39 



the triglyceride in the wnterphase may be taken constant. As will 

 appear in § 19 the saponification in alcalic surroundings takes place 

 however practically directly from triglyceride to glycerine -f- fatty 

 acid. Then the second term of the second member of (2) disappears, 

 and we sliould have a velocity of saponification which does not 

 change with the time. The facts, however, are different. 



If the reaction takes place on the boundary of the two phases, 

 the increase of reaction velocity is at once apparent. At the begirming 

 we have namely a not very intimate emulsion of lye and triglyce- 

 ride. As the saponification advances, the soap concentration in the 

 waterphase increases, the surface tension between fat- and water- 

 phase accordingly decreases; hence the emulsion becomes more 

 intimate, and the surface where the reaction can take place, be- 

 comes greater. 



After what precedes we may, therefore, put aside the first possi- 

 bility as very improbable. 



§ 3. 2. The reaction takes place in the fat phase. 



This supposition is still less tenable, as a reaction which is cata- 

 lytically accelerated by H" or OH' ions, is very improbable in not 

 aqueous surroundings. 



§ 4. So the last possibility remains, namely : 



3. The reaction takes place on the boundary of the two phases. 



In the saponification in acid solution the velocity is a function of 

 the number of collisions in the unity of time between an ester 

 molecule and an H' ion. For a given concentration and a definite 

 temperature this number of collisions is fixed and therefore the 

 velocity constant also. 



If, however, as in the Twitchell process we have an emulsion 

 of fat- and water particles, which move through one another in fine 

 division, and if the reaction takes place on the boundary of the two 

 phases, the velocity will be a function of the extent of the surface 

 where the collisions can take place, i. e. of the fineness of the 

 emulsion ; hence the velocity constant will not be definite at a 

 given temperature. 



In the Twitchell process the accelerating influence of the reagent 

 must chiefly, if not entirely, be found in the enlargement of the 

 surface of contact between fat- and waterphase, in other words in 

 the decrease of the surface tension between fat and water. That 

 actually this surface tension is considerably decreased by traces of 



