CHAPTER XXVI 

 URINE : QUANTITATIVE ANALYSIS 



IN analyzing a normal or pathological urine quantitatively for 

 any of its constituents it is particularly necessary that the complete 

 and exact 24-hour sample be obtained. For directions with regard to 

 the collection and preservation of urine for analysis see Chapter 

 XXI on General Characteristics of Normal and Pathological Urine. 

 Methods for the determination of the specific gravity of the urine are 

 also there described. Before any urine is taken for analysis its total 

 volume should be measured, using a large graduated cylinder, and this 

 volume is thereafter taken as a basis for the calculations of the daily 

 output of the individual constituents determined. If the urine be 

 pathological it is of course necessary to precede its quantitative 

 analysis by qualitative tests for the pathological constituents. 



Acidity by Titration 



Folin's Method. Principle. The urine is titrated with standard 

 sodium hydroxide solution, using phenolphthalein as an indicator. 

 Potassium oxalate is added to precipitate the calcium which would 

 otherwise 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 and add 

 15-20 grams of finely pulverized potassium oxalate and 1-2 drops of a i per cent 

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

 minutes and titrate it immediately with N/io 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/io sodium 

 hydroxide used and y' represents the volume of urine excreted in 24 hours, the 

 total acidity of the 24-hour urine specimen may be calculated by means of the 

 following proportion: 



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