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Cobalt Colours

  1. Mar 12, 2013 #1
    I have heard, quite simplistically, that "CoCl2 goes blue to pink with water" and "the reverse occurs with HCl solution". I have also heard that Co, and CoCl2, are pink in solution with water (in both cases with a different complex ion formed), and in both cases adding HCl again turns the solution blue.

    So there are three cases: solid CoCl2, CoCl2 solution, and plain Co in solution. In each case I will need to know which complex ions are responsible for each colour produced.

    The Internet has helped but I can't find out more from it than I already have, which is that Co2+ immediately forms [Co(H2O)6]2+ in solution, which is responsible for the pink colour, and that adding Cl- ions (e.g. HCl solution) then converts this to the blue [CoCl4]2- ion. So the plain Co in solution case is solved.

    But what happens in the other two cases?
     
    Last edited: Mar 12, 2013
  2. jcsd
  3. Mar 24, 2013 #2
    with Co being a metal, are you sure that it is soluble in water?
     
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