182 III. CHEMISTRY OF NEUTRAL FATS 



High-vacuum procedures have practically always been used for the 

 fractionations of fatty acids. Caldwell and Hurtley^^^ used a procedure of 

 this nature for the distillation of fatty acids of butter and coconut oil. 

 Palmitic and stearic acids were first separated by vacuum distillation. ^^^-^^^ 

 In recent work vacuum and fractional distillation have been frequently 

 employed by using the methyl and ethyl esters,"'' as in the case of palm 

 kernel oil,^* coconut butter (copra), "^ cod-liver oil,"^ butter,^^'^-""^^^ 

 cottonseed oil,^^^ human milk fat,^" hydrogenated herring oil,^'^ chaul- 

 moogra oil,^-' peanut oil,^^" and brain lipids. ^^^ Molecular distillation 

 which involves a much higher degree of vacuum is seldom employed for the 

 isolation of fatty acids, but it usually finds an application in the distillation 

 of triglycerides or of other high-boiling compounds. 



For the identification of the resulting fractions, saponification equiva- 

 lents, iodine and thiocyanogen numbers, refractive indices, ultraviolet, 

 infrared, or Raman spectral patterns, and, in special cases, other physical 

 and chemical constants, are employed. Such procedures are discussed in 

 detail by Harper et aZ./^^ Hilditch,^^' and Longenecker."^ 



(c) Non-solvent Crystallization. In some cases higher melting fatty acids 

 can be separated from those of lower melting point by chilling. This 

 procedure has an exceedingly limited application and is generally quite 

 unsatisfactory. 



(d) Crystallization from Solvents. Several types of procedure can be 

 listed under this category. The most widely employed method is that 



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"6 H. Kreis and A. Hafner, Ber., 36, 2766-2773 (1903). 



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127 A. W. Bosworth, /. Biol. Chem., 106, 235-244 (1934). 



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 5th Congr., Can., 5, 3647-3661 (1933). G. Hefter and H. Schonfeld, Chemie und Tech- 

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