[zeoblade]

According to Housecroft and Sharpe, Inorganic Chemistry, 3rd edition;

[Fe(CN)₆]^4- + Fe³⁺ --> Prussian blue
[Fe(CN)₆]^3- + Fe²⁺ --> Turnbull blue

due to Fe^III₄[Fe^II(CN)₆]₃ complex where there is an electron transfer between Fe(II) and Fe(III) for Prussian blue. I'm wondering would the situation be reversed in Turnbull blue Fe^II₃[Fe^III(CN)₆]₂?

I couldn't observe any difference in colour between Prussian and Turnbull.

I tried [Fe(CN)₆]^4- in Fe²⁺ and it produced this dirty milky blue green and then
[Fe(CN)₆]^3- in Fe³⁺ and it produced this opaque brown. Can I write these two reactions as:

[Fe(CN)₆]^4- + Fe²⁺ --> Fe^II₂[Fe^II(CN)₆]
[Fe(CN)₆]^3- + Fe³⁺ --> Fe^III[Fe^III(CN)₆]

Also, SCN^- with Fe³⁺ gave an opaque crimson blood red [Fe(OH₂)₅(SCN-N)]²⁺
However SCN^- with Fe²⁺ gave a red not as opaque so could I write the product as [Fe(OH₂)₅(SCN-N)]⁺?

Lastly, I made a solution using FeSO₄.(NH₄)₂SO₄.6H₂O and found it to be clear in colour (maybe with a green tinge if longer path length) and free of Fe³⁺ and consisting only of Fe²⁺. Adding [Fe(CN)₆]^4- and [Fe(CN)₆]^3- to separate solutions gave milky blue green and Turnbull blue respectively. So if the previous controls mentioned at the beginning of this post are true, I can say FeSO₄.(NH₄)₂SO₄.6H₂O is Fe(II), right?

[Borek]

I couldn't observe any difference in colour between Prussian and Turnbull.

Hardly surprising, as far as I know it is the same compound.

I can say FeSO₄.(NH₄)₂SO₄.6H₂O is Fe(II), right?

Yep, from what I remember that's the only common Fe(II) compound that is not easily oxidized by air oxygen, hence it is often used in chemistry as a source of Fe²⁺.

[zeoblade]

Thanks for confirming that Prussian and Turnbull are the same, I just read something about them.

How about the following reactions:

[Fe(CN)₆]^4- + Fe²⁺ --> Fe₂[Fe(CN)₆] (dirty milky blue green)
[Fe(CN)₆]^3- + Fe³⁺ --> Fe[Fe(CN)₆] (opaque brown)

Is it wrong if I write these precipitates like this? The Prussian blue Fe₄[Fe(CN)₆]₃.14H₂O complex is due to electron transfer between Fe(II) and Fe(III). In those above reactions, there is only electron transfer between one Fe(II) to the other Fe(II) and Fe(III) to Fe(III), is that the reason why the dirty milk blue green of Fe(II) and opaque brown of Fe(III) developed instead of Prussian blue?

Similarly, SCN^- in Fe³⁺ gave opaque blood red [Fe(OH₂)₅(SCN-N)]²⁺
So if SCN^- in Fe²⁺gave a deep red can I write the product [Fe(OH₂)₅(SCN-N)]⁺ or is that the wrong product to represent the deep red solution?

[AdiDex]

Fe²⁺ + [Fe(CN)₆]^3- Fe³⁺ + [Fe(CN)₆]^4-

First their is a redox reaction , Fe²⁺ get converted into Fe³⁺ (as shown above).

Then they form Fe₄[Fe(CN)₆]₃

There is nothing like Ferro-Ferri Complex .