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Description of experiment
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experiment.
Needed compounds: ----------------- hydrogen peroxide : H2O2 potassium ferricyanide : K3 [Fe(CN)6] potassium ferrocyanide : K4 [Fe(CN)6] . 3H2O sulphuric acid : H2SO4
Class: ------ elem=Fe redox
Summary: -------- Ferrocyanide and ferricyanide decompose on heating with dilute sulphuric acid. When the decomposition product of ferrocyanide is treated with hydrogen peroxide, then it looks very much like the decomposition product of ferricyanide.
Description: ------------ Sequence 1: ------------ Add a small amount of potassium ferrocyanide to dilute sulphuric acid (appr. 2 mol/l): The solid dissolves, the liquid becomes very light yellow and clear.
Heat, until the liquid just boils: The liquid becomes turbid and green/blue. There is no evolution of a gas. When the liquid is allowed to stand for a while, then the color shift to blue and a blue/green solid slowly sinks to the bottom.
Add some hydrogen peroxide (appr. 3% by weight): The liquid becomes very dark, almost black.
Sequence 2: ------------ Add a small amount of potassium ferricyanide to dilute sulphuric acid (appr. 2 mol/l): The solid dissolves, the liquid becomes bright yellow and clear.
Heat, until the liquid just boils: The liquid becomes turbid and dark brown, almost black. There is no evolution of a gas.
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