353 



in which A is now positive or negative according as /) is smaller 

 or greater than unity. Then follows again from (15) and (16): 



i-= ' + ^ <1 (12) 



T' (1 + I A)' ^ ^ ' 



We see therefore that also in the esteritication g is always <^ T', 

 when /) departs from the value 1, as here too A <^ — 9 is impossible. 



When now equilibrium sets in, the reactions in saponifying and 

 esterizing sense take place simultaneously. When one estergioup 

 deviates from the two others, every change in either direction leads 

 to a relation g <^ T\ in other words y <[ T^ holds also here for 

 the reaction of equilibrium. 



When we shortly sum up what precedes, it appears that: 



Both in the saponiiication of triglycerides and in the ester ification 

 of equivalent quantities of glycerine and fatty acid the relative 

 concentration of the free glycerine is equal to or smaller than the 

 third poiner of the relative concentration of the free fatty acid, 

 according as the different groups are equivalent or not, provided no 

 further complications (as e. g. in the saponification in emulsion) 

 take place. 



The situation of the experimentally determined curve A (see the 

 figure) under the curve g = T^ can therefore have been caused 

 either by a saponification of the secondary estergroup that proceeds 

 more rapidly and by one that proceeds less rapidly compared with 

 the primary ester groups. 



It is, however, natural to assume that the latter is the case. 



§ 5. After the foregoing it is clear that the experimentally 

 determined curve B of the figure can never find its explanation in 

 inequivalence of the ester groups; accordingly there must be another 

 reason that causes ^ to be > T' in the esterification. This reason 

 is probably the bivaience of the sulphuric acid which seives as 

 medium. 



To realise this let us tirst inquire a little more closely into the 

 process of saponification : 



When trilaurine is put in contact with sulphuric acid, addition 

 compounds are formed. The sulphuric acid is very loosely bound in 

 these compounds, in water it is immediately split off again. The 

 binding between sulphuric acid and laurinic acid may perhaps be 

 most fitly compared with that between water and salt in a salt 

 hydrate. However this may be, the saponification may now be 

 imagined as follows: 



