 of juice samples, wherein it is shown in Table 1 that the fixed acids 

 other than tartaric disappear to a marked extent as the fruit ripens. 

 The results presented in Table 7 also support this contention. While 

 it is also true that the total tartaric acid is shown by Table 1 to 

 decline, this is not so marked and does not nearly account for the 

 actual loss in weight of acid shown in Table 5. 



