The increase in the absorbance of copper ferrocyanide suggested a reduction of copper ions or ferricyanide. With the standard reduction-oxidation potential of 0.58 V for Mn(II)/Mn(III)-citrate (Sanjeeva Reddy 2007 ), it is possible that the ferricyanide and copper system oxidizes Mn 2+ in the presence of citrate.

It is used more commonly as a confirmatory test. Potassium Ferricyanide Potassium ferricyanide will give a brown coloration but no precipitate with Fe 3 +. With Fe 2 +, a dark blue precipitate is formed. Although this precipitate is known as Turnbull's blue, it is identical with Prussian blue (from Equation 5 ).

Potassium ferrocyanide is used to determine potassium permanganate concentration in the laboratory, which is a compound often used in titrations according to the redox reactions. The potassium ferrocyanide compound is used in a mixture with the phosphate-buffered solution and potassium ferricyanide to give a buffer for beta-galactosidase.