Organic Exothermic Reaction

Purpose:

To demonstrate that a strong oxidizing agent, combined with a combustible material, will burst into flame.

Materials:

• Crucible
• Microspatula
• Asbestos/fire retardant pad

Reagents:

• Sugar
• Sulfuric acid (H₂SO₄)
• Potassium chlorate (KClO₃)

Hazards and PPE:

• Potassium chlorate is an oxidizer, acute irritant, and aquatic hazard. Store, dispose of, and handle with care.
• Sulfuric acid is acutely corrosive and toxic. Avoid skin contact and inhalation of fumes.
• Wear approved safety goggles and gloves.

Protocol:

Preparation

1. With a microspatula, carefully mix 6g of KClO₃ with 2g of sugar in a crucible.
   1. If the amounts are doubled, the reaction is more impressive.
2. Pile the mixture in the middle of the asbestos pad.

Demonstration

1. Make a small conical depression in the top of the pile with the spatula.
2. Add ~0.5mL conc. sulfuric acid into the depression and stand back immediately.
   1. The reaction begins quickly, evolving smoke after 1-3 seconds, and then the pile will burst into a purplish flame.

Additional Notes:

• The beautiful purple color of the flame is due to the combustion of potassium.

Disposal:

• Allow the leftover black carbon to cool, then flush down the drain with water.

Reactions:

• The stoichiometry of the reaction between KIO3, H2SO4, and sugar is not known. Chloric acid (HClO3), an explosive gas, is formed when KClO3 and H2SO4 are mixed. Chloric acid decomposes organic substances such as sugar very rapidly, often with inflammation.

Citations:

1. Shakashiri, Bassam. Chemical Demonstrations, Volume I, 1983.

Videos:

• Quick Chemistry - Sugar, Potassium Chlorate, And Sulphuric Acid

  Bill Gilmour