URINE.. 337 



acid. This test is frequently used in urine examination to differen- 

 tiate lactose and galactose from other reducing sugars. 



EXPERIMENTS. 



1. Mucic Acid Test. Treat 100 c.c. of the urine under examina- 

 tion with 20 c.c. 1 of concentrated nitric acid and evaporate the mix- 

 ture 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 

 add 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 differentiate these two 

 sugars from all other reducing sugars. A satisfactory differentia- 

 tion between lactose and galactose may be made by means of 

 Bar feed's test, p. 313. 



2. Rubner's Test. To 10 ^c.c. of urine in a small beaker add 

 some plumbic 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 dextrose gives a 

 coffee-brown color, maltose a light yellow coloj and Isevulose no 

 color at all under the same conditions. 



3. Compound Test. Try the phenylhydrazine test, the fermen- 

 tation test and Barfoed's test according to directions given under 

 Dextrose, pages 306, 313 and 314. If these are negative, try 

 Nylander's test, page 312. If this last test is positive, the presence 

 of lactose is indicated. 



GALACTOSE. 



Galactose has occasionally been detected in the urine, and in par- 

 ticular in that of nursing infants afflicted with a deranged digestive 

 function. Lactose and galactose may be differentiated from other 

 reducing sugars which may be present in the urine by means of the 

 mucic acid test. This test simply consists in the production of 

 mucic acid through oxidation of the sugar with nitric acid. 



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. 

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