« Down the Chute: Your Call |
| More Purple Radiance »
July 10, 2006
Aluminum: Friend or Foe?
One of the comments to the previous post mentioned having some trouble with a procedure out of one of the lesser journals. "Trouble", in this sense, meant "vigorous unexpected fire". But when he mentioned that it involved a mixture with aluminum chloride, I knew to look out.
Chemists everywhere live by thermodynamics. And one of the basic principles is that if a reaction's starting materials are more energetic than its products, then it's favorable. It doesn't mean that it's always just going to take off spontaneously - sometimes the intermediate step is much higher in energy, and the reaction can't get over the hump. But if there's not too high a levee between the two energy states, things will indeed flow downhill for you.
It's a good thing, too, since one such reaction is burning the nitrogen in the air, thereby changing it into poisonous nitrogen oxides. (Correction: late-night brain freeze there - I had in mind the fixation of nitrogen to ammonia, which is energetically favorable but has a high activation energy. Oxidation of nitrogen itself to NO is an uphill process, but under high temperature/high pressure conditions, like those found in your car engine, it does take place). Another one of those is burning aluminum, which also has a good-sized barrier to get past (otherwise using aluminum foil in your oven would be a spectacularly bad idea). The product of that reaction, aluminum oxide (or alumina) is one of the most below-sea-level compounds I can think of, compared to the metal or many of its compounds. Give 'em a chance, and they'll take off on you.
The classic example of this is the thermite reaction: aluminum + iron oxide goes to aluminum oxide + iron. Oh, and some heat. Well, OK, a lot of heat, enough to spray molten iron all over the place. (YouTube) You have to set the reaction off with something pretty hot (burning magnesium ribbon is traditional), but once it gets going, it tosses off enough spare heat to roll right along.
So no, I'm not surprised that some aluminum chloride would take off on someone. Regard all aluminum compounds without a bond to oxygen with a little suspicion. Many of the them (and all the aluminum metal you see) came from alumina, and they're scheming to get back.
+ TrackBacks (0) | Category: General Scientific News
POST A COMMENT
- RELATED ENTRIES
- Merck's Aftermath
- Models and Reality
- Rewriting History at the Smithsonian?
- The FDA: Too Loose, Or Appropriately Brave?
- More Magic Methyls, Please
- Totaling Up a Job Search
- Humble Enzyme Dodges Spotlight
- Unraveling An Off-Rate