On Kreatinins. 



495 



Repeated Observations have confirmed the Existence of Reducing Agents 

 in Normal Human Urine. 



It was probably owing to the impossibility of accounting otherwise 

 for the reducing action which normal urine invariably exerts upon 

 cupric oxide in boiling alkaline solutions, that physiological chemists 

 were led to assert that dextrose is present in the urine of healthy men. 



In a paper published in the Medico- Chirurgical Society's 

 ' Transactions' (vol. 63, p. 222), Dr. F. W. Pavy, F.R.S., writes as 

 follows : — " The reducing action before the addition of acetate of lead 

 is due partly to uric acid and partly to the small amount of sugar 

 naturally present in urine. It is doubtful if there is any other body 

 worthy of consideration to exert any sensible reducing effect." And 

 Dr. Pavy finds that one-fourth of the total reduction of copper oxide 

 by normal urine is due to uric acid. This result Dr. Pavy arrived at 

 by estimating the cupric oxide reduction of the urine before and after 

 precipitation by lead acetate, which removes from solution the uric 

 acid, but not the other reducing agent to which three-fourths of the 

 total reducing effect must be ascribed, and which Dr. Pavy con- 

 cludes is sugar. Briicke's views on this subject are too well known to 

 need comment. 



Amongst the known substances other than glucose, which reduce 

 potassium picrate to picramate in boiling alkaline solutions, are — 



(1.) Potassium ferrocyanide, a salt which is not likely to be found 

 in urine, since it is devoid of medicinal properties, and is therefore 

 not likely to be administered. 



(2.) Sulphides of the alkali metals. I have shown (' Chemical 

 News,' vol. 47, 1883, p. 87) that in boiling dilute solutions of potassium 

 hydrate, albumen yields potassium tetrathionate, and not potassium 

 sulphide, and as potassium tetrathionate does not reduce potassium 

 picrate in boiling dilute solutions of potassium hydrate, and as a very 

 dilute solution of potassium hydrate is employed in the quantitative 

 estimation of glucose by picric acid, viz., 30 minims of the liquor 

 potassse of the British Pharmacopoeia, diluted to 4 drachms, there is no 

 possibility of reduction of picric acid by alkaline sulphides, formed by 

 the action of potassium hydrate upon unoxidised sulphur compounds 

 in the urine at the boiling temperature. 



Kreatinin has been suggested by Dr. Oliver as the reducing agent 

 of normal urine ('Bedside Urinary Testing'). The sample of 

 kreatinin which he examined was sold by Messrs. Hopkin and 

 Williams. I have examined a portion of this sample, and found that 

 it was very deficient in reducing power. Allowing most liberally for 

 its presence in the urine, only about one-twentieth of the total reduc- 

 tion of cupric oxide effected by that secretion in its normal condition 

 could be accounted for by this substance. 



