Potassium Ferricyanide NOT FOR SALE

Potassium ferricyanide is also one of two compounds present in ferroxyl indicator solution (along with phenolphthalein) which turns blue (Prussian blue) in the presence of Fe2+ ions, and which can therefore be used to detect metal oxidation that will lead to rust. It is possible to calculate the number of moles of Fe2+ ions by using a colorimeter, because of the very intense color of Prussian blue Fe4[Fe(CN)6]3.

SAFETY :

Potassium ferricyanide has very low toxicity, its main hazard being that it is a mild irritant to the eyes and skin. However, under very strongly acidic conditions, highly toxic hydrogen cyanide gas is evolved, according to the equation:

6 H+ + [Fe(CN)6]3− → 6 HCN + Fe3+[9]

The reaction with hydrochloric acid is as follows:

6 HCl + K3[Fe(CN)6] → 6 HCN + FeCl3 + 3 KCl