Those alternatives used to be the Freons, but they are history. Nitrogen slush 
is a good medium, but that requires equipment.
Liquid propane cooled by liquid nitrogen is not exactly non-flammable, but when 
used in a fumehood with any kind of care and in small amounts may be the best 
coolant for snap freezing.
Cheers
Jim Darley
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On Tuesday, May 16, 2000 2:55 AM, Victor Tobias [SMTP:vtobias@u.washington.edu] 
wrote:
> I was contacted by a researcher looking for a non-flammable substitute
> for Isopentane for snap freezing tissue. Is there anything?
>
> Victor Tobias
> Histology Supervisor
> University of Washington Medical Center
> Seattle, WA
>