2068 REPORT OF THE CHEMIST. OF THE 
acid of less concentration than 13.8 mgs. per cc. was placed in con- 
tact with diphenylamine, 70 combination occurred. 
From the preceding discussion of adsorption reactions and of 
hydrolysis in which, of the reacting substances, only the acid has 
variable concentration (that is, is soluble), it is evident that the two 
kinds of reactions are represented by curves which characteristic 
differences as shown in Figs. 16 and 17. 
G oncentrabion Aad.— > 

Duration of Reaction ——> 
Fic. 16—Typical curves for combination of acid to form hydrolyzible salt, 
both base and salt being insoluble. 
The four curves in each of the diagrams represent the theoretical 
effect of contact with an excess of insoluble base (Fig. 16) and 
with an adsorbent mass (Fig. 17), respectively, upon portions of 
acid of varying concentration, the conditions used, other than con- 
centration of acid, being the same for the four cases represented in 
each figure. 
