URINE. U9 



DEXTROSE. 



All of the methods for the quantitative estimation of 

 dextrose in the urine are founded upon the following proper- 

 ties of this carbohydrate: 



1. Reducing action on copper and bismuth. 



2. Effect on the plane of polarized light. 



3. Fermentation by yeast. 



1. The methods of this type assume that the total reducing 

 power of the urine may be ascribed to dextrose. This is 

 probably true in most instances, but the fact of the pos- 

 sible presence in appreciable quantities of other copper- 

 reducing bodies must not be neglected in critical examina- 

 tions, especially when the reduction is small and at the same 

 time atypical. 



The Allihn method is by far the most accurate in results 

 and satisfactory in its performance. Its accuracy, how- 

 ever, is entirely dependent upon the strict attention with 

 which all the details of the procedure are followed out. The 

 cuprous oxide produced by the reducing action of an unknown 

 amount of dextrose upon a definite volume of Fehling's 

 solution is filtered off and further reduced to metallic cop- 

 per by a stream of hydrogen gas. This metallic copper is 

 then weighed. The quantity of sugar which corresponds 

 to this weight of copper is found upon consultation of tables. 

 The details are too numerous to allow of their explanation 

 in a limited space, but the method is to be recommended 

 highly. 



The most common clinical method depends upon the 

 complete reduction as indicated by the entire loss of color, 

 of a given quantity of Fehling's solution, by means of titra- 

 tion with diluted urine. 



