374 PHYSIOLOGICAL CHEMISTRY. 



in a given volume of urine and determine its reducing value 

 in terms of CuO with the same ammoniacal solution. If the 

 reducing power of the creatinine and uric acid be subtracted 

 from the total, the reduction due to glucose and other bodies 

 is arrived at. To illustrate, in the examination of a large 

 number of urines these values were found : 



Total reducing power of I cc. of urine in mg. of CuO = 6.204 

 Reducing power of the creatinine present in same terms = 1.961 

 Reducing power of the uric acid present in same terms 0.935 

 Reducing power of the sum of uric acid and creatinine = 2.896 



Nearly one-half of the total reduction then corresponds to 

 the action of these two nitrogen bodies, while the reduction of 

 the other substances is equivalent to 3.308 mg. of CuO per cc. 

 If this is calculated as glucose it represents 1.27 mg. per cc. 

 As several other bodies contribute to this reducing action the 

 value of any saccharine substance present must be still smaller. 

 It has been found by earlier investigations that on concentra- 

 tion urine loses a part of its reducing power. This suggests 

 that some volatile substances may be responsible for part of it. 

 It should be mentioned in addition, that the relative extent of 

 the reducing action varies with the reagent employed. 

 Knapp's mercury solution has been used for the purpose but 

 it is not as convenient as the ammoniacal copper solutions. 



A knowledge of this normal reducing action is not without 

 value, since very frequently the mistake has been made of as- 

 suming the presence of sugar in suspicious quantities in the 

 urine merely from a reduction test. In some of the extreme 

 cases quoted in one of the statements above, the normal reduc- 

 tion was equivalent to over 0.3 per cent of glucose, when in 

 reality it was largely due to uric acid and creatinine. This 

 point has importance in clinical observations. In another 

 direction also the question is important, as the reducing power 

 of the urine is a measure of the extent of certain kinds of excre- 

 tion. Creatinine and uric acid are probably perfectly normal 

 end products of metabolism, and when large in amount the 

 reduction is high. It will be recalled further that, as men- 



