English: Self-ignition of a mixture of sugar and potassium chlorate with a drop of concentrated sulfuric acid

A mixture is prepared of powdered potassium chlorate and powdered sugar (in a volume ratio of 1 : 1). One drop of H 2 SO 4 (conc) is added to the mixture. After about one second the mixture spontaneously catches fire and burns.

The concentrated sulfuric acid reacts with the potassium chlorate. At first, chloric acid is being displaced by the sulfuric acid:

KClO₃(s) + H₂SO₄(l) = HClO₃(l) + KHSO₄(s)

The chloric acid is unstable at weight ratios > 40 % and disproportionates into perchloric acid, chlorine dioxide and water:

3HClO₃(l) = HClO₄(l) + 2ClO₂(g) + H₂O(l)

All three compounds (HClO₃, HClO₄ и ClO₂) are very strong oxidizers, hence the organic substances (including sugar) inflame spontaneously in their presence. Once the mixture inflames, it easily continues to burn as a mixture of an oxidizer (KClO 3 ) and a reducing agent (the sugar).

Performed by the retired Prof. PhD Vladimir Petruševski. The planning of the experiment also included the Prof. PhD Miha Bukleski and the students Mihail Trajkov and Darko Stojčev, Department of Chemistry, FNSM, Ss. Cyril and Methodius University, Skopje, Macedonia.