PHYSICAL PROPERTIES OF FATTY ACIDS 71 



been used by several workers in isolating and purifying clupanodonic acid 

 from fish oils.^^^^-'"^ Lovern^^^ combined the lead-salt-alcohol and the 

 lithium-salt-acetone method for the examination of a number of oils of 

 aquatic origin. The procedure has been found to agree excellently with 

 the hexabromide method for the determination of arachidonic acid in supra- 

 renal phospholipids. ^^^ However, the lithium salts of the monoethenoid 

 acid, erucic acid,^^^ were found by Doree and Pepper^*"* to be quite soluble in 

 acetone, which precludes the use of this procedure with the fatty acids of 

 rapeseed or mustardseed oils. 



(d) Magnesium Salts in Alcohol. Still another soap-solvent combina- 

 tion which has proved useful has been the magnesium-salt-alcohol proce- 

 dure. This method was used by Kerr^*^ and also by Thomas and Yu^^^ 

 to separate the arachidic acid from peanut oil, although it has subse- 

 quently been shown to be somewhat unsatisfactory from a quantitative 

 standpoint. ^^^ The magnesium-salt-alcohol method has been used also by 

 Chibnall et aZ.,^^" for the purification of the hydroxy-acids in the cerebro- 

 sides, phrenosine, and cerasine. 



f. Anomalous Solubility and Association. Although solubility values 

 for the various fatty acids in the different solvents under standardized 

 conditions can readily be duplicated, the results are quite unpredictable 

 when two or more fatty acids are present in the same mixture. Waentig 

 and Pescheck^^^ have reported that the solubility of palmitic acid in carbon 

 tetrachloride is increased as much as 250% when lauric acid is present. 

 The solubility of the first component is decreased when the concentration 

 of the second component is increased until a limiting concentration is 

 reached. Many instances are known in which anomalous results occur due 

 to the effect of association on solubility. The failure to obtain crystalliza- 

 tion from a mixture of acids (especially unsaturated acids), the inability to 

 obtain hexabromostearic acid from a large amount of tetra- or dibromo- 

 stearic acid, or of tetrabromostearic acid from an excess of dibromostearic 

 acid, are all well-recognized examples of this phenomenon. Likewise, the 

 separation of a crystalline mixture having the properties of margaric acid 



"8 M. Tsujimoto, Bull. Chem. Soc. Japan, 3, 299-307 (1928). 



239 ^i Tsujimoto and H. Koyanagi, /. Soc. Clieni. Ind. Japan, suppl., 38, 271-272B 

 (1935). 



2« Y. Toyama and T. Tsuchiya, Bull. Chem. Soc. Japan, 10, 441-453 (1935). 



2^1 J. A. Lovern, "The Composition of the Depot Fats of Aquatic Animals," Dept. Sci. 

 Ind. Research, Brit. Food Investigation, Special Report, No. 51, II. M. Stationery Office, 

 London, 1942; Chern. Abst., 36, 4727 (1942). 



"» W. C. Ault and J. B. Brown, /. Biol. Chem., 107, 615-622 (1934). 



"3 D. Holde and C. Wilke, Z. angew. Chem., 35, 105; 289-291 (1922). 



"* C. Doree and A. C. Pepper, /. Chem. Soc, 1942, 477-483. 



2« R. H. Kerr, /. Ind. Eng. Chem., 8, 904 (1916). 



"-'"■ A. W. Thomas and C. L. Yu, J. Am. Chem. Soc, 45, 113-128 (1923). 



2^' 8. T. Voorhies and S. T. Bauer, Oil & Soap, 20, 175-178 (1943). 



2" P. Waentig and G. Pescheck, Z. physiol. Chem., 93, 529-569 (1919). 



