CHAP. IV.] 



TAUROCHOLIC ACID. 



301 



2. From ox bile by precipitation with basic lead acetate. Having 

 by means of neutral lead acetate precipitated the whole glykocholic 

 acid (see page 295) a further 'addition of solution of lead acetate and 

 of ammonia causes the precipitation of lead taurocholate. 



This precipitate is treated exactly as was directed in the case of 

 the corresponding salt of glykocholic acid. The acid obtained in this 

 way is, however, amorphous. 



Physical and Taurocholic acid can, as has already been stated, 



chemical pro- be obtained in a crystalline condition, though with 

 perties. much greater difficulty than glykocholic acid. The 



needle-shaped crystals rapidly deliquesce in air; they are readily 

 soluble in water and alcohol, the solutions having a strongly acid 

 reaction. On evaporating the aqueous solution to dryness it under- 

 goes decomposition. Solutions of taurocholic acid possess a bitter- 

 sweet taste. Both aqueous and alcoholic solutions are dextrogyrous, 

 the rotatory power of the latter being greater than that of the former. 

 Sp. Rot. (a)D of taurocholic acid in alcoh. sol. = + 25'0 1 . 



The alkaline salts of taurocholic acid are neutral, possess a taste 

 which is first of all sweet and then bitter, are hygroscopic, readily 

 soluble in water and alcohol. Their aqueous solutions foam like 

 solutions of soap. Solutions in absolute alcohol are precipitated by 

 a large excess of ether. The solutions of the alkaline salts are 

 more stable than the free acid, so that they can be evaporated to 

 dryness without undergoing decomposition. When acetic or any 

 mineral acid, is added to the solution of a pure taurocholate, neither 

 turbidity nor precipitation follows. Solutions of alkaline tauro- 

 cholate dissolve and emulsify small quantities of neutral fats; they 

 possess the property, which is probably of great physiological import- 

 ance, of holding small quantities of cholesterin in solution. 



Aqueous solution of taurocholic acid, or solutions of the alkaline 

 salts of taurocholic acid if acidified with dilute hydrochloric acid 

 completely precipitate solutions of albumin, of acid albumin and of 

 parapeptone (antialbumat). Solutions of albumoses and of peptones, 

 on the other hand, throw down the acid itself in the form of a milky 

 precipitate 2 . 



Potassium taurocholate C^H^KNSC^ is in many fishes the only 

 taurocholate present (Strecker). 



Sodium taurocholate C 2 6H 44 NaNS0 7 , of which the properties have 

 already been described, has in alcoholic solution a specific rotation 

 (a)D = + 24-5 (Hoppe-Seyler). 



Products of Taurocholic acid and its salts are much more 

 decomposition, unstable than glykocholic acid and its salts. When 

 heated with alkalies or with acids, it yields, therefore, much more 

 readily the primary products of decomposition or derivatives of these. 



1 Parke, op. cit. p. 161. 



2 E. Maly u. F. Emich, ' Ueber das Verhalten der Gallensauren zu Eiweiss und 

 Peptonen, &c.' Monat. f. Chemie, Vol. 4, 1883, pp. 89 120. 



