[Histonet] low temp thermometer

Karen Weidenheim kweidenh <@t> montefiore.org
Thu Jul 14 12:39:26 CDT 2005

Dear Steve, I presume you are freezing muscle biopsies, or possibly
research material.
This isopentane/liquid nitrogen method is more an art than a science. 
Altitude of your lab and humidity of your ambient air, are the 2 major
limiting factors.  The most important thing in the freezing is not
measuring the temperature but rather visual assessment of the state of
the isopentane.  We put the isopentane in a 250 ml stainless steel
beaker and lower it slowly into the liquid nitrogen.  We wait to freeze,
until the isopentane has formed ice all around the walls of the beaker
and all the way up the wall of the beaker, and completely across the
bottom of the beaker.  It will be syrupy.  We use 25 seconds of freezing
(I know the books say 5-10 seconds).
Our lab is at sea level.  It is also often humid here.  We discard the
isopentane every 3 months when there is no major humidity and more often
(every 6 weeks) when we have a run of humid weather, or when we have a
problem with freezing artifact, or when I think my assistant has been
sloppy with its storage.
We keep the beaker very clean i.e. we scour with steel wool.  We make
sure there is no residual water in the beaker (I keep 2 beakers so one
is freshly clean and dry at all times).
I have not used the thermometer since I was a young attending a long
time ago!!!

Karen M. Weidenheim, M.D.
Professor of Pathology, Clinical Neurology and Clinical Neurosurgery
Albert Einstein College of Medicine
Chief, Division of Neuropathology
Montefiore Medical Center
111 East 210th Street
Bronx, NY   10467 
(718) 920-4446
FAX (718) 653-3409
Beeper (917) 556 3696
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>>> Steven Coakley <sjchtascp <@t> yahoo.com> 7/14/2005 12:07:15 PM >>>
We're doing allot of liquid nitrogen/isopentane snap freezing and I'd
like to purchase a good low temp thermometer.  Any suggestions or advise
out there?

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