Potassium hexacyanoferrate(III) solution

This is a yellow solution containing the complex ion, hexacyanoferrate(III), Fe(CN)₆^3-. It is used as a very sensitive test for iron(II) ions in solution as it forms a distinctive blue complex, called Prussian blue, on addition to a solution containing iron(II) ions. Potassium hexacyanoferrate(II) solution is similarly used as a test for iron(III) ions.