Nitrates

The explosion of a vast amount of ammonium nitrate in Beirut is a tragedy of immense proportions, both for the multitudes killed or injured, and for the damage to Beirut's infrastructure.  Strangely, and perversely, it brings back memories of an enjoyable childhood experience, if one fraught with danger.

I had a microscope set as a young teenager, which came with a number of stoppered test tubes.  Some were filled with interesting things -- a bee, for example, preserved in alcohol -- to examine microscopically.  Some contained various chemicals useful in preserving exhibits, or preparing them for placement on a slide, or for other uses that I don't now recall.

I especially don't recall why there was a tube full of potassium nitrate (saltpeter).  I can't imagine what use it had in the context of my microscope, but if I were better trained in that direction, its use might be obvious.  But it had a quite different use at my young hands.

10KNO₃ + 8C + 3S → 2K₂O₃ + 3 K₂SO₄ + 6CO₂ + 5N₂

This is the rough equation for the explosion of gunpowder.  It's a "rough" equation, because the constituents of gunpowder -- potassium nitrate, sulfur, and charcoal -- react with each other in a number of complicated ways, depending partly on their proportions as combined by the chemist.  Or by the trembling hands of a young teenager.  A young teenager who was damn lucky it didn't blow up in his trembling hands and face.

Yes, I'm afraid all of my potassium nitrate was consumed for recreational purposes.  I packed the resulting gunpowder carefully into a small cardboard container, which I then wrapped tightly in duct tape.  My brother and I took it to a nearby park, lit the firecracker fuse we'd inserted, and ran for our dear lives.

The result was highly satisfactory.  Luckily, no arrests were made.

As every serial murderer knows, one killing only whets one's appetite for the next.  I had plenty of sulfur and charcoal.  What I needed was more potassium nitrate.  I wisely sent my younger brother to a local pharmacy to see how much he could hustle up.  The answer -- not one gram.  The pharmacist took a peculiar interest in what a 12-year-old kid was planning to do with potassium nitrate, and wisely decided not to sell him any.  (If he even had it in stock.)

Did he care nothing for our education?  As the Nobel prize-winning chemist Linus Pauling has said, as quoted by Oliver Sacks in his memoir Uncle Tungsten:

Just think of the differences today.  A young person gets interested in chemistry and is given a chemical set.  But it doesn't contain potassium cyanide.  It doesn't even contain copper sulfate or anything else interesting, because all the interesting chemicals are considered dangerous substances.  Therefore, these budding young chemists don't have a chance to do anything engrossing with their chemistry sets.  As I look back, I think it pretty remarkable that Mr. Ziegler, this friend of the family, would have so easily turned over one-third of an ounce of potassium cyanide to me, an eleven-year old boy.

More's the pity.  My career in explosives came to an early end, due to the excessive caution of a small town pharmacist.

But Beirut has shared my early experience on a grandiose scale.  The stored substance was ammonium nitrate ((NH₄NO₃), not potassium nitrate (KNO₃), but the chemical reactions would be essentially the same.  Just substitute the radical NH₄ for K in the equation given above.  In either case, huge amounts of expanding carbon dioxide and nitrogen gases are released, together with a substantial amount of heat.

And for me as a kid, and for Beirut this week, the heat and explosive power of the gases released are far more impressive than the nature of the resulting chemical compounds.