6lO PHYSIOLOGICAL CHEMISTRY 



(b) Uric Acid Reagent for Colorimetric Method. Place 100 grams of 

 sodium tungstate, 80 c.c. of 85 per cent phosphoric acid, and 750 c.c. of 

 distilled water in a liter flask. Boil the mixture with a reflux condenser 

 for two hours, cool and dilute to i liter, filtering if necessary. 



(c) Sodium Carbonate Solution. Dissolve 200 grams anhydrous 

 sodium carbonate in warm water and make up to i liter. 



(d) Uric Acid Formaldehyde Standard. Place i gram of uric acid in 

 a liter volumetric flask and dissolve with 200 c.c. of a 0.4 per cent lithium 

 carbonate solution. Add to the solution 40 c.c. of 40 per cent formalde- 

 hyde solution, shake the mixture and allow to stand for a few minutes. 

 Acidify the clear solution with 20 c.c. of normal acetic acid and dilute 

 to mark with distilled water The solution should remain perfectly 

 clear and the next day (not before) may be standardized against a 

 freshly prepared solution of uric acid in lithium carbonate. The color 

 produced by 5 c.c. of this solution corresponds very closely to that 

 produced from i mg. of pure uric acid. The colorimeter reading ob- 

 tained from the solution when thus compared with pure uric acid (i mg.) 

 is, of course, thereafter used as the standard value corresponding to i mg. 

 of uric acid. 



(e) Uric Acid Standard in Phosphate Solution. Dissolve 9 grams of 

 pure crystallized disodium hydrogen phosphate, together with i gram 

 of crystallized sodium dihydrogen phosphate, in 200 to 300 c.c. of hot 

 water, and filter if the solution is not perfectly clear. Make this 

 filtrate up to about 500 c.c. with hot water, and pour this hot or warm 

 (and perfectly clear) solution upon exactly 200 mg. of pure uric acid 

 suspended in a few cubic centimeters of water in a liter volumetric 

 flask. Agitate the mixture for a few minutes until the uric acid com- 

 pletely dissolves. Cool, add exactly 1.4 c.c. of glacial acetic acid, 

 dilute to the mark, and mix. Add about 5 c.c. of chloroform to pre- 

 vent the growth of bacteria or moulds in the solution. Five c.c. of 

 this solution contain exactly i mg. of uric acid. 



The solution of uric acid in the phosphate solution is very readily 

 prepared, does not need to be standardized, and appears to keep 

 indefinitely. 



