686 PHYSIOLOGICAL CHEMISTRY. 



Test for biliary acids. The biliary acids and their salts show a 

 characteristic reaction known as Pettenkofer's test. This reaction is 

 shown by adding very little cane-sugar to the liquid substance under 

 examination, and adding concentrated sulphuric acid in such a 

 manner that the temperature does not rise above 70 C. (158 F.). 

 In the presence of biliary acids a beautiful cherry-red color is devel- 

 oped, which gradually changes to dark reddish-purple. The red 

 liquid when examined spectroscopically shows two absorption-bands, 

 one at F, the other near E, between D and E. Bile acids are not 

 the only substances which show the colors of Pettenkofer's test, but 

 the spectroscopic examination will clear up doubtful cases. 



Experiment 84. Evaporate ox-bile to a thick syrup, digest it with 5 parts of 

 pure, cold alcohol for two hours, and filter. Mix the filtrate, which contains 

 sodium glycocholate and taurocholate, with freshly prepared animal charcoal, 

 boil and filter ; evaporate to dryness in a water-bath, redissolve in the smallest 

 possible amount of pure alcohol, and add ether until the solution becomes 

 markedly turbid. A white, crystalline mass is deposited in a few hours or days ; 

 this is known as Planner's crystallized bile, and is a mixture of the two sodium 

 salts mentioned. 



Dissolve the mass in a small volume of water, adding a little ether and then 

 dilute sulphuric acid; glycocholic acid crystallizes out in shining needles. 

 Taurocholic acid is easiest prepared by using -dog's bile, which contains no 

 glycocholic acid. 



Apply the Pettenkofer test to the glycocholic acid obtained. 



Cholesterin and lecithin in the bile are present in considerable 

 amount. They are regarded here as waste products. 



Siiiary calculi consist chiefly of cholesterin, and in addition they 

 contain bile-pigment, the bile acids combined with calcium, calcium 

 soaps, and calcium carbonate. 



Experiment 85. (Examination of biliary calculi.} Boil the freshly powdered 

 stones with water to remove bile, filter, and extract the dry residue with a 

 mixture of alcohol and ether. Filter, and evaporate the filtrate to a small 

 volume, when crystals of cholesterin will be deposited. Purify the crystals by 

 dissolving them in boiling alcohol to which a fragment of sodium hydroxide 

 has been added, and treating the mixture in a separatory funnel with ether. 

 By evaporation of the ethereal solution cholesterin is obtained in a pure con- 

 dition. Apply the tests for the same (see Index). 



The residue of the calculi, insoluble in ether and alcohol, consists of the 

 inorganic salts and bile-pigments. Dissolve the salts by pouring dilute hydro- 

 chloric acid over the contents in the filter, and show in filtrate the presence of 

 calcium by neutralizing with ammonia, acidifying with acetic acid, and adding 

 ammonium oxalate, when calcium oxalate is precipitated. To a portion of the 

 hydrochloric acid solution add potassium ferrocyanide ; sometimes a red pre- 

 cipitate is formed, due to the presence of traces of copper in the calculus. 



