110 THE CARBOHYDRATES. [CH. V. 



1 08. To 2 cc. of the solution add a large " knife point " of an- 

 hydrous sodium carbonate and a rather smaller amount of solid 

 picric acid. Boil for about a minute. A deep reddish brown 

 colour is produced. Repeat the experiment with 2 cc. of the solu- 

 tion diluted i in 10. A distinct colouration is produced. 



s* (N0 2 ) 3 

 NOTE. Picric acid. C 6 H 2 ^ 



^OH 



/(NO,), 



is reduced to picramic acid, C 6 H 2 ^ -NH 2 



\OH. 



by various substances in alkaline solution. The reaction serves as a basis 

 for the colorimetric method of estimation of sugar in blood (Ex. 311). 



109. To 10 cc. of the solution add i cc. of strong acetic acid. 

 Add as much solid phenyl-hydrazine hydrochloride as will lie on a 

 sixpenny piece, and at least twice this amount of solid sodium 

 acetate. Dissolve by warming, mix thoroughly, and filter into a 

 clean tube. Place this in a beaker of boiling water for 30 minutes, 

 keeping the water boiling the whole time. Remove the flame from 

 under the beaker, and allow the solution to cool slowly. A yellow 

 crystalline precipitate of phenyl-glucosazone appears, often before 

 the solution has been heated for more than 20 minutes. Collect 

 some of this by means of a pipette, transfer to a slide, cover with 

 a slip, and examine under both powers of the microscope. Note 

 the characteristic arrangement of the fine yellow needles in fan- 

 shaped aggregates, sheaves, or crosses. 



NOTES. I. Glucose is an aldehyde, and, like all aldehydes and ketones, 

 forms a compound with phenyl-hydrazine. But this phenyl-hydrazone of 

 glucose is very soluble, and cannot be readily separated. However, in the 

 presence of an excess of phenyl-hydrazine at 100 C. an insoluble osazone is 

 formed. 



CHO CH : N.NH.C 6 H 5 



CHOH C : N.NH.C 6 H 5 



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



(CHOH) 3 (CHOH) 3 



CH 2 OH CH 2 OH 



Glucose Phenyl-osazone of glucose 



(phenyl-glucosazone) 

 NH 3 + C 6 H 5 .NH 2 

 Aniline. 



2. Phenyl-hydrazine is a yellow basic liquid, insoluble in water, but 

 soluble in dilute acids to form salts. If the base itself is used, two or three 



