94 METHODS FOR THE ANALYSIS OF BLOOD 



sodium sulphite, 0.5 c.c. of a 5 per cent solution of sodium cyanide, 

 and 3 c.c. of a 20 per cent solution of sodium carbonate. Prepare 

 simultaneously two standard uric acid solutions as follows: 



Transfer to one 50 c.c. volumetric flask 1 c.c. and to another 

 50 c.c. flask 2 c.c. of the standard uric acid sulphite solution 

 described above. To the first flask add also 1 c.c. of 10 per cent 

 sodium sulphite solution. Then add to each flask 4 c.c. of the acidi- 

 fied sodium chloride solution, 1 c.c. of the sodium cyanide solution, 

 and 6 c.c. of the sodium carbonate solution. Dilute with water 

 to about 45 c.c. When the two standard solutions and the unknown 

 have been prepared as described, they are ready for the addition 

 of the uric acid reagent. Add 0.5 c.c. of this reagent to the unknown 

 and 1 c.c. to each of the standards, and mix. Let stand for ten 

 minutes, fill to the mark with water, mix, and make the color 

 comparison. 



Calculation. In connection with the calculation it is to be 

 noted (a) that the blood filtrate taken corresponds to 2 c.c. of blood, 

 (6) that the standard is diluted to twice the volume of the unknown, 

 and (c) that the standard used contains 0.1 or 0.2 mg. of uric acid. 

 The blood filtrate from blood containing 2.5 mg. of uric acid will 

 be just equal in color to the weaker standard. Twenty times 2.5 

 divided by the reading of the unknown, gives, therefore, the uric 

 acid content of the blood when the weaker standard is set at 20 

 mm. 



Remarks. At times the uric acid content may sink to as low 

 as 1 mg. of uric acid per 100 c.c. of blood. A standard correspond- 

 ing to the color obtained from 1.25 mg. of uric acid per 100 c.c. 

 of blood can be quickly prepared as follows: 



Transfer 1 c.c. of 10 per cent sulphite solution, 3 c.c. of 20 per 

 cent sodium carbonate, 2 c.c. of the acidified sodium chloride, 0.5 

 c.c. of the sodium cyanide solution, and 25 c.c. of the weaker one 

 of the two regular standard solutions already on hand. Dilute 

 to 50 c.c. and mix. Or, simply add 5 c.c. of 20 per cent sodium 

 carbonate to 25 c.c. of the regular weaker standard, and dilute 

 to 50 c.c. 



If a low uric acid value is expected, an alternate procedure is 

 to dilute the unknown to a final volume of 10 c.c. with correspond- 

 ing reduction in the amount of the reagents used. 



The uric acid reagent must invariably be added after, and not 

 before, the addition of the sodium carbonate, because in acid 



