Description of experiment
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Needed compounds:
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potassium dichromate : K2Cr2O7
Class:
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elem=Cr
precipitation
Summary:
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Potassium dichromate dissolves very well in hot water. In the cold nice
crystals separate out of the solution.
Description:
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Add a fairly large amount of K2Cr2O7 to some water and shake: just a small
part of the dichromate dissolves. The liquid turns orange and a layer of
solid potassium dichromate remains in the bottom of the test tube.
Heat the liquid, until it starts boiling: all potassium dichromate dissolves.
The liquid turns dark orange/red. On standing, little crystals of potassium
dichromate separate from the liquid. After one day, a thick crust of orange
crystals covers the bottom of the test tube, the liquid above the crust is
bright orange.