| MadSci Network: Physics |
Robert,
A typical disposable lighter is made of thin plastic and contains a few cc's of butane, under sufficient pressure to keep it in a liquid state. Butane, both I and N type, boils well under the melting point of water. Somewhere between 13 and 32 degrees farenheit, butane boils into a gas. So at a standard temperature (70 farenheit, for example) butane is a gas which ignites and burns quickly in the presence of oxygen. In a lighter, butane is compressed sufficiently to keep it liquid. Inside the lighter, therefore, there is only butane in both a liquid and gas form. ( As the lighter is slowly drained of gas, volume of butane decreases but the container volume remains static, so some of the butaine boils into butane gas) That apparently empty part of the lighter is not air, it is clear butane gas. The gas itself will not burn in the absence of oxygen, so the internal spark theory is not likely.
A lighter could be pressurized to the point that it bursts and suddenly releases all of its butane into the air, quickly boiling into volatile butane gas. Any sudden spark would then produce a sudden gaseous combustion, an explosive fireball. Without a spark, it would simply pop, like a balloon. With a spark you would have a gaseous fireball that would also make a loud noise and burn quite brightly, but chances are it would not be a powerful explosion.
Now then, in a pants pocket someone would have to have a leak in the lighter to facilitate an explosion (letting air and butane mix) beforehand, or you would have to paddle someone pretty hard with an iron rod. (hard enough to create a spark when it struck the lighter) Thats my theory anyway !
-danny fletcher
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