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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: kamiyu on February 10, 2014, 04:52:25 AM

Title: Temperature of dry-ice acetone bath
Post by: kamiyu on February 10, 2014, 04:52:25 AM

Hi guys

Do you think it is possible to have a dry ice acetone bath at -40^oC???

Title: Re: Temperature of dry-ice acetone bath
Post by: discodermolide on February 10, 2014, 04:54:34 AM

Yes, if you control how much dry-ice you add.
But using CCl₄ dry-ice gives you about -38°C.

Title: Re: Temperature of dry-ice acetone bath
Post by: kamiyu on February 10, 2014, 05:14:57 AM

You mean add dry ice until the acetone becomes -40oC ? I think in this case you are saying that the cooling bath does not have any solid dry ice anymore..

If there is solid dry ice, then the temp must be -78oC, right?

Quote from: discodermolide on February 10, 2014, 04:54:34 AM

Yes, if you control how much dry-ice you add.
But using CCl₄ dry-ice gives you about -38°C.

Title: Re: Temperature of dry-ice acetone bath
Post by: discodermolide on February 10, 2014, 05:55:10 AM

Just add small bits of dry-ice until the temp is -40°C, you can maintain this just by adding dry ice in portions to keep the temp at -40°C.

Title: Re: Temperature of dry-ice acetone bath
Post by: TheUnassuming on February 10, 2014, 08:28:38 AM

You can definitely use dry ice/acetone system to hit -40 ºC, but it will take a close eye and lots of maintenance to keep it there.  Its much easier to use a system that has a melting point at the temperature you want the bath to be.  CCl4 only hits -23 ºC (its freezing point), but if you use acetonitrile you can hit -41 ºC.