646 



APPENDICES 



Amides- — If the amidogen molecule takes the place of the hydroxyl in 

 the carboxyl of an acid, an amide results, thus : — 



H 



I II • 

 H— C— C— 



H 



Acetic acid. 



0-H— H 



H 



-N 



I 

 H 



H H 



I II I 

 H— C-C-N 



I \ 



H H 



Acetamide. 

 Compare Methylamwe, CHjNH.j, with Acetamide, CH3 — CO — NH., 



From the divalent carbonic acid — 





 H— 0— C— O— H 



is formed- 







H\ II H 



>N— C— N\ 



the important substance Urea or Carbonic Diamide. 

 Urea molecules may link together — 

 (a) By dropping NH3 when Biuret is produced- 



H 



H\ II I II /H 

 >N— C— N— C— N( 



(b) By holding on to an intermediate radicle of an acid, e.g. an unsatu- 

 rated three carbon acid. These are Diureides, or Piirins, of which the most 

 important is Uric Acid — 



-N— H 

 ">C=0 



-N— H 



