COMPOSITION OP NATURAL FATS AND OILS 183 



which involves fractional crystallization of the fatty acids generally from 

 acetone solutions at low temperatures, as developed in the laboratory of 

 J. B. Brown."*"^*^ By its use, many naturally occurring unsaturated 

 acids such as oleic, linoleic, linolenic, erucic, and ricinoleic acids have been 

 separated from each other, as well as from the saturated acids. 



Another application of fractional crystallization from solvents involves 

 the separation of the hexabromides from the tetrabromides. These addi- 

 tion products of the unsaturated acids are both insoluble in petroleum 

 ether, but to different extents. However, the usefulness of the method is 

 diminished by the fact that variations in solubility obtain in the presence of 

 mixtures. 



Finally, the separation of the barium, magnesium, and lead soaps 

 of the solid acids from those of the liquid acids, as described in an earlier 

 section, is another example of crystallization from solvents. 



(e) Chromatographic Separation. One of the most recently developed 

 fields of fatty acid analysis is partition chromatography. Various types of 

 procedures have been suggested, and the particular method to be used de- 

 pends somewhat upon the fatty acids to be separated. By the use of a 

 silica gel column, Smith^*^ has been able to resolve chloroform+1% 

 butanol solutions of formic, acetic, propionic, n-butyric, and n-valerianic 

 acids into their component compounds. Although the butanol-chloro- 

 form-water system has been shown by others ^^^-^^^ to give a satisfactory 

 separation of Ci to C4 acids, it is not effective for longer chain acids. 

 When the silica gel tube is buffered, such a system may be used for the C2 

 to Cs acids including n- and fso-valeric acids. ^*^ Peterson and Johnson^*^ 

 were able to isolate the C2 to Cw acids by employing benzene-aqueous sul- 

 furic acid in Celite-packed tubes. The adsorption technic with an alumi- 

 num oxide column has been used to separate oleic from linoleic acids. ^^^ A 

 methanol-isooctane mixture has found application in partition chromatog- 

 raphy of the saturated acids of intermediate length. ^*^ The analysis of 

 mixtures of Cu to Cig acids can be accomplished by the use of furfuryl 



»s< J. B. Brown, /. Biol. Chem., 90, 133-139 (1931). 

 i» D. L. Cramer and J. B. Brown, J. Biol. Chem., 151, 427-438 (1943). 

 •3« J. S. Frankel and J. B. Brown, J. Am. Chem. Soc, 63, 1483 (1941). 

 1" R. C. Millican and J. B. Brown, J. Biol. Chem., 154, 437-449 (1944). 

 I's J. B. Brown and G. G. Stoner, /. Am. Chem. Soc, 59, 3-6 (1937). 

 "9 J. S. Frankel, W. Stoneburner, and J. B. Brown, /. Am. Chem. Soc, 65, 259-262 

 (1943). 



'« F. A. Smith and J. B. Brown, Oil & Soap, 22, 277-283 (1945). 



"' J. B. Brown, Chem. Revs., 29, 333-354 (1941). 



'" E. L. Smith, Biochem. J., 36, xxii-xxiii (1942). 



1" S. R. Elsden, Biochem. J., 40, 252-256 (1946). 



»" L. L. Ramsey and W. I. Patterson, /. Assoc Official Agr. Chem., 28, 644-656 (1945). 



•« V. Moyle, E. Baldwin, and R. Scarisbrick, Biochem. J., 43, 308-317 (1948). 



»^« M. H. Peterson and M. J. .Johnson, J. Biol. Chem., 174, 775-789 (1948). 



i« C. L. Reinbold and H. J. Button, /. Am. Oil Chemists' Soc, 25, 117-120 (1948). 



"» L. L. Ramsey and W. I. Patterson, J. Assoc Official Agr. Chem., SI, 139-150 (1948). 



