46 



columns 2 — 6 the purity of the examined triglycerides appears 

 sufficiently. 



It now appears from columns 7 and 8 that the surface tensions 

 of the examined triglycerides in contact with water and a 1 Vo 

 solution of TwiTCHELL reagent diverge but little ijiter se, and it is 

 clearly visible that in the presence of reagent the drops get sooner 

 detached, the surface tension between fat and water phase has 

 therefore decreased. 



In alcalic surroundings greater divergencies were found between 

 the different triglycerides inter se (see columns 9 and 10). It is, 

 however, very much the question if they are essential. In triglycerides 

 which cannot, like trilaurine, be purified by recrystallisation from 

 alcohol, it is exceedingly difficult to remove the last traces of free 

 fatty acid. In alcalic surroundings these traces cause a lowering of 

 the surface tension, and give nioreover rise to irregular moistening 

 of the capillary mouth, which is the cause that often great deviations 

 are found in repeated determinations. The values which are little 

 reliable for this reason, have been placed between ( ). The lowest 

 number of drops (rounded off to tens) that was found on repeated 

 determination, has always been given. These values are of importance 

 in so far, that they show clearly the influence of the molecular 

 weight of the soap which is dissolved in the water. 



As appears from Thum and Stiepei/s observations and from the 

 results with Donnan's pipette described in this §, no difference need 

 in general be made in the derivation of an equation \p{z,s)=:Q 

 between natural fats and simple triglycerides. A function derived 

 on this supposition must, however first be tested by different fats 

 in the fermentative saponification, before further conclusions are 

 drawn from it. 



Derivation of an equation if^ {z, s) = 0. 



§ 8. As the reaction takes place on the boundary of fat and 

 water phase, the velocity with which each of the stages of saponi- 

 fication proceeds, will be governed by the surface tension of tri-, 

 di- and monoglycerides against saponifying surroundings. For if e.g. 

 the surface tension of the diglyceride against the water phase is 

 smaller than that of the tri-glyceride, the diglyceride will directly 

 after its formation be adsorbed at the surface of contact, and there- 

 fore reach a greater concentration in the surface layer than when 

 no adsorption took place. The consequence of this will be that an 

 estergroup of a molecule of diglyceride has on an average a greater 



