APPENDIX 447 



From the divalent carbonic acid 



O 

 II 



H 0-C H 

 is formed 



O 

 H x || /H 



\N-C- N< 

 W X H 



the important substance urea. 



Urea molecules may link together 



(a) By dropping hydrogens, when Biuret is produced. 

 H ; H O 



\N-C- N-;-N C N<f 



H/ ' \TJ 



JjL 



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

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

 is Uric Acid 



H N-i-C j 



= ! C-I-NVH 



| i || ; ^0 = 



H N-i-C-i-N-H 



