LEYTON SIXTH FORM COLLEGE

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LEYTON SIXTH FORM COLLEGE

• CHEMISTRY SAFETY PROJECT 2003-2004
• A SAFER METHOD OF DEMONSTRATING THE THERMITE
  REACTION. A DEMONSTRATION VIDEO TO BE PREPARED
  AFTER THE EXAMS IN JUNE

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THERMITE REACTION

• Aluminium powder displaces iron from iron (III)
  oxide
• Mg ribbon is used as a fuse
• 2Al Fe203 -------? Al203 2 Fe
• A similar reaction occurs using Chromium (III)
  oxide Cr203 or Manganese(II), dimanganese(III)
  oxide Mn304.

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Dangers and Hazards of this demonstration

• When performed outside the powders have blown
  into the flames, caught fire causing burns to the
  hand or face
• Siting the demonstration in a fume cupboard has
  caused damage to the the cupboard
• The bench has been damaged
• Students must shield their eyes and not look at
  the glare of the Mg flare.

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Modified underwater method recommended by CLEAPSS

• This underwater method is performed on a bench
  and does not produce many fumes
• It produces results within seconds of setting it
  off because the water cools the iron down very
  quickly
• Eye protection and safety screens are essential,
  laboratory coat to be worn by the demonstrator
• Students to stand 4m away from the reaction

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Diagram of Apparatus
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Method

• Fold two 12 cm diameter circles of filter paper
  into fluted cones,
• Place one cone inside the other
• Into a 1 litre thick walled beaker pour sand
  until it is one third full and then add water
  until it is two thirds full
• Protect the surrounding bench by laying
  protective mats and remove any combustible
  material
• Wearing eye protection set the beaker on a bench
  mat and set up the diagram as shown in the
  previous slide.

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Thermite mixture

• Add 12g of the thermite mixture 9g of iron (III)
  oxide and 3 g of aluminium powder (medium grade)
  to the fluted filter paper
• Make a depression in the Thermite mixture with a
  spatula and place the igniter mixture (0.2 g of
  magnesium powder and 2 g of barium nitrate this
  is a ratio of 1 10)
• Insert the magnesium ribbon fuse upright into the
  igniter mixture it MUST extend above the fluted
  filter paper. Light the magnesium fuse with a
  bunsen burner and retreat.

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What happens!

• Once the reaction has stopped, remove the beaker
  and decant the water down the sink and retrieve
  the iron formed.
• Check it is iron by using a magnet
• See if it conducts electricity