1% Ferric Chloride is combined with 1% Potassium ferrocyanide in the Schmorl’s staining method. This staining technique identifies reducing activity in formalin-fixed paraffin tissue. The positive staining target or melanin demonstration is achieved via melanin reducing ferric ions present in the staining solution to the ferrous form and the ferrous form then combines with the ferricyanide which is also present in the staining solution. . The end product is the Turnbull blue (ferrous ferricyanide) reaction.