BILE. 157 



of furfurol and 5-6 drops of concentrated sulphuric acid. A blue 

 color indicates bile acids. 



(/) Hay's Test. This test is based upon the principle that bile 

 acids have the property of reducing the surface tension of fluids 

 in which they are contained. The test is performed as follows : 

 Cool about 10 c.c. of diluted bile in a test-tube to 17 C. or lower 

 and sprinkle a little finely pulverized sulphur upon the surface of 

 the fluid. The presence of bile acids is indicated if the sulphur 

 sinks to the bottom of the liquid, the rapidity with which the sulphur 

 sinks depending upon the quantity of bile acids present in the mix- 

 ture. The test is said to react with bile acids when they are present 

 in the proportion I : 120,000. 



Some investigators claim that it is impossible to differentiate be- 

 tween bile acids and bile pigments by this test. 



6. Crystallization of Bile Salts. To 25 c.c. of undiluted bile 

 in an evaporating dish add enough animal charcoal to form a 

 paste and evaporate to dryness on a water-bath. Remove the resi- 

 due, grind it in a mortar and transfer it to a small flask. Add 

 about 50 c.c. of 95 per cent alcohol and boil on a water-bath for 

 20 minutes. Filter, and add ether to the filtrate until there is a 

 slight permanent cloudiness. Cover the vessel and stand it away 

 until crystallization is complete. Examine the crystals under the 

 microscope and compare them with those shown in Fig. 40, page 152. 

 Try one of the tests for bile acids upon some of the crystals. 



