210 CHOLALIC ACID. 



when boiling, or in ether, but readily soluble in alcohol. This acid may 

 also be obtained in an amorphous form by concentrating its solutions 

 to dryness and is now less insoluble than when crystallised. If the 

 amorphous acid is dissolved in ether it may be separated out by 

 evaporation in four or six-sided prisms which are anhydrous. When 

 the sodium salt of cholalic acid is decomposed under ether by the 

 addition of hydrochloric acid, the acid may be obtained in rhombic 

 plates containing one molecule of water. The alkali and barium salts of 

 cholalic acid are soluble in water and in alcohol especially when warm, 

 and yield, like the free acid, dextro-rotatory solutions. For solutions of 

 the anhydrous acid(a) D = + 50. When crystallised with 2 JH 2 O, (a) D = + 35. 

 In alcoholic solutions of the sodium salt (a) D = + 31'4 (Hoppe-Seyler). 

 The constitution of cholalic acid is scarcely as yet definitely known 



/COOK 

 but may be represented by C 20 H 31 ^(CHoOH)^ 1 It yields with iodine 



ICHOH 



a compound which like that resulting from the interaction of iodine 

 and starch possesses a brilliantly blue colour and is specifically 

 distinctive, since it cannot be obtained either from the bile-acids or 

 choleic acid (see below) or the products of the decomposition of cholalic 

 acid 2 . 



When cholalic acid is prepared from human bile it exhibits certain 

 differences, more especially as regards the lesser solubilities of its 

 alkali and barium salts, which led to its being regarded as distinct 

 from that obtained from ox-bile and hence it was called anthropo- 

 cholalic acid. It appears however that the bulk of the acid is 

 identical with that from ox-bile, the slight difference being due to an 

 admixture with another acid either choleic, as was first supposed, or 

 fellic 3 . 



Choleic acid, C 23 H 42 4 . Is obtained in small amounts mixed with cholalic acid 

 during the preparation of the latter from ox-bile. It differs from cholalic acid in 

 the solubility of its salts and the products of its oxidational decomposition 4 . 



Fellic acid 5 , C 23 H 40 4 . Obtained in small amounts from human bile during 

 the preparation of ordinary cholalic acid. It is characterised by the extreme 

 insolubility of its barium and magnesium salts. It also yields a less brilliant 

 Pettenkofer reaction (see below) than does cholalic acid. 



The bile-acids of the pig and goose when decomposed yield forms of cholalic 

 acid called respectively byo-cholalic acid C 25 H 40 4 , and cheno-cholalic C^ 



1 Mylius, Bcr. d. d. chem. Gesell. Bd. xx. (1887), S. 1968. 



2 Mylius, Ibid. S. 683 and Zt.f. physiol. Chem. Bd. xi. (1887), S. 306. See also 

 Bd. xii. (1888), S. 262. 



3 Schotten, Zt. f. physiol. Chem. Bd. x. (1886), S. 175 ; xi. S. 268. 



4 Latschinoff, Ber. d. d. chem. Gesell. Bd. xvm. (1885), S. 3039. 



5 Schotten, loc. cit. 



