NATURAL WAXES 369 



melting point in given a.s 36-41 °C.''^* while the wax sohdifies at about 

 30°C.3" The refract i\-e index of Yorkshire grease is 1.4781 at 40°C.^^* 

 and 1.465 at 60 °C. It is optically active, showing a specific rotation of 

 +6.70° at 35°C.^^^ Some of the chemical constants are as follows: 



Wool fat: 



Acid value 0.5 + 



Saponificatioii value 82-127 



Iodine number (\\'i.js) 15-47 



Reichert-Meissl numlxT 4.7-6.9 



Acetyl value 23 . 3 



Mixed acids: 



Melting point 41 .8°C. 



Iodine numi)er 17 



Molecular weight 327 . 5 



Mixed alcohols: 



Melting point 33.5°C. 



Iodine number 26-36 



Acetj^l value 144 



Molecular \v(>ight 239 



The term lanolin is generally reserved for the refined wax. It was early 

 recognized that lanolin possessed many characteristic differences in com- 

 position as compared with other waxes. In the first place, it was demon- 

 strated that the alcohol components were mainly cyclic alcohols, and 

 cholesterol was found to be the chief one. The so-called "isocholesterol," 

 which comprises an appreciable fraction of the wax, is now known to have a 

 structure distinctly different from that of cholesterol"'^; it consists of at 

 least two separate alcohols, which are tritcrpenes. These are discussed in 

 the section on triterpenes (see Section 2). 



Another unique feature in the composition of lanolin is the fact that the 

 saturated acids differ considerably from the isomeric aliphatic acids. The 

 so-called lano series, i.e., lanomyristic, lanopalmitic, lanostearic, lanoara- 

 chidic, and lanocerotic, are believed to be iso or forked-chain compounds 

 with one or more side chains. This structural difference from the aliphatic 

 series accounts for their optical isomerism. The methyl side chain cannot 

 be situated solely on the terminal (or w) carbon, as asymmetry would not 

 be established by this arrangement. If more than one carbon side chain 

 occurs in such an acid, this would not preclude a side chain on the terminal 

 carbon. For a discussion of the iso and antc-iso acids of wool fat, see pages 

 36 and 37. 



Another characteristic group of acids in wool fat are the hydroxy acids, 

 which contain one or two hydroxy groups. The asymmetry of the carbon 

 atoms to which the hydroxyl or methyl groups are attached accounts for 



»" F. Utz, Rev. Fett-Harz. Ind., 13, 249-250, 27.5-277 (1906); Chem. AbsL, 1, 492-493 

 (1907). 



33*L. Ruzicka, E. Roy, and A. C. Muhr, Helv. Chim. Ada, 27, 472-489 (1944). 



