Description of experiment
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Needed compounds:
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sodium dithionite : Na2S2O4 . 2H2O
hydrochloric acid : HCl
ferric chloride : FeCl3 . 6H2O
Class:
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elem=Fe
redox
Summary:
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Dithionite reduces ferric ions to ferrous ions quickly in acidic
environments.
Description:
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Add a slightly acidified solution (with a few drops of 10% HCl) of ferric
chloride to a freshly prepared solution of sodium dithionite: On contact
between the two liquids a dark reddish brown compound is formed, which
quickly disappears again. Finally the liquid is almost colorless and clear.
A faint yellow color remains, but this appears quite soon in a dithionite
solution, even if no other chemicals are added.