Al_{2}O_{3} + 3C + N_{2}   —­>   2AlN  +  3CO
aluminum   carbon nitrogen    aluminum  carbon
oxide                         nitride   monoxide

Then the aluminum nitride is treated with steam under pressure, which produces ammonia and gives back the original aluminum oxide, but in a purer form than the mineral from which was made

  2AlN + 3H_{2}O —­> 2NH_{3} + Al_{2}O_{3}
  Aluminum water ammonia aluminum oxide
   nitride

The Serpek process is employed to some extent in France in connection with the aluminum industry.  These are the principal processes for the fixation of nitrogen now in use, but they by no means exhaust the possibilities.  For instance, Professor John C. Bucher, of Brown University, created a sensation in 1917 by announcing a new process which he had worked out with admirable completeness and which has some very attractive features.  It needs no electric power or high pressure retorts or liquid air apparatus.  He simply fills a twenty-foot tube with briquets made out of soda ash, iron and coke and passes producer gas through the heated tube.  Producer gas contains nitrogen since it is made by passing air over hot coal.  The reaction is: 

2Na_{2}CO_{3} + 4C + N_{2}   =   2NaCN + 3CO
sodium       carbon  nitrogen    sodium   carbon
carbonate                        cyanide   monoxide

The iron here acts as the catalyst and converts two harmless substances, sodium carbonate, which is common washing soda, and carbon, into two of the most deadly compounds known to man, cyanide and carbon monoxide, which is what kills you when you blow out the gas.  Sodium cyanide is a salt of hydrocyanic acid, which for, some curious reason is called “Prussic acid.”  It is so violent a poison that, as the freshman said in a chemistry recitation, “a single drop of it placed on the tongue of a dog will kill a man.”

But sodium cyanide is not only useful in itself, for the extraction of gold and cleaning of silver, but can be converted into ammonia, and a variety of other compounds such as urea and oxamid, which are good fertilizers; sodium ferrocyanide, that makes Prussian blue; and oxalic acid used in dyeing.  Professor Bucher claimed that his furnace could be set up in a day at a cost of less than $100 and could turn out 150 pounds of sodium cyanide in twenty-four hours.  This process was placed freely at the disposal of the United States Government for the war and a 10-ton plant was built at Saltville, Va., by the Ordnance Department.  But the armistice put a stop to its operations and left the future of the process undetermined.

[Illustration:  A CHEMICAL REACTION ON A LARGE SCALE

From the chemist’s standpoint modern warfare consists in the rapid liberation of nitrogen from its compounds]

[Illustration:  Courtesy of E.I. du Pont de Nemours Co.

BURNING AIR IN A BIRKELAND-EYDE FURNACE AT THE DU PONT PLANT