306 THE MICROSCOPIST. 



volume of test fluid, boil it and cool; if no yellow or red 

 suboxide falls, it is free from sugar. Prolonged boiling 

 must be avoided, as well as boiling the urine before add- 

 ing the test. 



To determine the quantity of sugar by the copper test 

 Fehling's solution is made of such strength that 200 grains 

 (by measure) are completely reduced by one grain of dia- 

 betic sugar. The test fluid is boiled in a flask, etc., and 

 a quantity of pure water equal to one or two volumes of 

 test fluid poured in also. The saccharine urine, diluted 

 with one volume urine to nine of water if suffar is abun- 



Z3 



dant, is placed iu a burette, graduated to grains, and is 

 gradually added to the boiling copper solution till the 

 blue color is quite discharged. The number of grains of 

 urine consumed representing one grain of sugar is 

 read off, and it is then a matter of calculation how many 

 grains are contained in the ounce of urine, making allow- 

 ance for the degree of dilution. 



fermentation Test. This is sometimes more convenient 

 or preferred from uncertain results of the copper test. A 

 small tube is filled with suspected urine, a little fluid or 

 solid (German) yeast is added, and the tube is inverted 

 over a saucer containing urine and placed in a warm situ- 

 ation for twenty -four hours. If sugar is present it under- 

 goes fermentation, yielding alcohol and carbonic acid. 

 The latter rises in the tube and displaces the liquid. The 

 quantitative test by fermentation consists in determining 

 the specific gravity of the urine before and after complete 

 fermentation. It has been found, empirically, that one 

 degree of specific gravity lost by fermentation corre- 

 sponds with one grain of sugar per fluid ounce of urine. 



Bismuth Test. Mix an equal volume of suspected urine 

 with a solution of carbonate of soda one part of the 

 crystals to three parts water (or with half as much liquor 

 potassae). Put in a little basic nitrate, or subnitrate of 

 bismuth, and boil. If sugar be present the bismuth be- 



