70 METHODS FOR THE ANALYSIS OF URINE 



Procedure. Removal of Interfering Substances. Place 10 c.c. 

 of ordinary urine, or 20 c.c. of a dilute urine in a 50 c.c. volumetric 

 flask. To this add an acid silver lactate solution (from 2 to 20 

 c.c. of a 3 per cent solution of silver lactate in 3 per cent lactic 

 acid) until no further precipitate is obtained. Add a few drops 

 of colloidal iron, shake the flask, dilute to mark with distilled 

 water, shake again, and filter the contents through a dry filter. 

 Phenols are not precipitated by this procedure but are recovered 

 quantitatively in the filtrate. Transfer 25 c.c. of the filtrate to 

 a 50 c.c. volumetric flask, and add a sufficient quantity of saturated 

 sodium chloride solution, containing 10 c.c. of strong hydrochloric 

 acid per liter, to precipitate all the silver. Fill the flask to the 

 mark with distilled water, mix thoroughly, and filter through a 

 dry- filter. This filtrate, which contains half the phenol from the 

 urine taken for analysis, is used for the determination of free and 

 total phenols. 



Free Phenols. Place 20 c.c. of the filtrate mentioned above 

 in a 50 c.c. volumetric flask, add 5 c.c. of the phosphotungstic- 

 phosphomolybdic acid reagent and 15 c.c. of a saturated solution 

 of sodium carbonate. Dilute to volume with lukewarm water 

 (30 to 35 C.), mix thoroughly and after allowing to stand for 

 twenty minutes compare the deep blue color in the Duboscq 

 colorimeter against a standard solution of phenol (see below) 

 similarly treated. 



Total Phenols (Free and Conjugated). Place 20 c.c. of the 

 same filtrate used for the determination of free phenols in a large 

 test-tube, add 10 drops of concentrated hydrochloric acid, cover 

 the tube with a small funnel, heat rapidly to boiling over a free 

 flame, and then place in a boiling water-bath for ten minutes. 

 This process serves to decompose the conjugated phenols. At 

 the end of the ten minutes, remove the tube, cool, and transfer 

 the contents to a 100 c.c. volumetric flask. Add 10 c.c. of the 

 phosphotungstic-phosphomolybdic reagent, 25 c.c. of saturated 

 sodium carbonate solution, dilute to mark with lukewarm water 

 (30 to 35 C.), mix thoroughly, allow to stand for twenty minutes, 

 and read in the Duboscq colorimeter against a standard solution 

 of phenol (see below). 



Standard Solution of Phenol. The standard used is a solution 

 of pure phenol in N/100 hydrochloric acid containing 1 mg. of 

 phenol in 10 c.c. standardized by means of the iodometric titration. 



