372 



PHYSIOLOGICAL CHEMISTRY. 



the phenylhydrazine combination and the formation of benzoic 

 esters, the question of the passage of traces of carbohydrates 

 into the urine seems to be finally settled in the affirmative, but 

 the amount of sugar which may be so identified is too small 

 to account for the total reduction easily measured by copper 

 solutions. This normal reduction cannot be quantitatively 

 followed with the ordinary Fehling solution, but if a dilute 

 Pavy solution, as described by the writer in his work on Urine 

 Analysis, is used, a very satisfactory determination may be 

 made. This modified Pavy solution is given such a strength 

 that i cc. oxidizes i mg. of glucose in very dilute solution, 

 approximating 0.2 per cent strength or less. 



In a large number of tests made in the author's laboratory 

 a few years ago it was found that to reduce 50 cc. of such a 

 solution urine volumes ranging between 14.9 cc. and 58 cc. 

 were required. The mean of all the determinations on these 

 normal urines was 23 cc. In hundreds of normal urines ex- 

 amined since similar results have been obtained. In all these 

 urines the creatinine and uric acid present were accurately 

 determined and an attempt was made to connect these bodies 

 with the reduction. 



The Reducing Power of Creatinine. The reducing power 

 of creatinine may be easily found by the method referred to, 

 using the weak ammoniacal copper solution. A liter of this 

 solution contains 8.166 gm. of CuSO 4 '5H 2 O, corresponding 

 to 2.6042 gm. of CuO. A measured volume of this, usually 

 25 or 50 cc., is reduced by a creatinine solution of definite 

 strength and the volume required noted. The details of some 

 experiments are given in the following table. The copper 

 solution was diluted to 100 cc. before the titration : 



