180 III. CHEMISTRY OF NEUTRAL FATS 



tion of the fat or oil, the mixture of fatty acids is taken up in alcohol and 

 treated with lead hydroxide. The lead salts of the saturated acids are in- 

 soluble, while those of the unsaturated acids are, in general, soluble in alco- 

 hol. However, this difference does not hold for the short-chain saturated 

 acids (C6-C12), which dissolve quite well in alcohol. Hence, this procedure 

 for the separation of saturated and unsaturated acids is not satisfactory for 

 fatty acid mixtures from butter fat, coconut oil, or palm oil in which large 

 proportions of saturated short-chain acids are present. On the other hand, 

 not all unsaturated acids have lead salts which are readily soluble in alco- 

 hol. Thus, petroselinic and other isooleic acids, elaeostearic acid, erucic 

 acid, and hydroxy-acids may also be present to some extent in the alcohol- 

 insoluble fraction. Even lead oleate may occur to the extent of 1-2% in 

 the precipitate. Data obtained by the use of this so-called Twitchell 

 method*' must therefore be accepted with reservations. 



(6) Fractional Distillation of Fatty Acid Mixtures. The separation of 

 fatty acids from each other by fractional distillation, particularly at re- 

 duced pressures, has been widely employed in the analyses of fats.**~*^ 

 This procedure is of little use in the separation of most triglyceride mix- 

 tures, because of the complexity of their composition. However, in the 

 case of the free fatty acids or of their methyl or ethyl esters, a relatively 

 sharp separation into the individual components may be effected. 



Although, as recently as 1924, Channon and his associates^' stated that 

 the fractionation method is of little quantitative use, many recent im- 

 provements have made it considerably more precise. Of particular im- 

 portance has been the development of the electrically heated packed 

 column with an evacuated jacket to protect it against temperatiu'e fluc- 

 tuations.^* By means of this innovation, Jantzen and Tiedcke were able 

 to separate the methyl esters of palmitic and stearic acids, as well as the 

 high-melting acids of peanut oil. Further modifications were incorporated 

 by Bush and Schwartz,^^ as well as by Lepkovsky and his collaborators.^^-'^ 



8^ E. F. Armstrong, J. Allan, and C. W. Moore, J. Soc. Chem. Ind., U, 63-68T (1925) 

 86 E. F. Armstrong, J. Allan, and C. W. Moore, J. Soc. Chem. Ind., 44, 143-144T 

 (1925). 



8« W. F. Baughman and G. S. Jamieson, J. Am. Chem. Soc., 42, 152-157 (1920). 

 *^ H. E. Longenecker, J. Soc. Chem. Ind., 56, 199-202 T(1937). 



88 A. W. Weitkamp and L. C. Brunstrum, Oil (fc Soap, 18, 47-50 (1941). 



89 A. E. Bailey, Industrial Oil and Fat Products, 2nd Ed., Interscience, New York, 

 1951. 



9" F. A. Norris and D. E. Terry, Oil & Soap, 22, 41-46 (1945). 



91 F. C. Williams and J. O. Osburn, J. Am. Oil Chemists' Soc, 26, 663-668 (1949). 



92 A. W. Ralston, Fatty Acids and Their Derivatives, Wiley, New York, 1948. 



93 H. J. Channon, J. C. Drummond, and J. Golding, Analyst, 49, 311-327 (1924). 

 9^ E. Jantzen and C. Tiedcke, /. prakt. Chem., 127, 277-291 (1930). 



95 M. T. Bush and A. M. Schwartz, Ind. Eng. Chem., Anal. Ed., 4, 142-143 (1932). 



9« H. M. Evans, R. E. Cornish, S. Lepkovsky, R. C. Archibald, and G. Feskov, Ind. 

 Eng. Chem., Anal. Ed., 2, 339-343 (1930). 



9' S. Lepkovsky, G. V. Feskov, and H. M. Evans, /. Am. Chem. Soc, 58, 978-981 

 (1936). 



