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Alcohol gel cooled with dry ice

by mishima
Tags: alcohol, cooled
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mishima
#1
Apr1-14, 12:52 PM
P: 303
Hi I tried cooling down some 91% isopropyl alcohol with dry ice. After a few minutes, the alcohol became a thick gel. I am wondering what is going on there, thanks.
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mishima
#2
Apr1-14, 07:50 PM
P: 303
I mean why does it become gel? I tried putting some in a graduated cylinder and only noticed a slight (1mL) increase in volume after it returned to room temperature. However it also contained a great deal of CO2 gas bubbles making the cold reading difficult.
Borek
#3
Apr2-14, 01:49 AM
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Perhaps 9% of water is what makes it gelling instead of nicely solidifying.

mishima
#4
Apr2-14, 08:01 AM
P: 303
Alcohol gel cooled with dry ice

I'm not sure, dry ice gets a shell/coating of water ice when submerged in water. Could it extract the 9% from solution? I wasn't specifically looking for such a shell so I don't know if that happens/is possible. I was thinking intermolecular forces might be coming into play at the low temperature.
Borek
#5
Apr2-14, 09:52 AM
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No doubt about intermolecular forces playing their part - but they are responsible both for gelling and for solidifying (actually they are also responsible for keeping liquid in place).
mishima
#6
Apr2-14, 07:24 PM
P: 303
Do you think its the hydrogen bonds coming off the alcohol group, specifically?

I actually don't know the technical definition of a gel, I thought it was like a colloid but I did not see the Tyndall effect. I don't think it was quite viscous enough to stay put in an inverted cup, it bubbled violently and evaporated rapidly when poured on a room temperature surface. It was below range of both my non-contact thermometer and my normal alcohol thermometer, but I assume close to the temperature of dry ice.


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