44 II. CHEMISTRY OF FATTY ACIDS AND GLYCEROL 



principally in muscle tissue, as the derivative, a-ketogiutaric acid. Adipic 

 acid is present in beet extracts. ^^* Thapsic acid, the Cie dicarboxylic acid, 

 is another example of this group of acids which occur in "death-carrot" 

 root (Thapsia garganica) .^^^ Suberic acid obtains its name from the fact 

 that it originates on oxidation of cork with nitric acid (suberose means cork- 

 like). 



The rather widespread occurrence of azelaic acid can, in some cases at 

 least, be traced to its origin as an oxidation product of unsaturated fatty 

 acid.^"** This is obviously the explanation for the presence of this acid in 

 the specimens of ointment removed from Egyptian tombs, where it had 

 been exposed to the air for 5000 years. ^"^ A similar explanation should 

 also hold for its presence in some samples of linseed oil.^"'^ It has been re- 

 ported to result from the hydrolysis of a substance present in mold spores, ^"^ 

 as well as from the oxidation of keratin. ^"^ 



The higher weight dicarboxylic acids occur in different plant waxes. 

 In Japan wax, 5 to 7% of the fat is composed of dicarboxylic acids of high 

 molecular weight; the C20, Csi, C22, and C.3 acids have been detected. ^"5 -2 n 

 Sumac berry wax has also been found to contain some of the higher di- 

 carboxylic acids.'^^- 



3. Physical Properties of Fatty Acids 



(/) General Physical Properties 



The physical properties of the fatty acids are of interest as regards their 

 structure and molecular size. Melting point, boiling point, density, and re- 

 fractive index are properties which are quite distinctive for the different 

 types of fatty acids, and which vary progressively with the length of the 

 carbon chain, as well as with the number and position of the double bonds. 

 The values of these constants for the different acid series are included in 

 Tables 7 to 11 (pp. 45-49), while the basic factors on which they depend are 

 included in later sections. Crystal structure, polymorphism and spectral 



198 E. O. V. Lippmann, Ber., 24, 3299-3306 (1891). 



199 F. Canzoiieri, Gazz. chim. ital, 13, 514-521 (1883). 



ao" B. H. Nicolet and L. M. Liddle, /. hul. Eng. Chcm., 8, 416-417 (1916). 

 2«' A. Banks and T. P. Hilditch, Analyst, 58 265-269 (1933). 



202 L. C. A. Nunn and I. Smedlev-MacLean, Biochem. J., 32, 1974-1981 (1938). 



203 A. Kiesel, Z. phi/siol. Chem., Uy, 231-258 (1925). 

 2»^ T. Lissizin, Z. physiol. ('hern., 62, 226-228 (1909). 



2»s A. C. Geitel and G. van der Want, J. prakt. Chem. [2], 61, 151-156 (1900). 

 2o« R. Majima and S. Cho, Ber., 40, 4390-4397 (1907). 

 20' R. Schaal, Ber., 40, 4784-4788 (1907). 



208 E. Tassillv, Bull. soc. chim. [4], 9, 608-615 (1911). 



209 G. J. Fels, Seifenfabrik., 36, 141-142 (1916); Chem. Ahst., 10, 1443 (1916). 



210 B. Flaschentrager, and F. Halle, Z. physiol. Chem., 190, 120-140 (1930). 

 2'i M. Tsujimoto, Bull. Chem. Soc. Japan, 6, 325-337 (1931). 



2'2 M. Tsujimoto, Bull. Chem. Soc. Japan, 6, 337-341 (1931). 



