Experimenting with potassium ferricyanide

Potassium ferricyanide, or potassium hexacyanoferrate, is an interesting salt used in cyanotype photography. It exists as deep red crystals, or as a yellow powder if finely ground. Despite the name it's pretty non-toxic and safe to work with. I acquired some recently and decided to try a few experiments with it.

I tried combining potassium ferricyanide with copper sulphate (both in solution) and immediately a dirty brown coloured precipitate of copper ferricyanide formed. The equation for this is:

2 K3Fe(CN)6 + 3 CuSO4 ==> Cu3(C6N6Fe)2 + 3 K2SO4

Another thing I tried was making Prussian blue, Fe7(CN)18. You may have heard of Prussian blue. It's a very common blue dye used in fabrics and painting. Its chemical name is ferric ferrocyanide, or ferrous ferricyanide. I made it by combining solutions of ferrous sulphate and potassium ferricyanide. The Prussian blue forms as a beautiful dark blue precipitate. Unfortunately I am unable to calculate the equation for this.

Here's some pictures of the products:










LEFT = copper ferricyanide
RIGHT = ferric ferrocyanide