Description of experiment
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Needed compounds:
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sulphur : S8
potassium perchlorate : KClO4
phosphorus red : P
Class:
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elem=P,S,Cl
redox
Summary:
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A mix of potassium perchlorate and sulphur cannot easily be ignited. When just
a tiny pinch of red phosphorus is mixed in, then the mix is ignited very easily
and it burns very fast with a bright flash.
Description:
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Mix some finely powdered potassium perchlorate with finely powdered sulphur.
Take approximately 2 times as much potassium perchlorate as sulphur (by
weight). Put some of the mix on the tip of a small screwdriver and put this in
the flame of an alcohol burner: The sulphur in the mix melts, fizzles somewhat
and nothing else happens. The smell of burning sulphur can be observed.
Prepare a similar mix, but now with a tiny amount of finely powdered red
phosphorus added as well and put some of this mix on the tip of a small
screwdriver and put this in the flame: Even before the mix really comes into
the flame, it ignites. It burns very fast with a bright flash.
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Even with very small amounts of red phosphorus added in the mix, it can be
ignited very easily, a mix of KClO4 : S : P = 2 : 1 : 0.02 by weight already
can be ignited just by keeping it near a flame.