Chemical Constituents of the Animal Body. 197 



From Dextrose. From Lsevulose. 



CH 2 (OH) CH 2 OH 



I ! 



CH(OH) CH(OH) 



CH(OH) CH(OH) 



CH(OH) CH(OH) 



CO C:NNHC 6 H 5 



CH:NH-NHC 6 H 5 CHO 



As these contain, in the case of dextrose, an extra ketone 

 group, and in the case of laevulose an extra aldehyde 

 group, they are capable of reacting with another molecule 

 of phenylhydrazine, and they yield thereby characteristic 

 yellow crystalline substances known as the osazones. 

 Both dextrose and laevulose will yield the same osazone, 

 which has the formula 



CH 2 (OH) 



CH(OH) 



I 

 CH(OH) 



CH(OH) 

 C:NNHC 6 H 5 



::N-NHC 6 H 8 



As substances of this class are readily obtained in a 

 crystalline form, and have generally definite melting points 

 and other properties, they serve well for the characteriza- 

 tion of dextrose and laevulose and other sugars, the pro- 

 perties of which will be discussed later. 



On heating the osazones with hydrochloric acid they 

 undergo scission, yielding phenylhydrazine hydrochloride 

 and a substance known as an " osone " 



