CHARACTERIZATION OF FATS 29 



This number is determined by dissolving I or 2 grams 

 of the sample in 1 5 or 20 c.c. of a mixture of I part of alcohol 

 with 2 parts of ether, and titrating the solution with N/io 

 alcoholic potash in the presence of phenolphthalein. 



(2) The Saponification Value. 



This is the number of milligrams of potassium hydroxide 

 required for saponifying I gram of the fat. 



From i to 2 grams of the sample are weighed out into a 

 250 c.c. conical flask; 25 c.c. of approximately seminormal 

 alcoholic potash are then added, and the flask is attached to a 

 reflux condenser and heated over a water bath for about half 

 an hour; the solution is then diluted with 25 c.c. of water and 

 cooled, then the excess of potash is titrated back by means 

 of N/2 hydrochloric acid. In order to determine the strength 

 of the alcoholic potash 25 c.c. of it are heated at the same 

 time under exactly similar conditions in a second conical flask, 

 but without any fat ; in this way any error due to the effect 

 of the alkali on the glass vessel is eliminated. The difference 

 in the two titration readings gives the amount of acid equiva- 

 lent to the potash used up in saponifying the fat, from which 

 the number of milligrams of alkali required for I gram of fat 

 may be calculated. 



Since one molecule of any monobasic acid requires one mole- 

 cule of potash, the magnitude of the saponification value is 

 inversely proportional to the molecular weight of the acids 

 contained in the fat. 



Molecular Saponification 



Weight. Value. 



Butyrin . . 302 557-3 



Palmitin . . 

 Stearin , 



Olein 



Coco-nut oil . 

 Palm-kernel oil * 

 Palm oil f 

 Olive oil . 



806 208-8 



890 189-1 



884 190*4 



246-260 

 242-250 



196-202 



185-196 



(3) Iodine Value. 



It was first observed by Hiibl that an alcoholic solution 

 of iodine containing mercuric chloride reacted at ordinary 

 temperatures both with the free unsaturated acids and with 



* The oil contained in the kernel of the palm fruit, 

 t The oil contained in the fleshy part of the fruit. 



