48 



monolaurine and water, so that there is no question of "drops". 

 To be able to form in spite of this an opinion about the surface 

 tension of monolaurine against aqueous solutions, the number of 

 drops that mounted of a mixture of 90 "/o trilaurine and 10 7o mono- 

 laurine, has been given in table 2, while for a comparison the thus 

 obtained values of dilaurine have been given. 



From table 2 the following conclusions can be drawn : 



1. In acid and neutral surroundings the surface tensions of tri- 

 and dilaurine in contact with the saponifying medium differ little, 

 that of monolaurine is much less. We must therefore expect that 

 in case of saponification in non alcalic surroundings the monoglyce- 

 ride will be adsorbed at the boundary of fat- and water phase, and 

 will, therefore, be saponified with a velocity greater than that with 

 which it has been formed, 



2. In alcalic surroundings both the surface tensions of di- and of 

 monolaurine in contact with the saponifying medium are much 

 smaller than that of trilaurine. Both di- and monoglycerides will, 

 therefore, be absorbed here at the boundary layer; hence they are 

 saponified with velocities greater than that with which they have 

 been formed. 



As appears from what precedes the increase of concentration of 

 the lower glycerides at the surface of contact between fat and water 

 phase must be taken into account in the derivation of an equation 

 \p(z, s) =: 0. We now put: 



p resp. q^= the number of times that the concentration of the dig I y- 

 ceride, resp. monoglyceride at the boundary layer is greater in conse- 

 quence of the adsorption than if no adsorptiori had taken place, and 

 ive put p and q both constant. 



This assumption is an approximation, because the adsorption is 

 not proportional to the total concentration of the adsorbed sub- 

 stance. ') This approximation will be the closer as the concentration 

 of the lower glycerides will vary between a narrower margin during 

 the saponification. 



§ 9. Since the difference in velocity of saponification between 

 esters of primary and secondary alcohols is only slight, and the 

 isomeric di- and monoglycerides can therefore be considered here as 

 equivalent with close approximation (which also follows from Geitei/s 

 and J. Meyer's results), we come to the following scheme for the 

 saponification of fat : 



1) See Feeundlich, Z. f. phys. Ghem. 57, 385 (1907). 



