Recently, in the lab, I've been working with a lot of iron powder. The stuff is great in that it does exactly what I want it to with minimal side reactions. For a chemist, that's like getting a lap dance with a happy ending. There's very little mess, it gets the job done, and the only danger is leaving some of the iron in your sample when you take an NMR. That's the equivalent of lipstick on your collar and an angry wife.
Anyway, aside from its electron-donating capabilities (making it a reductant...remember kids, LEO the lion goes GER!), iron is pretty cool stuff, chemically-speaking. Of the myriad of reactions I've done in my day, the ones involving iron seem to work the best. It might not be the sexiest metal to throw into your reaction, but it sure is reliable and it gets the job done. Iron is kind of the Pittsburgh of the periodic table.
Now that I'm done with metaphors for iron and its chemical potential (I see it as a metal with HUGE upside!), there was one thing that caught my eye on the side of the bottle when I cracked it open and started slinging the fine, steely-gray powder around the balance area. It caught my eye because it was colored over in pink highlighter: CAUTION! Highly Flammable!
Flammable? Iron? Oh really?
And then I thought on it some more. Iron, by its very nature, enjoys coupling with oxygen. A lot. In fact, iron and oxygen get rather kinky: two irons and three oxygens are known to bind up and share one another freely back and forth. We tend to call it rust.
So, it only makes sense that iron would be more than happy to react with the oxygen in the air. And, as I hope I've shown you time and again, fine powders love to react explosively in the presence of an ignition source. And if you don't believe me, well, here is a safety video about iron "fileings" (it hurt to type that) that you may tickle your eyeballs with:
Despite the lack of production quality, the terrible misspellings (which I shan't repeat here) and the diligent commentary...I actually like that video quite a bit. I'm being quite honest here. Essentially, the reaction was the one I described above, iron + oxygen + flame = fast rust.
Now, if you're like me (that is to say, "girthy"), you've used those heating pads before, where you open the pad up and put it on your body and you eventually begin to feel it warming up. It's supposed to help loosen "tightened" muscles, and provide all the relief that icy hot gives, just without the burn and the cloying aroma of menthol. Usually, I start to purr like a kitten about five minutes after they're on and then scream like a banshee thirty minutes later, because they've become too warm. I'm a sensitive little spanker.
It's the same reaction, though. The pads are packaged in nitrogen, which won't bind to the iron, meaning no reaction. Once exposed to air, and the 21% oxygen therein, the iron begins to rust, releasing energy in the form of heat. The heat is then transferred to your muscles, where it acts like a topless Thai massage therapist, working away all the tension and soreness that a spate of failed reactions in the lab can leave you with. Science can be sexy!
Oh, and then there's that other thing about iron being reactive and explosive. We've seen it several times before, just under the a different name. When we mix iron(III)oxide (rust) with aluminum powder, we get one of the formulas for thermite.
Thermite always leaves me a little worked up after watching it do its thing.
The lesson here is, yes, even iron can be flammable. And you should totally read and believe the labels on the sides of the chemicals and practice the utmost in safety in all lab settings. Nothing good will ever come of an accident in the lab.