RELATIONS TO OTHER SCIENCES 279 



present at any moment, or to that of the free base, or to either indiffer- 

 ently, to the total substance, as expressed in: 



(i) ^=^(Salt) 



dx 

 (n) -k b x (Base) 



clot 



(in) - = k su x (Substance) 



dt 



In order to decide between these three possibilities and thus answer 

 our question, it was necessary to determine two things experimentally, 

 first the actual change, x in time t, and second the proportions of 

 salt, free base, and acid present at any moment t. The latter may be 

 determined on the basis of the well-known equation for the solution 

 of a hydrolyzed salt, namely, according to Arrhenius: 



(Positive Ion) fc base 



A/i, 



(Base) x (H) fc^ ' 

 The constant k was determined experimentally by conductivity 

 measurements, and with its aid the concentrations of salt, base, and 

 acid for the above differential equations calculated. The experi- 

 mental results show unmistakably that the true course of the reac- 

 tion is given by equation (i) , which alone leads to a true constant. 



For instance, we have among our many results for methyl imido 

 benzoate : 



43430 fc sall = 246; 246; 256; 238; 236; 234. 



257; 239; 259; 249; 237; 242; 252; 248. 

 43430 fc subst = 202; 184; 183; 172. 



231; 201; 188; 175; 168; 163; 158; 138. 

 100fc base = 72; 67; 59; 51; 46; 42. 

 58; 49; 44; 41; 35; 33. 



For the corresponding nitrobenzoate we have: 

 10,000 fc salt = 256; 252; 246; 255; 252; 248; 263; 261; 257. 

 4343 & subst = 102; 98; 96; 93; 90; 87; 



fc base = 1.17; 1.23; 1.01; 0.78; 0.69. 



It is therefore certain that hydrochloric acid, which enormously 

 increases the velocity of saponification of the imido-ester according 

 to equation (n), does so simply and quantitatively through salt 

 formation, as was expected. As the experiments were carried out 

 in dilute solutions in which the salts are practically completely 

 ionized, it is obvious that it is the positive ion which is decomposing 

 in the direction given and the acceleration is exclusively due to the 

 formation of more such active or unstable ions. 



The accelerating, or let us call it the catalytic, action of the acid 

 is here surely due then to salt or ion formation, or in other words, 



