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Author: Subject: Making ferrate(Fe VI+)
Foeskes
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[*] posted on 9-7-2017 at 23:40
Making ferrate(Fe VI+)


I tried to make ferrate starting from Fe2(SO4)3 and NaOCl
I made a solution of Fe2(SO4)3 and added a excess of NaOCl, then I boiled it until it started sputtering. And after filtering it has a yellow color. Since ferrates are pink to purple, it failed. What did I do wrong?
The procedure is from Wikipedia: https://en.m.wikipedia.org/wiki/Ferrate(VI)

[Edited on 10-7-2017 by Foeskes]
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ave369
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[*] posted on 10-7-2017 at 20:17


Heating is the wrong way to go. And the synth also needs a strong base.

You should first make Fe (OH) 3 by adding alkali. Then you should prepare a mixture of NaOCl and more alkali, the more basic the solution, the better. After that, you dissolve your goop of Fe (OH) 3 in this solution, without heating or with only gentle heating. After that, you'll see the liquid clear out and change color from brown to purple.

What you did was catalytic decomposition of hypochlorite: whatever ferrate you made was immediately decomposed by heat back into Fe (III) and oxygen.

Do not trust Wikipedia on those matters: our own Sciencemadness wiki has a tested procedure of ferrate synthesis.

http://www.sciencemadness.org/smwiki/index.php/Potassium_fer...

[Edited on 11-7-2017 by ave369]




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Foeskes
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[*] posted on 11-7-2017 at 03:36


Is mixing iron filings and KNO3 and igniting a viable option?
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ave369
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[*] posted on 11-7-2017 at 11:43


Well, the ferrate volcano kinda works, but the yield will be low and the leachings will be too dilute and low-grade to be of any use.



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Rhodanide
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[*] posted on 5-10-2017 at 10:19


Seeing as aqueous chemistry likely hates my guts, I'm gonna try the volcano-whatchamacallit, if/when I can get any damn nitrate.



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Foeskes
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[*] posted on 6-10-2017 at 01:15


I tried the volcano method, but it seems like unless you have extremely fine iron powder(like fine beach sand) it's not going to work well.(I got iron(III) oxide instead of the Ferrate)
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Rhodanide
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[*] posted on 6-10-2017 at 04:31


Quote: Originally posted by Foeskes  
I tried the volcano method, but it seems like unless you have extremely fine iron powder(like fine beach sand) it's not going to work well.(I got iron(III) oxide instead of the Ferrate)


Luckily, that's exactly what I've got! :D




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[*] posted on 6-10-2017 at 09:03


Quote: Originally posted by ave369  
Heating is the wrong way to go. And the synth also needs a strong base.

You should first make Fe (OH)3 by adding alkali. Then you should prepare a mixture of NaOCl and more alkali, the more basic the solution, the better. ........

[Edited on 11-7-2017 by ave369]


I am suspect on the statement "prepare a mixture of NaOCl and more alkali, the more basic the solution, the better" as the oxidation-reduction potential (ORP) of bleach, a mixture of HOCl and OCl-, which displays an increased concentration of hypochlorite versus hyochlorous acid with elevation in pH, also demonstrates (see https://www.apsnet.org/publications/PlantDisease/BackIssues/... ) similarly a drop in ORP with an increase in pH. Explainable as the cited ORP for HOCl/Cl- is +1.50 versus 0.9 mV for hypochlorite.

I say suspect becomes I would guess the ORP of the solution could positively influence ferrate formation, but not sure on this point for ferrate chemistry (requiring an elevated pH). In short, someone may have found a target pH for ferrate formation from bleach.

[EDIT] Found a ferrate preparation patent (see http://www.google.sr/patents/US8663607 ), with the following recommendation, which may support my contention:

"Buffers to regulate the pH of the composition and solutions resulting from use of the compositions can include any oxidation resistant buffer system with a pH of 6 to 12, preferably 7 to 8. "

which possibly suggests a target pH range of 7 to 8, including interestingly the highest ORP in a non-acidic environment.

[Edited on 6-10-2017 by AJKOER]
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