nitrogen products which could be sold even in America at about half what
the farmer has been paying for South American saltpeter.

Besides the Haber or direct process there are other methods of making
ammonia which are, at least outside of Germany, of more importance. Most
prominent of these is the cyanamid process. This requires electrical
power since it starts with a product of the electrical furnace, calcium
carbide, familiar to us all as a source of acetylene gas.

If a stream of nitrogen is passed over hot calcium carbide it is taken
up by the carbide according to the following equation:

CaC_{2} + N_{2} --> CaCN_{2} + C
calcium carbide nitrogen calcium cyanamid carbon

Calcium cyanamid was discovered in 1895 by Caro and Franke when they
were trying to work out a new process for making cyanide to use in
extracting gold. It looks like stone and, under the name of
lime-nitrogen, or Kalkstickstoff, or nitrolim, is sold as a fertilizer.
If it is desired to get ammonia, it is treated with superheated steam.
The reaction produces heat and pressure, so it is necessary to carry it
on in stout autoclaves or enclosed kettles. The cyanamid is completely
and quickly converted into pure ammonia and calcium carbonate, which is
the same as the limestone from which carbide was made. The reaction is:

CaCN_{2} + 3H_{2}O --> CaCO_{3} + 2NH_{3}
calcium cyanamid water calcium carbonate ammonia

Another electrical furnace method, the Serpek process, uses aluminum
instead of calcium for the fixation of nitrogen. Bauxite, or impure