Description of experiment
Below follows a plain text transcript of the selected experiment.
Needed compounds:
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hydroxyl amine sulfate : (NH3OH)2 SO4
sulphuric acid : H2SO4
ferric ammonium citrate brown : Fe C6H5O7 . 2NH3 . 2H2O
ferric ammonium citrate green : Fe2 (NH4 C6H5O7)3
Class:
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elem=Fe
redox
coordination
Summary:
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The ferric ammonium citrate complex is destroyed by acid. The green one
is destroyed instantaneously, the brown one slowly is decomposed.
The resulting ferric ions can be reduced to almost colorless ferrous ions.
Description:
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Sequence 1:
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Dissolve some ferric ammonium citrate green in water: The liquid becomes
yellow/green, fairly intensely colored.
Add a large excess amount of dilute sulfuric acid (appr. 15% by weight):
The solution becomes light yellow/brown, the color of ferric ions in acidic
environments.
Add some solid hydroxyl amine sulfate: The solid dissolves, no further
visible changes.
Heat liquid, almost up to boiling: A gas is evolved, liquid starts foaming.
The color of the liquid becomes much lighter. It remains clear.
Sequence 2:
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Dissolve some ferric ammonium citrate brown in water: The liquid becomes
yellow/brown, fairly intensely colored (much more intensive than color
of plain aqueous ferric ions).
Add a large excess amount of dilute sulfuric acid (appr. 15% by weight):
The solution becomes light yellow/brown, color of ferric ions in acidic
environments. The change of color is slow and it takes approximately
1 minute before the lightening of the color has completed. This is in
strong contrast with the green citrate, where the change of color is
instantaneous.