X-Message-Number: 3414
Date: Wed, 16 Nov 1994 22:15:31 -0500
From: "Keith F. Lynch" <>
Subject: Re: SCI.CRYONICS: High Pressure LN boiloff

Yes, you can reduce the storage temperature either by using liquid
nitrogen under negative pressure or by using liquid helium.  Both
would be expensive.  Liquid helium is extremely expensive, and has a
higher boiloff rate (due mostly to the greater difference from room
temperature).

I've always heard that liquid nitrogen is about as expensive as milk,
and liquid helium is about as expensive as fine brandy.

But what would be the point in a lower temperature?  Liquid nitrogen at
normal pressure is more than cold enough to stop all chemistry.  Lower
temperatures merely make tissue cracking worse.

In fact, one might want to do storage at a *higher* temperature than
liquid nitrogen's usual boiling point, perhaps by using liquid nitrogen
under pressure.  This would reduce both cracking and boiloff rates.
Of course this adds complexity, risk, and expense.

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