Efforts to combine nitrogen with oxygen go back further than those aimed
at combining it with hydrogen. The basic fact of the combination of nitrogen with oxygen during sparking had already been observed by Cavendish
and Priestley. In this case the first product is nitric oxide, which converts
to nitric acid in a spontaneous reaction with oxygen and water. The nitric
oxide synthesis is a process requiring heat, and unless energy is supplied can,
for thermodynamic reasons, only occur spontaneously to any appreciable
extent at extremely high temperatures. However, the supply of energy required
at normal temperatures is so small that disadvantage of having to provide
it is outweighed by the advantage of needing only air and water as raw
materials. No better and more economical process for the binding of nitrogen
could therefore be devised if some means could be found for converting
electrical energy into this kind of chemical energy without waste.The example of Nature, which produces the reaction via lightning and
Cavendish’s earlier successful imitation of this with electric sparks, coupled
with the outstanding electrotechnical developments of the final decades of
previous century, increasingly brought this method of solving the nitrogen
problem to the fore, as professional circles became less and less satisfied with
the progress achieved through combining nitrogen with hydrogen. The
brilliant developments which these efforts produced in the early years of
this century are general knowledge. The main outlines of the technical design
coupled particularly with the names of Birkeland and Eyde, of Schoenherr
and of Pauling, have for years been the object of a great deal of interest
among experts.
Installations on a considerable scale were built in a number of places and
the method was evidently well suited to making use of the vast supply of
energy which could be derived from waterfalls for chemical purposes; but
this method of synthesizing nitrogen has still not reached the levels of production
which it appeared to promise. Its progress is limited by the fact that
with a consumption of one kilowatt-hour no more than 16 grams of nitrogen
are converted into nitric acid, whilst a complete conversion of electrical
to chemical energy ought to yield 30 times as much. An explanation of this
has been given by Muthmann and Hofer, who have demonstrated that the
high-tension arc used in this process, acts as a Deville’s heat evaporation
chamber.