cent 



URINE: QUANTITATIVE ANALYSIS. 371 



ent or over). In this event the urine may be diluted with 2-3 

 volumes of water and the proper correction made in the calculation. 

 Calculation. Thirty-five c.c. of Purdy's solution is completely 

 reduced by 0.02 gram of dextrose. If 3; represents the number of 

 cubic centimeters of undiluted urine necessary to reduce 35 c.c. of 

 Purdy's solution, we have the following proportion : 



y : 0.02 : : 100 : x (percentage of dextrose) . 



4. Fermentation Method. This method consists in the meas- 

 urement of the volume of carbon dioxide evolved when the dex- 

 trose of the urine undergoes fermentation with yeast. None of the 

 various methods whose manipulation is based upon this principle 

 is absolutely accurate. The method in which Einhorn's saccharo- 

 meter (Fig. 2, page 31) is the apparatus employed is perhaps as 

 satisfactory as any for clinical purposes. The procedure is as 

 follows: Place about 15 c.c. of urine in a mortar, add about i 

 gram of yeast (% 6 of the ordinary cake of compressed yeast) and 

 carefully crush the latter by means of a pestle. Transfer the mix- 

 ture to the saccharometer, being careful to note that the graduated 

 tube is completely filled and that no air bubbles gather at the top. 

 Allow the apparatus to stand in a warm place (30 C.) for 12 hours 

 and observe the percentage of dextrose as indicated by the grad- 

 uated scale of the instrument. Both the percentage of dextrose and 

 the number of cubic centimeters of carbon dioxide are indicated 

 by the graduations on the side of the saccharometer tube. 



5. Polariscopic Examination. Before subjecting urine to a 

 polariscopic examination the slightly acid fluid should be decolor- 

 ized as thoroughly as possible by the addition of a little plumbic 

 acetate. The urine should be well stirred and then filtered through 

 a filter paper which has not been previously moistened. In this 

 way a perfectly clear and almost colorless liquid is obtained. 



In determining dextrose by means of the polariscope it should be 

 borne in mind that this carbohydrate is often accompanied by other 

 optically active substances, such as proteins, Isevulose, /?-oxybutyric 

 acid and conjugate glycuronates which may introduce an error into 

 the polariscopic reading; the method is, however, sufficiently accur- 

 ate for practical purposes. 



For directions as to the manipulation of the polariscope see page 

 3 2 - 



