126 THE NEW WORLD OF SCIENCE 



This gives us a product, CaCN 2 , called " cyanamide," which 

 contains some unchanged carbide and some lime and graphite. 

 For the production of ammonia the cyanamide is next treated 

 with steam, whereupon the following reaction takes place : 



CaCN 2 + 3H,O = CaCO 3 + 2NH 3 . 



This process is carried out in huge autoclaves about 20 or 30 

 feet high and 5 to 6 feet in diameter. The powdered cyanamide 

 is fed into an alkaline solution, and then steam is blown in; 

 the mass heats up, the reaction begins and becomes violent, and 

 the ammonia is liberated. After it has attained a pressure of 

 12 to 15 atmospheres, it is blown: off into gas-holders. After 

 the reaction has spent itself, the residue is again charged with 

 steam so as to get a complete removal of the ammonia. When 

 carried out properly, it is practicable to get substantially all of 

 the nitrogen in the form of ammonia. 



2. The synthetic ammonia process is an extremely simple 

 one chemically, involving the following reaction : 



There is an interesting history connected with the develop- 

 ment of this process. The proportion of ammonia which 

 forms from the elements (hydrogen and nitrogen) at atmos- 

 pheric pressure was known to be extremely small at tempera- 

 tures where the rate of combination was reasonably rapid; 

 thus it is only 0.13 per cent, at 500, and still less, only 0.02 

 per cent., at 700 centigrade. The facts that the equilibrium 

 conditions become less favorable as the temperature rises, and 

 that on the other hand a high temperature seemed necessary in 

 order to give a rapid rate of reaction led to the belief that there 

 was little hope of basing a technical process upon this chemical 

 reaction. However, a German chemist, Prof. Haber, guided 

 by theoretical considerations which show that the proportion 

 of ammonia formed must greatly increase with increasing 



