SECTION II.-ORGANIC NITROGEN 

 FERTILIZERS 



Calcium Cyanamide. The first step in the manufacture of 

 calcium cyanamide is to prepare calcium carbide, which 

 usually forms a separate industry. Calcium carbide is 

 made by heating lime and coke in an electric furnace. 

 (See Witherspoon in References to this section.) The 

 other material necessary for the manufacture of calcium 

 cyanamide is pure nitrogen, the preparation of which has 

 been described on p. 77. It is of the greatest importance 

 for the manufacture of calcium cyanamide that the nitrogen 

 should be pure. The presence of water in the nitrogen 

 would decompose calcium carbide, with the production of 

 calcium hydrate and acetylene, the presence of oxygen 

 would produce calcium oxide and carbon, and either carbon 

 monoxide or carbon dioxide would produce calcium oxide 

 and carbon, according to the reactions : 



CaC 2 +2H 2 =Ca(OH) 2 +C 2 H 2 

 CaC 2 +0 =CaO-j-2C 

 CaC 2 4-CO =CaO-f3C 

 2CaC 2 +C0 2 =2CaO+5C 



The nitrogen is passed over the calcium carbide, which is 

 heated in an electric furnace. The temperature at which 

 calcium carbide is produced in an electric furnace, viz. 

 about 3000 C. (5500 F.), is far too high. The calcium 

 carbide after manufacture is cooled and ground, and then 

 heated again in separate furnaces. The absorption of 

 nitrogen takes place according to the reaction : CaC 2 -fN 2 

 = CaCN 2 + C. By adding calcium chloride, the reaction 

 temperature for absorption of nitrogen is lowered to about 

 800 C. (1470 F.), whilst the addition of calcium fluoride 

 permits absorption to take place at 900 C. (1650 F.). 



