A scientific observation by French scientist Joseph Louis Gay-Lussac (1778–1850) where for a gas held at constant volume, there is a direct correlation between temperature and pressure. That is, if you take a gas and put it into a rigid container and double the temperature (as measured from absolute zero), then you double the pressure.

Usually written mathematically as:

P1 / T1 = P2 / T2

The lack of a volume component means that the actual volume of the gas is unimportant as long as it is held constant.

Gay-Lussac's Law is subsumed by the Ideal Gas Law after unification with Boyle's Law and Charles' Law. Like the Ideal Gas Law, Gay-Lussac's Law deviates from reality slightly when measuring real gasses at high accuracy.

This is, surprisingly, a law that really sticks in my mind, after it was forcefully demonstrated to me on a Saturday afternoon, far from my chemistry and physics classes...

Bein' the percussionist that I am, I don't have to watch what I eat and drink during marching band games, as I don't have to worry about ruining reeds and growing mold in my horn. September Saturday afternoons in California can get exceedingly hot, and as our uniforms are made of wool, during football games everyone drinks as much liquid as possible. Having been liberated from plain ol' water by my drummer-ness, I naturally chose to ingest something cold, caffeinated, and carbonated. Carbonated would be the key word here.

So, halfway through first quarter I take my ice cold Diet Pepsi from the cool shelter of my stickbag and, after marveling at the fact that it's not near to boiling (the temperature at this time is around 95 degrees, Farenheit), uncap the lid as usual and drink, under the envious gazes of several wind players with their water bottles. I savour it; the bottle is nearly full when I'm finished. I recap it tightly (my first mistake) and set it on the bench slightly behind me, atop my black cymbal bag (my second). Ten, fifteen minutes later...

I loosen the cap on my soda without looking, assuming from prior experience that the carbon dioxide will have not built up enough to emit more than a brief hiss. Disaster strikes. Diet Pepsi sprays the snare, the snare player, my set, my lap, me... I quickly retighten it, but the damage is done. The snare player gives me a menacing glare. I return a bewildered shrug, and a hasty apology. Only then do I observe the warnings that could have fended off disaster, had I only been a better scientific thinker.

  • The bottle was warm to the touch.
  • The sides, instead of having the slight give they should have had, were rock hard.
  • Gay-Lussac's law states that, assuming a fixed amount of gas at a fixed volume, pressure is proportional to temperature. When the temperature rises, so does the pressure.

My theory is that the sun warming the carbon dioxide gas inside, along with accelerating the natural tendancy of all carbonated beverages to give off same. The heat may have caused the soda to bubble more than normally, as well. All I know is this - that bottle should not have exploded, but explode it did.

Let my experience serve as a warning for future generations - chemistry has practical applications far outside anything ever mentioned in lab. Take this to heart, or your dry-cleaning bills, too, may skyrocket.

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