What is the greatest discovery of the last twenty-five years? Probably
you will say the wireless telegraph, the flying machine, moving pictures
or the phonograph, but it would be none of these, according to the
_Scientific American_. This publication discussed at great length the
subject of what invention of the last twenty-five years was of greatest
value to mankind. First place was given not to the wonderful inventions
that are so large in the public eye, but to the fixation of nitrogen
from the air for fertilizer purposes. Why? Simply because this discovery
stands between man and starvation. Other inventions are vastly
important, but this one is vital. Looking at it from the broadest view
there can be no other decision. The time is here when to feed the world
is becoming a more and more difficult problem.
During the past ten years our population has increased at the rate of
two per cent per annum, while our crop production has increased only
one-half as fast. In six years the number of beef cattle produced in
this country has fallen off about five per cent per annum. The cost of
foodstuffs recently has been increasing at the rate of five per cent per
annum. The hardships experienced by wage-earners, particularly in the
United States, have been very great in view of the fact that the cost of
food increased more rapidly than wages--at a rate approximately double.
The same tendencies apply with some modifications to the clothing of
mankind. These facts point to the necessity of increasing the yields
both of the food crops and the crops that are used in the making of
clothing.
[Illustration: WRAPPER LEAF TOBACCO CROP FERTILIZED WITH CYANAMID
MIXTURES. GROWN IN HATFIELD, MASS.]
The problem of decreasing the cost of living has been given far more
attention abroad than it has in this country, owing to the much greater
density of population in the principal nations of Europe. For a long
time it has been known that plants require food the same as animals and
human beings. Without food plants cannot live and grow, and just to the
extent that plant food is present in the soil, to that extent will a
crop be produced. The most important of plant foods is nitrogen. While
the earth is literally bathed in nitrogen, this element is found to only
a very slight degree in the soil. That is to say, the air which we
breathe and in which we move is four-fifths nitrogen, yet in the richest
soil there is seldom more than one-tenth or two-tenths of one per cent
of nitrogen. Put on a wheat crop one pound of nitrogen and you can take
off twenty pounds more wheat and forty pounds more straw than you could
if you failed to make this application. One pound of nitrogen properly
applied to a cornfield will add thirty-five pounds to the crop; one
pound of nitrogen will produce one hundred pounds of increase in the
potato crop; one pound of nitrogen will produce five pounds of cotton,
without any extra labor being devoted to the production of the crop.
Nitrogen is the heart and soul of the problem of growing more crops and
cheaper crops. Take any nation that produces large crop yields per acre
and you will find that the nation that uses the most nitrogen per acre
grows the largest crops.
For years the nations of Europe have been depending to a great extent
upon supplies of nitrate of soda obtained from Chile, in South America.
Germany alone imported nearly a million tons of this salt annually
before the war. Then, too, the by-products of many industries furnish a
quantity of nitrogen, but all this, it was realized, furnished but a
small part of what was required to combat the constantly rising cost of
producing food.
For years it was the dream and life-ambition of the world’s greatest
scientists to discover how to make the supplies of nitrogen in the air
available to plants as food. The only way that this could be done in
nature was through the agency of bacteria working on the roots of
certain plants, such as clovers, but this process was entirely too slow
for practical purposes and could be applied on only a small acreage at
one time. The free nitrogen of the air cannot be utilized directly by
plants. It must first be converted into some combination with other
chemicals, as a solid or liquid, which can be absorbed by the plant.
Among others who worked on the problem of fixing atmospheric nitrogen
were two German chemists, Doctors Caro and Frank, who found that a
compound of calcium and carbon heated to a high temperature would absorb
nitrogen and retain it in a form that could be applied to the soil and
serve as a food for plants.
[Illustration: SUGAR CANE CROP FERTILIZED WITH CYANAMID MIXTURES. GROWN
IN CALUMET, LA.]
This discovery is the basis of the Cyanamid “Atmospheric Nitrogen”
industry or the making of fertilizer from the nitrogen in the air. After
the discovery was made and tested on the laboratory scale it took
several years to put it on a practical basis, as can well be imagined
when it is understood what the problems involved were. Besides air this
process required as raw materials limestone and coke. The limestone must
be burned to quicklime and the quicklime and coke must be fused together
to form calcium carbide. Only the most powerful electric furnaces are
capable of performing this work. Any other means of heating is far from
adequate. For instance, the hottest flame that can be produced by the
burning of gas, namely, the oxy-hydrogen blow-pipe flame, can be
directed against a stick of burnt lime without doing anything beyond
making the lime glow brilliantly, thus producing the calcium or
lime-light formerly much used in theaters as a spot-light. In the
electric furnaces, however, the lime is heated so powerfully that it
actually melts to a liquid, and in this condition it dissolves the coke
with which it is mixed and the compound resulting is calcium carbide
which can be run off from the interior of the furnace in liquid form.
[Illustration: TWO OF THE CARBIDE FURNACES AND ELECTRODE REGULATORS]
At the cyanamid plant at Niagara Falls, in Canada, there are seven of
these great carbide furnaces, each about fifteen feet long and half as
wide and one-third as deep. We all have some idea of how much heat is
generated in the ordinary electric arc light such as is used for street
lighting. In the carbide furnace the carbon pencil, instead of being six
or eight inches long and as large around as your finger, is six feet
long and two feet in diameter. There are three of these in each furnace,
and when the furnace is in full action it can be imagined that there is
a terrific heat generated; in fact, when the fused lime and coke come
out of the furnace in the form of molten carbide the brightness of the
molten material is so dazzling that one cannot look at it with the naked
eyes without injury.
[Illustration: ONE OF THE CARBIDE MILLS]
Then there is the problem of producing pure nitrogen gas, that is,
separating the eighty per cent of nitrogen in the air from the twenty
per cent of oxygen. The latter is the element that we breathe and which
passes into the body, there to combine with the impurities resulting
from the various life activities. If the nitrogen and the oxygen were
both allowed to act upon calcium carbide the oxygen would burn up the
carbide before the nitrogen could be fixed in it, hence these two
elements must be separated and all other impurities removed so that only
chemically pure nitrogen is brought to the calcium carbide for fixation.
The separation is accomplished by means of liquid air machines. This
industry, therefore, not only utilizes the greatest heat obtainable on a
practical scale, but it also utilizes the greatest cold. While the
electric furnaces produce a temperature of over 4000° F., or about twice
as hot as molten cast-iron, the liquid air machines work at a
temperature of 372° F. below zero. The air must first be purified and
dried. It is then compressed, cooled while under pressure, and then
expanded. The expansion lowers its temperature considerably. If this
extra cool air is used for cooling another batch of air under pressure,
the latter upon expansion becomes still colder than the first batch
expanded. By repeating this operation the final temperature of 372°
below zero is reached, at which the air liquifies.
How cold this is can be seen from some simple experiments. For instance,
if a dipper full of the liquid air is drawn, in an instant the outside
of the dipper is covered with a coating of frost deposited upon it from
the surrounding atmosphere. The surrounding air is so much hotter than
the liquid air that the liquid boils violently. If a piece of rubber
hose is held in the liquid air for eight or ten seconds and then struck
with a hammer the rubber flies into pieces just like glass. To dip one’s
finger into this liquid air would freeze it solid in a second and would
be as disastrous as dipping it in red-hot iron.
[Illustration: LIQUID AIR PLANT]
When the liquid air is allowed to warm up a little, the nitrogen gas
evaporates, while the oxygen remains behind in the liquid. The pure
nitrogen then can be pumped into the fixation ovens.
To fix the nitrogen in the carbide it is necessary to cool the latter
after it comes from the electric furnaces and grind it to a very fine
powder. This powder is then placed in furnaces that look like steel
barrels but are three or four times larger than an ordinary barrel. The
oven filled with calcium carbide is then electrically heated with a
carbon rod running through the center. When the temperature is about as
hot as that of molten iron the pure nitrogen gas from the liquid air
plant is pumped in and allowed to act on the calcium carbide for about a
day and a half. When the carbide has absorbed all it will absorb the
crude cyanamid formed is removed from the oven as a single large cake
which is run through pulverizing drums and then put through an elaborate
process of refinement and finally bagged for shipment in carload lots to
fertilizer factories throughout the country.
The fertilizer manufacturers mix the cyanamid with other ingredients to
make a balanced plant food and so ship it to farmers for feeding their
crops. In 1914 7,500,000 tons of fertilizer worth $175,000,000 were
consumed in this country. This seems like a large quantity, but it
allows only a scanty application per acre cultivated. Germany, on
one-fourth of our cultivated acreage, uses almost twice as much
fertilizer as the entire United States. As a consequence she raises 30
bushels of wheat where we average 14 bushels per acre; 52 bushels of
oats where we average 30; and 196 bushels of potatoes per acre where we
raise 97 bushels per acre. The explanation is simple, German farmers pay
only about one-half as much for their plant food as American farmers
pay. Where the German farmer gains $2.00 to $3.00 increase in crop from
fertilizer that costs him $1.00 the American farmer pays $2.00 for the
same fertilizer, which leaves him less profit and less incentive to use
fertilizer.
[Illustration: A CARBIDE COOLING SHED]
[Illustration: CYANAMID OVEN ROOM]
[Illustration: _Photo by William H. Rau_