APPENDIX 425 



Urea molecules may link together 



(a) By dropping hydrogens when Biuret is produced, 



H H 



Hv || | || H 



\N C N N C N< 



is/ X H 



(b) By holding on to an intermediate radical of an acid, e.g. 

 the unsaturated three carbon acrylic acid. These are Diureides of 

 which the most important is Uric Acid. 







H N C N H; 



0=0 C=0 



I I 

 H N N H 



Y 

 4 



