URINE 449 



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 absorbed 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. 



Tests for Bile Acids 



1. Sucrose H 2 SO 4 Test (Pettenkofer). To 5 c.c. of urine in a test-tube add 

 5 drops of a 5 per cent solution of sucrose. Now incline the tube, run about 

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

 comes warm, it should be cooled in running water in order that the tempera- 

 ture may not rise about 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. 



2. Furfural H 2 SC>4 Test (Mylius). To approximately 5 c.c. of urine hi a 

 test-tube add 3 drops of a very dilute (i : 1000) aqueous solution of furfural, 



HC CH 



II II 

 HC C.CHO. 



Now incline the tube, run about 2-3 c.c. of concentrated sulphuric acid carefully 

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

 the tube, the whole solution is colored red. Keep the temperature below 7oC. 

 as before. 



3. Foam Test (v. Udransky). To 5 c.c. of urine 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 until a thick foam is formed. By means of a small 

 pipette add 2-3 drops of concentrated sulphuric acid to the foam and observe the 

 dark pink coloration produced. 



4. 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 

 urine in a test-tube to I7C. or lower, and sprinkle a little finely pulverized sul- 

 phur 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 amount of bile acids present in the urine. The test is said to 

 react with bile acids when the latter are present in the proportion i : 120,000. 

 Allen 1 has recently suggested the quantitative determination of bile acids by a 



1 Allen: Jour. Biol. Chem., 22, 505, 1915. 

 29 



