THE CARBOHYDRATES AND THEIR METABOLISM 227 



of plant tissues. It greatly accelerates the action of a proteolytic enzyme 

 (papain) which it may do by means of a reaction somewhat similar to the 

 first stage indicated above. 



3. Conversion of a higher to a lower monosaccliarose. By the action 

 of hydroxylamine upon glucose, glucose-oxime is produced. This product 

 is converted to gluconic nitrile by the action of acetic anhydrid and sodium 

 acetate, removing one molecule of water and acetylating the hydroxyl 

 groups, forming pcnta-acetyl gluconic acid. Ammoniacal silver solution re- 

 moves hydrocyanic acid from this substance, leaving the acetyl derivative 

 of the pentose arabinosc. Ammonia will form an acetamid arabinose, 

 which in turn yields arabinose by the action of dilute sulphuric acid. 



/o 



c 



I\H 

 HCOH 



I 

 HOCH 



HCOH 



I 

 HCOH 



CH 2 OH 



Glucose 



VN 



HCO.OC CH 3 



I 

 ILCO OCH 



I 

 HCO.OC CH 3 



I 

 HCO.OC CH 3 



CH 2 O.OC CH 3 



CH:1S T OH 



I 

 HCOH 



plus 



Acetic 

 Anhydrid 



CH 2 OH 



Glucose 

 Oxime 



plus 



H CO.OC OEL 



ammoniacal 



silver CH 3 CO.OCH 

 solution 



HCO.OC CH 3 



HCO.OC CH 3 



CH a O.OC CH 3 



arabinose pentacetate 



By this reaction glucose has been converted successively into arabinose, 

 erythrose, glycerose and glycollic aldehyde. 



Oxidation. Action of alkalies. Most of the simpler carbohydrates 

 are unstable in alkaline solution and undergo a great variety of changes, 



