COMMERCIAL FERTILIZER MATERIALS 453 



deliquescence, it must either be treated in some way, whicli 

 raises the cost of manufacture, or must be shipped in sealed 

 casks. It is very soluble in water and is immediately available 

 to plants. It leaves no harmful residue in the soil 



252. Other methods of nitrogen fixation. — Calcium ni- 

 trate, because of its cost, cannot compete either with sodium 

 nitrate or ammonium sulfate and is not manufactured in this 

 country. Calcium cyanamid is produced only in amounts 

 sufficient to satisfy the demands of mixed fertilizer manu- 

 facture. Its dry character makes it valuable in such com- 

 pounding. 



At the present time a number of more efficient methods of 

 artificially fixing nitrogen are known. The Haber process 

 proved extremely successful in Germany, especially when 

 supplemented by the Oswald method of converting ammonia 

 into nitric acid. In the Haber method a mixture of nitrogen 

 and hydrogen are placed under pressure and moderately 

 heated in the presence of a catalyst. A good yield of ammonia 

 results. 



N, + 3H2 = 2NH3 



In the Oswald method this ammonia is passed over a cata- 

 lytic agent in the presence of oxygen. 



NH3 + 20, = HNO3 + H2O 



The advantage of producing both ammonia and nitric acid 

 is obvious, as ammoniun nitrate (NH4NO3), ammonium phos- 

 phate ((NH4)3P04), and potassium nitrate (KNO3) ^^7 be 

 produced at one plant. 



During the war Professor Bueher of Brown University per- 

 fected a simple and inexpensive method of producing sodium 

 cyanide synthetically. Producers gas, formed by passing air 

 over hot coal, is forced through a heated revolving drum con- 

 taining soda ash, iron, and coke. The reaction is as follows : 



Na^COs + 40 + N2 = 2NaCN + SCO 



