196 III. CHEMISTRY OF NEUTRAL FATS 



c. Vegetable Fats. In most cases, vegetable fats have fewer varieties 

 of component fatty acids than do those from animal sources. Palmitic 

 and oleic acids are the predominant acids in the vegetable lipids, just as 

 they are in the animal fats; however, the other chief acid in the plant 

 group, i.e., linoleic acid, is present in extremely limited amounts in the 

 animal. On the other hand, stearic acid, which plays such a prominent 

 role in the animal kingdom, is absent or present in very small amounts in 

 most of the vegetable fats; only one series of plant lipids, the members of 

 which are mostly of tropical origin, contains appreciable quantities of 

 stearic acid. 



The fatty acid content of the plant products is related to the family and 

 species. In listing the composition of the various fats, it has seemed best 

 to arrange them according to their botanical classification, by the system 

 employed by Hilditch.^" In this procedure the fats especially rich in cer- 

 tain fatty acids are grouped together. In the present tables, only those 

 fats of fairly wide commercial application are included in the compila- 

 tions. 



(a) Fats with a High Content of Linoleic Acid. Seed oils have the 

 highest proportion of linoleic acid of any of the common vegetable fats. 

 In some cases, the linoleic acid msiy exceed 75% of the total fatty acid con- 

 tent. This acid is especially rich in the seeds of the large trees such as the 

 pine and walnut. Certain herbaceous plants, including flax, perilla, and 

 hemp, also contain a high proportion of linoleic acid coupled with con- 

 siderable amounts of linolenic acid. The composition of some of these oils 

 is summarized in Table 9. Another group of fats also high in linoleic acid 

 but which contains no linolenic acid, or only traces of it, is listed in Table 

 10. In Table 11 the fats which are high not only in oleic and linoleic acids 

 but also in palmitic acid are assembled. 



(6) Fats Containing Elaeostearic, Petroselinic, or Erucic Acid. Several 

 important unsaturated acids are frequently found in certain fats, in addi- 

 tion to the more common oleic, linoleic, and linolenic acids. Elaeostearic 

 acid (9,10,11, 12,13, 14-octadecatrienoic acid) is the best known of these, 

 on account of its application in the paint and varnish industry. Because of 

 the conjugate position of the double bonds, this acid is especially effective 

 as a "drying oil." Tung oil may contain as much as 80-95% of the fatty 

 acids in the form of elaeostearic acid.-"""^"^ 



^ H. P. Kaufmann and J. Baltes, Ber., 69, 2676-2679 (1936). 



201 J. Van Loon, Farben-Ztg., 35, 1767-1769 (1930); Chem. Abst., S/,, 4178 (1930). 

 Cited by T. P. Hilditch, The Chemical Constitution of the Natural Fats, 2nd ed., Wiley, 

 New York, 1947, p. 167. 



202 R. S. McKinney and G. S. Jamieson, Oil & Soap, 12, 92-93 (1935). 



203 R. S. McKinney and G. S. Jamieson, Oil & Soap, U, 2Z (1937). 



204 R. S. McKinney and G. S. Jamieson, Oil & Soap, 15, 30-32 (1938). 

 "OS A. Steger and J. Van Loon, J. Soc. Chem. Ind., 47, 361-363T (1928). 



