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When I was a kid I remember a thing an adult showed me where you would take a piece of strike paper from a matchbox, rest it on a "copper" coin (I have no idea what these coins are made of), and set it alight.

This left a residue which you could rub on your fingers, which would glow when you rubbed your fingers together.

What is that? I remember it only worked with copper coins, so what does the coin contribute, here?

I was going to show this to my own kids, but I realised I don't know how safe it is. We did a lot of dumb things back then, so I shouldn't assume it's safe just because I'm still alive.

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    $\begingroup$ Strike paper contained red phosphorus, which upon heating could convert to white phosphorus, which in turn could be collected on the cold metal surface. Yes, it will glow. No, by today's standards it is not considered safe. $\endgroup$ Dec 10, 2021 at 10:36
  • $\begingroup$ The type of coin seemed to be relevant to whether or not it worked, and it only glowed when you rubbed it. Is it possible that it produced something else besides (or alongside) white phosphorus? As the experiment seems overcomplicated if that's all that is needed. Maybe the coin just provided thermal regulation so it wasn't all burned up and lost, and the rubbing was just a catalyst for oxidation. I don't know. In any case it sounds like white phosphorus must be present and this isn't for kids. $\endgroup$
    – sh1
    Dec 10, 2021 at 18:18
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    $\begingroup$ @sh1 White phosphorus is not meant for anyone. It is best left untouched. $\endgroup$ Dec 11, 2021 at 3:39
  • $\begingroup$ I’m voting to close this question because not only is it not clear in terms of a "chemical question", it is about "playing with fire" which is something we should not encourage or condone here $\endgroup$ Dec 23, 2021 at 17:05

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An opening comment from Wikipedia on phosphorus:

The glow of phosphorus is caused by oxidation of the white (but not red) phosphorus — a process now called chemiluminescence.

Now, my take, first from a source on the history of matches to quote:

The modern "safety-match" The match head now consists of a paste containing an oxidant such as KClO3 and phosphorus sesquisulfide (P4S3), instead of a mixture or red phosphorus and sulfur. (P4S3 was possibly first suggested in 1872 by Frederick Zaiss of Philadelphia in US Patent 125,874 on coloured and scented parlour matches). These "safety-matches" were consider non-toxic and unaffected by the atmosphere and did not react readily with water.

Further, not surprising in the presence of some water (from touching, also adding NaCl), a source of H+ by the reaction:

$\ce{P4S3 + H2O = H2S + H3PO3 + H3PO2 }$

Claim, a metal/air battery cell is formed (from placing the extracted P4S3 mix on a copper penny in air) liberating electrons, which can further react creating the hydrogen radical:

$\ce{H+ + e- <-> .H}$

Source: See Science Direct cited Reaction (1), which per Buxton, is claimed to be the major reducing species in acidic solutions.

As such, upon placing P4S3 (after being touched with the human hand adding NaCl and moisture) on copper metal in air could create a galvanic corrosion cell with a possible further attack of the moist, now acidic P4S3, by generated hydrogen atom radicals, liberating P4 as follows:

$\ce{6 .H + P4S3 = P4 + 3 H2S}$

where this reactions mirrors the following cited reaction: $\ce{ PbS + 2 •H = Pb + H2S}$ (5) from the Hydrometallury literature.

Finally, as already noted, the liberated P4 undergoes oxidation in air resulting in chemiluminescence.

The reaction may not be safe as the indicated liberated substance, per my suggested chemistry, is white phosphorus, albeit, likely in small amounts.

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