448 PHYSIOLOGICAL CHEMISTRY 



3. Potassium Hydroxide Test (Donne). Separate the sediment from the 

 urine (by decantation, filtration or centrifugation) ; place a small piece of solid 

 potassium hydroxide on the sediment and stir. If pus is present (and particu- 

 larly H it be fresh pus and not disintegrated) the sediment will become slimy and 

 tough. If the sediment is mucus it will more or less pass into solution in the 

 concentrated alkali. 



BILE 



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

 urine under certain pathological conditions. Of the pigments, bilirubin 

 is the only one which has been positively identified in fresh urine; the 

 other pigments, when present, are probably derived from the bilirubin. 

 A urine containing bile may be yellowish-green to brown in color and 

 when shaken foams readily. The staining of the various tissues of the 

 body through the absorption of bile due to occlusion of the bile duct 

 is a prominent symptom of the condition 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 



Practically all of these tests for bile pigments are based on the 

 oxidation of the pigment by a variety of reagents with the formation 

 of a series of colored derivatives, e.g., biliverdin (green), bilicyanin 

 (blue), choletelin (yellow). 



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

 dish-yellow. 



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

 a small filter paper. Introduce a drop of concentrated nitric acid into the cone 

 of the paper and observe the succession of colors as given hi Gmelin's test. 



3. Huppert-Cole Test. 1 Boil about 15 c.c. of the fluid in a test tube. Add 

 two drops of a saturated solution of magnesium sulphate, then add a 10 per cent 

 solution of barium chloride, drop by drop, boiling between each addition. Con- 

 tinue to add the barium chloride until no further precipitate is obtained. Allow 

 the tube to stand for a minute. Pour off the supernatant fluid as cleanly as 

 possible or use a centrifuge. To the precipitate add 3 to 5 c.c. of 97 per cent 

 alcohol, two drops of strong sulphuric acid, and two drops of a 5 per cent aqueous 

 solution of potassium chlorate. Boil for half a minute and allow the barium 

 sulphate to settle. The presence of bile pigments is indicated by the alcohol 

 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- 

 1 Cole's "Practical Physiological Chemistry" 6th Edition, p. 268, 1920. 



