30 PHYSIOLOGICAL CHEMISTRY. 



Ex. To a small amount of a dilute sugar solution add two drops of a 

 solution of a-naphthol, containing about 20 gm. in 100 cc. On shaking the 

 liquid becomes turbid. Now add to it an equal, or slightly greater, volume 

 of pure strong sulphuric acid and shake. A deep violet color appears, 

 which gives place to a violet precipitate on addition of water. This reac- 

 tion has been shown to be due to the combination of the a-naphthol with 

 furfuraldehyde produced by the action of sulphuric acid on the sugar 

 present. 



Ex. PHENYL HYDRAZINE TEST. A characteristic reaction of great prac- 

 tical value, referred to above, is given on the addition of phenyl hydrazine 

 to a solution of glucose under certain definite conditions. 



To 20 cc. of a dilute glucose solution add about a gram of phenyl 

 hydrazine hydrochloride, and two grams of sodium acetate. Heat on the 

 water-bath half an hour, and then allow the liquid to cool. There will now 

 be found a beautiful yellow crystalline precipitate of phenyl glucosazone, 

 the nature of which is best seen under the microscope. This test is one 

 of great delicacy, and has been applied to the detection of traces of sugar 

 in urine. But care must be taken to keep the reagent in considerable ex- 

 cess, since otherwise the soluble hydrazone may be formed. The melting 

 point of the pure osazone is 205 C. The following reactions illustrate the 

 combination of the phenyl hydrazine: 



GH 12 6 + C 6 H 5 .NH.NH 2 = C 6 H 12 O 5 .N.NH.C 6 H 5 + H 2 O, 



C 6 H 12 O 6 + 2C 6 H 5 NH.NH 2 C 6 H 10 O4. (N.NH.C 6 H 5 ) 2 + 2H 2 O + H 2 , 



Phenyl glucosazone 



C 6 H 5 .NH.NH 2 + H 2 = C 6 H 5 NH 2 + NH 3 . 



By treatment with strong hydrochloric acid the osazone decomposes to 

 yield an osone and phenyl hydrazine hydrochloride : 



C6H 10 O4.(N.NH.C 6 H 5 ) 2 -f 2HC1 + 2H 2 O = 



2C 6 H 5 .NH.NH 2 .HC1 + CH 2 OH.(CHOH) 3 .CO.CHO. 



Glucosone 



This osone on reduction with nascent hydrogen yields a sugar, not glu- 

 cose, but d-f ructose, or levulose : 



CH,OH.(CHOH) 3 .CO.CHO + H 2 = CH 2 OH(CHOH) 3 .CO.CH 2 OH. 



Glucose and levulose (d-fructose) yield the same glucosazone; we are 

 therefore able by this reaction to pass from one sugar to the other. 



The ready fermentation of glucose will be shown later in the 

 discussion of fermentation reactions in general. The produc- 

 tion of glucose from cane sugar will also be explained. The 

 specific rotation of glucose in 20 per cent solution is given 

 by the formula [a]^ = 53, and increases slightly with the 

 concentration. 



