f water. On the sides of the chamber are seen the
openings through which the air passes impinging directly on both sides
of the surface of the disk of flame. This flame is approximately seven
feet in diameter and appears to be continuous although an alternating
current of fifty cycles a second is used. The electric arc is spread
into this disk flame by the repellent power of an electro-magnet the
pointed pole of which is seen at bottom of the picture. Under this
intense heat a part of the nitrogen and oxygen of the air combine to
form oxides of nitrogen which when dissolved in water form the nitric
acid used in explosives.]

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

A BATTERY OF BIRKELAND-EYDE FURNACES FOR THE FIXATION OF NITROGEN AT THE
DU PONT PLANT]

We might have expected that the fixation of nitrogen by passing an
electrical spark through hot air would have been an American invention,
since it was Franklin who snatched the lightning from the heavens as
well as the scepter from the tyrant and since our output of hot air is
unequaled by any other nation. But little attention was paid to the
nitrogen problem until 1916 when it became evident that we should soon
be drawn into a war "with a first class power." On June 3, 1916,
Congress placed $20,000,000 at the disposal of the president for
investigation of "the best, cheapest and most available means for the
production of nitrate and other products for munitions of war and useful
in the manufacture of fertilizers and other useful products by water
power or any other power." But by the time war was declared on April 6,
1917, no definite program had been approved and by the time the
armistice was signed on November 11, 1918, no plants were in active
operation. But five plants had been started and two of them were nearly
ready to begin work when they were closed by the ending of the war.
United States Nitrate Plant No. 1 was located at Sheffield, Alabama, and
was designed for the production of ammonia by "direct action" from
nitrogen and hydrogen according to the plans of the American Chemical
Company. Its capacity was calculated at 60,000 pounds of anhydrous
ammonia a day, half of which was to be oxidized to nitric acid. Plant
No. 2 was erected at Muscle Shoals, Alabama, to use the process of the
American Cyanamid Company. This was contracted to produce 110,000 tons
of ammonium nitrate a year and later two other cyanamid plants of half
that capacity were