The Vespiary

The Hive => Newbee Forum => Topic started by: abolt on March 09, 2004, 07:32:00 PM

Title: Dewar Condenser
Post by: abolt on March 09, 2004, 07:32:00 PM

Has anyone had any experience utilising a Dewar condenser and/or dry ice for condensing a nitro Al/Hg?

Theoretical advice welcome. :)

Title: huh?
Post by: hypo on March 10, 2004, 04:07:00 AM

what is a dewar condensor, for the ignorants (like me) who never
heard of such a thing?
the dewar i know of does the opposite of what a condensor does:
it keeps heat inside (or outside).

> and/or dry ice for condensing a nitro Al/Hg?

unnecessary. i'd fear that the condensor breaks due to termal stress.
(it should survive, but why risk?)
don't take the MM-document too serious.

Title: UTFSE you stupid BITCH!!!!!
Post by: hypo on March 10, 2004, 04:33:00 AM

ok, i see. those are nice thingies, but overkill for an Al/Hg.
they are nice if you want to condense NH3 or stuff like that...

Title: Well apart from hypo going spaz, hypo is ...
Post by: ApprenticeCook on March 10, 2004, 08:39:00 PM

Well apart from hypo going spaz, hypo is correct, total overkill for the Al/Hg rxn, dewar condenser as far as swim knows is like a bucket, fill the bucket with collant and the vapours go up inside the "walls" of the bucket, right?

A normal condenser is fine for it, dont get too stressed, just ice water flowing through the condenser is all that is required.

Title: heh...
Post by: hypo on March 10, 2004, 10:05:00 PM

just for the record: the bitch was to myself for not checking
google.  ;D  (feeling weird)

and yes, you fill them with a cooling mixture. usually dry ice/
acetone or something like that

Title: unnecessary. i'd fear that the condensor ...
Post by: abolt on March 12, 2004, 09:24:00 PM

unnecessary. i'd fear that the condensor breaks due to termal stress.
(it should survive, but why risk?)

I don't think thermal stress would be an issue. A solution of dry ice/IPA (much safer than dry ice/acetone) would give a solution of ~ minus 78 Celcius. The reflux temp of an Al/Hg would be 65-70 Celcius, using MeOH as the solvent.

Pyrex has a thermal shock rating of around 160 Celcius so I think thermal stress would not be an issue.

The M.P. of MeOH is minus 98 Celcius and the M.P. of Methylamine is minus 93 Celcius. So this should not be a problem

I was just wondering if the buildup of pressure in the reaction could be a problem, otherwise I think this would be the best way to do an Al/Hg as no Methylamine would be lost out of the condenser and Nitromethane could be added in one go.

Title: thermal shock
Post by: Rhodium on March 12, 2004, 09:30:00 PM

A solution of dry ice/IPA (much safer than dry ice/acetone) would give a solution of ~ minus 78 Celcius. The reflux temp of an Al/Hg would be 65-70 Celcius, using MeOH as the solvent.

Pyrex has a thermal shock rating of around 160 Celcius so I think thermal stress would not be an issue.

The temp difference you give is ~150°C, so that's not too far off. And I'm not sure that rating is the same if the glass is at cryogenic temps...

Title: Good point chief
Post by: abolt on March 12, 2004, 09:46:00 PM

Either another material (stainless steel) or a standard condenser in between the reaction vessel and the Dewar condenser, in order to spread out the thermal stress, would probably be the best way to go.