184 III. CHEMISTRY OF NEUTRAL FATS 



alcohol and 2-aminopyridine as the immobile solvent, with /i-hexane as the 

 mobile phase on a silica gel column. ^^^ 



Although the elution technic, when applied to chromatography, does not 

 afford complete separations, ^^""^^^ a modified procedure, called "displace- 

 ment analysis," appears to be effective. By the use of silica gel columns 

 with heptane as the solvent, Claesson^^^ has been able to separate satu- 

 rated, unsaturated, and branched-chain acids. By the use of cetylpyr- 

 idinium chloride or picric acid as the displacing agent on a column of char- 

 coal or Hyflo Super Cel, Holman and HagdahP*^ demonstrated a fair sepa- 

 ration of acids from C12 to C22- In a later study, the same workers^** ef- 

 fected a separation of Ci to C22 acids by using the fatty acids themselves as 

 the displacing agents. 



(/) Counter current Distribution. This technic, which recently came 

 into prominence as a new analytical procedure, ^*^~^"" has been used for 

 the quantitative estimation of the C2 to C5 acids. ^^^ When an isopropyl 

 ether-2.2 M phosphate buffer system at a pH of 5.17 was employed, the ac- 

 curacy was within 2 to 3%. 



b. Animal Fats. The animal fats differ in composition from the vege- 

 table fats in containing a larger variety of fatty acids. Both saturated 

 and unsaturated fatty acids of the C20, C22, and even the C24 series are 

 found in many animal fats, in addition to the usual components of all fats, 

 namely, the fatty acids of the Cie and Cig series, palmitic, stearic, and 

 oleic acids. In addition to the latter three acids, vegetable fats frequently 

 contain large proportions of linoleic acid, while this diethenoid acid is 

 seldom found in appreciable quantity in animal fats unless it has been 

 fed to the animal previously. 



Gross differences in composition are to be noted between the fat from 

 aquatic animals and from those species which live on land. The fats of 

 marine origin tend to be more complex, and contain only 15 to 20% of the 

 saturated acids. Palmitic acid is the predominant member of this group, 

 but small amounts of stearic, myristic, lauric, capric, and even caprylic 



i« L. L. Ramsey and W. I. Patterson, J. Assoc. Official Agr. Chem., 31, 441-452 (1948). 



15° H. G. Cassidy, J. Am. Chem. Soc, 62, 3073-3076, 3077-3079 (1940). 



'" H. G. Cassidy, J. Am. Chem. Soc, 68, 2735-2739 (1941). 



1" H. P. Kaufmann and W. Wolf, Fette u. Self en, 50, 519-521 (1943) ; Chem. AbsL, 39, 

 205 (1945). 



«3 S. Claesson, Rec. trav. chirn., 65, 571-575 (1946). 



1" R. T. Holman and L. Hagdahl, Arch. Biochem., 17, 301-310 (1948). 



«5 R. T. Holman and L. Hagdahl, J. Dairy Set., 32, 700 (1949). 



166 L. C. Craig, J. Biol. Chem., 155, 519-534 (1944). 



1" L. C. Craig, C. Golumbic, H. Mighton, and E. Titus, /. Biol. Chem., 161, 321-332 

 (1945). 



i"" L. C. Craig and D. Craig, in Technique of Organic Chemistry, Vol. Ill, A. Weiss- 

 berger, ed., Chap. IV, "Extraction and Distribution," pages 171-311, Interscience, New 

 York, 1950. 



iM Y. Sato, G. T. Barry, and L. C. Craig, J. Biol. Chem., 170, 501-507 (1947). 



