compressed carbon dioxide

[the guy]

would the 'cooling' section of this page: http://en.wikipedia.org/wiki/Canned_air work with carbon dioxide as the propellant? (i know carbon dioxide is used as an aerosol propellant in cooking spray cans)

or does it only work with the chemicals they use?

[John Cuthber]

It would work with most gases; CO2 should work quite well.

The interesting problem is that the material might freeze to "dry ice".

[the guy]

so would it work with just compressed air (by air i mean normal atmosphere - nitrogen, oxygen etc.)

 

also, does it have to be liquified in the canister? or can it just be under pressure?

[John Cuthber]

Yes, but not nearly so well.

The CO2 or freon in a tin of "canned air" is a liquid and when the pressure is released it boils. To do so it takes heat from the surroundings and gets very cold.

 

For air the effect of expanding is much smaller. (And for a few gases like helium and hydrogen, they actually get hotter when you let the compressed gas escape).

This page

http://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect

probably tells you more about that than you want to know.

[the guy]

i thought CO2 didn't have a liquid phase....

 

oh, never mind, ignore that

[John Cuthber]

I take it you realised that it does under pressure.

[the guy]

yes

[CaptainPanic]

i thought CO2 didn't have a liquid phase....

 

It does, but as soon as the temperature exceeds 31°C, or the pressure exceeds 72.9 atm, it becomes supercritical.

Wikipedia shows a picture of the phase diagram.