I02 



Journal of Agricultural Research 



Vol. XV, No. a 



of cubic centimeters of Njio acid or Njio alkali is plotted on the x-axis and 

 Ch on the y-axis. The graph for midrib juice has a much steeper slope 

 than the graph for juice expressed from the rest of the leaf, indicating a 

 lesser ability to combine with, the acid or alkali added. Precipitation 

 was observed at the points marked x. This shows the point of precipita- 

 tion on neutralization of the free hydrogen, ion of both samples to be 

 about lo'^" Ch. On adding acid the albumens of the petiole juice are 

 precipated at a lesser hydrogen-ion concentration than that for juice of 

 the rest of the Leaf. To reach the higher hydrogen-ion concentration a 

 considerably greater amount of acid is required. For instance, 50 cc. of 



Fig. 3. — Titration graphs for cabbage juices: i, juice from midrib: 2, juice from rest of leaf. Precipitation 

 was observed at pojnts marked " x." For explanation see text. 



fresh petiole juice required 0.67 cc. of Nji ortho-phosphoric acid (H3PO4) 

 to change its acidity from 1.56 X lo'^ to 14.6 X lo'^ H+, while the same 

 amount of juice from the re^t of the leaf required i .48 cc. of Nji ortho- 

 phosphoric acid to change it from 2.1 X lo'^ to 14.6 X lo'^ H+. 



HYDROGEN-ION CONCENTRATION NECESSARY FOR NORMAL CONDI- 

 TION OF THE PROTEINS 



From figure 3 it is seen that there is an optimum hydrogen-ion concen- 

 tration at which the proteins are held in solution in the cell sap. This 

 extends from Ch io*®-^' to about lo"*-^ when instantaneous precipi- 

 tation of the proteins is taken as the measure. If a longer time is 



