Description of experiment
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Needed compounds:
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sulphuric acid : H2SO4
sodium nitrite : NaNO2
potassium ferrocyanide : K4 [Fe(CN)6] . 3H2O
Class:
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elem=Fe
redox
Summary:
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Ferrocyanide is oxidized quickly by nitrite in acidic environments. On
prolonged standing, a darker green/brown compound is formed.
Description:
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Dissolve some potassium ferrocyanide in dilute H2SO4 (appr. 1 mol/l): The
liquid becomes very light yellow.
Add a solution of sodium nitrite (excess amount, relative to the potassium
ferrocyanide): The liquid becomes intense yellow at once (formation of
ferricyanide?) and there is a slight evolution of a gas. The air above the
liquid becomes very pale brown.
Let stand for a few days at room temperature: Liquid has become brown/green
and darker.