380 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



the ammonium salt of oxyethylsulphonic acid to 230 C., when a 

 molecular rearrangement takes place, thus : 



/C 2 H 4 .OH ,C 2 



SO/ = SO/ 



X ONH 4 X)H 



Cholalic acid is the usual partner with glycocoll or taurine in the 

 formation of the bile acids ; it is also found in the intestinal contents, 

 and sometimes, in cases of jaundice, in the urine. One method of 

 obtaining it has already been incidentally mentioned, but it is better 

 prepared by the following method : 1 



Ox bile is boiled for about twenty-four hours with the fifth part of its 

 volume of 30 per cent, caustic soda solutjpn, the water being replaced as it is 

 removed by evaporation. The solution is then saturated with carbon-dioxide 

 gas, and evaporated almost to dryness. The residue is extracted with 96 per 

 cent, alcohol, and the extract, diluted so that it does not contain above 20 

 per cent, of alcohol, is completely precipitated with a solution of barium chloride. 

 The precipitate, which consists of impure barium choleate, is filtered off, and 

 cholalic acid is precipitated from the filtrate by the addition of hydrochloric acid. 

 The acid slowly becomes crystalline on standing, when it is separated and puri- 

 fied by repeated recrystallisation from alcohol. Cholalic acid occurs in many 

 crystalline forms. 2 Anhydrous crystals forming flat- ended 4- to 6-sided prisms, 

 may be obtained by dissolving the amorphous form of the acid, produced by 

 drying one of the other crystalline forms, in ether and allowing the solution 

 to crystallise out. 



From strong alcohol the acid crystallises, on the addition of a very little 

 water, in octohedra and tetrahedra, belonging to the orthorhombic system, and 

 containing two and a half molecules of water of crystallisation ; from dilute alcohol 

 it crystallises in fine shining flat needles or plates, containing only one molecule 

 of water of crystallisation. 3 It also crystallises in large rhombic tetrahedra, or 

 octohedra containing one molecule of alcohol. Pure anhydrous cholalic acid 

 melts at 194 to 195 to a colourless liquid; and on heating above this temperature, 

 loses water and is converted into its anhydride or dyslysin ; on further heating, 

 it loses more water and yields a viscid yellow or yellow-brown oil with a 

 green fluorescence ; this is another anhydride, with the composition C 48 H 66 ;5 . 



All forms of the acid are sparingly soluble in water and ether, and easily 

 soluble in alcohol. The solutions possess the bitter-sweet taste of bile. The 

 alkaline salts are crystalline and soluble in water, but precipitated by strong 

 solutions of alkalies or their carbonates. The barium salt is much more 

 soluble in cold water (1-30) than the corresponding salts of the allied acids 

 described below. Cholalic acid and its soluble salts turn the plane of polarisa- 

 tion to the right. 4 Methyl and ethyl ethers of cholalic acid have been 

 obtained. 



The formula of cholalic acid was first established by Strecker 5 as 

 C 24 H 40 5 , and this formula, after some dissent, 6 is now generally 

 accepted. With regard to its constitution, in spite of a vast amount of 

 labour on the subject, we are still only possessed of very fragmentary 

 and uncertain information. It is certainly a monobasic acid, and must 



1 Mylius, Ztschr. f. physiol. Chem., Strassbnrg, 1888, Bd. xii. S. 262. 



2 See Maly, Hermann's " Handbuch," Bd. v. (2), S. 136. 



3 Schotten, Ztschr. f. physiol. Chem., Strassburg, 1886-7, Bd. x. S. 175; xi. S. 268. 



4 Hoppe-Seyler, Journ. f. prakt. Chem., Leipzig, 1863, Bd. Ixxxix. S. 265; E. Vahlan, 

 Ztschr. f. physiol. Chem., Strassburg, 1896, Bd. xxi. S. 253. 



5 Loc. cit. 



6 Latschinoff, Bar. d. deutsch. chem. Gesellsch., Berlin, 1887, Bd. xx. S. 1968. 



