Why doesnt a volatile gas like acetylene undergo autoignition when pressurized

assuming temperature increases with pressure, why doesnt an acetylene cylinder explode? is it the lack of oxygen? one would assume a compressed gas would contain some oxygen, and therefore auto-ignite under the intense pressure.
just wondering whats goin on here

thanks guys

Acetylene, when compressed, can indeed be detonated under the right conditions, even in the absence of oxygen (see link). It is an explosive in this sense, not merely flammable as everyone answering so far believes. However, you have a misconception about heating that results from compression. Temperature of a gas increases with pressure during *adiabatic* compression. That means you compress the gas quickly enough so that heat does not escape by thermal conduction through the container walls. The acetylene in the cylinder was originally liquidized slowly in a refrigerated vessel so that it remained cool at all times. When stored at room temperature, the gas itself equilibrates to room temperature.

Actually, this isn't correct. I was writing my answer when you chose this one:
It would, but acetelyne is dissolved in acetone to make it more stable and it is absorbed into a porous material inside the cylinder. Once it's out of the cylinder, it needs to be kept under 15 psi, or it can explode.

Report Abuse

If I'm not mistaken, when they sell acetylene cylinders you have pure acetylene in them and not a mixture of acetylene and oxygen. Furthermore, I would guess that the compression of acetylene is done isothermally (ie. no change in temperature due to loss of heat to the surroundings), so that the gas does not ignite automatically.

The gases have to be in the right ratio for them to explode. At some point even a small amount of oxygen in there would probably reach the flash point and explode. It would probably take more heat than you would get from just compressing it. I definitely wouldn't try to compress a mixture of them.

Acetylene needs oxygen to burn. I strongly suggest that you never attempt to compress an acetylene/oxygen mixture to a high pressure.

The acetylene is contained within ACETONE liquid, which is absorbed into a type of clay.
Acelylene is otherwise LIKELY to self- ignite at pressures above 15PSI., or approx. 1 atm. above atmospheric pressure.