BILE 211 



allow the barium sulphate to settle. The presence of bile pigments is indicated 

 by the alcoholic solution being colored a greenish blue. 



NOTES. To render the test more delicate, pour off the alcoholic solution from 

 the barium sulphate into a dry tube. Add about one-third its volume of chloro- 

 form and mix. To the solution add about an equal volume of water, place the 

 thumb on the tube, invert once or twice and allow the chloroform to separate. 

 It contains the bluish pigment in solution. 



The bile pigment is adsorbed on to the barium sulphate precipitate, but passes 

 into solution again in acid alcohol. The chlorate acts as a very weak oxidizing 

 reagent, converting bilirubin and biliverdin to the characteristic blue compound. 



The author claims that it is a very much more delicate test than Gmelin's 

 Test. 



5. Test for Bile Acids. (a) Sucrose-H 2 SO 4 Test (Pettenkofer). To 5 c.c. 

 of diluted bile in a test-tube add 5 drops of a 5 per cent solution of sucrose. Now 

 run about 2-3 c.c. of concentrated sulphuric acid carefully down the side of the 

 tube and note the red ring at the point of contact. Upon slightly agitating the 

 contents of the tube the whole solution gradually assumes a reddish color. As 

 the tube becomes warm, it should be cooled in running water in order that the 

 temperature of the solution may not rise above 7oC. 



It is claimed that this test is not satisfactory in the presence of 

 protein and chromogenic substances which yield interfering colors 

 with sulphuric acid. 



(b) Furfural-H 2 SO 4 Test Mylius's Modification of Pettenkofer's Test 

 To approximately 5 c.c. of diluted bile in a test-tube add 3 drops of a very dilute 

 (i : 1000) aqueous solution of furfural, 



HC CH 



II II 

 HC C-CHO. 



v 



Now run about 2-3 c.c. of concentrated sulphuric acid carefully down the side of 

 the tube and note the red ring as above. In this case, also, upon shaking the 

 tube the whole solution is colored red. Keep the temperature of the solution be- 

 low 7oC. as before. 



(c) Foam Test (v. Udransky). To 5 c.c. of diluted bile in a test-tube add 3-4 

 drops of a very dilute (i : 1000) aqueous solution of furfural. Place the thumb 

 over the top of the tube and shake the tube until a thick foam is formed. By 

 means of a small pipette add 2-3 drops of concentrated sulphuric acid to the foam 

 and note the dark pink coloration produced. 



(d) Surface Tension Test (Hay). 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 hi a test-tube to i7C. 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 smks to the bottom of the liquid, the rapidity with which the sulphur sinks 

 depending upon the quantity of bile acids present in the mixture. The test is said 

 to react with bile acids when they are present in the ratio of i : 120,000. 



