10 



The Philippine Journal of Science 



1913 



Table I. — Saponification of methyl benzoate with NaOH 0.0920 Normal. 

 T=80°±0.1° Corallin indicator. 



t 



minutes. 



a— x. 



K x . 



0.01568. 





 6 



0. 0920 

 0.0610 







0. 0685 



4.369 



12 



0.0400 



0. 0693 



4.420 



17 



0. 0280 



0. 0699 



4.458 



23 



0. 0180 



0. 0709 



4.522 



28 



0.0125 



0.0711 



4.535 



33 



0. 0085 



0. 0720 



4.592 



38 



0. 0058 



0.0725 



4.624 



43 



0.0042 



0. 0718 



4.579 



50 



0.0027 



0. 0705 



4.497 



63 



0. 0015 



0.0654 



4.172 



78 



0.0005 



0.0668 



4.261 



Average com- 







puted after dis- 







carding the 







first one and 







last two values . 



0. 0710 



4.529 



In order to compute K from K x , determinations of the solubility 

 of methyl benzoate in water were made. 



Freshly boiled, distilled water and pure methyl benzoate were 

 employed for the purpose. The water and an excess of the 

 ester were shaken violently, producing an emulsion, for three 

 hours at 30° in glass-stoppered bottles. Twenty-five cubic- 

 centimeter portions of the water were then saponified in the cold 

 with standard sodium hydroxide solution, and the excess titrated. 

 The following values were obtained. 



Experiment No. 



N/10 NaOH 

 per 25 cc. 

 saturated es- 

 ter solution. 



Molar solu- 

 bility. 



1 



3.88 

 3.96 



0. 01552 

 0. 01584 



2 





Average 



0. 01568 





Any reaction between a difficultly soluble ester and a base 

 will be monomolecular so long as conditions are such that the 

 concentration of the ester is kept at the maximum allowed by 

 its solubility. It is, of course, apparent that the solubility of 

 the ester may be increased by the formation of alcohol in the 

 reaction mixture. However, the error from this source in dilute 

 solution is small. 



