126 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



Urines containing sulphides cannot be tested by this method. 

 Why? 



(d) Phenylhydrazin Test. Perform this test as given under 

 the Monosaccharides, using 15 c.c. of urine. As other sub- 

 stances in the urine may give a precipitate with the reagent, 

 a mere separation of an insoluble body is not sufficient 

 evidence for the presence of a sugar. The precipitate must 

 be yellow and must be examined carefully and critically 

 under the microscope. If sufficient quantities are obtainable 

 for a melting-point determination, this procedure should be 

 carried out. Phenylglucosazone melts at 204-205 C. 



(e) Polarization Test. As it was stated in the discussion 

 of the value of this test for quantitative purposes, the results 

 obtained are apt to be misleading, especially when no polar- 

 ization of the urine can be detected. When taken as evidence 

 confirmatory of other tests it may serve a useful purpose. The 

 dextro-rotation must completely disappear aftei fermentation. 



BILE. 



The presence of bile imparts to the urine a saffron color, 

 which upon standing takes on a greenish tinge. Icteric 

 urine is usually cloudy or turbid and the sediment, if any, is 

 rather strongly colored. 



In order to insure a positive identification of icteric urine 

 by means of the bile acids it is necessary to separate them 

 from the urine by a long and laborious procedure and then to 

 perform Pettenkofer's test. Though this is the more accurate 

 method, still it is more usual clinically to perform tests for 

 the presence of the biliary pigments directly on the urine. 



(a) Perform Gmelin's, Smith's, Hammarsten's, and Hup- 

 pert's tests. 



(6) Rosenbach's Modification of Gmelin's Test. Filter 



