uncompromisedfreedom
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Synthesis of Potassium Hexacyanoferrate(II) i.e. Potassium Ferrocyanide?
I see this chemical under two suppliers on the RAC list, but I was wondering if anyone could hazard a guess how to synthesize Potassium
Hexacyanoferrate(II) i.e. Potassium Ferrocyanide (K4Fe(CN)6 is the formula).
Thanks, in advance, for your help and "Hello, world" since this is my first post!
\"We get one shot at life. Give us our freedoms.\"
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garage chemist
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Today this is synthesized from an iron(II)salt and potassium cyanide.
On adding KCN solution to iron(II) solution, insoluble Fe(CN)2 precipitates first. Upon further addition of cyanide, it redissolves, forming the
hexacyanoferrate.
It would probably be advantageous to isolate the Fe(CN)2 by filtration first and then dissolve this in the stochiometric amount of KCN solution so
that a pure solution of K4Fe(CN)6 is obtained.
If the Fe(CN)2 is not isolated, you will have the anion from the iron(II)salt in there as well, making it necessary to employ fractional
crystallization to isolate the ferrocyanide.
The old methods using dried blood in KOH melt are of course obsolete.
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joeflsts
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Another method:
"If solutions of potassium ferricyanide and iron(II) sulphate are mixed, a redox reaction will occur and iron(III) ferrocyanide (AKA Prussian blue)
will precipitate out. Prolonged boiling of the precipitate in potassium hydroxide solution will convert this into potassium ferrocyanide and iron(III)
hydroxide. If a nominal excess of the iron(III) ferrocyanide is used, all the potassium hydroxide will react and so a pure solution of potassium
ferrocyanide can be obtained by filtration. "
Joe
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uncompromisedfreedom
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Thanks much! Now to make it happen!
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S.C. Wack
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A better way IMHO to make it from the usually but not always more expensive ferricyanide is reduction by H2O2 with the theoretical amount of base.
Beware gas evolution carrying off ferrocyanide and eventually turning everything blue.
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Organikum
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| Quote: | Originally posted by S.C. Wack
A better way IMHO to make it from the usually but not always more expensive ferricyanide is reduction by H2O2 with the theoretical amount of base.
Beware gas evolution carrying off ferrocyanide and eventually turning everything blue. |
Interesting. For
just today I discovered that my favorite drugstore sells ferricyanide and of course I could not resist to buy 100 grams and now I would like to do
some simple experiments - the conversion to ferrocyanide is on top of the list.
Any more detailed information on this? I suppose H2O2 being used in fairly low concentration to act as a reducing agent?
/ORG
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S.C. Wack
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I do not at all remember whether drugstore 3% or the more concentrated homemade stuff that I had at the time was used, but I'll assume it was the 3%.
Nor do I remember which K salt was used, but I'm leaning toward K bicarbonate. The reaction is instant and requires no heat or anthing. Dissolve the
ferricyanide in the minimum amount of water, add the theoretical quantity K to turn K3 to K4 (anion that leaves the solution was chosen, KOH would
have been a better choice if I had some at the time), add peroxide until it looks like you don't need to add more. Quantitative yield.
This was done on a large scale, and the ferrocyanide trihydrate crystallized out nicely in a fused mass on some concentration of the solution.
Dehydration to whiteness is some pain if desired.
I do keep notes of everything, but I don't save them.
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