Chemical Properties of Potassium Hexacyanoferrate (III)
- When potassium hexacyanoferrate (III) reacts with a strong acid, highly toxic hydrogen cyanide gas is evolved.
6H+ + [Fe(CN)6]3− → 6HCN + Fe3+
- Potassium ferrocyanide is obtained when potassium hexacyanoferrate (III) reacts with potassium hydroxide.
4KOH + 4K3[Fe(CN)6] → 2H2O + O2 + 4K4[Fe(CN)6]
- When potassium hexacyanoferrate (III) reacts with water, potassium monopentacyanoferrate and potassium cyanide are produced, and this reaction takes place in a boiling solution.
K3[Fe(CN)6] + H2O → K2[Fe(H2O)(CN)5] + KCN
- When potassium hexacyanoferrate (III) reacts with iron (III) chloride, iron (III) hexacyanoferrate (III) and potassium chloride are produced.
K3[Fe(CN)6] + FeCl3 → Fe[Fe(CN)6] + 3KCl
- When potassium hexacyanoferrate (III) reacts with freshly prepared iron (II) sulfate solution, a dark blue precipitate called Turnbull’s blue is produced.
4K3[Fe(CN)6] + 3FeSO4 → Fe4[Fe(CN)6]3 + 3K2SO4 + 6KCN
- When potassium hexacyanoferrate (III) reacts with lead (II) hydroxide and a diluted solution of potassium hydroxide, potassium hexacyanoferrate (II), lead (IV) oxide, and water are produced.
2K3[Fe(CN)6] + 2KOH + Pb(OH)2 → 2K4[Fe(CN)6] + PbO2 + 2H2O
Potassium Hexacyanoferrate III Formula
Potassium hexacyanoferrate (III) is also termed Red prussiate of Potash or Potassium ferricyanide whose chemical formula is K3[Fe(CN)6]. It was discovered by Leopold Gmelin in the year 1822. Potassium Hexacyanoferrate III is composed of potassium, iron, carbon, and nitrogen elements. It appears as deep red crystals, which decompose on heating. This compound contains the octahedrally coordinated [Fe(CN)6]3− ion. It is soluble in water and its solution exhibits slight green-yellow fluorescence. When it reacts with a strong acid, highly toxic hydrogen cyanide gas is evolved. It is prepared when chlorine is passed through a solution of potassium ferrocyanide. Potassium ferricyanide is widely used in photography and blueprint drawing. It is also used in calico printing, electroplating, and wool dyeing, as a laboratory reagent, and as an oxidant in organic chemistry. It is used to formulate Murakami’s etchant, which is used by metallographers.
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