102 



II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



dicated by the close correspondence of calculated and determined values 

 in the studies of Dorinson et al.^^^ INIolar volume was calculated by the 

 following formulas : 



At 20°C., Vm = 16.89 n + 23.62 



At 80°C., V^ = 17.25 n + 28.88 



where Vm is molecular volume, and w is the number of carbon atoms in the 

 chain. 



Table 35 gives a comparison of the values calculated by the above formu- 

 las with those actually determined. 



Table 35 



Comparison of Calculated and Experimentally Determined Values for Molar 

 Volumes of Saturated Fatty Acids" 



» A. Dorinson, M. R. McCorkle, and A. W. Ralston, J. Am. Chem. Soc, 64, 2739-2741 

 (1942). 



(c) Dilation of Faltij Acids. The expansion of fatty acids on heating, or 

 dilation, is another property related to the density. Such changes in molar 

 volume can be ascertained by determination of the density of the acid at a 

 series of different temperatures. However, this relatively cumbersome 

 procedure may be replaced by a much simpler method which involves 

 direct readings on a dilatometer. The latter instrument has the advantage 

 of permitting continuous measurements at all temperatures, and includes 

 determinations of the values of the solid vs. the liquid state, as well as those 



