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The first attempts at instantaneous matchboxes usually included some sort of oxidizer, usually potassium chlorate and an initiating fuel (first sugar was used then they moved on to $\ce{Sb2S3}$ etc.) However the stick had to be dipped into a sulphuric acid solution and withdrawn for it to catch fire.

My question is:- How come the matchstick tip had to be dipped in $\ce{H2SO4}$ in order for it to catch fire? What was the acid doing? Was the active oxidant $\ce{HClO3}$?

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  • $\begingroup$ Well, you gotta do something to set a match on fire - contact oxidiser with reducer. If one uses a solution for that, I doubt you could think of a better one. $\endgroup$
    – Mithoron
    Commented Jan 31 at 15:47
  • $\begingroup$ I don't think I get you, isn't sulphuric acid also an oxidant? $\endgroup$
    – Gaurav Sai Maddipati
    Commented Jan 31 at 15:52
  • $\begingroup$ H2SO4 is not much of an oxidant, certainly not enough to start a fire by itself. $\endgroup$
    – Ivan Neretin
    Commented Jan 31 at 15:55
  • $\begingroup$ chemistry.stackexchange.com/questions/4158/… It's the dehydrating nature of sulphuric acid i overlooked. I think this answers my question. Do i delete/close this? $\endgroup$
    – Gaurav Sai Maddipati
    Commented Jan 31 at 16:17
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    $\begingroup$ @GauravSaiMaddipati Instead of delete, you can self close the question by linking that question. $\endgroup$
    – Nilay Ghosh
    Commented Feb 1 at 11:49

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You are right. $\ce{HClO3}$ is at the origin of the flame, and the dehydrating power of $\ce{H2SO4}$ has nothing to do here.

Anhydrous $\ce{H2SO4}$ reacts with $\ce{KClO3}$ to produce $\ce{HClO3}$ (and $\ce{KHSO4}$). When anhydrous, this $\ce{HClO3}$ is the active oxidant, but it is also an unstable compound, which is quickly and spontaneously decomposed. As soon as it is in contact with a reducing agent, like sugar of $\ce{Sb2S3}$, $\ce{HClO3}$ reacts strongly, producing $\ce{KCl}$ and oxygen, and these oxygen atoms create a flame with the sugar or $\ce{Sb2S3}$. In the $19$th century, the first matches were made with a mixture of molten $\ce{KClO3}$ and sugar (or another flammable substance) which were deposited on bits of wood. To get a flame, the matches had to be wetted with a tiny amount of concentrated sulfuric acid.

Today the acid has been suppressed. Matches contain only $\ce{KClO3}$ on wooden sticks. To start a fire, the matches are rubbed on a thin layer of red phosphorous $\ce{P_\mathrm{n}}$ : the friction heats a bit, enough to produce a flame, due to the reaction of $\ce{KClO3}$ on $\ce{P_\mathrm{n}}$ (and $\ce{P_\mathrm{n}}$ is probably partially transformed by friction into white phosphorous $\ce{P4}$, which is much more flammable).

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  • $\begingroup$ Didn't we dip it into solution? How would it be anhydrous? $\endgroup$
    – Gaurav Sai Maddipati
    Commented Feb 1 at 5:29
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    $\begingroup$ The last paragraph reminds me on Walter White (Breaking Bad) and the scene where he explains the modern design (link to a snippet on youtube). But how would one carry safely anhydrous $\ce{H2SO4}$ around? Fuming $\ce{H2SO4}$ is the closest one to your description I came to use so far, and I'm glad it was stored in a solid glass bottle. $\endgroup$
    – Buttonwood
    Commented Feb 1 at 11:05
  • $\begingroup$ These old fire-kits certainly werent carried around, that's for sure. $\endgroup$
    – Gaurav Sai Maddipati
    Commented Feb 1 at 12:05

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