8 METABOLISM IN SEVERE DIABETES. 



DETERMINATION OF SUGAR IN THE URINE. 



General dissatisfaction with the methods commonly used for the estima- 

 tion of reducing sugars was expressed in our first report and it was there pointed 

 out that the newly-introduced Citron method, Avhile of value from the clinical 

 standpoint, was of little value from the standpoint of exact scientific research. 

 In our new experiments the Citron method was used for only the earlier deter- 

 minations of sugar. Those made in the private laboratory of E. P. J. w r ere for 

 the most part carried out by a method suggested by Dr. Stanley R. Benedict, 1 

 of the Cornell University Medical College. For the more recent analyses, 

 especially those made in connection with the best experiments, a highly 

 improved method w r as used which was devised by Dr. A. W. Peters, of the 

 Nutrition Laboratory. After a most careful study of the conditions affecting 

 reduction, temperature conditions, and concentration, Dr. Peters developed a 

 method using the old Fehling or Allihn solution of copper sulphate and the 

 alkaline tartrate, and has determined the amount of unreduced copper remain- 

 ing in the solution by a titrimetric method. By this means the most accurate 

 determinations of sugar are possible, this being without doubt the most exact 

 method of sugar determination that has thus far been devised. While the 

 method may be readily used in hospital laboratories, it will probably never be 

 acceptable for private practice. Inasmuch as it represents the most scientific 

 attempt to study quantitatively the method of sugar reduction, it is given 

 herewith in considerable detail. For this presentation of the method we are 

 indebted to its author, Dr. A. W. Peters. 



A COPPER-REDUCTION METHOD OF SUGAR ANALYSIS (A. W. PETERS). 



The construction of this method of sugar analysis is based upon precedi ng 

 developments for (1) the accurate volumetric determination of copper in alka- 

 line tartrate liquids; (2) the standardization of the heating power used; and (3) 

 the determination of constant and controllable conditions for the reduction. 

 For more detail reference must be made to the original descriptions. 2 When 

 the apparatus and reagents have once been prepared a single determination 

 occupies from 12 to 15 minutes. 



The Heating Power. 



A heating apparatus should be set up of such power that it will heat 

 60 c.c. of distilled water under described conditions through the temperature 

 interval of 35 to 95 C. in 120 seconds == 5 seconds. The water is placed in an 

 Erlenmeyer flask of the best Jena glass, with a capacity of about 200 cm. and a 

 basal diameter of about 6 cm., so that the depth of the liquid will be about 18 

 mm. The flask is partially closed with a two-hole stopper, one hole of which 



x Dr. S. R. Benedict's method is based upon the reducing action of sugars upon an 

 alkaline sulphocyanate solution of copper.. See Benedict, Journ. Biol. Chem., 1911, 9, p. 57. 



5 Peters, Amos W., The sources of error and the electrolytic standardization of the iodide 

 method of copper analysis, Journ. Am. Chem. Soc, 1912, 34, pp. 422; and A critical study 

 of sugar analysis by copper-reduction methods, Journ. Am. Chem. Soc, 1912, 34, p. 928. 



