Nitrogen: Food or Flames
Nitrogen gas surrounds us all, yet we barely notice this benign
substance exists (78% of the atmosphere is composed of nitrogen gas, N2).
However, when combined with other elements, nitrogen can have a very
schizophrenic personality. Nitrogen compounds can be used to feed, or
kill, with equal ease. This ironic nature of nitrogen was tragically
demonstrated in the Oklahoma City Bombing when fertilizer was used as an
explosive, killing hundreds.
A
Little Chemistry
All living things require nitrogen to live (it is the "amino" in
"amino acids", a major component in DNA, RNA, and proteins) however few
creatures can make direct use of the sea of nitrogen surrounding us all. This is
because the two nitrogen atoms that make up a nitrogen molecule are held firmly
together by a triple bond which is exceedingly difficult to break.
Because of this bond, nitrogen gas simply does not participate in any
reactions at room temperature (or even at the higher temperatures found in small
fires), and is therefore described as inert. Only at extremely high
temperatures (such as those found near a lightning bolt or in an
automobile's engine), or through the magic of "nitrogen fixing" bacteria
(who work their trick with a complex set of enzymes instead of heat), can this
triple bond energy be overcome, making nitrogen gas momentarily reactive while
in an excited state.
If this excited nitrogen molecule is combined with oxygen (which
incidentally composes the rest of the atmosphere) nitrogen oxide (NO) is
produced. This readily oxidizes to nitrogen dioxide (NO2), which
provides the brownish haze seen in smog (as all Los Angeles residents are
well aware).
If, on the other hand, the excited nitrogen gas combines with hydrogen,
it forms ammonia (NH3). And ammonia, unlike smog, is a very
useful compound indeed. It can be used to make fertilizers, high explosives,
nitric acid, and household cleaning agents.
The
Nitrogen Cycle
Converting nitrogen gas into more reactive (and useful) nitrogen compounds,
such as ammonia, encompasses the first stage in the "nitrogen cycle".
Once converted from its gaseous form, fixed nitrogen compounds allow plants
to grow large and healthy. Animals gain access to this nitrogen by
eating the plants, and deposit excess nitrogen in their feces. Fixed
nitrogen is also returned to the soil when plants and animals die.
Bacteria then decompose this organic matter first into ammonia, then
into nitrites (like potassium nitrite: KNO2), and finally into
nitrates (like potassium nitrate: KNO3), which are again used
by plants. Additional bacteria return some of the fixed nitrogen back to the
atmosphere (in the form of nitrogen gas), thereby regulating the whole cycle.
The
State of Affairs in 1913
For thousands of years, humans had little impact on the nitrogen cycle. The
strong bond found in nitrogen gas prevented its simple conversion to other, much
more useful, nitrogen compounds. People were therefore entirely dependent upon
bacteria for the initial nitrogen fixation. Once fixed in the cycle, nitrogen
compounds could be collected.
One of the best, and largest, sources of this fixed nitrogen
was found in Chile. This outcrop was due to a vast number of sea birds
which nested, and went to the bathroom, along its coasts. Over thousands
of years these "natural" deposits called "Guano" accumulated and
became several feet thick. A huge industry developed to supply this Chilean
saltpeter to the rest of the world.
With synthetic production almost non-existent, the world was entirely
dependent on the Chilean resource for fertilizers and high
explosives. This was a fact which military leaders did not overlook. They
realized that if war broke out, the countries which lacked (or were denied)
access to the Chilean supply (like Germany) would quickly run out of
munitions.
In 1913 if you were an up and coming nation, intent on feeding your people,
or conquering your enemies through conquest, you needed as much
Chilean saltpeter as possible. In short, the fate of the world depended upon
who could get their hands on the most bird shit. It is therefor no coincidence
that the first major naval battle of World War I occured off the coast of Chile.
Synthetic
Ammonia Production
Shortly before the outbreak of World War I, two patriotic Germans developed a
method for producing synthetic ammonia. The first plants using this "Haber-Bosch
Process" were constructed shortly after the outbreak of the war. They had
discovered that ammonia could be made by placing nitrogen gas and
hydrogen gas in a high pressure chamber. With the addition of a
suitable catalyst, and a little heat to speed things up, vast
quantities of fixed nitrogen could be produced. Without the Haber-Bosch
Process, Germany would have run out of munitions in 1916 thereby ending
the war.
To compete with this, other countries copied the process and quickly scaled
up their own synthetic ammonia production capabilities. When the war was over,
fixed nitrogen continued to be produced in large amounts because of its use as a
fertilizer. By 1934 Chile was supplying only 7% of the worlds fixed nitrogen (a
huge drop from the 56% supplied in 1913). Synthetic ammonia production had
arrived in force.
Tabulated data for previous two graphs is shown below...
As these figures show, synthetic ammonia production eliminated
the worlds dependence upon Chilean saltpeter. Chemical engineers played a
large role in designing, building, and operating the ammonia plants that made
this possible. In 1934 if you wanted to feed your country or wage a
war you turned to a chemical engineer. This fact brought with it a moral
dilemma for the chemical engineer asked to build an ammonia plant...
A
Few Important Nitrogen Compounds
Amino
Acids are the building blocks of life. All living things are composed
of only 20 such compounds, with the amino group (NH2) common to them
all.
Nitrous
Oxide (dinitrogen oxide) (N2O) Otherwise known as laughing gas,
this compound is a colorless gas at room temperatures and pressures.
Nitrogen
Oxide (NO) A colorless bi-product formed in internal combustion engines
where high temperatures and pressures are capable of combining the nitrogen and
oxygen gases found in the air.
Nitrogen Dioxide (NO2) Otherwise known as smog, this
brown gas comes about as nitrogen oxide is spontaneously oxidized in the
atmosphere.
Potassium Nitrate (KNO3) Often referred to as saltpeter,
it can be placed directly on the soil as a fertilizer, or when mixed with
sulfur and coal forms gunpowder. Saltpeter is prized by both farmers
and generals.
Trinitrotoluene (TNT, CH3C6H2(NO)3)
A high explosive used as the explosive charge in shells and bombs.
Nitroglycerin (C3H5(ONO2)3)
Being the principle explosive ingredient in dynamite, this chemical packs
quite a punch. It is three times as powerful as an equal amount of gunpowder, is
smokeless, and its explosive wave travels 25 times faster. Because of its many
uses, and high demand, dynamite producers were able to amass great fortunes.
Alfred Nobel was one early manufacturer, and his fortune continues to
finance the Nobel Prize Award today.
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