Last week, I wrote about Fritz Haber and how his process for
making ammonia affected the course of history. After posting
the column, I had this feeling that I had missed something
important. While anticipating my 55th reunion at Dickinson
College last week, I realized what it was. It was a remark made
by Professor E. A. Vuilleumier in our freshman chemistry class
some 58 years ago. Vuilleumier was a colorful teacher and had a
peculiar way of illustrating the difference between concentrated
hydrochloric and sulfuric acids. He poured the two acids into
beakers and then dipped his hands into the beaker with the
hydrochloric acid. As I recall, he also quickly washed his hands
under the tap. Turning to the other beaker, he did not dip his
hands in the sulfuric acid. Sulfuric acid is really nasty stuff. I
hasten to say that I don”t recommend you dip your hands in either
acid!
But we”re concerned here with ammonia. It was in one of Prof.
Vuiileumier”s classes that a coed classmate fainted. As she was
coming to, someone handed her a container with ammonia to
sniff. She drank it! I”m happy to report that this feisty coed was
none the worse for the incident. But let”s get to Professor
Vuilleumier”s remark that made such a lasting impression on me.
We were considering the chemistry of ammonium salts,
particularly ammonium nitrate, when Vuilleumier told us in no
uncertain terms to “Remember Oppau!”
Last week, we noted that one of the uses for the ammonia is to
make ammonium nitrate for use as a fertilizer. Oppau, Germany,
was the location of the first synthesis plant for ammonia
production using the Haber-Bosch process. At the Oppau plant,
established in 1913 by the German company BASF, ammonium
nitrate and ammonium sulfate were two of the fertilizers that
were being produced. What BASF did was to make these
compounds and pile them up in big piles – I mean really big piles
containing several thousand tons of the materials. The particles
of these ammonium salts tended to stick together, making clumps
of material that were hard to break up when ready to be shipped.
Rather than go in with sledgehammers or the like, they typically
used a brute force method of breaking up the piles. They broke
them apart with blasting powder!
This blasting method had apparently been used many, many
times without incident so there was no reason for concern on
September 21, 1921. BASF had a pile containing roughly equal
amounts of ammonium nitrate and ammonium sulfate. The pile
contained well over 4,000 tons of the stuff. You”ve probably
guessed that “Remember Oppau!” concerns this date. The
explosion was devastating, killing over 500 people and injuring
over a thousand more! The plant and a goodly portion of the
town were leveled. Until Oppau, there was no indication that
ammonium nitrate was hazardous. Now the world knew that
ammonium nitrate is one of those compounds that can be treated
with impunity most of the time but, under the right conditions, it
can be deadly.
The Oppau explosion was prophetic of things to come. Only
three years after I heard Professor Vuilleumier”s remark, Texas
City, Texas had its own encounter with ammonium nitrate. This
waterfront boomtown of 18,000 was full of chemical plants and
oil refineries and occasional fires and even explosions were not
out of the ordinary. The populace was used to stopping work and
watching the fires if they seemed particularly interesting. On
April 16, 1947, when a small fire broke out on the French ship,
the S. S. Grandcamp, the peach or reddish orange color of the
smoke attracted more than the usual amount of spectators. The
Grandcamp was already loaded with such things as peanuts, sisal
twine and oil field machinery. It was docked in Texas City to be
loaded with ammonium nitrate destined for Europe.
It became clear to the crew on the Grandcamp that the fire
needed more than just jugs of water or portable extinguishers.
The hatches were closed and covered with tarpaulins to protect
the cargo. Now came a mistake in chemistry. To preserve the
contents of the ship from water damage, instead of hosing down
the fire, the decision was made to employ the ship”s steam fire-
fighting system. The steam was intended to smother the fire,
avoiding using all that water. The problem is that ammonium
nitrate doesn”t like high temperature. The hot steam heated up
the compound, which started decomposing. The gases emitted
blew the hatches and the ship became so hot that, when the Texas
City Volunteer Fire Department started spraying water on the
deck, the water vaporized! Remember Oppau! The ship blew
up.
But that wasn”t all. There was another ship in the harbor that
day, the High Flyer. Guess what that ship contained –
ammonium nitrate! Over 900 tons of it! It too caught fire and
some 16 hours later it also blew up. The two explosions sent
debris onto the oil tanks and pipes and secondary fires and
explosions abounded. When it was all over, at least 581 people
were dead and 3,500 injured. No resident of the town was
untouched by the tragedy, which is profiled in detail on what I
believe is the Houston Chronicle Web site chron.com.
Fast forward to today, Monday, June 11. The person who
represents the essence of evil, Timothy McVeigh, is history.
What was his choice of fertilizer to use in his bomb destined for
Oklahoma City? Ammonium nitrate!
In writing this gloomy piece, I”ve been trying to think of some
way of ending on a positive note. Brian Trumbore just dropped
off a page from the June 11 issue of Business Week that might
serve the purpose and can be connected to our discussion of
ammonia. Last week, I mentioned that lightning ”fixes” nitrogen
and that, before Haber”s process, electric arcs were used in the
production of ammonia. The Business Week article deals with
the process of arc welding, which involves the striking of an
electric arc from the welding rod to the metal being welded.
Arc welding is a relatively cheap process but, like the lightning
the arc resembles, the arc can follow an unpredictable path from
the welding rod to the object being welded. This means the weld
can be somewhat problematic as far as its location and quality is
concerned. If you really need a precise weld just where you want
it, there”s a better way. It”s laser welding. You might not be
surprised at this since lasers are used in eye surgery that can be
pretty much like making little welds in the eye. The downside of
industrial laser welding is cost. A laser capable of doing large
jobs may cost a couple hundred thousand dollars, and you also
need a hefty power supply of many kilowatts. The cost of these
laser-welding systems has generally limited their use to large
industrial outfits like the auto or aerospace companies.
Now Prof. Charles Albright and his colleagues at Ohio State
University have come up with a new approach combining the
laser and arc welding techniques. This new welder is called the
Laser Assisted Arc Welder (LAAW) and its operation is pretty
neat. The Albright team sticks some carbon monoxide in the
welding chamber and hits it with a laser that uses about the same
power as a Christmas tree bulb (7 measly watts). The laser
beam strips electrons off the carbon monoxide forming a beam of
positively charged ions. (The article didn”t say they were
positively charged, or ions – that”s my conclusion.) Now bring
your electric arc with its stream of negatively charged electrons
close to the beam of ions. Opposites attract, as they say, and the
electrons follow the laser/ion beam precisely. Now you have a
welder that will have the precision of a laser welder but should
cost a tenth as much, thanks to the low power of the laser in the
LAAW.
According to the article, the LAAW has just been patented and
Albright and colleagues hope to find support for a commercial
venture. I may be wrong, but it seems to me that I saw a
suggestion in an article about a year ago that a laser beam might
be used as a kind of lightning rod. If I”m correct, I suspect it
would be along the same lines, the laser forming a path of ions to
guide the lightning.
Well, I”m back from my 55th reunion, a most enjoyable affair
with a dozen of us from the class of 1946 in attendance. That
may not seem like many but during World War II there weren”t
too many of us at Dickinson. And the ratio of 5 females to 1
male held true at our reunion – Bob and I were the only men.
And would you believe that Bob said he had a challenge – could
anyone spell Vuilleumier (pronounced Vee-yuh-may)? Having
started this column before the reunion I could whip it off with no
hesitation!
Allen F. Bortrum
