PART II 

 METHODS FOR THE ANALYSIS OF URINE 



ACIDITY OF URINE BY TITRATION 



Folin's Method 1 



Principle. The urine is titrated with standard sodium 

 hydroxide solution, using phenolphthalein as an indicator. Potas- 

 sium oxalate is added to precipitate the calcium which would other- 

 wise interfere with the end-point due to the precipitation of 

 calcium phosphate on neutralization of the urine. The acidity 

 of the urine as determined in this way is not a correct measure of 

 the true acidity, which is dependent upon the concentration of 

 hydrogen ions. The results obtained do, however, ordinarily 

 show a certain parallelism with the hydrogen ion concentration 

 and are of value for comparative purposes. 



Procedure. Place 25 c.c. of urine in a 200 c.c. Erlenmeyer 

 flask or beaker and add 15-20 gms. of finely pulverized neutral 

 potassium oxalate and 1 to 2 drops of a 1 per cent phenolphthalein 

 solution to the fluid. Shake the mixture vigorously for 1 to 2 

 minutes and titrate it immediately with N/10 sodium hydroxide 

 until a faint but unmistakable pink remains permanent on further 

 shaking. Take the burette reading and calculate the acidity 

 of the urine under examination. 



Calculation. If y represents the number of cubic centimeters 

 of N/10 sodium hydroxide and used y' represents the volume of 

 urine excreted in twenty-four hours, the total acidity of the 



: Am. Jour. Physiol., 1905, 13, 45. 

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