347 



— ^ ST», 

 dT 



independent of the value of m. 



As further the equilibrium reaction begins at the same point as 



one of the finishing reactions (viz. y ■= T=iO, or </ = 7'=^!), the 



equation ^= T^ must hold also for the equilibrium reaction: 



9 = T\ 



If the saponification did not take place stagewise, but if triacetine 

 directly split up into glycerine and acetic acid, then Ijn of the 

 acetic acid would be present in free state, when l//i of the glycerine 

 was split off, so that in this case the relative concentrations of 

 glycerine and acetic acid would be equal to each other. For 

 the esterification of equivalent quantities of glycerine and acetic 

 acid the same thing holds of course. 



The comparison of the relative concentrations of initial resp. final 

 products furnishes, therefore, a direct quantitative proof whether or 

 no a leaction takes place in stages. 



§ 2. The case of the saponification of triacetine in aqueous solution 

 is not easy to study experimentally on account of the difficulty to 

 determine the free glycerine here quantitatively. 



Esters, for which free alcohol and free acid is easier to 

 determine, are the fats. Glycerine is soluble in water, the glycerides 

 of the higher fatty acids are hardly so, no more than these fatty 

 acids themselves, so that the split off glycerine will be easily 

 separated from it. 



The slight solubility in water of tlie higher glycerides, however, 

 involves that most of the saponification processes do not take place 

 in solution, but in emulsion. 



A procedure, however, that takes place in solution at least partially, 

 is the so-called sulphuric acid saponification. 



Van Eldik Thieme^) has isolated the lower glycerides in this 

 method of saponification, which quantitatively proves the stagewise 

 course of the reaction. 



The method comes to this: 5 — 10"/„ strong sulphuric acid is added 

 to the fat, which is heated to 120° or higher. The action of the 

 acid is allowed to continue for some time, then the reaction product 

 is led into boiling water, and the formed emulsion is boiled, till the 

 required degree of decomposition is attained. 



During the first phase of the process the reaction takes place in 

 solution. The action of the sulphuric acid is here twofold: 1 the 



1) Thesis for the Doctorate, Delft 1911. J. f. pr. Ghem. (2) 85 284 (1912). 



23* 



