352 PHYSIOLOGICAL CHEMISTRY 



Dissolve the carbonate, citrate and thiocyanate in about 700 

 c.c. of water and filter if necessary. Dissolve the copper sul- 

 phate in 100 c.c. of water, and add slowly, stirring constantly, 

 to the 700 c.c. Add the ferrocyanide and make up to exactly 

 1 liter. The only ingredient which need be weighed exactly 

 is the copper sulphate. 



Analysis. Measure 25 c.c. (pipette) of the reagent into a 25-30 

 cm. evaporating dish. Add 10-20 grams crystalline Na 2 C0 3 , or 

 !/2 this amount of the anhydrous salt, some talcum or powdered 

 pumice and heat to boiling over a free flame until the carbonate 

 has dissolved. 



Accurately dilute 10 c.c. of urine to 100 c.c. unless the 

 amount of sugar in it is small, Avhen it can be used without 

 dilution. Fill a burette with the urine, and run it into the 

 boiling copper solution, rapidly at first and then more slowly 

 as the color grows less, then a few drops at a time until the 

 solution is colorless. A white precipitate forms during the 

 titration. If the liquid in the dish becomes too concentrated, 

 add water. 



Calculation. Exactly 50 mg. of glucose will reduce the 25 c.c. 

 of the copper reagent. This amount of glucose must have been 

 present in the volume of urine used, provided no other reducing 

 substances were present. If the urine was diluted 10 times, 

 then the per cent of glucose in the original urine was 

 0.050 X 1000 where x is the volume of urine used from the 



x 

 burette. 



58. FERMENTATION TESTS. 



Perform a fermentation test on carbohydrate urine. 



This test is a very satisfactory one, as the other reducing sub- 

 stances in the urine do not ferment. It furnishes also a means 

 of differentiation between dextrose and lactose as certain 

 varieties of yeast will ferment dextrose but not lactose. 



