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Topic: ethylene glycol cooling bath  (Read 13132 times)

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Offline yxmsoccer

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ethylene glycol cooling bath
« on: October 12, 2011, 06:19:32 PM »
I was trying to do a reaction at -10C, so I checked the cooling bath list and decided to use ethylene glycol and dry ice. But when I added a little bit more dry ice, the temperature started to drop until around -40C. It is quite different from acetone/dry ice mixture which can always stay around -75C. I was wondering if there is any stiochiometric relationship between ml of ethylene glycol and g of dry ice you need to make -10C. Thank you!

Offline Honclbrif

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Re: ethylene glycol cooling bath
« Reply #1 on: October 12, 2011, 07:37:03 PM »
Jensen. C. M. Dry-Ice Bath Based on Ethylene Glycol Mixtures. J. Chem. Ed. 2000, 77, 629
 
http://www.che.psu.edu/faculty/rioux/group/group_info/references/dry_ice_bath_based_on_ethylene_glycol_mixtures.pdf
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Offline yxmsoccer

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Re: ethylene glycol cooling bath
« Reply #2 on: October 13, 2011, 10:16:07 AM »
Just tried. Working perfectly. Thanks a lot!

Offline opsomath

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Re: ethylene glycol cooling bath
« Reply #3 on: October 13, 2011, 11:09:35 AM »
Dude. Salt, ice, go. This is way too complicated.

Offline Honclbrif

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Re: ethylene glycol cooling bath
« Reply #4 on: October 13, 2011, 11:51:30 AM »
Opsomath does have a pretty good point there. For -10 salt and ice is perfectly sufficient. The EtOH/glycol mixtures are really only useful if you have to maintain an intermediate temp. Another problem with them is they have a tendency to freeze solid, so don't immerse your flasks above the equator...
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Offline yxmsoccer

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Re: ethylene glycol cooling bath
« Reply #5 on: October 13, 2011, 02:26:13 PM »
Got it! Do you also have any ways to keep it overnight? What if I have a automatic cooling bath machine in my lab!

Offline Honclbrif

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Re: ethylene glycol cooling bath
« Reply #6 on: October 13, 2011, 03:41:08 PM »
If you have an automatic cooling bath with a thermostat it should take care of itself, as long as it can reach the temp range you need.
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Offline Halogenator

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Re: ethylene glycol cooling bath
« Reply #7 on: October 21, 2011, 06:22:55 PM »
I was trying to do a reaction at -10C, so I checked the cooling bath list and decided to use ethylene glycol and dry ice. But when I added a little bit more dry ice, the temperature started to drop until around -40C. It is quite different from acetone/dry ice mixture which can always stay around -75C. I was wondering if there is any stiochiometric relationship between ml of ethylene glycol and g of dry ice you need to make -10C. Thank you!

You added too much dry ice. Ethylene glycol freezes at -13C. Any CO2/solvent bath must have liquid and frozen solvent in equilibrium for proper temperature control, otherwise it will approach -78ish.

Opsomath does have a pretty good point there. For -10 salt and ice is perfectly sufficient. The EtOH/glycol mixtures are really only useful if you have to maintain an intermediate temp. Another problem with them is they have a tendency to freeze solid, so don't immerse your flasks above the equator...

Except salt and ice gives you about -20 unless heat transfer is lousy which it frequently is because salt/ice freezes solid. If I want -20 I use dry ice/brine.
If I want -10 I use the automatic cooling bath with ethylene glycol/H20 for the bath fluid.

Offline Honclbrif

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Re: ethylene glycol cooling bath
« Reply #8 on: October 21, 2011, 11:00:13 PM »
Every time I've done salt + ice I've gotten -10C, with a healthy amt of salt well mixed.
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