URINE: QUANTITATIVE ANALYSIS. 373 



Because of the solubility of the ammonium urate a correction of 

 3 milligrams should be added to the final result. 



Calculate the quantity of uric acid in the twenty-four hour urine 

 specimen. 



2. Heintz Method. This is a very simple method and was the 

 first one in general use for the quantitative determination of uric 

 acid. It is believed to be somewhat less accurate than the method 

 just described. The procedure is as follows : Place 100 c.c. of 

 filtered urine in a beaker, add 5 c.c. of concentrated hydrochloric 

 acid, stir the fluid thoroughly and stand it away in a cool place for 

 24 hours. Filter off the uric acid crystals upon a washed, dried and 

 iveighed filter paper and wash them with cold distilled water, a few 

 cubic centimeters at a time until the chlorides are removed. Now 

 wash, in turn, with alcohol and with ether and finally dry the 

 paper and crystals to constant weight at 110 C. In the process 

 of washing the uric acid free from chlorides an error is introduced, 

 since every cubic centimeter of water so used dissolves 0.00004 

 gram of uric acid. For this reason a correction is necessary. It 

 has been suggested that the pigment of the crystals is equivalent 

 in weight to the amount of uric acid dissolved by the first 30 c.c. 

 of water, and this factor should be taken into account in the 

 computation of the percentage of uric acid. 



Calculation. Since 100 c.c. of urine was used the corrected 

 weight of the uric acid crystals, in grams, will express the percent- 

 age of uric acid present. 



3. Kriiger and Schmidt's Method. This method serves for 

 the detection 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 decom- 

 position 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 pre- 

 cipitates of uric acid and purine bases is then determined by means 

 of the Kjeldahl method (see p. 381) and the corresponding values 

 for uric acid and purine bases calculated. The method is as fol- 

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



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 twenty-four hours should be sufficiently 

 diluted with water to make the total volume of the solution 1600-2000 c.c. 



