62 METHODS FOR THE ANALYSIS OF URINE 



are measured with a pipette into a porcelain evaporation dish 

 (25 to 30 cm. in diameter), 10 to 20 gms. of crystallized sodium 

 carbonate (or one-half the weight of the anhydrous salt) are 

 added, together with a small quantity of powdered pumice or 

 talcum, and the mixture heated to boiling over a free flame 

 until the carbonate has entirely dissolved. The diluted urine 

 is now run in from the burette, rather rapidly, until a chalk- 

 white precipitate forms and the blue color of the mixture begins 

 to lessen perceptibly, after which the solution 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 solu- 

 tion must be kept vigorously boiling throughout the entire titra- 

 tion. If the mixture becomes too concentrated during the proc- 

 ess, water may be added from time to tune to replace the volume 

 lost by evaporation. 



Calculation. The calculation of the percentage of sugar in 

 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 reduction contained 

 50 mg. of the sugar. When the urine is diluted 1:10, as in the 

 usual titration of diabetic urines, the formula for calculating the 

 per cent of the sugar is the following: 



0.050 



X 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. 



ACETONE BODIES 



Van Slyke's Methods 1 



Principle. The method is based on a combination of Shaf- 

 fer's oxidation of /3-hydroxybutyric acid to acetone, and 

 Denige's precipitation of acetone as a basic mercuric sulphate 



Van Slyke; Jour. Biol Chem., 1917, 32, 455. 



