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| Pretty crystals | | Date Created: May 18, 2005, 09:38 AM |
 So this is the first (perhaps the last) entry about what I do during the day. (We'll see how it goes.) There are a number of other bloggers that I've read who go into detail about their work and what they do from day to day, so I thought I'd share too. There's a slight problem with this idea, though:
I'm a chemist. I work in a lab.
If you're not already asleep, I promise that I'll try to 1) keep this interesting, and 2) keep this understandable.
One of the things that chemists do all the time is purify things. Nature is extremely messy, and we rarely get our ingredients in pure form. And, when we mix stuff together, we rarely get our products in pure form, either. There's always some crud in there somewhere, from some little side reaction or something. So before many reactions we have to purify our ingredients (we call them reagents), and after most reactions are finished we have to purify our products.
We've got a zillion different ways to purify things, but one of the grooviest is called "recrystallization." This method of purification is used for solids. It's nice because, unlike other methods, it uses relatively little solvent. For example, in the picture, there's about 400 mL of chloroform. That's worth about $14.00. Some methods of purification would use much more solvent, and thus, be much more expensive. Since your tax money is paying for this stuff, we try to be good stewards of your money. (Thanks for your generous contribution, by the way. We who suckle from the public teat salute you.)
The idea behind recrystallization is simple. Many compounds dissolve in warm liquids, but precipitate out of those same liquids when they're cold. If you've ever made tea, and left it for a long time and noticed all sorts of crud in the tea when it cools down, that's the same thing happening. Tea crud dissolves in hot water, but it precipitates in cold water. (That's why iced tea can often be cloudy.)
The idea behind recrystallization is to dissolve your compound (along with the impurities) in a hot solvent. Then cool the solvent down, and (hopefully) your compound will precipitate out of solution but leave the impurities in the solution. Then you can just filter out your pure compound leaving all those nasty impurities behind.
In the picture, you can see the recrystallization of a compound I made. The beaker is frosty because it has been in the freezer all night. The solvent is chloroform, which is usually clear and colorless. You can see the slightly green impurities remaining in the chloroform, while the yummy pure white crystals float on top, ready to be filtered. (I should have taken a "before" picture so you could have seen the greenish, impure crystals before I did the recrystallization.) You can see the final fluffy white yummy pretty crystals in the right-hand picture, after they've been filtered.
Anyway, this is one of the things I do all the time. Just thought I'd share. Maybe I'll do some more of these posts in the future if people don't find them too mind numbing. |
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