URINE 539 



from the burette must be run in a few drops at a time, until the disappearance of 

 the last trace of blue color, which marks the end point. The solution must be 

 kept vigorously boiling throughout the entire titration. If the mixture becomes 

 too concentrated during the process, water may be added from time to time to 

 replace the volume lost by evaporation. 



Calculation. The calculation of the percentage of sugar hi the original sample 

 of urine is very simple. The 25 c.c. of copper solution are reduced by exactly 50 

 mg. of glucose. Therefore the volume run out of the burette to effect the reduc- 

 tion contained 50 mg. of the sugar. When the urine is diluted i : 10, as in the 

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

 sugar is the following : 



0.050 



-X 1 000 = per cent hi original sample, wherein X 



A 



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 hi 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. Benedict's Micro - Method . Principle. See Benedict's 

 Method above. 



Procedure. Five c.c. of Benedict's volumetric solution are pipetted into a 

 test tube (25 X 150 mm.) and i to 2 gm. of sodium carbonate added. (If 

 preferred a 25 c.c. Erlenmeyer flask may be employed, instead of the test tube, 

 and the flask placed over a wire gauze.) The solution is now brought to a 

 vigorous boil with continued gentle agitation, the tube being held in the left 

 hand, employing a folded paper as a test tube holder. With the right hand the 

 urine is run in, a drop at a time, until a chalk-white precipitate begins to form. 

 The urine is now run in more slowly until one drop dissipates the last trace of 

 color, indicating the end point in the reaction. 



f'jj Calculation. Since the 5 c.c. of the Benedict solution require exactly 10 mg. 

 (o.oi gm.) of glucose for reduction, the calculation may be made very simple. 



100 



The following formula may be used : - X o.oi = glucose in per 



Burette reading 



cent, or more simply, the urine used in c.c. may be divided into i. 



