42 



stratum at the bottom. If the bile pigments are present 

 at the line of junction of the fluids, a play of colors takes 

 place — from above downwards — green, blue, violet or dirty 

 red, and yellow. Nearly all urines give a play of colors, 

 but green is the necessary and characteristic color to prove 

 the presence of the bile pigments. 



Pettenkofer's Test for Bile Acids. Take about 2 cc. 

 of suspected urine in a test tube and add 4 drops of a 10% 

 solution of the cane sugar. Add strong sulphuric acid, 

 drop by drop, cooling the tube in a dish of cold water im- 

 mediately after adding the acid. Not more than 2 cc. of 

 the acid should be used. Too much heat causes carboniza- 

 tion of the sugar and the test is ruined. If bile acids are 

 present, the fluid at first becomes opaque, then clear and 

 successively brown, red and purple. It may require an 

 hour or more to accomplish the test. This reaction de- 

 pends upon the production of furfurol by the destruction 

 of the sugar when the sulphuric acid is used. Furfurol in 

 turn combines with cholalic acid, formed by the action of 

 the sulphuric acid on the bile acids, giving the color. 



Pettenkofer's test may also be quite satisfactorily 

 performed more quickly by putting a little of the sus- 

 pected urine in a porcelain capsule, adding a few drops of 

 a solution of cane sugar and then a few drops of strong 

 sulphuric acid, keeping the mixture cool to prevent car- 

 bonization. 



.. tldranszky has modified Pettenkofer's test by using 

 furfurol directly instead of waiting for its formation by 

 the action of the sulphuric acid upon the sug^r. His pro- 

 cedure is as follows : One cubic centimeter of the urine is 

 treated with one drop of a D.1% solution of furfurol. and 

 slowly superposed upon 1 cc. of sulphuric acid, care being 

 taken to prevent too great heating of the mixture. A 

 purple color appears at the plane of contact, that gradu- 

 ally extends upward into the superposed solution ; on 

 standing, the color turns bluish. In alcoholic solution a 

 green flourescence is seen. The pigment gives a typical 

 spectrum. 



Hay 's Test. Use two test tubes ; in one place a little 



