X-Message-Number: 13840
Date: Mon, 5 Jun 2000 00:30:43 -0400
From: "Stephen W. Bridge" <>
Subject: Liquid Nitrogen

To Cryonet
From Steve Bridge
June 4, 2000

In response to:  Message #13827
                              Date: Fri, 02 Jun 2000 16:37:50 -0400
                              From: James Swayze <>
                              Subject: Re: CryoNet #13812 - #13821

>I have a few stupid questions and you all may yell at me for not looking
it all up
>elsewhere. Why does LN2 need to be topped off so much? Is it's molecule so
small it
>leaks through the metal container? Or, are the seals not good enough? Why
can't it
>be locked in? Will it not stay cold even if vacuum contained like a
thermos bottle?
>Does it require constant replenishing to replace warmed LN2 with new cold
LN2? That
>last one seems almost oxymoronic. ;)

Bob Ettinger's answer seems to address the higher-level part of James's
question, but didn't fully explain the more elemental, physics part of it.

Putting liquid nitrogen in a tightly-sealed container will eventually
explode the container.   We can only place liquids in sealed thermos
bottles which are still liquids at room temperature.  At room temperature,
nitrogen is a gas, remember.  No level of insulation will totally prevent
heat from entering the system and converting the liquid to a gas.  As gas
is formed, it expands, and increases the outward pressure on the container.
 All containers which contain elements of liquified air (including
nitrogen, oxygen, and helium) must be vented to prevent pressure build-up
beyond the limits of the container.  It doesn't have much to do with the
size of the molecule.  Better insulation can slow down the evaporation but
not stop it.  As the nitrogen gas is vented, more liquid must be added to
keep the subjects immersed in the liquid.

There have been occasional injuries (not in cryonics) from people
carelessly or stupidly trying to put liquid nitrogen in a sealed container.
 One student at Un. of Alabama was blinded several years ago during a
practical joke, where she filled a glass soft-drink bottle (with screw-on
lid) with LN2 then ran down a hall with it.  The bottle exploded.

Helium is even harder to store, because its molecule IS small enough to
tunnel through stainless steel.

Steve Bridge

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