8 Professor William Caldwell on 



place with the formation of ammonia. But the yield of ammonia 

 under these conditions is A'ery small. It has, however, been 

 found that if a mixture of nitrogen and hydrogen be passed 

 over a catalyser — in this case finely divided osium or uranium — 

 heated to a definite temperature, the two gases readily unite and 

 ammonia may be separated in quantities suflficiently large to 

 prove a commercial success. 



In 1913 Germany spent £2,000,000 on works to secure the 

 production of ammonia on an enormous scale by this process. 

 The nitrogen is obtained from liquid air, and the hydrogen may 

 be obtained by several interesting methods. Hydrogen may be 

 prepared very cheaply by the electrolysis of a solution of potas- 

 sium carbonate or of a solution of caustic potash at a temperature 

 of 60°C. The cost is reduced by making use of the oxygen 

 which is evolved at the same time. A second method is to use 

 water gas and to pass it at the required temperature through 

 gauzes composed of catalytic metals, iron, nickel or platinum. 

 The mixture of gases necessary for the production of ammonia 

 may be also obtained from air and steam. The mixture is 

 deprived of oxygen by passing it over heated copper, and then 

 over heated iron to decompose the steam. The oxides of the 

 metals are in turn reduced, and may be used again and again. 



Ammonia may also be made from the nitrides — compounds 

 of nitrogen with metals. The process has been developed by 

 Serpek, who uses aluminium nitride, and subsequently decomposes 

 the nitride with the production of ammonia, and aluminium is 

 obtained as a bye-product. The process might be developed in 

 the North of Ireland, where Bauxite, a naturally occurring 

 hydrated alumina, is found in County Antrim. 



Again, the carbides, for example calcium carbide, absorbs 

 nitrogen and forms cyanamide. This substance may be used 

 direct as a fertilizer, or it may be decomposed and ammonia 

 obtained under certain conditions. 



The cyanamide industry is being developed on a large scale 

 in (Tcrmany, France, Italy, Norway, Japan and America, 



