DETERMINATION OF URIC ACID 93 



a series of volumetric liter flasks. Add 200 c.c. to 300 c.c. of water, 

 then 500 c.c. of filtered 20 per cent sodium sulphite solution, and 

 finally make up to volume, and mix well. Fill a series of 200 c.c. 

 bottles, and stopper very tightly with rubber stoppers. The solu- 

 tion in a bottle which is opened daily will keep for at least three to 

 four months. In unopened bottles the uric acid will probably 

 keep for years. Of this solution 3 c.c. is to be used for each series 

 of determinations. 



2. A 10 per cent sodium sulphite solution. The surplus 20 per 

 cent sulphite solution from the preparation of the standard uric 

 acid sulphite solution should be diluted to a concentration of 10 

 per cent and then be transferred to a series of small, tightly 

 stoppered bottles. This sulphite is added to the unknown in order 

 to offset the sulphite content of the standard. Two c.c. of this solu- 

 tion are used for each determination. 



3. A 5 per cent sodium cyanide solution, to be added from a 

 burette, 2.5 to 5 c.c. used for each series of determinations. 



4. A 10 per cent solution of sodium chloride in 0.1 normal 

 hydrochloric acid. Ten to 20 c.c. to be used for each series of 

 determinations. 



5. The uric acid reagent. Boil together 100 gms. of sodium 

 tungstate. 80 c.c. of phosphoric acid (85 per cent) and 700 c.c. of 

 water for two hours under a reflux condenser. Dilute the solution 

 to 1 liter. 



6. A solution of 5 per cent silver lactate in 5 per cent lactic acid. 

 Four to 5 c.c. of this solution are needed for each determination. 



Procedure. To 10 c.c. of blood filtrate in each of two centrifuge 

 tubes (capacity 15 c.c.) or 20 c.c. of blood filtrate in 30 c.c. test- 

 tubes, add 2 c.c. of a 5 per cent solution of silver lactate in 5 per 

 cent lactic acid and stir with a very fine glass rod. Centrifuge; 

 add a drop of silver lactate to the supernatant solution which 

 should be almost perfectly clear and should not become turbid 

 when the last drop of silver solution is added. Remove the super- 

 natant liquid by decantation as completely as possible. Add to 

 each tube 1 c.c. of a solution of 10 per cent sodium chloride in 0.1 

 normal hydrochloric acid and stir thoroughly with a glass rod. 

 Then add 5 to 6 c.c. of water, stir again, and centrifuge once more. 

 By this chloride treatment the uric acid is set free from the pre- 

 cipitate. Transfer the two supernatant liquids by decantation to 

 a 25 c.c. volumetric flask. Add 1 c.c. of a 10 per cent solution of 



