E. J. COHN, J. GROSS, AND O. C. JOHNSON 



153 



that which would have resulted from the added acid or alkaH had 

 there been no combination. It is indicated by the changing slope 

 of the curve representing the titration if the amount of normal acid 

 or alkah is represented as ordinate and the hydrogen ion concentration 

 as abscissae (Fig. 3). 



The curve representing the titration of potato juice with acid 

 and alkali passes through a point of inflection at a hydrogen ion 



'a 



(0 -^ 





SI 



o 



u 

 U 



u 



..-I 



O Vh 

 «3 O 



2 o 



O Oi) 



. xi 

 O <3 



20 



16 



12 



12 



16 



20 

 pH 2 



3 4 5 6 7 8 



Fig. 3. Titration of vegetable juices. 



10 



