Society of Biological Chemists Xxl 
marked gain in weight and edema developed. On withdrawing 
sodium bicarbonate and allowing sodium chloride loss of weight 
occurred. 
OBSERVATIONS ON THE PERMANGANATE TITRATION OF URIC 
ACID CONTENT OF BLOOD. 
By J. LUCIEN MORRIS. 
(From the College of Medicine, University of Illinois, Chicago.) 
The determination of the small amounts of uric acid in blood 
by permanganate titration in acid solution is subject to a rela- 
tively large error. This is due to the continued reduction of 
permanganate after all uric acid has been oxidized. ‘The transi- 
tory nature of the pink color end-point gives an error of only 
2 to 3 per cent of the 2 mg. of uric acid in the titration following 
precipitation from urine as zinc urate. The error is 20 to 30 per 
cent of the 0.2 mg. of uric acid present in the usual quantity of 
blood taken for analysis: Oxidation of uric acid by permanga- 
nate in the slightly alkaline solution of sodium bicarbonate is a 
much less vigorous reaction and affords an opportunity of meas- 
uring the conclusion of the oxidation. The end-point used is the 
very delicate iodostarch color, which can be*applied to the de- 
tection of an excess of permanganate because oxidation of potas- 
sium iodide does not take place in the weakly alkaline solution 
until all uric acid has been oxidized. 
The precipitated zinc urate and zinc carbonate are dissolved 
in hydrochloric acid and disodium phosphate is added until all 
the zi,ne has been precipitated. ‘To the resulting solution of uric 
acid n sodium phosphates, with which the zine phosphate is 
present as a precipitate, 25 cc. of a saturated solution of sodium 
bicarbonate, 5 cc. of a 10 per cent potassium iodide solution, and 
1 ec. of a 0.5 per cent soluble starch solution are added. 0.002 N 
permanganate is run in from a burette until the blue color of the 
iodide of starch appears. Using this procedure, 0.2 mg. of uric 
acid (the amount found in 20 cc. of blood) can be determined 
with an accuracy of 5 per cent or better. The results in blood, 
as well as the application of this new titration to other organic 
substances, are being studied further. 
