URINE. 125 



DEXTROSE. 



Before testing for dextrose in the urine, protein, if present, 

 must be removed by heat and acetic acid. The following 

 tests depend upon the power of dextrose to reduce metallic 

 oxides, as evidenced by the formation of precipitates or color 

 changes. It must be remembered that the urine may also 

 contain other bodies such as creatinine, uric acid, allantoin, 

 hydroquinol, alkaptonic acid, urine and bile pigments, and 

 conjugate glycuronic acids, which also reduce metallic 

 oxides to a slighter degree, however. It is, therefore, better 

 never to base a decision entirely upon reduction tests. 



Never allow the urine to boil more than a few seconds in 

 performing the tests. This will tend to eliminate the possi- 

 bility of a reduction caused by the above-mentioned sub- 

 stances. 



(a) Trommer's, Fehling's, and Fermentation Tests. Per- 

 form these tests as suggested under Monosaccharides (p. 4), 

 using the urine instead of the dextrose solution. 



(6) Benedict's Modification of Fehling's Test. To 5 c.c. of 

 Benedict's solution add five to eight drops of urine. Boil 

 the mixture vigorously for one or two minutes and allow the 

 test tube and contents to cool on the rack. A precipitate 

 will form in the solution, the color of which may be red, 

 yellow, or green, according to the amount of dextrose present. 

 This test is more sensitive than Fehling's and has the advantage 

 that the test solution does not deteriorate upon longstanding^ 



(e) Nylander's Test. To 10 volumes of urine add 1 volume 

 of Nylander's reagent and heat. The presence of sugar is 

 indicated by a dark coloration of the urine followed by a 

 separation of a black precipitate. By this very sensitive test 

 the reducing character of some normal urines may be shown. 



