Sciencemadness Discussion Board

Freezing propane

vmelkon - 23-2-2014 at 20:02

Anyone though about freezing propane by vacuum pumping it the same way it is done to other liquids like water and nitrogen?
The bp of propane is -42 °C and mp = -187 °C.
The liquid range is very high but after a long time of pumping, I'm assuming 250 mL, it should eventually give some solid propane.
This is cold enough to condense oxygen from the air.

I don't have a vacuum pump so I can't do it.

thesmug - 23-2-2014 at 20:18

I'm no expert on this so I can't help you but I'm extremely curious, what would you need solid propane for?

vmelkon - 24-2-2014 at 05:20

Do you mean what I would do personally? I would get oxygen from the air. I would use the oxygen for a torch. I could use the oxygen for a cold trap. I could test if oxygen is paramagnetic (for the fun of it). I could use it to liquify or freeze a bunch of other substances.

I could also do some bio experiments. Freeze some animals and thaw them back and do the same for plants, the same to seeds.

Metacelsus - 24-2-2014 at 05:50

Why not just make liquid oxygen then?

By the way, liquid oxygen is prone to reacting with organic compounds (sometimes explosively).

vmelkon - 24-2-2014 at 10:38

Quote: Originally posted by Cheddite Cheese  
Why not just make liquid oxygen then?


What do you mean?
Perhaps I wasn't clear with the propane. You can just invert a propane tank and open the valve. Eventually, liquid propane flows out (-42 C). You can fill a cup, place it into a vacuum chamber and pump it.
This is something simple that someone with a high power vacuum pump can do. For extra safety, you can surround the thing with CO2.

[Edited on 24-2-2014 by vmelkon]

DJF90 - 24-2-2014 at 10:53

You don't want to be sucking a flammable gas through a vacuum pump, thats just bad practice (and dangerous). Use a water aspirator instead.

Zyklon-A - 24-2-2014 at 10:56

I'm pretty sure liquid oxygen would react with solid, liquid, or gasses propane. And even if it didn't, it would not be safe at all.

testimento - 25-2-2014 at 10:01

Mixing liquid oxygen with carbon (...or hydrocarbon) has been known well in the thermobaric weapons institute development history.

Maybe one could try to condense propane into cold-trap with calcium chloride - ice mixture (mp -54C) or with ethanol - dry ice, and then evacuate the trap with high power vacuum pump. This should yield quite high amount of solid propane. I have been able to freeze acetone with common ejector pump once.

jock88 - 25-2-2014 at 11:47


What the original poster is trying to do is create a very low temperature so that you could condense air (oxygen) on the outside of the vessell.