100 METHODS FOR THE ANALYSIS OF BLOOD 



reagent, 10 c.c. of 20 per cent sodium carbonate solution, and 

 diluting to the mark at the end of about one-half minute. The 

 standard solution is best set at a height of 15 mm. in the colorim- 

 eter. 



Calculation. The reading of the standard divided by the read- 

 ing of the urine gives the number of milligrams of uric acid in the 

 amount of sample taken. 



If the amount of uric acid present is very small the addition 

 of 1 drop of cyanide solution, 1 c.c. of uric acid reagent, 5 c.c. of 

 20 per cent sodium carbonate solution, and dilution to 25 c.c. 

 are carried out rather than using the larger quantities given for 

 the determination in the urine. 



Preparation of Solutions. Ammoniacal Silver Magnesium Solu- 

 tion. This solution has the following composition: 



3 per cent silver lactate solution 70 c.c. 



Magnesia mixture 30 c.c. 



Concentrated ammonium hydroxide solution . . . 100 c'.c. 



Uric Acid Reagent. Boil together 100 gms.of sodium tungstate, 

 30 c.c. of 85 per cent phosphoric acid, 20 c.c. of concentrated 

 hydrochloric acid, and 750 c.c. of distilled water under a reflux 

 condenser for 1^ hours. Cool and make up to 1 liter. This 

 modified solution shows less tendency to develop turbidity than 

 does the original Folin-Denis reagent. 



Sodium Carbonate Solution. Dissolve 200 gms. of anhydrous 

 sodium carbonate in warm water and make up to 1 liter. 



Standard Uric Acid Solution. The solution of uric acid in 

 phosphate solution is very readily prepared, does not need to be 

 standardized, and appears to keep indefinitely. It is prepared 

 in the following manner: Dissolve 9 gms. of pure crystallized 

 disodium hydrogen phosphate, together with 1 gm. 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 per- 

 fectly clear) solution upon exactly 200 mg. of pure uric acid sus- 

 pended 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 ehlo. reform, to 



