EXAMINATION OF NORMAL AND ABNORMAL URINE. 389 



sodium carbonate. Under the second limb of the bent glass 

 tube is placed a beaker. 



The apparatus, thus prepared, is placed in a room having a 

 temperature of about 18-28. If sugar be present, fermentation 

 will commence within 12 hours, and will manifest itself by the 

 formation of carbon dioxide, which will force a portion of the 

 fluid through the bent tube into the beaker placed there for 

 its reception. 



The disadvantages of this process are the length of time re- 

 quired for its performance, the unreliability of the ferment, and 

 the fact that small quantities of sugar (less than 0.5 per cent.) 

 evolve so little carbon dioxide that a doubt may be felt as to the 

 presence of sugar at all. 



Quantitative estimation of sugar. Various methods for the de- 

 termination of sugar in urine have been suggested, some of 

 which depend on the loss in weight caused by the escape of 

 carbon dioxide during fermentation. The disadvantages of the 

 fermentation test for qualitative determination have been pointed 

 out above, and apply also to quantitative determinations. 



By far the best method is the decomposition of a copper 

 solution of a known strength, and Fehling's solution, prepared 

 as stated above, answers this purpose well. 



1000 c.c. of Fehling's solution, containing 34.65 grams of 

 crystallized cupric sulphate, CuSO 4 .5H 2 0, are exactly decom- 

 posed by 5 grams of grape-sugar, or 1 c.c. solution by 0.005 of 

 grape-sugar. 



To make the quantitative determination, operate as follows : 

 10 c.c. of Fehling's solution are poured into a porcelain dish of 

 about 200 c.c. capacity, placed over a flame. The copper solu- 

 tion is diluted with about 40 c.c. of water, and heated to boil- 

 ing; to the boiling liquid, urine (which has been previously 

 diluted with 9 parts of water) is added from a burette very 

 gradually, until the blue color of the solution has disappeared, 

 and there remains, upon subsidence of the cuprous oxide, an 

 almost colorless, clear liquid. A filtered portion of this liquid, 

 acidified with hydrochloric acid, should not give a reddish-brown 

 precipitate with potassium ferrocyanide (a precipitate would 

 show that all copper had not been precipitated, and that more 



