CHAP. IV.] CHOLALIC ACID. 303 



SECT. 6. THE ACIDS RESULTING FROM THE DECOMPOSITION OF 

 THE CONJUGATED BILE ACIDS. 



1. Cholalic Acid, C^H^O,. Syn.: Cholic Acid. 



This acid is not a constituent of fresh bile ; it is found, however, 

 in decomposed bile, and, in minute quantities, in the contents of the 

 small and large intestine and in the faeces. As has already been said, 

 it is chiefly known as the product of the decomposition of the normal 

 bile acids by alkalies or acids. 



Modes of In the preparation of cholalic acid, alkalies are 



preparation. preferable to acids, inasmuch as with the former the 

 process of decomposition of the bile acids is better under control. 

 When acids are employed, cholonic acid, an anhydride of glyko- 

 cholic acid, is apt to be formed (see p. 297), and at a later stage 

 dyslysin, an anhydride of cholalic acid. 



1. By the Action of Caustic Baryta on ox bile 1 . 500 c.c. of 

 bile are treated with 75 grms. of barium hydrate and the mixture 

 boiled for 24 hours, on a sand bath, in a flask furnished with an 

 inverted condenser (see Fig. 20, p. 309). The liquid is allowed to 

 cool and filtered. Concentrated hydrochloric acid is then added, 

 which decomposes the barium cholalate and throws down impure 

 cholalic acid. The precipitate is thoroughly kneaded in water, and is 

 dissolved in solution of caustic soda ; it is then mixed with 30 grms. 

 of pure animal charcoal with which it should remain in contact for 

 some days ; the liquid is filtered, again precipitated with hydrochloric 

 acid, thoroughly washed with water and dissolved in the smallest 

 possible quantity of hot alcohol. The alcoholic solution is treated 

 with water until turbidity appears. On the liquid being cooled, 

 cholalic acid separates in the form of hard transparent tetrahedra 

 and in clumps of radiating needles. 



2. By Boiling Ox Bile with Caustic Soda 2 . Ox bile is mixed 

 with one-fifth its weight of a 30 per cent, solution of sodium hydrate 

 and is boiled for 24 hours, as in process 1. The liquid is then 

 saturated with C0 2 and evaporated almost to dryness ; the residue 

 is extracted with strong alcohol, which dissolves the sodium salts 

 of cholalic acid as well as those of choleic and stearic acids. The 

 solution is then diluted with water until the quantity of alcohol in 

 it does not exceed 20 per cent., and a dilute solution of barium 

 chloride is added so long as a precipitate occurs, which is then 

 separated by filtration. The filtrate should yield no further pre- 

 cipitate with barium chloride ; to it is then added hydrochloric acid 

 which precipitates the cholalic acid. The fluid with the precipitate 



1 F. Mylius, ' Notiz iiber die Darstellung und Zusammensetzung der Cholsaure. ' 

 Zeitschrift f. physiol. Chern., Vol. xn. p. 262. 



- Mylius, op. cit. /I ' G 



