What are some tests for identifying ferric ions in a solution?

Answer 1

There are several simple tests for identifying Iron(III) ions.

• Add some ammonia solution to the testing solution, if Fe3+ present, there will be a green precipitate; Fe(OH)3.
• Add some ammonium sulphide to the testing solution, if Fe3+ present, Fe2S3 would be observed as a black precipitate.
• To the given solution, add a few milliliters from a K4[Fe(CN)6] solution, a Prussian blue solution or precipitate indicates that there is Fe3+ present.
• To the given solution, add a few milliliters from a K3[Fe(CN)6] solution, a clear solution which is yellowish brown in colour, indicates that there is Fe3+ present. (If the Prussian blue solution or precipitate is observed in this instance, there is Fe2+ present in the solution).
• To the given solution, add a solution of ammonium thiocyanate. A deep red colour, (actually the colour intensity depends on the quantity of ammonium thiocyanate added) depicts that there is Fe3+ in the solution.

The related link below is posted to observe the contrasts between identifying Iron (II) ions and Iron (III) ions.

OR A BETTER ANSWER TO MAKE YOUR UNDERSTANDING CLEAR:

For Fe2+,

Test: few drops of NaOH

Result: formation of pale green precipitate of Fe(OH)2,which is insoluble in excess of NaOH.

Test: few drops of ammonia.

Result:formation of pale green precipitate.

For Fe3+,

Test:few drops of NaOH.

Result: Formation of red-brown precipitate of Fe(OH)3, which is insoluble in excess of NaOH.

Test: Few drops of ammonia.

Result: Formation of red-brown precipitate.

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