SCIENCE AND INDUSTRY. 
could we expect to raise the production of wheat per acre to the amount 
soon to be demanded for the feeding of the world’s population; he in- 
sisted that the securing of large supplies of simple nitrogenous products 
was purely a problem for the chemist, and that the question was clamant 
in view of the limited available supplies of Chili saltpetre. 
Having made clear the necessity for increased supplies of simple 
nitrogen compounds, another side of the whole large subject may be 
reviewed. Atmospheric air is a mixture of four volumes of nitrogen 
to each one of oxygen; the nitrogen which is thus available in limitless 
quantity is in an uncombined state, and, for all practical purposes, 
practically unassimilable by vegetable life. The task before the chemist 
is indicated as that of devising processes for the conversion of this 
gaseous nitrogen into the simple combined form in which it exists in 
ammonia, nitrates, or urea, so as to render atmospheric nitrogen avail- 
able for manurial purposes. This task has been accomplished, and the 
intense needs of the last five years have led to this result of pure scien- 
tific investigation being translated into large-scale technical practice; 
the vast quantities of simple nitrogen compounds required by Germany 
during these years of war have been obtained almost entirely from 
atmospheric nitrogen by chemical methods. 
In 1785 Cavendish showed that nitrogen and oxygen could be caused 
to combine by the passage of an electric spark; this observation has 
been utilized to bring about.the conversion of atmospheric nitrogen into 
nitric acid on a large scale ‘by heating air in the electric are. | In 1864 
Deville observed that ammonia could be produced by the action of the 
electric spark on a mixture of nitrogen and hydrogen. <A technical 
method for the production of ammonia by heating a mixture of nitrogen 
and hydrogen under pressure and in contact with some material which 
hastens combination has been elaborated as the so-called Haber process; 
this process has been established-in Germany on a scale capable of 
producing 650 tons of ammonia per day. _ Later, Moissan showed that 
an intimate mixture of carbon and lime, when heated by: the electric 
are, gives the now familiar substance, calcium carbide; it was then 
found that when calcium carbide is heated in a stream of nitrogen, 
combination occurs to yield a product, calcium cyanamide, which is 
converted by water into urea and ammonium salts. This series of 
operations is now in production on an industrial scale. 
It is interesting to notice that the scientific observations upon which 
the three above-mentioned technical methods for the utilization of 
atmospheric nitrogen are based were made in England and in France, 
but that the technical processes themselves were first worked out and 
installed by Germany. Tt is further of importance to note that such 
simple nitrogen compounds as nitric acid and ammonia are ~prime 
essentials in the manufacture of military explosives, that the chief 
sources of these nitrogen compounds were until quite recently found in 
Chili saltpetre, and that the import of Chili saltpetre into Central 
Europe would be at’ once stopped by war; also that Germany did not 
embark upon a world war until the several methods for converting 
atmosphéric nitrogen into the nitric acid required for the manufacture - 
of great supplies of. both propellant and shattering explosives had been 
worked out, upon such a scale as rendered Central Europe independent 
of imported Chili saltpetre as a raw material. a 
412 
