Ammonium Nitrate: the Jekyll and Hyde Chemical

Chemistry contains a few Jekyll and Hydes.

There are chemicals, like DDT, that are capable of achieving great good and great evil.  At the top of this list is ammonium nitrate.

In the early years of the 20th century, the world had a problem.  Fertilisers were hard to make.  The only source of saltpetre, the chemical that was used as the basis of most fertilisers, was in Chile.  Digging it out, and transporting it around the world, was an expensive and time-consuming process.

The problem was the nitrogen.  Nitrogen is required to make nitrates, and of course ammonium nitrate, which contains two nitrogen atoms.

And while there is plenty of it around us – the air we breathe is 70% nitrogen – no one had worked out a way to get it out of the air, and so the only way left was digging it out of the ground in Chile.

Along came Fritz Haber.

Haber worked out a way to get nitrogen out of the air, and convert it to nitrates.  And so suddenly the world had a plentiful and cheap supply of fertiliser, and vast tracts of land could be made arable, and millions of people could be fed.

That is the Dr Jekyll part.

This all happened in 1913, which you may notice was the year before the First World War started.

As it happened, the Germans had another problem.  Explosives.  They couldn’t make them in any great amount, because they were nitrate-based, and the British had cut off their supply of saltpetre from Chile.  The only source they had was urine and bird droppings, which was never going to yield much.

Suddenly, as if by magic, along came the Haber process.  Suddenly, now the Germans had a plentiful supply of nitrates, and they could make as many explosives as they wanted.

That is the Mr Hyde part.

In fairness to Haber, who developed it as a fertiliser, he was not to know that this chemical would be used to make the explosives that were killing millions of people. But let’s be realistic about this – were it not for the Haber process, World War I would not be what it was – the British would have had the ability to make explosives, and the Germans wouldn’t, and the war would have been much, much shorter.

And today the ammonium nitrate is used for both sources.  It is used by terrorists, and it is used by mines as an explosive.  It is also used by farmers as a fertiliser.

Incidentally, although it was known as explosive compound, this knowledge was not very widely disseminated, and it led to the second greatest industrial accident of all time.

In fact, it has led to a few industrial accidents – in years gone by, before people knew how explosive it was, they would actually break it up with a hammer and chisel if it had caked together.

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