356, THE BILE ACIDS. 



basic lead acetate, a precipitate of lead taurocholate is formed, from which the 

 acid may be obtained in the same way as described above (Strecker). 



When human bile is similarly treated, instead of the "crystallised bile," a 

 resinous non -crystalline precipitate is obtained. Boiling with baryta water isolates 

 the cholalic acid from it, which is obtained from its barium salt by adding hydro- 

 chloric acid. When dissolved in ether, it occurs in the form of prismatic crystals 

 if petroleum-ether is added. The anthropocholic acid (C 18 H 28 4 H. Bayer), so 

 obtained is not soluble in water, but readily so in alcohol, and rotates the ray of 

 polarised light to the left. 



With regard to the decomposition products of the bile acids, 

 as such, does not occur in the body, but only in the bile in combination 

 with cholalic acid, in urine in combination with benzoic acid, as 

 hippuric acid, and lastly, in gelatin in complex combination. 



Cholalic acid rotates the ray of polarised light to the right, and its 

 chemical composition is unknown (perhaps it is to be regarded as 

 benzoic acid, in which a complex of atoms similar to oleic acid is intro- 

 duced Hoppe-Seyler). It occurs free only in the intestine, where it is 

 derived from the splitting up of taurocholic acid, and it passes in part 

 into the faeces. It is insoluble in water, soluble in alcohol, but soluble 

 with difficulty in ether, from which it separates in prisms. Its 

 crystalline alkaline salts are readily soluble in water. 



Cholalic acid is replaced in the bile of many animals by a nearly related acid, 

 e.g., in pig's bile, by hyo-cholalic acid (Strecker, Gundlach); in the bile of the 

 goose, cheno-cholalic acid is present (Marsson, Otto). 



When cholalic acid is boiled with concentrated HC1, or dried at 

 200C, it becomes an anhydride, thus: 



Cholalic acid . = C 2 4H 40 5 , produces 



Choloidinic acid = C 2 4H 38 04 + H 2 0, and this again yields 



Dyslysin . . = C 2 4H 36 3 = H 2 0. 



(Choloidinic acid is, however, not improbably a mixture of cholalic acid and 

 dyslysin ; dyslysin, when fused with caustic potash, is changed into cholalate 

 of potash Hoppe-Seyler). If anthropocholic acid be heated to 185C, it gives up 

 1 molecule of water, and yields anthropochol-dyslysin (Bayer). 



By oxidation cholalic acid yields a tribasic acid, as yet uninvestigated, and a 

 fair amount of oxalic acid, but no fatty acids (Cleve). 



Pettenkofer's Test. The bile acids, cholalic acids, and their anhy- 

 drides, when dissolved in water, yield on the addition of f concentrated 

 sulphuric acid (added in drops so as not to heat the fluid above 70C), 

 and several drops of a 10 p. c. solution of cane-sugar, a reddish purple 

 transparent fluid, which shows two absorption-bands at E & F (Schenk). 



[A very good method is to mix a few drops of the cane-sugar solu- 

 tion with the bile, and to shake the mixture until a copious froth is 

 obtained. Pour the sulphuric acid down the side of the test-tube, and 

 then the characteristic colour is seen in the froth.] 



According to Drechsel, it is better to add phosphoric acid, instead of sulphuric 



