ROLE OF BILE IN LIPID ABSORPTION 105 



of the unsaturated acid was only 24%. 541 The structure of apocholic acid 

 (XI) has been established by Callow 542 and others. 543 - 544 



Table 15 summarizes the known data concerning the melting points and 

 coordination numbers of various apocholeic acids. 



Table 15 

 Melting Points and Coordination Numbers of Various Apocholeic Acids" 



Coordination 

 Acholic component M.p., °C. number" 



Cetyl alcohol 6 177.5 8 



Acetone* d — 



Acetic acid c ca. 135 1 



Butyric acid ca. 170 4 



Palmitic acid 6 -' 184-185 8 



Stearic acid 6 -* 185-186 8 



Tiglicacid 168-168.5 4 



Sorbic acid" 170-171 4 



Ethyl acetate d 



Hexadecyl acetate^ 189 8 



Benzene d 



Naphthalene 173-174 2 



Xylene 171-172 2 



Camphor 179-180 1 



176.5-177.5 



178-179 2 



Benzaldehyde 156 



° Most of the* data are adapted from H. Sobotka, The Chemistry of the Sterids, Williams 

 and Wilkins, Baltimore, 1938, p. 121. 



6 H. Rheinboldt, Z. physiol. Chem., 180, 180-186 (1928). 

 F. Boedecker, Ber., 53, 1852-1862 (1920). 

 d Unstable. 



• H. Rheinboldt and M. Kircheisen, /. prakt. Chem., 118, 199-211 (1926). 



* H. Rheinboldt, O. Konig, and R. Otten, Ann., 473, 249-259 (1929). 

 » H. Rheinboldt, Z. physiol. Chem., 1S2, 255-258 (1929). 



(/) Physical Properties of Choleic Acids. The melting point of the choleic 

 acid is frequently higher than that of either component. This offers a 

 convenient way to determine the composition of choleic acid by the use 

 of the melting point diagram. 526 - 531,545 Various mixtures of the desoxy- 

 cholic acid and the acholic compound are fused together ; the melting point 

 is determined after complete homogeneity of the product is attained. In 



641 P. L. Plattner, L. Ruzicka, and S. Holtermann, Helv. Chim. Acta, 28, 1660-1669 

 (1945). 



642 R. K. Callow, J. Chem. Soc, 1936, 462-469. 



543 D. H. R. Barton, J. Chem. Soc, 1946, 1116-1123. 



544 E. Berner, A. Lardon, and T. Reichstein, Helv. Chim. Acta, 30, 1542-1553 (1947). 

 *«H. Rheinboldt, J. prakt. Chem. (II), 111, 242-272 (1925). 



