URINE 523 



usual titration of diabetic urines, the formula for calculating the per cent of the 

 sugar is the following: 



5 X 1000 = per cent in original sample, wherein X 



X 



is the number of cubic centimeters of the diluted urine required to reduce 25 c.c. 

 of the copper solution. 



In the use of this method chloroform must not be present during the titration. 

 If used as a preservative in the urine it may be removed by boiling a sample for 

 a few minutes, and then diluting to its original volume. 



Interpretation. Sugar in the urine in amounts sufficient to be de- 

 tected by the commonly employed qualitative tests indicates a patho- 

 logical condition, unless very large amounts of sugar have been ingested 

 just previously, in which case the condition is spoken of as an alimentary 

 glycosuria. Persistent glycosuria thus indicates diabetes mellitus, a 

 disorder in which the amount of sugar may rise as high as 10 per cent 

 and averages 3-5 per cent. The volume of urine excreted per day is 

 usually also large and the absolute sugar excretion may thus be very 

 great (100 grams of glucose per day are not.uncommon) . The quantita- 

 tive methods for the estimation of sugar in urine enable us to deter- 

 mine the severity of the disorder as well as to follow its course under 

 treatment, etc. 



2. Fehling's Method. Principle. Diluted urine is run into a 

 measured amount of Fehling's solution at the boiling-point until all 

 of the copper it contains is reduced as indicated by the loss of blue color. 

 This method has several disadvantages over Benedict's method. The 

 end point is difficult to determine and the mixed solution is unstable. 

 It gives less accurate results. 



Procedure. Place 10 c.c. of the urine under examination in a 100 c.c. volu- 

 metric flask and make the volume up to 100 c.c. with distilled water. (If the 

 urine contains less than 0.5 per cent of sugar it may be used without dilution. A 

 concentration of about 0.5 per cent is the most satisfactory for this titration.) 

 Thoroughly rniy this diluted urine by pouring it into a beaker and stirring with 

 a glass rod, then transfer a portion of it to a burette which is properly supported 

 in a clamp. 



Now place 10 c.c. of Fehling's solution 1 in a small beaker, dilute it with approxi- 

 mately 40 c.c. of distilled water, heat to boiling, and observe whether decomposi- 

 tion of the Fehling's solution itself has occurred as indicated by the production of 

 a turbidity. If such turbidity is produced the Fehling's solution is unfit for use. 

 Clamp the burette containing the dilute urine immediately over the beaker and 

 carefully allow from 0.5-1 c.c. of the diluted urine to flow into the boiling Fehl- 

 ing's solution. Bring the solution to the boiling-point after each addition of 

 urine and continue running the urine from the burette, 0.5-1 c.c. at a time, as in- 

 dicated, until the Filing's solution is completely reduced, i.e., until all the cupric 



1 Directions for the preparation of Fehling's solution are given in a note at the bottom 

 of p. 26. 



