502 



DIGESTION. 



allowing it to cooi, a resinous mass (cholalic acid and dyslysin) 

 separates. The fluid is poured off from the resin and evapo- 

 ruU-d. The residue is then dissolved in water warmed with 

 hydrated lead oxide, and tiltered ; the filtrate decomposed by 

 hydrogen-sulphide, filtered, and the filtrate evaporated. 



The transparent rhomboidal crystals of glycocine thus ob- 

 tained are then washed with absolute alcohol. They have a 

 sweet taste, and are readily soluble in cold water ; almost in- 

 soluble in ether and alcohol. 



* 144. Taurocholic Acid (C., 6 H 45 NSO.) is present along 

 with glycocholic acid in ox-bile ; it is the chief acid in human 

 bile, and the only one in that of dogs. Preparation. Sus- 

 pend the lead taurocholate obtained from crystallized bile in 

 alcohol, and decompose it by hydrogen-sulphide : filter ; evapo- 

 rate the filtrate at a moderate temperature to a small bulk, 

 place it in a stoppered bottle, and precipitate by a great excess 

 of ether. The acid is precipitated as a syrup. After standing, 

 it changes, if the process is successful, to fine silky crystals, 

 which, when exposed to air, dissolve, or form a syrup. 



Taurocholic acid is soluble in water and alcohol, insoluble 

 in ether. It is recognized as a bile acid by giving Petten- 

 knler's reaction, and is distinguished from glycocholic acid 

 by not being precipitated by lead acetate alone, but by lead 

 acetate and ammonia, and from any other bile acid by yielding 

 taurin when decomposed by boiling with hydrochloric acid. 

 It may be prepared from taurocholic acid or from crude bile. 



145. Taurine (C 2 H 7 NS0 3 ). Preparation. Boil ox-gall 

 with dilute hydrochloric acid for several hours. The bile 

 acids are thus decomposed : Taurine and glycocine combine 

 with the hydrochloric acid, and remain in solution, cholic acid 

 separating as a resinous mass. Filter the fluid, evaporate the 

 filtrate to dryness, extract the residue with absolute alcohol to 

 remove the glycocine-hydrochlorate, dissolve the residue in 

 water, and allow it to stand and crystallize. In order to 

 purify it, dissolve it in spirit, precipitate it with lead acetate, 

 decompose the precipitate with hydrogen-sulphide, filter, evapo- 

 rate the filtrate to dryness, extract the residue with absolute 

 alcohol, dissolve the taurine which remains in a very little 

 water, and allow it to crystallize. Taurine is soluble in fifteen 



crystallizes out in rhombic prisms resembling thick needles (fig. 313). 

 Qlycocine is prepared by boiling hippuric acid with strong hydrochloric 

 acid for several hours, and evaporating the solution almost to dryness. 

 The hippuric acid is decomposed, yielding benzoic acid and glycocine. 

 The residue is extracted with cold water, which dissolves but little of 

 the beneoic acid. To the watery extract hydrated lead oxide is then 

 added, to remove the hydrochloric acid. The liquid is filtered, and the' 

 d precipitated from the filtrate by hydrogen sulphide. The precipi- 

 e having been removed by filtration, the filtrate is evaporated to a 

 small bulk. 



