eqilibrium

[Ralph]

just wondering does any one know any good visual equilibrium reactions because i can only think of NO₂ to N₂O₄ which I dont really want to be playing with or Chlorine in water or cobalt chloride (currently what im thinking of doing but its kinda expensive) any one know any relatively safe visual equilibrium reactions that can be used in a demo

[Twotails]

I think theres a Copper (Sylicate?) tut on Skylighter, I know during the reaction you can see the crystals growing. Also theres The Simple Hotice reaction.