are two cast iron tubes curving upward and outward like the horns of a
Texas steer and cooled by a stream of water passing through them. These
electric furnaces produce two or three ounces of nitric acid for each
kilowatt-hour of current consumed. Whether they can compete with the
natural nitrates and the products of other processes depends upon how
cheaply they can get their electricity. Before the war there were
several large installations in Norway and elsewhere where abundant water
power was available and now the Norwegians are using half a million
horse power continuously in the fixation of nitrogen and the rest of the
world as much again. The Germans had invested largely in these foreign
oxidation plants, but shortly before the war they had sold out and
turned their attention to other processes not requiring so much
electrical energy, for their country is poorly provided with water
power. The Haber process, that they made most of, is based upon as
simple a reaction as that we have been considering, for it consists in
uniting two elemental gases to make a compound, but the elements in this
case are not nitrogen and oxygen, but nitrogen and hydrogen. This gives
ammonia instead of nitric acid, but ammonia is useful for its own
purposes and it can be converted into nitric acid if this is desired.
The reaction is:

NN + HH + HH + HH --> NHHH + NHHH
Nitrogen hydrogen ammonia

The animals go in two by two, but they come out four by four. Four
molecules of the mixed elements are turned into two molecules and so the
gas shrinks to half its volume. At the same time it acquires an
odor--familiar to us when we are curing a cold--that neither of the
original gases had. The agent that effects the transformation in this
case is not the electric spark--for this would tend to work the reaction