324 PHYSIOLOGICAL CHEMISTRY. 



BILE. 



Both the pigments and the acids of the bile may be detected 

 in the urine under certain pathological conditions. Of the pig- 

 ments, bilirubin is the only one which has been positively identi- 

 fied in fresh urine; the other pigments, when present, are probably 

 derived from the bilirubin. A urine containing bile may be yel- 

 lowish-green to brown in color and when shaken foams readily. 

 The staining of the various tissues of the body through the ab- 

 sorption of bile due to occlusion of the bile duct causes a condi- 

 tion known as icterus or jaundice. Bile is always present in the 

 urine under such conditions unless the amount of bile reaching 

 the tissues is extremely small. 



EXPERIMENTS. 



Tests for Bile Pigments. 



1. Gmelin's Test. To about 5 c.c. of concentrated nitric acid 

 in a test-tube add an equal volume of urine carefully so that the 

 two fluids do not mix. At the point of contact note the various 

 colored rings,* green, blue, violet, red and reddish-yellow. 



2. Rosenbach's Modification of Gmelin's Test. Filter 5 c.c. 

 of urine through a small filter paper. Introduce a drop of con- 

 centrated nitric acid into the cone of the paper and observe the 

 succession of colors as given in Gmelin's test. 



3. Nakayama's Reaction. To 5 c.c. of urine in a test-tube add 

 an equal volume of a 10 per cent solution of barium chloride. Cen- 

 trifugate the mixture, pour off the supernatant fluid and heat the 

 precipitate with 2 c.c. of Nakayama's reagent. 1 In the presence 

 of bile pigments the solution assumes a blue or green color. 



3. Huppert's Reaction. Thoroughly shake equal volumes of 

 urine and milk of lime in a test-tube. The pigments unite with 

 the calcium and are precipitated. Filter off the precipitate, wash 

 it with water and transfer to a small beaker. Add alcohol acidified 

 slightly with hydrochloric acid and warm upon a water-bath until 

 the solution becomes colored an emerald green. 



According to Steensma, this procedure may give negative results 

 even in the presence of the pigments, owing to the fact that the 

 acid-alcohol is not a sufficiently strong oxidizing agent. He there- 

 fore suggests the addition of a drop of a 0.5 per cent solution of 



1 Prepared by combining 99 c.c. of alcohol and I c.c. of fuming hydrochloric 

 acid containing 4 grams of ferric chloride per liter. 



