URINE 351 



Before starting the experiment read through the entire direc- 

 tions for the process. 



With a pipette measure 10 c.c. of each part of the quantita- 

 tive Fehling's solution into an Erlenmeyer flask (or evaporat- 

 ing dish). Add 80 c.c. of water measured with a graduate. 

 Dilute 5 c.c. of urine (measured with a pipette) with 20 c.c. 

 distilled water (also measured with a pipette). Diluting in a 

 volumetric flask is preferable, but the method described is 

 satisfactory. 



Fill a burette with the diluted urine. Heat the diluted 

 Fehling's solution in the Erlenmeyer with a small flame, and 

 run in the urine, first a few drops at a time, boiling a few 

 seconds after each addition. If the liquid remains blue after 

 the addition of 2 c.c. of urine, continue the process, adding the 

 urine in 0.2 -0.3 c.c. portions until the blue or green color has 

 almost disappeared, then drop by drop until no blue or green 

 tinge can be detected. Observe over a white paper. Do not 

 look through the liquid at the blue sky. The volume of urine 

 required to reduce the 20 c.c. of Fehling's will contain 0.1 gm. 

 dextrose or 0.134 gm. lactose. Perform duplicate analyses. 

 Time may be saved by running through a trial titration before 

 the actual determination, in order to find roughly the volume 

 of urine required to reduce the Fehling's solution. 



Calculate the weight of sugar in 100 c.c. of urine. If the 

 sugar content of the urine is so high that less than 2 c.c. are 

 required to reduce 20 c.c. of Fehling's solution, the urine must 

 be further diluted. 



57. Benedict's Method. The greater accuracy of this method 

 is due to several facts: the solution is less strongly alkaline, so 

 that the decomposition of the sugar on boiling is less, and the 

 end point is perhaps sharper than in the original Fehling 

 method. 



Standard Copper Solution. Eighteen grams pure crystalline 

 CuSO 4 ; 200 grams crystalline Na 2 C0 3 ; 200 grams sodium or 

 potassium citrate; 125 grams KCNS; 5 c.c. of a 5% solution of 

 K 4 Fe(CN) 6 ; distilled water to make a total volume of 1 liter. 



