DETERMINATION OF FATTY ACIDS IN BUTTER FAT: V 



By E. B. Holland, Associate Chemist, and J. P. Buckley, Jr., Assistant Chemist, 

 Massachusetts Agricultural Experiment Station . 



INTRODUCTION 



Since reporting a method (14) ^ for the determination of stearic acid 

 in butter fat, work has been continued with a \'iew of evolving a process 

 for determining some of the remaining fatty acids. The object of the 

 investigation was to deduce practical analytical methods which might 

 serve to measure the effect of feed upon the composition of the resulting 

 butter fat. Such methods, however, if quantitative and reasonably 

 workable, would be applicable to other fixed oils and fats and play a part 

 in the so-called technical examination of such products. 



There are several distinct lines of procedure upon which methods 

 for determining different fatty acids in a mixture might be based : 

 (i) Crystallization of the acids ; 



(2) Solubility of various salts; 



(3) Fractionation of the acids in vacuo; 



(4) Fractionation of methyl or ethyl esters. 



The iodin absorption and the acetyl substitution are measures of 

 unsaturated and of hydroxy acids, respectively. They are valuable 

 adjuncts, but of limited rather than of general application. 



Attention has been called in several instances to some of the inherent 

 faults (jj, 14) of the different schemes of separation, and a discussion 

 of their relative merits appears unnecessary at this time. It will suffice 

 to summarize the present application and limitation of the schemes. 



Crystallization methods have been employed for the quantitative 

 separation of stearic and of arachic (27) acids but seldom for other acids. 



The lead-salt-ether method, or Gusserow (7)-Varrentrapp (29) process, 

 for the separation of liquid from solid acids is the most prominent illus- 

 tration of the salt-soluble methods which, as a rule, have not proved 

 sufficiently discriminative for quantitative use. 



Fractionation of the acids in vactw has failed as an analytical process. 



Fractionation of ethyl esters appeared applicable to many fatty acids, 

 although chemists generally consider the process as having little quanti- 

 tative significance. The experience gained in purifying fatty acids indi- 

 cated that the method was practicable and at least worthy of additional 

 study. 



> From the Department of Chemistry, Massachusetts Agricultural Experiment Station. Printed with 

 the permission of the Director of the Station. 

 2 Reference is made by number (italic) to " Literature cited," pp. 73i-7,i2- 



Journal of Agricultural Research, Vol. XII, No. ii 



Washington, D. C. Mar. i8. igiS 



mn (719) Key No. Mass. 4 



