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I was teaching the lime cycle to some children yesterday. I had a limestone chip (about 10g) held at the tip of a blue Bunsen flame for several minutes. It decomposed and disintegrated but only glowed very slightly, and was mostly orange with a bit of white at the tip.

It certainly gave off white light, but nowhere near the quantities required to light a theatre stage, which is what this stuff is famous for, not by a few orders of magnitude.

I tried sitting it on gauze and bringing in a second Bunsen flame from the side, but this did not improve the effect. I recall seeing quite a bright light when this was shown to me as a child.

Any theories on what went wrong? Any gotchas for doing this kind of experiment?

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Perhaps your flame wasn't hot enough. Real limelights used oxyhydrogen torches, not wimpy natural gas flames.

Or perhaps your limestone chip wasn't just $\ce{CaCO3}$. If it was dolomitic limestone, there was a lot of $\ce{MgCO3}$, too, and $\ce{MgO}$ doesn't do the trick like $\ce{CaO}$ does.

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