URINE AND ITS CONSTITUENTS. 717 



phuric acid, uric acid is set free and the amount is titrated with ^ 

 potassium permanganate solution. 

 Reagents used : 



1. Ammonium sulphate, 500; uranium acetate, 5; acetic acid 

 (10 per cent.), 60 ; water, 650. 



2. Ammonium sulphate, 10 per cent, solution. 



3. f-Q potassium permanganate. . 



To 100 c.c. of urine add 25 c.c. of reagent 1 ; let stand until the 

 precipitate has settled (five to ten minutes) and filter through two 

 folded filter-papers. To 100 c.c. of filtrate add 5 c.c. of concentrated 

 ammonia water and let stand for twenty-four hours. Pour off the 

 supernatant fluid through a filter and collect on it the precipitate of 

 ammonium urate with the aid of some 10 per cent, ammonium sul- 

 phate ; wash with the same solution for a short time. Open the 

 filter and collect the precipitate in a beaker with about 100 c.c. of 

 water. Add 15 c.c. of concentrated sulphuric acid, which will dis- 

 solve it. Titrate at once (while hot) with potassium permanganate 

 -/-$. The end-reaction is the first trace of rose color present through- 

 out the beaker after the addition of two drops of the reagent in 

 excess. 



Calculation : As there is used in the titration only of the original 

 amount of urine (taking 100 c.c. of the first filtrate, not the whole 

 125 c.c.), J of the result of the titration is the amount of permanga- 

 nate which would correspond to 100 c.c. of urine. Each cubic centi- 

 meter of the permanganate corresponds to 0.00375 gramme of uric 

 acid from which it is simple to calculate the amount of uric acid 

 present in the urine. 



Correction : As ammonium urate dissolves to the extent of 0.003 

 gramme in 100 c.c., this amount must be added for every 100 c.c. of 

 urine. 



Xanthine bodies. The xanthine bodies are normally present in 

 urine in small amount. Those present in largest amount are para- 

 xanthine, heteroxanthine, and methylxanthine, which arise from the 

 similar bodies, caffeine, theobromine, and theophylline, in the food. 

 Otherwise the origin and significance of the purine bodies are thought 

 to be the same as those of uric acid. 



Allantoin (glyoxyldiureide), C 4 H 6 N 4 O 3 , is normally present in 

 minute amounts in adults, more abundantly in the newborn. While 

 it will reduce Fehling's solution, the amount present is never suf- 

 ficient to give a positive test. 



Hippuric acid, CgHgNOj (Benzoyl-glycocoll, Benzoyl-amino-acetic 



