126 



University of California Publications in Agricultural Sciences [Vol.3 



tartaric acid approaches the total acid, and in one case, (Musct, 1916), 

 actually became equal to the total acid, indicating that in this instance 

 no free acid remained. 



Second crop grapes were found to be higher in free acid than 

 first crop grapes of the same total solids and sugar content. The 

 Catawba grape grown under eastern conditions (fig. 9) exhibits rela- 

 tively high free acid. Alwood 6 has found this free acidity in eastern 

 grapes to be due largely to malic acid. No attempt was made in the 

 analyses of the California samples to identify the various acids making 

 up the free acidity which was calculated as tartaric acid. 



Mean Differences Between Total Solids and Sugar. — The following 

 table contains figures representing the differences between total solids 

 and sugar at the various percentages of total solids indicated at the 

 tops of the columns. The data represent a range of total solids from 

 5 per cent to 30 per cent. The figures were taken from the data 

 reported in tables 7 to 9, and represent several varieties of grapes. 

 Only a few determinations of total solids and sugar were available 

 for the lower concentrations (5 per cent to 15 per cent), and therefore 

 the figures for this range may not represent averages so accurately 

 as the figures above 15 per cent total solids. 



Between 5 per cent and 11 per cent solids, the average difference 

 between total solids and sugar remains practically constant. From 

 11 per cent to 17 per cent total solids, the mean difference decreases 

 quite rapidly. From 17 per cent to 30 per cent, the difference remains 

 fairly constant. The variations noted after 17 per cent total solids 



Qdfctaicm f^ct rr erM iota/ Ja/zdz 



Fig. 10 — Mean differences between total solids and sugar between 5 per cent 

 and 30 per cent total solids. 



o U. S. Dept. Agric. Bull. 335. 



