496 



Mr. G. IS. Johnson. 



The reducing action of kreatinin upon cupric oxide in boiling solu- 

 tions containing caustic alkali has been long known to German 

 chemists. Thus, Kuhne draws attention to this fact at page 505 of 

 his ' Lehrbuch der Physiologischen Chemie.' 



As regards the amount of cupric oxide reduction usually attributed 

 to kreatinin by German physiological chemists, I may quote a recent 

 paper by Professor E. Salkowski, in the ' Centralblatt fur die Medi- 

 cinischen Wissenschaften,' March, 1886, in which the reduction due 

 to uric acid and kreatinin combined is estimated as varying from 

 one-fifth to one-sixth of the total cupric oxide reduction effected by 

 normal urine, the remainder being attributed to other substances, and 

 probably to compounds of glycuronic acid (Glykuronsaurcverbin- 

 dungen). 



The Reducing Agent of Normal Urine is disintegrated by prolonged 

 Boiling with Dilute Solution of Potassium Hydrate. 



Whilst examining the reactions of the reducing agent in normal 

 urine, I found that by prolonged boiling with dilute potassium 

 hydrate solution, about three-fourths of the copper oxide reducing 

 power of the urine is lost, the remaining one-fourth being due to 

 survival of the uric acid. The urine which had been subjected to 

 this treatment did not reduce picric acid at all, for uric acid has no 

 reducing action upon picric acid in boiling alkaline solutions. 



The reducing agent of normal urine is therefore disintegrated by 

 prolonged ebullition with potassium hydrate. On comparing the beha- 

 viour of solutions of glucose in the same circumstances, I have since 

 found that such solutions lose their reducing action upon cupric oxide 

 with far greater rapidity than the reducing agent of normal urine. 



In the 'British Medical Journal,' (March 17th, 1883), will be 

 found a table of results of some determinations of the reducing 

 action of normal urines upon picric acid and cupric oxide respectively, 

 in which the effect of prolonged boiling with diluted potassium 

 hydrate solution upon the reducing agent of normal urine is visible 



I. 



Total indication 

 by picric acid. 



II. 



Total indication 

 by ammonio- 

 cupric method. 



III. 



Indication by 

 ammonio-cupric 

 method, after 

 boiling with 

 potash. 



IY. 



Difference between 

 II and III, normal 

 reducing agent. 



gr. per 1 fluid oz. 

 (1.) 0-6 

 (2.) 0-5 

 (3.) 0-35 

 (4.) -8 



gr. per 1 fluid oz. 

 '909 

 0-607 



0- 546 . 



1- 245 



gr. per 1 fluid oz. 

 -276 

 0-09 

 0-145 

 0-437 



gr. per 1 fluid oz. 

 0-63 

 0-517 

 0-401 

 -808 



