URINE 445 



It is rather difficult to show the presence of lactose in the urine in a 

 satisfactory manner, since the formation of the characteristic lactos- 

 azone is not attended with any great measure of success under these 

 conditions. It is, however, comparatively easy to show that it is not 

 glucose, for, while it responds to reduction tests, it does not ferment 

 with pure yeast and does not give a glucosazone. An absolutely 

 conclusive test, of course, is the isolation of the lactose in crystalline 

 form (Fig. 104, page 318) from the urine. 



Oh oxidation with nitric acid lactose and galactose yield mucic acid. 

 This test is frequently used in urine examination to differentiate lactose 

 and galactose from other reducing sugars. To differentiate lactose 

 from pentose, since neither ferments, we may apply the Orcinol HC1 

 test of Bial, see page 443. 



EXPERIMENTS 



1. Mucic Acid Test. Treat 100 c.c. of the urine under examination with 

 20 c.c. 1 of concentrated nitric acid and evaporate the mixture in a broad, shallow 

 glass vessel, upon a boiling water-bath until the volume of the solution is only 

 about 20 c.c. At this point the fluid should be clear and a fine white precipitate 

 of mucic acid should separate. 



If the percentage of lactose 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 dif- 

 ferentiate these two sugars from all other reducing sugars. A sat- 

 isfactory differentiation between lactose and galactose in pure solution 

 may be made by means of Barfoed's test, page 30. This test is, 

 however, not suited for urine examination. To differentiate galactose 

 and lactose in urine use the Phloroglucinol-Hydrochloric Acid Reaction 

 of Tollens, see pages 36 and 443. 



2. Rubner's Test. To 10 c.c. of urine in a small beaker add some lead acetate, 

 in substance, heat to boiling, and add NH 4 OH until no more precipitate is dissolved. 

 In the presence of lactose a brick-red or rose-red color develops, whereas glucose 

 gives a coffee-brown color, maltose a light yellow color, and fructose no color at all 

 under the same conditions. 



3. Compound Test. Try the Nylander reaction. If positive try the phenyl- 

 hydrazine test. If negative (the lactosazone is not readily formed in urine) apply 

 the fermentation test. If this test is also negative, differentiate between lactose 

 and pentose by Orcinol-HCl reaction (Bial) and mucic acid tests. 



1 If the specific gravity of the urine is 1020 or over it is necessary to use 25-35 c.c. of 

 nitric acid. Under these conditions the mixture should be evaporated until the remaining 

 volume is approximately equivalent to that of the nitric acid added. 



