348 



strong acid acts saponifying; and 2 it attacks the double binding 

 of the oleic acid present, in consequence of which this is partially 

 found back after the operation is over (saponification in emulsion 

 and distillation), as iso-oleic acid, which is solid at the ordinary 

 temperature. Accordingly this method of saponification is applied, 

 when a yield of solid fatty acid as high as possible is desired. 



In order to examine the stagewise course of the saponification 

 with strong sulphuric acid quantitatively, it is necessary to start from 

 a saturate triglyceride in order to avoid this complication. A suitable 

 material is the trilaurine (to be prepared from Tangkallak-fat by 

 re-crystallisation from alcohol), the same triglyceride that was used 

 by VAN Eldik Thieme. 



After repeated futile attempts to isolate the partially saponified fat 

 without further saponification in emulsion taking place, the following 

 method was applied : 



5 grammes of trilaurine were carefully weighed in a glass beaker 

 of 250 cc. It was carefully melted, a certain quantity of strong 

 sulphuric acid was added, and everything was thoroughly mixed. 

 Then the glass beaker was covered by a watch glass, and left for 

 some time either in a drying oven, or at room temperature, during 

 which the stirring was several times repeated. 



After the fixed time had elapsed, the beaker was cooled in ice, 

 and in order to separate glycerine and sulphuric acid from the 

 glycerides and the fatty acid, as much pounded ice was added as 

 was necessary to keep the temperatui'e under 0° C. After mixing, i 

 ether was added and it was all brought into a cock-funnel. After 

 shaking and separation of the layers ^) the water layer was poured 

 off as sharply as possible, and collected for the determination of the 

 quantity of free glycerine. 



The ether layer was rinsed with alcohol in a flask and titrated 

 with alcoholic KOH to fix the quantity of split off fatty acid. In this 

 titration a little sulphuric acid is always also titrated. This was 

 gravi-metiically determined after evaporation of ether and alcohol, 

 decomposition of the soap with hydrochloric acid, and removal of the 

 fatty acids with ether, and then deducted. 



The glycerine water was repeatedly shaken with ether to remove 

 traces of glycerides, then boiled till all the ether (and alcohol originating 

 from the ether) had again been removed. Then the glycerine was 

 determined by oxidation with potassium bichromate of known strength. 



M If a sufficient quantity of sulphuric acid is present a good separation is 

 obtained in a few minutes. 



