CHAP. IV.] DERIVATIVES OF CHOLALIC ACID. 307 



This acid possesses a pure bitter taste, devoid of the sweet taste 

 which is characteristic of cholalic acid and the conjugative bile acids. 

 It is much more readily soluble in cold alcohol than cholalic acid. 

 On spontaneous evaporation of the alcoholic solution a syrupy residue 

 is obtained which slowly crystallises. The acid melts at temperatures 

 between 160 and 170. Its alkaline salts are readily soluble in 

 water but possess a character which distinguishes them from the 

 alkaline cholalates, viz. they are precipitated from their solutions in 

 an oily form by the addition of 10 per cent, solutions of sodium 

 hydrate. The barium salt of this acid dissolved in very weak 

 solutions of ammonia is precipitated in the cold by barium chloride. 



Dy sly sin 1 C^HagOg. 



Anhydrides of Cholalic Acid. When bile, or one of the bile 

 acids (preferably cholalic acid), is subjected to long continued boiling 

 with hydrochloric acid, or when cholalic acid is heated to 300 C. 

 (Strecker 2 ), or according to Hoppe-Seyler 3 only to 200 C., a dark, 

 resinous body is obtained, which is insoluble in water, alcohol, dilute 

 acids and alkalies, but which is sparingly soluble in ether and soluble 

 in aqueous solutions of cholalic acid and its alkaline salts. This 

 body which received its name from Berzelius, who first obtained it 

 in an impure condition, and was first investigated by Strecker, is 

 dyslysin and has the composition C^H^Og. The body is obviously 

 an anhydride of cholalic acid, from which it differs by containing two 

 molecules less of water, and into which it can be reconverted by 

 boiling for an hour with an alcoholic solution of potassium hydrate, 

 when it passes into solution ; this reconversion also occurs on fusion 

 with potassium hydrate. From the potassium cholalate, thus re- 

 generated, pure cholalic acid can be obtained. 



Choloidic Acid 034113804 ? ? By this name has been described and 

 analysed by several chemists 4 a substance obtained by the action of acids 

 on cholalic acid, of which the composition nearly agrees with the formula 

 034X13804, presumably an anhydride of cholalic acid, differing from it by 

 containing one molecule less of water, whilst, as we have seen, dyslysin 

 contains two molecules less. Hoppe-Seyler 4 has shewn that it is impos- 

 sible, by the means which were employed to separate it, to obtain a pure 

 substance, and he has shewn that choloidic acid is a mixture of dyslysin 

 and cholalic acid, and that the choloidates are cholalates mixed with 

 dyslysin. Probably, however, as Hoppe-Seyler points out, such an anhy- 

 dride as choloidic acid (0,^3904) actually exists, though no proof of the 

 fact has hitherto been furnished. 



Hyocholalic Acid, C 25 H 40 O 4 . 



Is obtained by decomposing hyoglycocholic acid by boiling it with 

 barium hydrate. It has been obtained in the form of warty, crystalline 



1 From Svs and Xtf<m ; so called because of its insolubility in water and alcohol. 



2 Strecker, Annalen, Vol. LXVII. (1848), p. 1 et seq. 



3 Hoppe-Seyler quoted by Maly, Hermann's Handbuch, Vol. v. n. p. 139. 



4 Hoppe-Seyler, Physiologische Chemie, p. 291. 



202 



