218 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1923 



The best-developed process of this type is the so-called Serpek 

 process for making aluminum nitride from bauxite (aluminum ox- 

 ide), coke, and nitrogen according to the reaction: AL0 3 -f-3C-fN" 2 

 =2AlN+3 CO. 



Bauxite mixed with carbon is fed into the upper end of an in- 

 clined revolving kiln, the necessary heat for heating the mixture to 

 the required reaction temperature of around 3,200° F., being sup- 

 plied by electric current. Producer gas, containing about 30 per 

 cent CO and 70 per cent N 2 , enters the lower end of the kiln and 

 passes through the same in a direction opposite to that of the de- 

 scending charge, and in the electrically heated zone the nitrogen re- 

 acts with the alumina-carbon mixture and forms aluminum nitride, 

 containing about 26 per cent of fixed nitrogen. The carbon mon- 

 oxide also formed by the reaction is being used for preheating the 

 charge before it enters the kiln. 



Ammonia is then formed by treating the aluminum nitride in 

 autoclaves, this reaction being as follows: A1N+3H 2 0=A1 (OH) 3 



+NH, 



In addition to the ammonia, a very pure alumina is obtained, 

 which can be used for metallic aluminum production. The power 

 required is approximately the same as for the cyanamid process; 

 that is, about 2 horsepower years per ton nitrogen fixed as nitride. 



Like the cyanide process, the nitride process has not been of any 

 great importance in connection with the nitrogen-fixation problem. 

 A few moderate-size plants have been built in this country and 

 abroad, but it can hardly be said that the process has as yet been 

 fully developed. 



THE HABER PROCESS 



This process, named after its inventor, Prof. Fritz Haber, of Ger- 

 many, was introduced there shortly before the war, and was one of 

 the most important factors of insuring Germany of an ample supply 

 of nitrogen during the war, and this with a much lower power re- 

 quirement than any of the synthetic processes previously described. 

 Germany now possesses two enormous Haber plants at Oppau and at 

 Merseburg. The former, where the terrible explosion occurred in 1921, 

 has a productive capacity equivalent to 100,000 tons of fixed nitrogen 

 per year, and the Merseburg plant twice this ; thus a total of 300,000 

 tons nitrogen per year. Two plants, but of comparatively small 

 capacity, have been built in this country. One of these was built 

 by the Government at Sheffield, Ala., during the war, but has never 

 been in actual operation, except what might be termed experimental 

 operation. The other plant was built in 1921 by the Semet-Solvay 

 Co. at Syracuse, N. Y. The process of these two plants is a modi- 

 fication of the German Haber process developed by the General 



