URINE 533 



end point. If y represents the number of cubic centimeters of the permanganate 

 solution required, we may make the following calculation: 



y X 0.00375 = weight of uric acid in 100 c.c. of urine. 



Because of the solubility of the ammonium urate a correction of 3 mg. should 

 be added to the final, result. 



Calculate the quantity of uric acid in the 24-hour urine specimen. 



3. Kruger-Schmidt Method. Kriiger and Schmidt have devised a method 

 for the combined determination of uric acid and the other purine bodies of urine. 

 This procedure is described under Purine Bases, below. A modification of this 

 method by Hunter is also given. 



Purine Bases 



i. Kriiger and Schmidt's Method. Principle. This method serves 

 for the determination of both uric acid and the purine bases. The 

 principle involved is the precipitation of both the uric acid and the 

 purine bases in combination with copper oxide and the subsequent 

 decomposition of this precipitate by means of sodium sulphide. The 

 uric acid is then precipitated by means of hydrochloric acid and the 

 purine bases are separated from the filtrate in the form of their copper 

 or silver compounds. The nitrogen content of the precipitates of uric 

 acid and purine bases is then determined by means of the Kjeldahl 

 method (see page 504) and the corresponding values for uric acid and 

 purine bases calculated. 



Procedure. To 400 c.c. of albumin-free 'urine 1 in a liter flask, 2 add 24 

 grams of sodium acetate, 40 c.c. of a solution of sodium bisulphite 3 and heat 

 the mixture to boiling. Add 40-80 c.c. 4 of a 10 per cent solution of copper 

 sulphate and maintain the temperature of the mixture at the boiling-point for 

 at least three minutes. Filter off the flocculent precipitate, wash it with hot 

 water until the wash water is colorless, and return the washed precipitate to 

 the flask by puncturing the tip of the filter paper and washing the precipitate 

 through by means of hot water. Add water until the volume in the flask is 

 approximately 200 c.c., heat the mixture to boiling and decompose the precipi- 

 tate of copper oxide by the addition of 30 c.c. of sodium sulphide solution. 5 

 After decomposition is complete, the mixture should be acidified with acetic 

 acid and heated to boiling until the separating sulphur collects in. a mass. Filter 



1 If albumin is present, the urine should be heated to boiling, acidified with acetic acid 

 and filtered. 



2 The total volume of urine for the 24 hours should be sufficiently diluted with water lo 

 make the total volume of the solution 1600-2000 c.c. 



3 A solution containing 50 grams of Kahlbaum's commercial sodium bisulphite in ico 

 c.c. of water. 



4 The exact amount depending upon the content of the purine bases. 



5 This is made by saturating a i per cent solution of sodium hydroxide with hydrogen 

 sulphide gas and adding an equal volume of i per cent sodium hydroxide. 



Ordinarily the addition of 30 c.c. of this solution is sufficient, but the presence of an 

 excess of sulphide should be proven by adding a drop of lead acetate to a drop of the solution. 

 Under these conditions a dark brown color will show the presence of an excess of sodium 

 sulphide. 



