Yes, I know, I said I would be closing up shop for a few months. But I saw a paper just today that was kinda intriguing, so I couldn’t resist the temptation to share it here. Aside from this my blog will remain out of action for now…
It was April in Dallas when a string of unusual cases started to turn up at the ER. Four patients in four hours, all of them fainting from low blood pressure. All four had eaten at the same restaurant, and all four had ordered iced tea.
The police stopped by the restaurant to halt further sales of iced tea and take samples. But chemical testing for over a hundred possible poisons/drugs turned up negative. It wasn’t until five months later that an FBI laboratory identified the mystery poison: sodium azide.
Ordinarily you find nitrogen in our atmosphere in the form of N2, two nitrogen atoms joined by an exceptionally strong triple bond. If you give them the opportunity, the nitrogen atoms in the azide ion would really like to regroup and form N2, which is much more stable than this miserable-looking azide ion will ever be. The resulting reaction releases a lot of energy and (of course) nitrogen gas.
What do you call a reaction that releases a lot of heat and gas? An explosion, of course. And if it’s heated to high temperatures or brought in contact with certain metals (lead, copper), sodium azide can become lively indeed. Mixing sodium azide with acid makes hydrazoic acid (HN3), which is not only volatile and highly toxic but even more prone to violent misbehavior.
In labs like the one where I work, we sometimes use dilute solutions of sodium azide as a preservative, and although these don’t pose a serious explosion risk they can be hazardous for a different reason. The azide is lethal not only to bacteria but to humans as well, and yes, you can absorb it through your skin. The mechanism by which sodium azide kills you is very similar to the way cyanide works. Both compounds latch onto cytochrome c oxidase, a key enzyme in the electron transport chain in your mitochondria, the cellular powerplants that do most of the work in extracting chemical energy from glucose. And that’s especially dangerous for cells that rely heavily on aerobic respiration — the cells in your heart and central nervous system.
Sodium azide might sound like a rather unpleasant character, but it has its redeeming virtues. Car airbags work by zapping a mixture of sodium azide and a couple other compounds with an electric current. The sodium azide quite literally blows up, releasing a large amount of nitrogen in a split second, and the airbag inflates so fast you don’t even have time to hit the dash.
So there are several places you might expect to find sodium azide — in an auto airbag or a research lab. An urn of iced tea at a Dallas area restaurant, however, would not be one of them. All of the patients who drank iced tea on that April 2010 day survived; the dose they ingested was too small to be lethal. But the mystery remains. How the hell did sodium azide get into the iced tea? It’s not like it’s a compound you find just lying around everywhere.
If you ask me, I reckon somebody’s got some explaining to do…