CHAPTER XI 



THE FIXATION OF ATMOSPHERIC NITROGEN, 

 MANUFACTURE OF CYAN AMIDE AND NITRATE 

 OF LIME. EXPERIMENTS WITH CYANAMIDE 



ATMOSPHERIC air is an inexhaustible source 

 of nitrogen. It is calculated that the column 

 of air which covers two and a half acres of 

 ground contains 79,000 metric tons which gives 

 or is equal to 20,000 tons of nitrate of soda per 

 acre. But nitrogen exists in the free state in the 

 air, and to render it assimilable by plants, it 

 is necessary to convert it into appropriate com- 

 pounds. We know that this conversion can be 

 effected by certain bacteria of the soil, such 

 as leguminous bacteria, etc., likewise by certain 

 phenomena which occur in nature, such as 

 electrical discharges; especially lightning. But 

 the amount of nitrogen brought into the soil 

 in this way is far from being sufficient to cover 

 the requirements, of plants, and vigorous efforts 

 are now being made to capture atmospheric 

 nitrogen under an assimilable form. Experi- 

 ments made enable us to affirm that this is 

 possible. But all the tentatives made in this 

 direction show that the industrial fixing of atmos- 

 pheric nitrogen requires the use of great 



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