RegForte wrote:
>
> Dan Abel wrote:
>
> >
> > I believe that liquid nitrogen is a byproduct of the production of pure
> > oxygen from air. They freeze the air to a liquid and then distill the
> > oxygen. The nitrogen is left (or something like that). Places that
> > sell gases will often sell liquid nitrogen, and fairly cheaply,
> > depending on amount. I believe they don't sell it unless you have the
> > correct container. I don't know if you have to buy it (expensive) or if
> > the places that sell the nitrogen will rent a container, with sufficient
> > deposit. This came up on another group, I don't remember which. I
> > believe it was suggested to let your fingers do the walking (look in the
> > yellow pages of your phone book).
> >
>
> PraxAir - that have locations all over
>
> <http://www.praxair.com/na/us/praxairSL.nsf/StoresLoc>
>
> Seriously though, this stuff can be extremely dangerous if mishandled.
> That said, it's really fun to play with!

Actually, dry ice is more dangerous than liquid nitrogen. LN2 is colder,
however when it touches your skin it boils and forms an insulating gas
layer. This is why you can do the demo of rolling a bead of LN2 in the
palm of your hand. Dry ice, being solid will more readily give your
frostbite if you touch it. Either one boils or sublimates into gas that
can displace oxygen, but you'd need to be in a pretty small, non
ventilated room for that to be a problem.

I get my LN2 at Airgas. Dewars can be found on ebay at decent prices.