URINE 461 



If the percentage of galactose present in the urine is low it may be 

 necessary to cool the solution and permit it to stand for some time 

 before the precipitate will form. It is impossible to differentiate 

 between galactose and lactose by means of this test, but the reaction 

 does serve to differentiate these two sugars from all other reducing 

 sugars. A satisfactory differentiation between galactose and lactose 

 may be made by the Phloroglucinol-Hydrochloric Acid Test of Tollens, 

 below. 



2. Phloroglucinol-Hydrochloric Acid Reaction (Tollens). To equal volumes of 

 the urine and hydrochloric acid (sp. gr. 1.09) add a little phloroglucinol and heat 

 the mixture on a boiling water-bath. Galactose, pentose, and glycuronic acid will 

 be indicated by the appearance of a red color. Galactose may be differentiated 

 from the two latter substances in that its solutions exhibit no absorption bands 

 upon spectroscopical examination. 



FRUCTOSE 



Diabetic urine frequently possesses the power of rotating the plane of 

 polarized light to the left, thus indicating the presence of a levorotatory 

 substance. The levorotation is sometimes due to the presence of 

 fructose, although not necessarily confined to this carbohydrate, since 

 conjugate glycuronates and /3-hydroxybutyric acid, two other levo- 

 rotatory bodies, are frequently found in the urine of diabetics. Fructose 

 is invariably accompanied by glucose in diabetic urine, but fruc- 

 tosuria has been observed as a separate anomaly. The presence of 

 fructose may be inferred when the percentage of sugar, as determined 

 by the titration method, is greater than the percentage indicated by 

 the polariscopic examination. 



EXPERIMENTS 



i. Borchardt' s Reaction. To about 5 c.c. of urine in a test-tube add ah equal 

 volume of 25 per cent hydrochloric acid and a few crystals of resorcinol. Heat to 

 boiling and after the production of a red color, cool the tube under running water 

 and transfer to an evaporating dish or beaker. Make the mixture slightly alka- 

 line with solid potassium hydroxide, return it to a test-tube, add 2-3 c.c. of 

 acetic ether, and shake the tube vigorously. In the presence of fructose the 

 acetic ether is colored yellow. 



The only urinary constituents which interfere with the test are 

 nitrites and indican and these interfere only when they are simul- 

 taneously present. Under these conditions, the urine should be acidified 

 with acetic acid and heated to boiling for one minute to remove the 

 nitrites. In case the indican content is very large, it will impart a blue 

 color to the acetic ether, thus masking the yellow color due to fructose. 

 When such urines are to be examined, the indican should first be re- 



