View Full Version : C02 capsules contain LIQUID CO2?
10-06-2008, 12:08 PM
Hi I read everyone saying that the capsules (12g) contain liquid CO2 but when you shake them, even when half empty you can't hear any liquid "sloshing" about inside. I have found the same with CO2 fire extinguishers which everyone says contains liquid. Is it a common misconception that they contain liquid or is the liquid existing at some kind of double phase (half way between liquid and gas similar to it's triple point)?
I know the question is a bit "sciency" but I thought someone here would know and its been bugging me for a while. :D
10-06-2008, 12:44 PM
Liquid is CO2 at approximately 58 Bars of pressure.
The pressure increases with temperature, which is why the speed of the pellets changes with temperature.
Under normal atmoshperic pressure, obviously the CO2 exists as a gas.
In order to liquify it, you have to pressurise to about 58 Bars.
In order to get sloshing there has to be a gas above a liquid.
The CO2 under pressure can not exist as gas because the pressure is too high.
Instead it exists a liquid/gas state.
So the liquid/gas expands to fill the volume inside the capsule.
The CO2 remains in this state until the volume of CO2 drops to 30% of the original mass of gas.
This is when the power drops from shot to shot.
If you keep the ambient temperature the same, then the CO2 will produce exactly the same power from every shot, until you have used 70% of the mass of the CO2.
If you keep the temp constant and wait for CO2 gas to return to the ambient temperature between each shot, then you will have get very close pellet speeds from shot to shot.
Obviously this depends on the airgun you are using too.
My heavily modded Crosman 2240 was so consistant, the fps deviation averages out to about plus or minus 1/2 of a FPS.
10-06-2008, 01:37 PM
Hi Thanks for clearing that up for me in my head:D. I do have another question though:D. If you were to have a tank of CO2 standing upright and you were to connect it to another empty tank, would the empty tank fill up with liquid/gas seeing as the only a double phase is present or would it fill up with just gas (boiling off the liquid phase in the first tank)?
10-06-2008, 02:05 PM
The CO2 under pressure in the tank is a liquid/gas and remain liquid/gas at 56 BARS of pressure, until you use 70% of the CO2 in the tank that you are filling FROM.
After that point, all the pressure in the world can't liquify it.
So it changes to a gas.
This above link the phase diagram for CO2.
So it show which phase gas, liquid or solid the CO2 exists at a given pressure and temperature.
An atmoshpere of pressure is the same as 1 Bar.
10-06-2008, 02:52 PM
Ok yea I understand thanks for your input on that its been bugging me for ages lol:D
10-06-2008, 06:15 PM
what the hell are you two going on about?
10-06-2008, 06:41 PM
Bit of a misconception, and some other misunderstandings here - liquid CO2 is not like water.
CO2's liquification pressure, as I'm sure you know, varies with temperature.
Normally, at typical temperature, it's 50 to 60 bar.
If the pressure is ever higher than that, part of the gaseous CO2 will turn into a liquid until the pressure drops (as the liquid is more dense, it takes less space, and the pressure falls).
However, this is an equilibrium - liquid CO2 is rapidly turning to gas, and vice versa - at matched, and phenomenal, rates.
Because of this, the liquid cannot be thought to be like in water bottle, and thought to be sitting in the bottom of the tank, a considerable portion of it is suspended in "mid-air", so to speak.
Due to the way the CO2 is dispersed, and because of the constant exchange of liquid and gas - it won't slosh under normal circumstances.
Hope that helps.
10-06-2008, 06:56 PM
what are you lot like?
10-06-2008, 09:01 PM
If it changes from a liquid to a gas because of a change in temperature is it ' Boyle' ing?
I think they need to get out more.
10-06-2008, 09:23 PM
Interesting stuff, this. Never having dealt with CO2 under pressure I'd assumed it would always sublime directly to a gas. Always nice to learn a new thing :)
11-06-2008, 11:55 AM
Who's the sadder:confused:
Them for writing it, or us for reading it?.....:);) only joking.
(Actually, you can learn some clever stuff on here).
16-06-2008, 06:05 PM
Way back when... I used to be a pretty good paintballer. None of this automatic stuff... just modified Nelson 007 pump's... 'bout $700. worth of mods in my case (heh). Rifle (musket) chron'd 577 fps 'n the pistols at 534 (carried all three). 'None of this 'prepared field' stuff... or 'rules'. 'Straight out team attrition. (Manhunt)
Ennyhoo... we stuck those frozen 'fridge packs' in the C02 pouches for the cartridges 'n rigged a velcro 'wrap' for the constant air cylinder. 'Kept the C02denser. Consistant velocities and range. You'll use the C02 faster... but the trade-off is worth it.
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