100 



II. 



CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



The comparative values for the specific gravities of the saturated fatty 

 acids and of their methyl or ethyl esters at several temperatures are re- 

 corded in Table 33, together with data on densities of the acids obtained^^- 

 at a uniform temperature of 80° C. 



Table 33 



Specific Gravities op Saturated Fatty Acids or Their Esters, Usually at 20 °C., 

 AND Densities op Fatty Acids Determined at 80 °C. 



" Data from K. S. Markley, Fatty Acids, Interscience, New York, 1947, p. 211. 



* The superscripts refer to the temperature at which determinations were made and the 

 subscripts give the temperatures of the comparison substances; where neither figure is 

 given, the values are for 20°/4°C. 



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

 (1942). 



There is a progressive decrease in density with the lengthening of the 

 carbon chain. Since a volume expansion occurs on heating, the density is 

 further decreased as the temperature is raised. The regularity of the drop 

 in density with increased chain length is best demonstrated at a fixed tem- 

 perature sufficiently high so that all members of the series will be liquid. 



The density of unsaturated acids shows little variation from that of the 

 saturated fatty acids of corresponding chain length when determined at 

 the same temperature. Some of the values for specific gravity reported by 

 Markley* are as follows: petrosehnic, 0.868*°; erucic, 0.860f"^; linoleic, 

 0.903f ; and linolenic, 0.914^". The values for oleic acid and some alkyl 



3« A. Dorinson, M. R. McCorkle, and A. W. Ralston, /. Am. Chem. Soc, 64, 2739- 

 2741 (1942). 



