APPENDIX 445 



The oxidation may be carried on at each end of the line and the divalent 

 acids are thus produced 



O O 



II II 

 H C C O H Oxalic acid. 



If in the radical of one of these acids a hydrogen is replaced by hydroxyl 

 OH, an oxy-acid is formed, thus : 



H H 



I I II 

 H C C C H Propionic acid. 



i I 



H H 



may be converted to the two Lactic acids called (a) and () oxy-propionic 

 acid, according to the carbon which is oxidised 



H OH O 



H C C C H 



I I 

 H H 

 and 



OH H O 



H C C C H 



I I 

 H H 



Similar oxy-acids are formed from the divalent acids. 



CYCLIC COMPOUNDS 



An important series of carbon compounds contain a ring of six carbons, 

 each with an unsatisfied affinity, thus : 



A 



-C C- 

 -C C- 



\/ 



C 



I 



When each hand holds a hydrogen, Benzene is formed. 



These hydrogens may be replaced by various molecules giving r 

 large series of different compounds. 



