126 THE BILE. 



the water-bath. Then pulverize the mass in a mortar, 

 which operation is facilitated by the sand. Dissolve the 

 biliary salts by strong alcohol,, and filter. Evaporate this 

 solution to a small volume on the water-bath, allow it to 

 cool, pour it into a flask, and precipitate with an excess 

 of ether, shaking to mix thoroughly. After standing a few 

 hours the precipitated mass is converted into clusters of 

 silky crystals (sometimes called crystallized bile). These 

 are a mixture of the sodium salts of the taurocholic and 

 glycocholic acids. They can be purified by filtering, wash- 

 ing with water, dissolving in the smallest possible quantity 

 of water, and precipitating again with ether. They crys- 

 tallize then in long, thin, colorless crystals with a silky 

 luster. 



267. PETTENKOFER'S TEST FOR THE BILIARY ACIDS. 

 Use the salts or the ox-bile. Mix in a porcelain dish or 

 test-tube with a small amount of concentrated sulphuric 

 acid, being careful not to let the temperature rise above 

 70 C. It must, however, be above 50. Then add, drop 

 by drop, a 10-per-cent. solution of cane-sugar, stirring with 

 a glass rod. A red color appears. If too much sugar is 

 added or the temperature is too high the sugar is decom- 

 posed by the acid, giving dark-brown products, which con- 

 ceal the red color. 



268. The same result may be obtained by adding the 

 sugar to the liquid to be tested, acidifying with dilute sul- 

 phuric acid, and dipping into it a piece of filter-paper. 

 Allow the paper to dry, or dry it at a moderate heat, to 

 avoid charring. When it is completely dry, the red color 

 appears on the paper. If heated too highly it will be 

 turned black by the acid. 



