The Estimation of Sugar in Blood and Normal Urine

About a year ago the writer (1) described technique for the determination of sugar in blood which yields figures appreciably lower than those obtained by the use of the older methods. Since the publication of that paper two investigators, employing widely differing procedures, have reported results which indicate the correctness of the lower figures obtained with the new method. Harned (2), after completely precipitating the nitrogenous constituents from the blood by the use of mercuric nitrate and sodium bicarbonate, obtained figures for the sugar by use of the Folin-Wu method which agree quite closely with those obtained by the Benedict procedure on the tungstic acid filtrate. Folin (3) has proposed new reagents for the determination of sugar in blood and urine. The figures reported by the new procedure show essential agreement with those obtained by the new Benedict method. In this latest contribution to the subject of blood sugar determination Folin has subjected the new Benedict procedure to a very searching critique. Indeed Folin’s paper would seem to lead to the rather anomalous conclusion that while the new Benedict method yields figures which are probably correct, the method itself is quite unsatisfactory. Obviously the main point of interest is the question as to what figures most nearly represent the true glucose content of the blood. Of much less importance is the particular technique employed to obtain such figures. It is therefore only because we feel reasonably confident that our new technique, especially in the modified form described below, is somewhat more convenient and decidedly safer for general use in biochemical determinations of sugar than is the new method described by Folin, that the following discussion is presented.