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3D3DLiquid nitrogen.
This sample comes and goes: I like to have some around, but it keeps evaporating on me. Liquid nitrogen is lots of fun in general, great for making ice cream and freezing flowers. You get it at welding supply stores: It's about $20-30 to fill a 20 liter tank. The catch is the tank, which costs several hundred dollars and generally speaking welding shops will refuse to fill anything that isn't a proper LN2 transportation Dewar. LN2 is very cold, so frost tends to form in and around anything it's stored in. To take this picture (and the 359 others that make up the full rotation video for this sample) I had to put the glass Dewar containing the LN2 underneath a large glass dome, which I in turn heated with a hair dryer from the side. The LN2 evaporating inside the dome kept moisture from condensing on the Dewar, and the hair dryer kept the dome warm enough to prevent condensation on its outside surface. It might have been a bit easier if I wasn't trying to take the pictures in an un-air-conditioned shop in the middle of summer in the Midwest, when the temperature and humidity were both above 90 (F and % respectively). In the rotation you'll notice that by the end of the half hour time lapse about half an inch of liquid had gone missing. That's actually pretty good considering that there was a hair dryer blowing at the setup: Vacuum Dewars are remarkably good at retaining heat (or cold).

I chose this sample to represent its element in my Photographic Periodic Table Poster. The sample photograph includes text exactly as it appears in the poster, which you are encouraged to buy a copy of.
Periodic Table Poster

Source: Claudin Welding Supply
Contributor: Theodore Gray
Acquired: 15 July, 2005
Text Updated: 20 November, 2008
Price: $5
Size: 6"
Purity: 99%