504 soils: properties and management 



The acid calcium cyanamide quickly loses its calcium, 

 leaving free cyanamide. Investigators differ as to the 

 process involved in this change, but the ultimate condi- 

 tion of the calcium is carbonate. The three explanations 

 of the process may be represented by the following re- 

 actions : — 



1. (CN . NH) 2 Ca+C0 2 +H 2 = 2 CN . NH 2 +CaC0 3 



In this reaction the carbon dioxide of the soil water is 

 supposed to cause precipitation of the calcium. 



2. (CN . NH) 2 Ca + 2 H 2 = 2 CN . NH 2 + Ca(OH) 2 



In this case hydrolysis occasions the reaction. The 

 hydroxide would, of course, be converted into carbonate 

 in the soil. 



3. (CN . NH) 2 Ca + C0 2 = CN . NH 2 + CaCN 2 C0 2 



acid calcium carbon free calcium 



cyanamide dioxide cyanamide cyanamide 



carbonate 



CaCN 2 C0 2 + H 2 = CN . NH 2 + CaCO, 



free calcium 



cyanamide carbonate 



By this reaction calcium cyanamide carbonate is an in- 

 termediate product, but is at once hydrolyzed and free 

 cyanamide produced. 



The next step in the process is the formation of urea by 

 hydrolysis of the free cyanamide : — 



CN . NH 2 + H 2 - CO(NH 2 ) 2 



free cyanamide water urea 



The changes up to the production of urea are independent 

 of bacterial action. The urea is converted through bac- 

 terial action into ammonium carbonate : — 



