156 SOILS AND FERTILIZERS 



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maining 5 per cent being moisture and impurities. 

 Ammonium sulphate is not generally considered the 

 equivalent of sodium nitrate, as it is believed it must 

 undergo nitrification before being utilized as plant 

 food. It is, however, a valuable form of nitrogen. Ex- 

 periments show that plants may utilize ammonia directly 

 without nitrification processes first taking place. 68 The 

 statements regarding the use of sodium nitrate apply 

 equally well to the use of ammonium sulphate. Am- 

 monium chloride and ammonium carbonate are not 

 suitable for fertilizers on account of their destructive 

 action upon vegetation. 



175. Calcium Nitrate and Cyanamid, Ca(NO 3 ) 2 and 

 CaCN 2 . The nitrogen of these compounds is obtained 

 from the free nitrogen of the air by electrical processes. 

 Calcium nitrate is made by treating lime with nitric acid 

 resulting from the oxides of nitrogen produced in the 

 air by electrical action. It is a valuable form of nitrogen 

 fertilizer. Calcium cyanamid is made by heating together 

 coal and lime in an electrical furnace through which a 

 current of nitrogen gas, obtained from the air, is passed. 

 Experiments with calcium cyanamid as a fertilizer show 

 that the nitrogen undergoes nitrification and becomes 

 available as plant food. 68 It is claimed that these com- 

 pounds of nitrogen Ca(NO 3 ) 2 and CaCN 2 , in which the 

 nitrogen is obtained from the air, will eventually be pro- 

 duced at silch a low cost as to permit their extensive use 

 as fertilizers. 



