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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: 101why? on October 29, 2016, 04:35:25 AM

Title: Can the commercial reusable dry ice packs be used as dry ice in my experiment?
Post by: 101why? on October 29, 2016, 04:35:25 AM

I have a few packs of reusable dry ice-gel packs.

They are sent along with the chemicals in a box for keeping the chemicals cool.

Is it possible for me to use that "gel" as dry ice to reach the -78oC (dry ice bath) in one of my experimental step?

P/s: Is there any way to determine the -78oC temperature? As I do not have thermometer that can show the temperature this low.

Thanks.

Title: Re: Can the commercial reusable dry ice packs be used as dry ice in my experiment?
Post by: Dan on October 29, 2016, 06:11:15 AM

Quote from: 101why? on October 29, 2016, 04:35:25 AM

I have a few packs of reusable dry ice-gel packs.

They are sent along with the chemicals in a box for keeping the chemicals cool.

Is it possible for me to use that "gel" as dry ice to reach the -78oC (dry ice bath) in one of my experimental step?

If you can cool the packs down cold enough, then I suppose it is theoretically possible, but it seems like an impractical way of making a cryogenic bath.

Quote

P/s: Is there any way to determine the -78oC temperature? As I do not have thermometer that can show the temperature this low.

If you're using dry ice, the bath is at -78 °C when the CO₂ stops subliming.
If you have liquid nitrogen, you can use a frozen EtOAc bath, which is close to -78 °C (EtOAc freezes at -84 °C). We don't routinely have dry ice in our lab, so I use frozen EtOAc instead.

Title: Re: Can the commercial reusable dry ice packs be used as dry ice in my experiment?
Post by: 101why? on October 29, 2016, 11:05:38 AM

Quote from: Dan on October 29, 2016, 06:11:15 AM

If you're using dry ice, the bath is at -78 °C when the CO₂ stops subliming.
If you have liquid nitrogen, you can use a frozen EtOAc bath, which is close to -78 °C (EtOAc freezes at -84 °C). We don't routinely have dry ice in our lab, so I use frozen EtOAc instead.

Is the liquid nitrogen used to freeze the EtOAc?
Is it possible for me to freeze the EtOAc in an ultra-freezer (able to reach -82oC) and use it, without using liquid nitrogen?
P/s: Our lab has neither dry ice nor liquid nitrogen recently. TT

Would like to know that did you add acetone and NaCl when you are using dry ice to reach -78oC?

Title: Re: Can the commercial reusable dry ice packs be used as dry ice in my experiment?
Post by: Dan on October 30, 2016, 04:14:12 AM

Quote from: 101why? on October 29, 2016, 11:05:38 AM

Is the liquid nitrogen used to freeze the EtOAc?

Yes

Quote

Is it possible for me to freeze the EtOAc in an ultra-freezer (able to reach -82oC) and use it, without using liquid nitrogen?

No. The melting point of EtOAc is -84 °C.

You could look at data tables for common organic solvents and see if you can find something that freezes in the right range. Dimethoxyethane freezes at -69 °C, for example.

Quote

Would like to know that did you add acetone and NaCl when you are using dry ice to reach -78oC?

No NaCl.

Title: Re: Can the commercial reusable dry ice packs be used as dry ice in my experiment?
Post by: 101why? on October 30, 2016, 05:52:05 AM

Thanks Dan.