50 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



absorption, refraction, and viscosity are also properties of considerable in- 

 terest to the biochemist; these will be discussed later. For a more com- 

 plete discussion of properties such as thermal activity, and specific conduc- 

 tivity, which are of more concern to the fatty acid or soap chemist than to 

 the biochemist, one is referred to the recent treatise of ]MarkleJ^'' 



(^) Melting Points of Fatty Acids 



There are many factors which influence the melting points of the fatty 

 acids. Probably the most important of these are the chain length and the 

 degree of unsaturation. The position of the double bond in the molecule 

 is also of significance, as well as the geometric form of the acid. These 

 conditions will be discussed in successive sections. 



Table 12 

 Melting and Freezing Points of Even- and Odd-Chain Fatty Acids" 



" Adapted from K. S. Markley, Fatty Acids, Interscience, New York, 1947, p. 114. 



a. Melting and Boiling Points as Functions of Chain Length. In gen- 

 eral, it is well known that the melting points of fatty acids and of the tri- 

 glycerides increase progressively with the extension of the carbon chain. 

 When the melting points of the even-chain or of the odd-chain acids are 

 plotted against the number of carbon atoms, a practically straight-line 

 curve is obtained in either case. The odd-chain acids usually melt at a 

 lower temperature than do the even-chain acids containing one less carbon 



