CARBOHYDRATES 39 



containing one, two, three, four, or five carbon atoms. The 

 chain also may remain unbroken. 



This process is of biological interest for probably it has many 

 points of similarity with the breaking down of carbohydrates in 

 the body. Of course the body tissues are not strongly alkaline, 

 so that the agent bringing about the change must be some other 

 substance. In the body the fragments thus produced may be 

 used to construct new substances, or they may be further broken 

 down and oxidized to carbon dioxide. 



In case the strong alkali acts upon glucose when the oxygen 

 supply is limited, as would be the case if no air were bubbled 

 through the liquid, the reactive fragments produced will com- 

 bine with one another, forming complex brown substances of a 

 resinous nature, a mixture of which is known as caramel. Pos- 

 sibly this process is analogous to the building up of materials 

 from carbohydrate fragments in the interior of the body cells, 

 although in this latter case the conditions of synthesis are care- 

 fully controlled by agents in the cell so that particular sub- 

 stances result which are required by the cell. 



Behavior With Acids. On boiling with dilute acids the com- 

 plex carbohydrates take up water and are split into simpler 

 substances, ultimately the monosaccharides. If the monosac- 

 charides are boiled with strong hydrochloric acid they are de- 

 composed and yield a variety of products. The pentoses lose 

 water and form furfurol^ 



EH H [H H 



H 00000=0 HO OH 



/ I -* II II +3H 2 



n HO OHO 



V 



The formation of this compound serves to identify the pen- 

 toses, since it forms with various phenols colored substances 

 which may be identified easily. The hexoses, on boiling with 

 concentrated hydrochloric acid yield among other things oxy- 

 methyl furfurol, but in much larger quantities levulinic acid 



