Description of experiment
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Needed compounds:
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sodium hydroxide : NaOH
ferric chloride : FeCl3 . 6H2O
potassium ferrocyanide : K4 [Fe(CN)6] . 3H2O
Class:
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elem=Fe
precipitation
coordination
Summary:
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The blue precipitate, formed when ferrocyanide and ferric ions act
upon each other is not stable in alkaline environments.
Description:
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Add a solution of ferric chloride to a solution of potassium ferrocyanide:
Formation of a dark blue precipitate (Prussian blue, ferroferricyanide).
Add some concentrated solution of NaOH: The precipitate turns orange/brown
and becomes much less dark. The brown precipitate looks like a precipitate
of iron hydroxide, when ferric ions are precipitated with sodium hydroxide.