Thursday, September 28, 2006

Saturday morning cartoons

While channel flipping on a recent Saturday morning, I happened upon a children's show called "The Zula Patrol". The characters on the cartoon, who I believe were aliens from the planet Zula, were trying to restore Earth's water supply, which had mysteriously gone missing. Apparently the Hydrogen family and the Oxygen family were embroiled in a Hatfield and McCoy-esque feud and couldn't stand to be near each other, so there was no H2O anywhere to be found. In the end, Earth's water was recovered. The families got back together for the sake of two of their youngsters, who had fallen in love, or something like that. I can't remember whether the boy was oxygen and the girl was hydrogen, or whether it was the other way around. (I guess the writers tried to resolve the plot while glossing over the fact that the proper ratio is TWO hydrogen atoms to an oxygen atom. Good thing this show is aimed at kindergarteners.)
My impressions:
1) Cool! A TV show about chemistry!
2) Wait a minute. When I was growing up, Saturday morning cartoons were all about violence and slapstick. These kids are getting gypped.
3) I guess I'm a purist, but I don't like slick-looking computer animation as much as the lovingly hand-drawn kind.

I did a little digging on the web, and it turns out that "The Zula Patrol" aims to promote interest and understanding of science concepts to very young children, but also throws lessons in tolerance and advocates nonviolence. It was neat to read credits and see how many Ph.D.'s were involved in producing this cartoon. It looks like I caught one of only two episodes about chemistry-related topics, though. Most of the episodes are about space science, which makes sense given the setting and characters.


Tuesday, September 19, 2006

Dylan Tenders His Resignation

I just wanted to salute Dylan Stiles over at Tenderbutton, who has decided to close down his blog over the next couple of months. He really has a gift for writing with panache about what can be a really inaccessible field, and he will be missed. He's certainly leaving on a high note, what with a profile in the Chemical and Engineering Newsblog. Hats off to you, Dylan, and good luck with finishing up your Ph.D.


Maybe I'll get your attention with a list post

In honor of classes and labs starting up again for fall, and my colleagues in lab running off in the afternoons for their work as TA's (teaching assistants), I present:
"The All Time Top 3 Questions Students Asked Me in the Lab" blog entry.
Because of my funding situation, I've actually never TA'd a lab at Princeton (yes, we use "TA" as a verb). At Princeton, I lectured in weekly recitation/ problem solving sessions called precepts. I TA'd labs as an undergraduate; at my college many of the upperclass chemistry majors helped out around the general chemistry and organic chemistry labs to make a couple extra bucks, because there were no grad students.
Let me preface the list by saying that I thoroughly enjoyed being a TA. In fact, before stumbling onto this science writing gig, I wanted nothing more than to be a professor at a small college, milling about the labs every day. Even the most dedicated TA has to admit that redundant questions can be trying at times. I hope my post will help any gen chem/ orgo students that happen upon it (and maybe give all the current and former lab TA's out there a chuckle.)
If anyone has anything to add to my useful advice, please feel free to do so.
So, without further ado, the list of questions:
3. "Is this a precipitate?"
A precipitate is a product of a chemical reaction that is not soluble in the medium you've used to run the reaction. Precipitates come up in experiments that teach students important chemical concepts, like chemical equilibrium and general solubility properties of the elements. It can be tough to tell whether you've formed a precipitate when you've combined two solutions. It's important to make a note of the appearance of each solution before you combine them, and then compare to what you see afterward. I've seen precipitates range from cloudy white suspensions to yellow powder. Most of the time, the precipitate is more dense than the reaction solvent and sinks to the bottom of the test tube or beaker, but that's not always the case. This website has a couple of images of precipitates.
2. "Is this dry?"
In the organic chemistry lab, drying the solvent is one of the last steps in "working up" the product of the reaction, that is, isolating the product from the reaction medium and reagent byproducts. Many "workups" involve treating the reaction mixture with a solution of a base or an acid in water, and even if your organic solvent doesn't mix with water, there are probably small droplets of water that end up mingling with your solvent. You may be able to notice this if the solution is cloudy, or you see the droplets in there. To get rid of that residual water, we use "drying agents", a salt that absorbs the water. The drying agents I use these days are sodium sulfate and magnesium sulfate. At college, the labs stocked calcium chloride pellets. Regardless of what drying agent you use, the principle is the same.
-Make a note of your solution's appearance before adding drying agent. Is it cloudy?
-Add the drying agent a little at a time to the solution.
-Swirl the solution around for a little while (sodium sulfate is a little slower, so take your time there.)
-Watch for changes in cloudiness. If the solution's still cloudy, add a little more drying agent, etc.
-The best way someone's described how to tell when you're done is to look for "the snowglobe effect". Essentially, if the drying agent absorbs water, it clumps together at the bottom of the flask. If you add a little excess drying agent and the solution's dry, the drying agent swirls around like a snowglobe.
1. "Is this boiling?"
If you're asked this one, resist the urge to wonder whether your student has ever cooked pasta before. The evidence for boiling is usually the appearance of bubbles containing vapor from the liquid that rise to the liquid surface. Sometimes little bubbles form on the very hot bottom of the beaker before the liquid actually starts boiling, but don't be fooled.
See this wikipedia entry for a more detailed entry on boiling.

Finally, I think that the Not Voodoo website is a great resource for lab technique, and Zubrick's "Organic Chem Lab Survival Manual" is pretty good, too. If you're a little more experienced, I like "Advanced Practical Organic Chemistry" by Leonard, Gygo, and Procter.


Thursday, September 14, 2006

More to Glove

I've been using the glove box a lot lately. When my adviser moved to Princeton, he purchased a brand new one for the group with his startup funding from the University. It was one of our most expensive acquisitions, but the cost is well worth it. (Here's how much a used one of these puppies costs.)We use the glove box almost every day, when we work with air and moisture-sensitive materials.
If you were one of those lucky kids whose high school chemistry teacher showed you what happens when sodium metal reacts with water, then you understand the concern with keeping reactive chemicals isolated. Also keep in mind that in terms of flammability, toxicity, and general nastiness, sodium metal is barely even the tip of the iceberg. For example, we have a gas cylinder of trimethylgallium in our glove box. That stuff will ignite spontaneously in air. We don't work with a ton of very dangerous things, though; many of the chemicals we keep in our glove box just stay "fresh" longer than if we were to keep unscrewing the caps and exposing them to air.
The glove box (aka "dry box") is a sealed chamber with a window and an attached pair of arm-length gloves. The gloves are made of a very durable material that doesn't react with or absorb all the nasty chemicals (I'm not sure what the gloves attached to our box are made of... I'm guessing neoprene?) The chamber is filled with a gas that's not very chemically reactive (in our box, it's nitrogen, but apparently you can also use argon or helium). The box also has a vacuum pump and a sensor that detects vanishingly small concentrations of oxygen and water. It also has a gauge to control the gas pressure. Inside the box is a metal catalyst that scavenges residual oxygen, and zeolites to remove water. To get stuff into the box, there are two different-sized antechambers on its right hand side. The principle behind how they work is similar to that of an airlock. Just think of (insert name of your favorite space/ sci fi television show or movie here).
When I used the glovebox this AM, here's (in a nutshell) what I did. The most important thing is to be careful to prevent air and water from contaminating the box. I put my dry glass vial and spatula into the antechamber, and vacuum pumped out all the air/water, then refilled the antechamber with nitrogen. I repeat this a couple of times before it's safe to bring stuff into the box. Once the vial is in the box, I put my gloved hands into the big black gloves, which is annoying for me because the gloves are one size, so they have to be as large as possible. Also, sometimes people sweat in the gloves. I clumsily pick up the chemical from its shelf inside the box and weigh it out with the help of a little electronic gizmo that minimizes static, seal up my vial, and stick it back into the antechamber, where I do another cycle with the vacuum pump and the nitrogen before I can take it back out.
It takes about 45 minutes to do all that, and most of the time is taken up by vacuum pump/ refill cycles. Forty-five minutes to weigh one compound. Please consider this the next time you ask a chemist when he or she is going to graduate.


Friday, September 01, 2006

I try to update periodically

Back when I was a junior in high school, much of my chemistry-related work entailed memorizing the periodic table. Elements 110 and 111 had been discovered in Darmstadt, Germany around that time, and my science teacher made a rather large fuss about it. My classmates made a rather large fuss about having to memorize one more element. I figured that after memorizing 109, the 110th was just a drop in the bucket, but my logic was lost on them. Unfortunately, these days the pickings are slim when it comes to discovering new elements that are stable. Scientists have isolated the elements that are available to us on earth, things like helium, tin, gold, and mercury. These elements are probably tangible to you; you can imagine a helium tank or some gold-plated jewelry. They're things that hang around; they aren't going anywhere. But elements like 110 and 111 are unstable, they can only survive for tiny fractions of seconds before decomposing to elements like lead. To understand why that is, we have to look at the problem at the atomic level. Every atom contains a nucleus composed of protons and neutrons. Protons have a positive charge and neutrons have no charge. Now, think about what it must take to tightly pack a bunch of protons together. They're all positively charged so they inherently repel, as though you forced together the wrong ends of two magnets. Physicists have described a force that keeps the nucleus from breaking apart, which solves the problem. Or does it?
It turns out that as elements become heavier (bigger than about 82 protons) and more protons are packed into that tiny little nucleus, the repulsion overwhelms the force that keeps the nucleus glued together. The story isn't quite that simple, however. For one thing, the number of neutrons also has an effect on how stable the nucleus is. Physicists have estimated that there are "magic combinations" of protons and neutrons that can confer stability even on superheavy elements. (I use "stability" loosely here. If element 110 and 111 last for only thousandths of a second, a lifetime of a day or two is very stable by comparison!) It's very challenging to do any experiments to verify and refine their calculations, but a paper published in Nature last week took a significant step in this direction.
The ref: Nature 2006 442, 896-899.
By probing how Nobelium (element 102) falls apart, researchers gained a window into the nucleus's underlying structure. They were able to hone in on numbers of protons and neutrons that they believe could exist stably.
I definitely wouldn't invest in Element 111 jewelry anytime soon, though. (Take a look at the periodic table; element 111 is located below copper, silver and gold and is likely to have similar properties.)

Image from