I propose a simple contraption to minimize the vapor layer in
cryocrystallography, using freezing in the liquid phase. This idea is
based on the findings in the citation below. It is modified from
designs used in the pet feeding industry. The novel aspect is that
liquid nitrogen is used rather than water or nutritional liquids and
that this particular contraption can be used for the freezing of
crystals rather than the satiation of animals.
The idea is to invert a dewar over a dish. The dewar sits on a block
to raise its opening while the block has a gap to allow liquid N2 to
escape from the dewar. The block is adjusted so that the opening to
the dewar is just below the brim of the dish, minimizing the vapor
head space. The cold vapor should either rise or fall depending on
its density relative to the atmosphere, minimizing the thickness of
the trapped vapor phase.
The dish should be deep enough to allow one to plunge a crystal in
the liquid N2 without easily hitting the bottom of the dish.
I call this invention "James's Petfeeder Contraption for
Cryocrystallography". A diagram is at:
http://www.jamesstroud.com/Contraptions/Petfeeder.pdf
James
On Feb 1, 2007, at 12:52 AM, Florian Brückner wrote:
Dear everyone,
has anyone tried removing the cold gas layer above liquid nitrogen
(or propane) by blowing or sucking to improve cooling rates in the
cryocooling of crystals. I would like to try and I would be happy
if someone could share some experience.
Florian.
P.S.: there is an interesting paper: J. Appl. Cryst. (2006). 39,
805-811.
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Florian Brueckner
AG Cramer
Gene Center
Feodor-Lynen-Str. 25
D-81377 Muenchen
Germany
Fon: +49 89 2180-76955
Fax: +49 89 2180-76999
