Description of experiment
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Needed compounds:
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sulphuric acid : H2SO4
ferric ammonium citrate green : Fe2 (NH4 C6H5O7)3
potassium ferricyanide : K3 [Fe(CN)6]
Class:
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elem=Fe
coordination
Summary:
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Ferric ions, bound to citrate, can coexist in solution with ferricyanide,
when the pH of the liquid is not too low. At lower pH the ferric citrate
complex is destroyed and the free ferric ions combine with the ferri-
cyanide ions.
Description:
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Add some solid potassium ferricyanide to a solution of ferric ammonium
citrate green: The liquid becomes intensely colored, bright yellow/green.
All potassium ferricyanide dissolves.
Add some sulfuric acid (15% by weight): The liquid becomes dark brown and
remains clear. After a few minutes the liquid appears to be even darker
than just after addition of the acid.