216 



III. CHEMISTRY OF NEUTRAL FATS 



tion of the triglycerides from liquid and solid fats in acetone at 0° to — 10°C., 

 or 0° to -60°C., is shown in Table 16. 



Table 16 

 Composition of Fractions of Triglycerides and of Natural Fats by Acetone at 



Low Temperatures 



Doerschuk and Daubert'^*" have markedly increased the usefulness of the 

 low-temperature crystallization technic by increasing the number of frac- 

 tions. In their study of the glyceride structure of corn oil, they collected 

 19 different precipitates from acetone at progressively decreasing tempera- 

 tures. The individual samples seldom contain more than two different 

 glycerides. By the use of the iodine number, saponification equivalents, 

 melting points, and the refractive indices, the proportion of each com- 

 ponent in the individual fractions could be deduced. The relative quanti- 

 ties of dienoic and trienoic acids were determined by spectrophotometric 

 analysis in the ultraviolet region, coupled with the thiocyanogen values, 

 while the oleic and the saturated acid contents were determined by the dif- 

 ferences noted. The efficacy of their procedure is attested to by the fact 

 that they were able to account for 982 g. in the fractions, out of the original 

 total of 1000 g. of corn oil. 



c. Theories Advanced to Explain the Glyceride Composition of Natural 

 Fats and Oils. There has been a great deal of discussion during the last 

 few years regarding the rides which govern the distribution of fatty acids 

 in the triglyceride molecules. Up to recently, three theories have been 



280 A. P. Doerschuk and B. F. Daubert, J. Am. Oil Chemists' Soc, 25, 425-433 (1948). 



