Thermite

Alternate titles:

Thermite Reaction

Purpose:

To demonstrate a spectacular exothermic reaction that produces enough heat to produce molten iron.

Materials:

• Dry sand in large ceramic pot
• Filter paper
• Heat resistant gloves
• Ring stand/ring sized for ceramic pots used
• Spatula
• 2 small ceramic flower pots (6.5 cm diameter with 1.0 cm hole in bottom)

Reagents:

• 15g Aluminum (Al) powder
• 25g Potassium permanganate (KMnO₄)
• 5-6mL Glycerol
• 50g Iron (III) oxide (Fe₂O₃) powder

Hazards and PPE:

• Never drop the iron into water or wet sand. A steam explosion can result sending hot iron into the audience.
• Sparks may be thrown two meters vertically and up to five meters horizontally. Use a safety shield.
• Perform the demonstration outdoors unless a large, well, ventilated room is available. The reaction produces a tremendous amount of smoke.
• Wear approved safety goggles and gloves.

Protocol:

Preparation

1. Place a piece of filter paper over the bottom opening of the first small clay pot.
2. Place the first small clay pot into the second small clay pot.
3. Mix 50 grams of ferric oxide (Fe₂O₃ powder with 15 grams of aluminum (Al) powder.
4. Place the powder mixture into the first clay pot as a pile and form a small cone-shaped indentation in the center of the mixture (about 2.0 cm deep and 1-2 cm wide).
5. Just before preforming the demo, grind 25 grams of potassium permanganate (KMnO₄) crystals to a powder and fill the indentation with the KMnO₄ powder.
6. Form another small cone-shaped indentation in the KMnO₄ powder.
7. Place the two clay pots inside an iron ring clamped high on the ring stand and place the container of sand on the ring stand base below the clay pots. Place this assembly behind a safety shield and done protective equipment.
8. Pour 5-6 mL of glycerol into a small beaker.

Demonstration

1. When ready to perform the demo, pour the glycerol into the depression formed in the KMnO₄ powder. Step back immediately. Ignition will occur in 15-60 seconds.
   1. If the reaction fails, wait 1-2 minutes after the initial flare from the glycerol-KMnO₄ reaction. Add more potassium permanganate and glycerol.
   2. Flame, flying sparks, smoke and dust are produced. Molten iron will run through the hole in the pot into the sand bath.

Additional Notes:

• This is a spectacular demonstration, but great care is required. Try this demonstration alone prior to performing before a group.

Disposal:

• After they have cooled, the ceramic pots can be collected and disposed of by relevant disposal services.

Reactions:

• 14KMnO_{4 (s)} + 4C₃H₅(OH)_{3 (l)} → 7K₂CO_{3 (s)} + 7Mn₂O_{3 (s)} + 5CO_2(g) + 16H₂O_(g)
• Fe₂O_{3 (s)} + Al_(s) → Fe_(s) + Al₂O_{3 (s)} + ΔH

Citations:

1. Shakhashiri, Bassam; Chemical Demonstrations, Volume I, 1983.

Videos:

• Thermite Reaction Demo

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