200 DR. ROBERTS ON THE ESTIMATION 



XIII. — On the Estimation of Sugar in Diabetic Urine by 



the loss of Density after Fermentation. 



By William Roberts, M.D. Lond,, Physician to the 



Manchester Royal Infirmary. 



Eead October i6tli, i860. 



When saccharine urine is fermented with yeast its specific 

 gravity, previously ranging from 1030 to 1050, falls to 

 1009 or 1002, or even below 1000. This result is chiefly 

 due to the destruction of the sugar it contained, but partly 

 also to the generation of alcohol, and its presence in the 

 fermented product. 



As the diminution of density must be proportional to 

 the quantity of sugar broken up by the ferment, the 

 amount of this diminution evidently supplies a means of 

 calculating how much sugar any urine contains, always pro- 

 vided that the remaining ingredients of the urine continue 

 unchanged, or become changed in some uniform ratio. 



In order to ascertain the exact relation subsisting be- 

 tween the density lost on fermentation and the sugar 

 destroyed, experiments were made on the fresh urine of 

 several diabetic patients in the Royal Infirmary. 



The following procedure was adopted : 



1. The amount of sugar per 100 parts was first accu- 

 rately determined by the volumetrical method, with 

 Fehling^s test solution. 



2. Next the density was taken by the specific gravity 

 bottle. 



