36 



The Philippine Journal of Science 



191$ 



The rates of saponification of the methyl esters of the above- 

 mentioned acids and the affinity constants of these acids are 

 tabulated as follows : 



Acid. 



.nate 01 saponi- 

 fication of the 

 methyl ester. 



Affinity 

 constant.' 



Salicylic acid 



6.36 



0.104 



Methyl ether of salicylic acid 



b 2.03- c 2.60 



0.0081 



Benzoic acid 



b 4.53- c 5.41 



0.0067 



* The affinity constants are taken from Derick, Journ. Am. Chem. Soc. (1912), 34, 76; 

 Lunden, "Affinitatsmessungen an schwachen Sauren und Basen," Sammlung chem. u. chem- 

 tech. Vortrage (1909), 14, 1; and Ostwald, Zeitschr. f. physik. Chem. (1889), 3, 241. 



b Calculated for reaction of the first order in nonhomogeneous solution. 



c Calculated for reaction of the second order in homogenous solution. 



These values show that the affinity constants are not in the 

 same order as the saponification constants. Similar irregular- 

 ities are shown in the values as given for propionic, butyric, 

 and isobutyric acids. 



Acid. 



Propionic 



Butyric 



Isobutyric 



Rate of saponi- 

 fication of the 

 ethyl-ester. a 



2.186 

 1.702 

 1.731 



Affinity 

 constant. 1 



0.00145 

 0.00175 

 0.00159 



London (1910), 163 



1 Values taken from Walker, Introduction to Physical Chemistry, 

 and 295. 



Since the affinity constants of benzoic acid and the methyl 

 ether of salicylic acid lie so close together, and we are at this 

 time most concerned with these two acids, we have redetermined 

 their constants and find that there is no question concerning their 

 relative values. The results are as follows: 



The specific conductivity of the water was 1.1910- 6 at 25°. 



Table I. — Benzoic acid. °= 00= 387. 



0/1000. 



A 



100 cc 



K = 100 k 



64 



23.48 



6.07 



0.0061 



128 



32.93 



8.51 



0.0062 



256 



45.89 



11.86 



0.0062 



512 



63.09 



16.31 



0.0062 



1,024 



83.80 



21.66 



0.0058 





K = 0.0061 





This value agrees with that found by Jones and others 6 when 

 their figures are recalculated in terms of the Kohlrausch units. 



Pub. Carnegie Inst. Wash. (1912), 170, 116. 



