CHEBIICAL COMPOSITION OF SORGHUM. 253 



The Acidity of Corn and Sorghn7n Juices. 



The juices of four varieties of sorghum and two of corn have been 

 examiued at various intervals during the growth of the canes to de- 

 termine their acidity, and with the result presented in the following 

 tables. 



While it is impossible to draw any very definite general conclusions, 

 owing to the great irregularity in the amount of acid present in juices 

 expressed from canes in the same stage of develo2)ment, it is apparent 

 that in all but one of the varieties which have been examined, there is 

 a greater amount of free acid in the juice during the later stages of 

 growth. Two of the sorghums show besides an apparent decrease 

 to about the eighth or ninth stage, followed by an increase later on 

 in the development of the canes. Beyond these conclusions it is im- 

 j^ossible to go. 



The determinations were made in the following manner : 



The method employed for the volumetric determination of the acid 

 present in sorghum or maize stalk juice was as follows: 



50 c. c. of the juice, usually of a greenish or greenish brown 

 coloi, was titrated with a fiftieth normal solution of sodium hydrate 



(foNaOn). 



The acitl was calculated as malic acid=(H2C4H405). 



1 c. c. of-^HNaO= .00134 raahc acid. 



50 



As the most practical indicator for the final test of saturation of the 

 acid juice by soda solution, a dilute solution of extract of logwood was 

 used, which, when added to the juice containing a slight excess of 

 NaOH, turned to a bluish purple or violet color. This final reaction 

 was made in small porcelain dishes, into which a few drops of juice 

 were brought and some drops of logwood added by means of a glass 

 rod. Before this point of neutrality was reached, red and blue lit- 

 mus paper was employed. 



The calculation was as follows : 



A sample of sorghum juice, 50 c. c. required — 



1. 44 c. c. of — HNaO solution for saturation ; hence 100 c. c. of juice 



50 

 44X2=88.0. 



2. 88 X. 00134 (malic acid)= .11792. 



o .11792 (malic acid) 



1 ,u'i-f \ / -n r ■ • s= .11051 gram oi malic acid m 



l.UbbO (specinc grav. oi juicej 



100 grams of juice. 



