EDIBLE OILS AND FATS. 29 



steam in run through or portions of water are 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. Multiply the number of 

 cubic centimeters of alkali employed by 5.61 and divide by the weight of substance 

 taken. This gives the acetyl value. 



(b) FILTRATION 1'KOCKSS. 



Add to the soap solution a quantity of standard sulphuric acid exactly correspond- 

 ing 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 deci-normal potassium hydroxid, using 

 phenolphthalein as indicator. Calculate the acetyl value as before. 



10. DETERMINATION OP PHYTOSTEROL AND CHOLESTEROL. a 



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 solution. 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 dry ness in porcelain dish and 

 shake the residue with ether. The ethereal solution is evaporated to dryness, taken 

 up with a little ether, filtered, again evaporated, dissolved in hot 95 per cent alco- 

 hol and allowed to crystallize. 



Cholesterol can easily be distinguished from phytosterol by the form and group- 

 ing of the crystals; also by the melting point, which is 14(> C., 1 ' while that <>f phy- 

 tosterol is from 130 to 137.5 C. c 



Phytosterol is found in most vegetable oils, with the notable exception of olive and 

 palm oil. The crystals as separated from hot alcohol appear in tufts of needles. 



Cholesterol is characteristic of animal fats. It crystalli/es in thin rhombic tables. 



11. DETERMINATION OF THE UNSAPONIFIABLE Ki>nx K.' 



Saponify 5 grams" of oil or fat with alcoholic potassium hydroxid and remove the 

 alcohol by evaporation. Wash into separatory funnel with from 70 to 100 cc of water 

 and extract with from 50 to 60 cc of ether. In case the two liquids do not separate, 

 a few cubic centimeters of alcohol may be added. Separate the water solution and 

 wash the ether with water containing a few drops of sodium hydroxid. Again extract 

 the soap solution and washings with ether and evaporate the combined extracts to 

 dryness. In most cases it is advisable to add a little alcoholic potassium hydroxid 

 to the residue and heat in order to saponify any traces of fats left unsaponified and 

 extract again with ether. Transfer to a weighed dish and dry as quickly as possible 

 in a water oven. 



Many of the hydrocarbon oils are volatile at 100 C., so that the drying should not 

 In- carried any further than necessary. With resin oil, paraffin wax, and the denser 

 mineral oils there is little danger of loss at 100. 



On account of the solubility of soap in ether and petroleum ether it is well to wash 

 the residue with warm water containing a little phenolphthalein. If it shows alka- 

 line reaction there is soap present. 



Forster and Reichelmann Analyst, 1897, 22, 131; E. Salkowski, Ztsch. anal. Chem., 1887. -';. 

 687; K. You Kiimn.T, Ztsch. angew. Chem., 1898, 18, 555-566; Jour. Soc. Chem. Iiid., 1898, 17. 771. 

 H. Kn-is mid O. Wolf, Jour. Soc. Chem. Ind., 1898, 17, 1075. 



' K. Siilkmvski. Xtschr. anal. Chem., 1887, -'. 587. 

 I'.r.in.T, y.tsHir. rntt-r. (1. Nahru. Gciiuss. iv.w, 1, 81. 



Allen, com. OI-K. Anal., 3d Ed., Vol. 2, pp. land 118, 



