CH. XII.] GLUCOSE. 3H 



5. Should there be any reason to suspect lactose the procedure should be 

 modified as follows : treat 20 cc. of the urine with i gram, of charcoal as de- 

 scribed above. Treat the whole of the nitrate with another gram, of charcoal 

 and repeat the process. To 5 cc. of this nitrate add the glycerol and sodium 

 carbonate and proceed as above directed. A reduction indicates the presence 

 of glucose, the whole of any lactose up to even I per cent, being removed by 

 this double adsorption, whilst 0-04 per cent, of glucose in the original urine still 

 shows in the nitrate. 



382. Fehling's test. Boil 3 to 5 cc. of Fehling's solution 

 (see p. 1 06) to ascertain whether the Rochelle salt has been de- 

 composed into reducing substances. If no reduction occurs boil 

 the same volume of urine in another tube. Reboil the Fehling's 

 solution and mix the two. Allow the tube to stand without further 

 heating. If any appreciable amount of glucose is present a red or 

 yellow precipitate will appear. 



NOTE. Prolonged boiling of the urine with Fehling's solution is very 

 apt to lead to the formation of a greenish-yellow precipitate owing to the 

 action of the strong alkali on the normal urinary constituents. 



383. Phenylhydrazine test. Treat 10 cc. of urine with i cc. 

 of strong acetic acid. Add enough phenylhydrazine hydrochloride 

 to cover a sixpenny piece and twice this bulk of solid sodium acetate. 

 Dissolve by the aid of heat and filter. Place the filtrate in a tube 

 and immerse this in a boiling water-bath for 30 to 60 minutes. 

 Turn out the flame and allow the tube to cool without removing it 

 from the bath. Examine the deposit microscopically for the 

 characteristic crystals of glucosazone (see p. no). 



NOTE. With small amounts of glucose the crystals are apt to separate 

 in small spherical clusters. 



384. Fermentation test. Fill a test-tube with urine and 

 then transfer the fluid to a mortar. Add a piece of washed yeast 

 about the size of a bean and pound it up with the urine. Transfer 

 the mixture to the test-tube and invert, placing the open end under 

 mercury or urine contained in a small dish. Clamp the tube in 

 position, and allow it to stand for at least eighteen hours in a warm 

 place. If glucose is present in the urine there is an accumulation 

 of gas (CO 2 ) at the top of the tube. 



NOTES. i. Lactose, pentoses and glycuronic acids are not fermented by 

 pure yeast. 



2. A special apparatus called Einhorn's saccharometer has been devised 

 to enable the test to be applied conveniently. Also the volume of CO 2 formed, 

 and the percentage of glucose present can be roughly determined by means 

 of it. 



