Alcohol gel cooled with dry ice

[mishima]

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.

 

[mishima]

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]

Perhaps 9% of water is what makes it gelling instead of nicely solidifying.

 

[mishima]

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]

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]

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.