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06/05/2001
Dead Leaves and Haber's Ammonia
Last week, I mentioned a trip with my grandson to the Liberty
Science Center and seeing Gus Grissom''s space capsule. Very
interesting, but most fascinating to me was a section of the
museum containing live animals ranging from unusual lizards to
huge cockroaches and millipedes. My grandson even got to pet a
boa constrictor. But what really blew my mind was a small
terrarium containing some small bushes covered with dried-up
leaves.
The dried-up leaves reminded me of my gardening days and
digging in some of the tons of oak leaves that covered our
property every autumn. I didn''t need fertilizer to grow huge
zucchinis. Fertilization happens to be one of the topics in an
article titled "Capturing Nitrogen Out of the Air" by David M.
Kiefer in the February 2001 issue of the American Chemical
Society publication "Today''s Chemist at Work". Kiefer cites a
British chemist, Sir William Crookes, as predicting about a
hundred years ago that mankind would soon face starvation. He
thought the world was running out of nitrogen in the form of
fertilizers that serve to nourish crops.
Nitrogen ranks with carbon, hydrogen and oxygen as the most
common elements in living tissues. In order to grow, a plant
needs nitrogen. You might say, "No problem. There''s lots of it.
After all, the air we breathe is almost 80 percent nitrogen." It''s
not that simple. Nitrogen gas in the air is pretty inert; otherwise
it wouldn''t still be there! For plants to take up nitrogen, it has to
be "fixed". Fixing nitrogen means it has to be transformed into a
nitrogen compound that the plants can assimilate.
An example of fixing nitrogen is to form compounds with
hydrogen or oxygen. In nature, thunderstorms don''t just supply
rain. Lightning in the storms fixes a healthy dose of the world''s
nitrogen by reacting it with oxygen and hydrogen to eventually
form compounds such as nitrates or ammonium salts. These
compounds can be used by the plants and are fertilizers. As an
organic gardener, I knew that peas and other legumes have
nodules underground that harbor bacteria that can also fix
nitrogen. These natural fixers were fine for millions of years
until really hungry animals like ourselves arrived on the planet.
But feeding billions of us, many of whom insist on eating other
animals that eat plants (very inefficient), is another matter. Back
in the 1800s, guano (a fancy name for bird droppings) and
saltpeter (sodium nitrate) deposits from South America were
major sources of fertilizer for European farmers. Crookes''
concern was that these sources were drying up; hence his
pessimism. However, he was prophetic when he said that it
would be up to the chemist to save the world from starvation.
I''m editing a history of The Electrochemical Society (ECS),
founded in 1902. One who joined the Society that year was an
eminent German chemist, Fritz Haber. Fritz was the chemist that
Crookes was hoping for. Most chemists will immediately know
the name of Haber and the Haber process. But I daresay most
people have not heard of him at all. Yet, Haber''s activities were
to result in (1) a Nobel Prize, (2) the feeding of millions, if not
billions of earth''s inhabitants, (3) the killing or wounding of
thousands of soldiers in World War I and (4) fertilizer runoff as a
major factor threatening our environment today.
To understand Haber''s contributions, you have to know a bit
about ammonia, a gas composed of a nitrogen atom attached to
three hydrogen atoms. You have a bottle of ammonia in water in
your laundry room perhaps, and you use it when you clean your
windows. Ammonia is an extremely important compound that
can be used to make ammonium salts as well as nitric acid.
Ammonium sulfate, for example, is an important fertilizer.
Nitric acid can be used to make nitrates. Ammonium nitrate is
another common fertilizer. Ammonia is used to "fix" nitrogen.
Remember that we said lightning fixes nitrogen? Similarly,
powerful electric arcs are sort of like lightning and were being
used to make ammonia. Back in the early 1900s, electric arcs
were also used to make another nitrogen compound, calcium
cyanamide, which became the dominant fertilizer into the 1920s.
These processes involving electric arcs and nitrogen required
huge amounts of power. The cost of the power was so high that
it wasn''t economically feasible except in a country like Norway
with vast amounts of cheap hydroelectric power.
Haber had been studying the thermodynamic properties of the
reaction of nitrogen and hydrogen - not exactly the most exciting
subject. He could get a little ammonia but nothing to write home
about. Others were working on this reaction but the consensus
was that to really get enough ammonia to make it commercially
viable would require very high temperatures and pressures. Such
extreme conditions were deemed unsuitable for industrial
production. But Haber persevered, trying to find a catalyst to
speed up the reaction. Finally, in 1908, he found that uranium or
osmium, both pretty exotic elements, did the trick. Haber found
that, by keeping the hydrogen and nitrogen moving around all the
time and by using the catalyst, significant amounts of ammonia
could be produced at much more reasonable pressures and
temperatures. The world would never be the same again.
The next year, two other German chemists, Karl Bosch and
Alwin Mittasch, viewed a demonstration of the process. They
worked for the large German chemical firm BASF (Badische
Anilin- und Soda Fabrik). Mittasch was an expert in catalysts.
BASF bought the rights to Haber''s patent and Haber received a
pfennig royalty for every kilogram of ammonia BASF produced.
Over the years, these pfennigs added up to millions of dollars for
Haber! Mittasch found a cheaper and improved iron catalyst
and Bosch''s team came up with high-pressure vessels and
cheaper methods of making liquid nitrogen and hydrogen to feed
into the vessels. The Haber-Bosch process was immensely
successful and by 1918 was producing half of Germany''s need
for nitrogen compounds.
Ammonia wasn''t used only for making fertilizers. It was also
used in making dyes and in refrigerant applications. (I wrote
some time ago about nearly being present in an ammonia plant
explosion in an ice cream factory.) Ammonia had another use -
making explosives and munitions. And World War I was in
progress. In 1918, the year of Haber''s Nobel Prize, one of my
predecessors as secretary of The Electrochemical Society, Joseph
Richards, remarked that without the Haber-Bosch process,
Germany would have had to quit the war in 6 months!
Germany''s sources of nitrates from South America were no
longer reliable.
So, one can attribute the length of World War I, and the ensuing
casualties, at least indirectly to Haber. Actually, Haber had a
very direct role in World War I. A true German patriot, he
volunteered to help out in the war effort and was put in charge of
the German army''s chemical warfare. He was in charge of the
poison gas projects involving chlorine and mustard gas. Haber
has even been called the father of chemical warfare. Haber''s
involvement in this aspect of the war did not sit well with many
scientists who felt that he should not have received the Nobel
Prize because of the poison gas connection.
Haber''s wife apparently felt even more strongly. She had
chemical training, and thought that the use of the chlorine and
mustard gas was a terrible application of science. So strong
were her feelings that one day in 1915, when Fritz left to
supervise the installation of poison gas cylinders at the front,
Clara committed suicide! Haber reportedly directed the first
large-scale use of chlorine gas personally. Estimates are that
some 5,000 to 15,000 Allied troops were either killed or
wounded that first day. There were also several hundred
German casualties, presumably due to gas drifting in their
direction.
After World War I, Haber felt that he was partly responsible for
the huge war reparations imposed on Germany by the Allied
powers. Haber decided to try to extract gold from seawater and
use that gold to help pay off the debt. Unfortunately, there
wasn''t as much gold in the oceans as Haber had figured and the
experiment was abandoned. Who knows, if Haber''s project had
succeeded, it may have prevented the terrible economic
conditions in Germany that supported Hitler''s rise to power.
When Hitler came to power, Haber was a director of the Kaiser
Wilhelm Institute for Physical Chemistry and Electrochemistry.
In 1933, Haber was ordered to fire all the Jewish scientists
working there. Haber resigned instead, being of Jewish descent
himself, and went to England for a brief stint at Cambridge. He
died in 1934. But Haber''s process lives on. Today, the huge
increase in nitrogen fertilization spurred by his invention and the
resulting runoff of fertilizers join many other nitrogen-containing
emissions threatening our air and waters. And we billions of
people who are being fed, thanks in part to Haber, are ourselves
the biggest threat to the world''s environment.
As usual, I''ve digressed. About those dead leaves, after turning
away from that terrarium, I decided to take another look and was
glad I did. Those dried-up leaves were the attraction! When I
looked more carefully, the leaves were moving, ever so slowly.
And they weren''t leaves at all! They were actually alive and the
most startling insect or bug I''ve seen. If ever there was a
demonstration of evolution to a form of life with virtually perfect
camouflage, this was it. As I recall, the "leaves" were an inch or
so in length with flat faces and very fine, spindly legs. I was so
shocked that I forgot to note the name of the creatures but think
they were from some place like Africa, South America or
Malaysia. I''ve looked on the Web and found there are so-called
"leaf insects" but didn''t see pictures of any that were quite like
the "leaves" in the museum. I''ll have to go back.
Allen F. Bortrum
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