Magpie
lab constructor
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coordination complex
I have been searching for Kf, the formation constant, for the hexafluoroferrate(III) complex, [FeF6]3- but have not had any luck. If anyone can
provide this I would much appreciate it.
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12AX7
Post Harlot
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I have only the first three,
Fe + F <--> FeF pKf = -6.04
FeF + F <--> FeF2 pKf = -4.43
FeF2 + F <--> FeF3 pKf = -3.15
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Magpie
lab constructor
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Thanks Tim. I went to the library today and found those Kf's also, but nothing higher. Perhaps they are unknown.
What got me interested in this was the use of KF as a complexing agent for Fe+++. It is specified in the qualitative analysis test for nitrogen using
sodium fusion of an organic unknown.
Edit: It is also used as a complexing agent for Fe+++ in the Group III qualitative test for Co++ to prevent the formation of [Fe(NCS)]++.
[Edited on 5-6-2008 by Magpie]
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kmno4
International Hazard
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pK for Fe(3+)F(-)^6/FeF<sub>6</sub>(3-) from my tables is -16,1
[Edited on 6-6-2008 by kmno4]
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chemrox
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What book or paper did that constant come from? If you don't mind sharing the information.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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kmno4
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This value is taken from paper book, titled "Chemical tables" (it is translation, oginal book is written in my native language), 1997 y. These tables
are the best ones I ever seen. I use it very often and all (almost) book is a set of separete pages  .
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Magpie
lab constructor
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I received some NaF today so gave it a try for complexing the Fe+++ in aqueous FeCl3. If I added enough it prevented the formation of Prussian blue
upon addition of potassium ferrocyanide.
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