6o 



dish tint, the sugar having reduced the cupric hydrate to- 

 cuprous oxide. 



274. Fehling's solution. Place some Fehling's solution 

 in a test-tube and boil it. If no yellow discoloration takes- 

 place it is in good condition. Add a few drops of the sus- 

 pected urine and boil. If the mixture .suddenly turns to an 

 opaque yellow or red color, the presence of a reducing sugar 

 is indicated. 



275. The principle of the bismuth test is the same as the 

 copper te.st. The glucose reduces the salt of bismuth in the 

 presence of an alkali. Put equal quantities of urine and 

 potassium hydrate in a test tube, and add a pinch of subni- 

 trate of bismuth. Boil the mixture and if glucose be pres- 

 ent the bismuth is reduced and turns black ; if no glucose 

 is present the powder remains white. Albumin and sul- 

 phur also reduce bismuth and mu.st be removed from the 

 urine, if the test is to be reliable. 



276. Take 25 cc. of suspected urine and add i gram of 

 phenyl-hydrazine hvdrochlorate, and i gram of sodium ace- 

 tate, and ID cc. of distilled water. Keep the solution nearly 

 to the boiling point for an hour. Even minute quantities 

 of sugar yield a yellow precipitate, which under the micro- 

 scope is seen to consist of fine, bright yellow cry.stals of 

 phenyl-glucosazone. This is one of the most delicate and 

 accurate tests known, and is said to be reliable in the 

 presence of albumin, and the products of decomposing urine. 



277. Picric acid test. To a small amount of the urine 

 add an equal volume of a saturated aqueous solution of pi- 

 cric acid. Boil ; an intensely deep red or reddish-brown 

 color indicates the presence of a reducing sugar. The 

 greater the amount of the sugar the greater the tint. The 

 coloration is due to the formation of picramic acid. 



278. Fermentation method. Robert's Differential Den- 

 sity Method. Take the specific gravity of the urine before 

 and after adding the yeast and record it. Mix well 2 fluid 



