Prussian blue is a dark blue pigment, the another name of Prussian blue is Berlin blue or Paris blue. It is formed by oxidation of ferrous ferrocyanide salts with FeCl3.
Colour of Prussian blue and turnbull’s blue is originated by charge transfer when electronic transition occurs from one part of the Complex to other part i.e such type are also called internal redox reaction (Charge transfer from metal to metal). Intensity of clour in such type transition is very high as they do not require follow any selection rule.
4FeCl3+3K4[Fe(CN)6]→Fe4[Fe(CN)6]3+12KCl
OR “Prussian blue is” or “Turn bull's blue”
FeCl3+K4[Fe(CN)6]→KFe[Fe(CN)6]+3KCl
OR
FeSO4+K3[Fe(CN)6]→KFe[Fe(CN)6]+K2SO4
“Turn bull's blue”
Related Question:
Colour of Complexes due to charge transfer:
Why violet colour of [Ti(H2O)6]Cl3 disapear (colourless) on heating heating ?
Why [Ni(CN)4]-2 is colourless while [Ni(H2O)4]-2 although both have +2 oxidation state and 3d*8 configuration ?
Why [FeF6]3– is colourless whereas [CoF6]3– is coloured ?
Why Fe(CO)5 is colourless while Fe(bipy)(CO)3 is intensely purple in colour ?
Why all the tetrahedral Complexes are high spin Complexes ?
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