BY DR. LAUDER BRUNTON. 503 



or sixteen parts of cold water, and in a much smaller quantit} r 

 of hot water. In cold alcohol it is sparingly soluble, more 

 easily in warm alcohol. It is insoluble in absolute alcohol and 

 ether. Taurine is recognized by its crystalline form, and by 

 its containing sulphur. Its crystals are colorless, transparent, 

 six-sided prisms, with four to six-sided pointed ends (fig. 312). 

 Taurine is proved to contain sulphur as follows: If a crystal 

 is heated on platinum foil, it swells, becomes brown, and fuses, 

 giving off fumes in which sulphurous acid is recognized by 

 its smell. If the crystals are ignited with sodium carbonate, 

 and a little acid is poured over the residue, hydric-sulphide is 

 evolved. If they are dissolved in caustic potash, and the 

 solution concentrated by boiling, ammonia is given off, and 

 potassium sulphate and acetate left in solution. 



146. Cholic Acid (C, 4 H JO O 5 ). Preparation. Boil bile 

 (or solution of glycocholic acid) with strong solution of caustic 

 potash, or hot saturated solution of baryta water, for twelve 

 or fourteen hours, precipitate by hydrochloric acid, wash the 

 precipitate with water, dissolve it in a little liquor potassae, 

 add ether, precipitate by hydrochloric acid, and allow the 

 liquid to stand for several days. The ether causes it to become 

 crystalline, and form quadrilateral prisms with pyramidal ends. 

 Pour off the ether, dry the crystals between folds of blotting 

 paper, dissolve them in hot alcohol, and add a little water 

 until a turbidity just commences. Cholic acid crystallizes 

 out on cooling in tetrahedra. Cholic acid exists in two con- 

 ditions. In one it is soft and waxy, and somewhat soluble in 

 water ; in ether tolerably, and in alcohol very readily soluble. 

 In the crystalline condition it is insoluble in water and ether, 

 but tolerably soluble in alcohol. When heated on platinum 

 foil,. it becomes brown, melts and burns, giving off incense-like 

 fumes. Heat, or boiling with sulphuric acid, converts it into 

 resinous-looking substances, choloidinic acid and dyslysin. 



* 147. Cholesterin. Cholesterin is not generally pre- 

 pared directly from bile, but from gall-stones, most of which 

 consist chiefl\ r of Cholesterin, along with a little bile pigment 

 and earthy salts. Preparation. Extract pulverized gall- 

 stones with boiling alcohol, and filter while boiling. Crystals 

 of chobesterin separate from the filtrate when cool. In order 

 to purify it, boil the crystals with alcoholic solution of caustic 

 potash/ On cooling they will again separate. Wash the pro- 

 duct with cold alcohol, and then with water; dissolve it in a 

 mixture of alcohol and ether; allow it to evaporate. Crystal- 

 lized cholesterin forms rhombic plates, the corners of which 

 are often broken (fig. 314). It is quite insoluble in water and 

 in cold alcohol. In boiling alcohol it dissolves with ease. Cho- 

 lesterin may be conveniently prepared from the ethereal extract 

 of gall stones obtained in the preparation of bilirubin by evapo- 



