380 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 
the ammonium salt of oxyethylsulphonic acid to 230° C, when a 
molecular rearrangement takes place, thus : 
/CH^OH .C 9 H 4 .NH. 7 
SO/ -SO/ +H 2 
X)iN T H 4 X)H 
Ckolalic acid is the usual partner with glyeocoll 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 solution, 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^H^O.,. 
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 O 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 Mvlius, Ztschr. f. physiol Chan., Strassburg, 1888, Bd. xii. S. 262. 
2 See Maly, Hermann's " Handbuch," Bd. v. (2), S. 136. 
:; >.-hotten, Ztschr. f. physiol. Cht m., Strassburg, 18S6-7, Bd. x. S. 175 ; xi. S. 268. 
4 Hoppe-Seyler, Journ. f. prakt. Ghem., Leipzig, 1863, Bd. lxxxix. S. 265; E. Vahlan, 
Ztschr. f. physiol. Chcm., Strassburg, 1S96, Bd. xxi. S. 253. 
5 Loc. cit. 
6 Latschinoff, Ber. d. deutsch. chcm. Gesellsch., Berlin, 1887, Bd. xx. S. 1968. 
