Thursday, 16 May 2013

5.2 describe and explain the extraction of aluminium from purified aluminium oxide by electrolysis

  • Bauxite is purified into aluminium oxide.
  • This is then dissolved in molten cryolite to bring down the boiling point
  • The walls of the tank are the negative electrode; here aluminium is made
  • The aluminium sinks to the bottom and is tapped off
  • Oxygen is formed at the positive electrode
  • The oxygen formed reacts with the graphite anode to from carbon dioxide; so the anode has to be replaced
It is very expensive to supply the electricity needed for this electrolysis.


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  3. Replies
    1. steel tank lined with heat resistant bricks, but doubt you need to know that

  4. Thanks so much for this wonderful blog! Just one thing: think it should be "bring down the melting point" rather than "bring down the boiling point".

  5. I don't think it matter as they are the same thing but seeing as you are melting the Aluminium it is safer to say melting point

  6. also do we need to say how bauxite is purified

  7. it should be carbon anode not graphite. that's why it forms c02 and needs to be replaced, all other electrolysis examples on the syllabus use graphite anodes tho

  8. You Wright a excellent post that is full of information I appreciate your work.

    White Fused Alumininum