EXAMINATION OF FATS. 1423 



added from time to time. From 500 to 700 cc of distillate will be 

 found to be sufficient. Filter the distillates to remove any insoluble 

 acids carried over by the steam, and titrate the filtrate with deci- 

 normal potassium hydroxid, using phenolphthalein as indicator. Mul- 

 tiply the number of cubic centimeters of alkali employed by 5.61 and 

 divide by the weight of substance taken. This gives the acetyl value. 



FILTRATION PROCESS. 



Add to the soap solution a quantity of standard sulphuric acid 

 exactly corresponding to the amount of alcoholic potash added, warm 

 gently, and the free fatty acids will collect on top. 



Filter off the liberated fatty acids, wash with boiling water until the 

 washings are no longer acid, and titrate the filtrate with decinormal 

 potash, using phenolphthalein as indicator. Calculate the acetyl value 

 as before. 



DETERMINATION OF PHYTOSTEROL AND CHOLESTEROL.* 



Boil 50 grams of fat or oil in a flask with reflux condenser with 75 cc 

 of 95 per cent alcohol for five minutes and separate alcoholic solu- 

 tion. Repeat with another portion of alcohol and separate. Mix the 

 alcoholic solution with 15 cc of 30 per cent sodium hydroxid and boil 

 in a flask with a condensation tube until one-fourth of the alcohol is 

 evaporated. Evaporate nearly to d^ness in porcelain dish and shake 

 the residue with ether. The ethereal solution is evaporated to dry ness, 

 taken up with a little ether, filtered, again evaporated, dissolved in 

 hot 95 per cent alcohol, and allowed to crystallize. 



Cholesterol can easily be distinguished from phytosterol by the form 

 and grouping of the crystals, also by its melting point, which is 146, b 

 while phytosterol is from 130 to 137. 5. c 



Phytosterol is found in most vegetable oils, with the notable excep- 

 tion of olive and palm oils. The crystals as separated from hot alcohol 

 appear in tufts of. needles. 



Cholesterol is characteristic of animal fats. It crystallizes in small, 

 thin, colorless rhombic plates from alcoholic solution. 



DETERMINATION OF THE UNSAPONIFIABLE RESIDUE/ 



Saponify 5 grams of oil or fat with alcoholic potassium hydroxid 

 and remove the alcohol by evaporation. Wash into separatory funnel 



a Forster and Reichelmann, Analyst, 1897, 22, 131; E. Salkowski, Ztsch. anal. 

 Chem., 1887, 26, 557; E. Von Raumer, Ztsch. angew. Chem., 1898, 13, 555-556; Jour. 

 Soc. Chem. Ind., 1898, 17, 774; H. Kreis and O. Wolf, Jour. Soc. Chem. Ind., 1898, 

 17, 1075. 



b E. Salkowski, Ztschr. anal. Chem., 1887, 26,557. 



Bomer, Ztschr. Unter. d. Nahr u. Genuss, 1898, 1, 81. 



d Allen. Com. Org. Anal., 3d ed., vol. 2, pp. 1 and 113. 



