Molecules: You'd better learn to live with them.
Nitrogen? What's so special about that? You're soaking in it - 78% of air is nitrogen. As anyone who's been to a middle school science demonstration can attest, it gets pretty neat when you cool it down. At 77 K (-321 F, -196 C) it'll freeze pretty much anything but good. That leads to its use in a lot of biological applications, such as preserving cells or even whole human bodies. Typically I use it for something more mundane, like freezing water faster than a freezer could, or keeping vapors from getting pulled into a vacuum pump. Google ads are targeted to specific keywords, so my GMail often gets some funny, mistargeted ads:
MVE Semen Tanks
MVE Semen Tanks XC Millenium $499 Buy the Best and Skp the Rest
sementank.net
I shall keep them in mind.
Physical Science
Medicine & Health
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Since you mentioned it - I hope you will be glad to know that there is a company named International Boar Semen, that offers frozen product in 1 mL and 5 mL straws, and also the completely fresh product packaged in the "SEMBAG" (name trademarked) containers, "with an easy-pour spout", and they can Fedex it overnight. Credit cards orders are accepted over the phone.
Posted by: milkshake | October 15, 2008 3:29 AM
First a word of caution: liquid oxygen (bp -183 degC) boils at a higher temperature than liquid nitrogen (bp -196 degC). This means that if you are pulling ambient air through your trap and pump you run the very real risk of condensing liquid oxygen in your pump trap. Condensed liquid oxygen in a confined space is a very real explosion hazard. May I suggest using dry ice/acetone for your pump trap. Our lab's been doing it that way for years.
Second a word of fun: we put on a 'magic show' for a group of students (maybe 13 years old) the other week. I was at the liquid nitrogen station. We did all the usual tricks. We froze apples and let the kids smash them with a hammer. We froze bananas and used the bananas AS a hammer to hammer nails into wood. Then I put my finger in the liquid nitrogen and let it sit for a while. I asked the kids if they thought my finger would be more apple like or more banana like - all while kinda playing with the hammer with my other hand. then I said, 'well, if I do it quick enough...' and I pulled my finger out of the liquid nitrogen and started SMASHING IT with the hammer. ... but it was ok, because I put a hot dog in the finger of my glove before the magic show started. So I was just smashing a frozen hot dog, and not my finger. The kids loved it.
Posted by: azmanam | October 15, 2008 8:52 AM
You're only condensing LOX if you pull air through, though - and -78C doesn't cut it for even acetonitrile on my ~100micron vacuum. I'm kind of stuck with LN2 if I want to pull off much beyond water under high vacuum.
Posted by: Molecule of the Day | October 15, 2008 9:31 AM
I'll wait to click on that link until I get home tonight, if you don't mind.
Posted by: NoAstronomer | October 15, 2008 9:32 AM
There are few thrills to match the one you get when you pull down a Dewar of liquid nitrogen that's around a tube on a vacuum line and see 50mL of a pale blue liquid.
Posted by: killinchy | October 15, 2008 1:07 PM
I actually had a lot of fun with semen tanks full of liquid N2 when I was a lad. We always had purebred cattle, so we invariably had a stash of straws of semen on the farm, and it was great fun to dip foxtails into the tank and shatter them against the barn. I vaguely recall having the good fortune to get our tank topped off in the spring when daffodils were blooming and being able to freeze one of them too.
Posted by: Conor H. | October 15, 2008 4:17 PM
One of my favorite things to do with LN2 is to condense liquid oxygen out of the air, I have done this dozens of times without incident, am I being too fearless?
Posted by: EricJuve | October 15, 2008 5:32 PM
As I understand things, the major hazards (in a typical academic or research lab) associated with liquid oxygen are as follows:
1. Condensation of any cryogen in an enclosed or semi-enclosed space (like a vacuum trap with a semi-functioning seal) is going to cause problems when rapidly warmed due to rapid uncontrolled expansion. In this sense, liquid O2 is really no more hazardous than liquid N2 - it is just that we don't tend to work with cryogens where N2 condensation is relevant.
2. The typical vacuum trap in an academic laboratory is rarely cleaned out, and is thus full of all kinds of organics. Liquid O2 is a rather furious oxidizing agent, which can lead to peroxide formation when it comes in contact with these organic witches' brews. Peroxides, or course, can be contact explosives.
Posted by: vtprof | October 15, 2008 9:38 PM
The best use for liquid nitrogen is to make ice cream with it.
Posted by: Eric Jablow | October 15, 2008 10:17 PM
dryice acetone is not adequate for condensing most organics removed by oil pump and will kill your pump's performance and lifespan. a good trick if you're terribly concerned about condensing ambient air is to apply the water aspirator to remove some of the air in the lines and then switch to high vacuum pump.
Posted by: chambro | October 15, 2008 11:31 PM
The big problem with LOX is mixing it with organics. It can form a very sensitive explosive. LOX on asphalt can detonate if walked on. http://en.wikipedia.org/wiki/Oxyliquit
Posted by: Jim | October 16, 2008 5:31 PM
I was aware of the furious oxidizing agent properties, it makes sawdust burn like blackpowder. Thanks for the link to the Wikipedia article. I will be more cautious in the future.
I of course make lots of ice cream with it. One thing I learned was that even though you can make ice cream with pure Baileys Irish Cream, you need to be careful eating it as it will frostbite your tongue. Another fun thing to demonstrate is an LN2 fountain using small bore brass tubing.
Posted by: EricJuve | October 17, 2008 3:50 PM
Tag.
Posted by: Lab Lemming | October 23, 2008 6:16 PM