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.

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4 Comments:

At 1:04 PM, Anonymous allan said...

all the glove-boxes I've had to use were very old, and sort of ghetto. when they were in use and had positive pressure in them the rubber arms would stick straight out from the box in either a menacing or "give me a hug" sort of way, depending on the ambient lighting.

a glove box humming and holding its arms out for a hug is always a welcome sight to this lonely chemist

 
At 1:30 AM, Anonymous Paul said...

My favorite nerdy science cartoon is about gloveboxes:

http://www.chem.tamu.edu/rgroup/miller/Images/glovebox.cartoon.jpg

 
At 1:32 AM, Anonymous Paul again said...

Ugh... if you do a google image search for "glovebox cartoon" it's the first hit.

 
At 3:26 PM, Blogger Carmen Drahl said...

thanks paul, hilarious..

 

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