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Cobalt Chloride Paper

Discussion in 'Science' started by XFSS, Feb 11, 2011.

  1. Help! I am a trainee chemistry teacher and I want to use cobalt chloride paper with one of my classes but have some fundamental questions I need answers to first. Even Wikipedia cannot help me! Why is cobalt chloride paper white? Why is it not pink to start with due to the humidity in the air or blue if you store it in a dessicator? Why does it only turn pink at the boundary between wet and dry? All assistance gratefully received.
     
  2. does the co-ordination number change? in different crytals fields the same transition metal ion will display different colours when surrounded by different ligands...
     
  3. Cobalt chloride paper is blue when dry, not white. I make it myself from soaking filter papers in cobalt chloride solution. The solution is pink when the pieces are dipped in and turn blue when dried in the oven. I believe the pink colour is due to a complex ion formation with the water.
     
  4. phlogiston

    phlogiston Star commenter

    We always make our own CoCl2 paper. Last time I saw the commercial stuff it didn't impress.
    Anhydrous CoCl2 is blue, when hydrated it acquires 6 water ligands and goes pink. If you put lots of water on the paper, the cobalt chloride dissolves and the paper goes white (or whatever colour the paper was before it became cobalt chloride paper).
    We make it the way chem1st describes
    P
     

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