Alcohol gel cooled with dry ice

  1. 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.
  2. jcsd
  3. 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.
  4. Borek

    Staff: Mentor

    Perhaps 9% of water is what makes it gelling instead of nicely solidifying.
  5. 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.
  6. Borek

    Staff: Mentor

    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).
  7. 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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