Optimum conditions for the reaction between uric and phosphotungstic acids in the presence of glycerol-silicate reagent, including a proposed modification of the Archibald method.

By controlling the alkalinity and the amount of phosphotungstic acid (PTA), turbidity and gelling in the final colored solution obtained in the reaction between uric acid and PTA in the presence of sodium glycerol silicate (NaGS) can be eliminated without using antiturbidity reagents. The optimum range of alkalinity is 0.55-0.76 mEq. of excessalkali in a total volumeof 7.75 ml. A modification of the Archibald (1) method is proposed to assure optimum color development between uric acid and PTA-whether the uric acid is in an acidic protein-free filtrate or in a practically neutral aqueousstandardsolution.