THE CHEMISTRY OF THE SUGARS 



89 



zine group, forming a ketone-aldehyde which on reduction 

 yields a sugar. Thus in the case of glucose-osazone we have 

 the following sequence of compounds : — 



4. By successive treatment with hydrocyanic acid and 

 hydrochloric acid, acids are formed as follows : — 



E-CHO + HCN = R-CH' 



OH 



OH 



"CN 



R-CH^ + 2H2O = R-CHOHCO2H + NH3 



CN 



On reduction by nascent hydrogen of the acid so formed, 

 an aldose containing one more carbon atom than the sugar first 

 taken is produced. 



E^CHOHCOOH + H2 = R-CHOHCHO + H^O 



It will be noted that an additional carbon atom is in this way 

 attached to the chain, and so a means is afforded of producing 

 a series of sugars, each member of which contains one carbon 

 atom more than the preceding one. By this method the sugars 

 above referred to containing seven, eight, and nine carbon 

 atoms have been produced. This reaction, which is of great 

 importance, was discovered by Kiliani, whose name it bears. 



5. Inasmuch as the aldoses and ketoses are capable of 

 oxidation, they themselves act as reducing agents, and so they 



