12AX7
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Interesting iron and chlorate reaction
While processing the goop from my rust bucket, I emptied the Fe(OH)3 suspension plus mixed iron salt solution into a nearby cut-down milk jug, which happened to be encrusted with
some residual sodium chlorate.
Coming back to the solution the following day, I was suprised to see that it didn't seem to be settling very quickly.
Waiting another day, I found it was clearly seperated into a drab yellow bottom layer, the Fe(OH)3, and remarkably, a red solution on top! The smell
was a somewhat fruity, tangy smell, which I identify as typical for Fe(III) and Cl- ions stored in HDPE vessels. Figuring I was on to something, I
poured the supernatant into another similarly encrusted milk jug. The following day, the solution became not only a deeper red, but on picking up the
jug I realized it had set into a viscoelastic liquid! The consistency was very much like thick cream of tomato soup, with a darker color about the
same hue.
Had the neutral Fe(II) solution oxidized into a gel of Fe(OH)3 and Fe(III) ions in solution? Had it complexed? ClO3 probably isn't a good ligand, but the color of this solution is much deeper than would be expected even if all the iron present were quantitatively
oxidized to Fe(III), which would also produce a noticable amount of Fe(OH)3, of distinctly different color (note: Fe2O3 has about the right color, but
I don't know how it would form in solution).
I shall do additional testing under more control to investigate this further.
Tim
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Ballermatz
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Chlorate in solution easily oxidizes Fe(+III) to Fe(+IV). I once made potassium chlorate from KOH+chlorine and it turned red-violett due to little
iron contaminations too. Very little potassium ferrate is formed, but in solution it has a very strong brilliant color, almost like permanganate.
If you fuse iron sulfate with potassium chlorate you can produce siginificant amounts of potassium ferrate. It decomposes quickly in solution, but you
can precipate it as barium ferrate.
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woelen
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I don't think this is the cause of what 12AX7 observed. Ferrate is only formed at very high pH and as you write, you made it from KOH+Cl2. This
contains a lot of hypochlorite, and that indeed does make ferrate at high pH.
I am more inclined to think that the red color and high viscosity is due to formation of some highly networked suspension of ferric hydroxide/oxide,
with chlorate ions encapsulated as well.
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not_important
International Hazard
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I'm going with woelen on this, the description sounds a lot like the published descriptions of ferric hydroxide gels.
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Xenoid
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I get colloidal ferric hydroxide in my chlorate cells when I use gouging rods but not when using pure graphite, so I assume the iron is coming from
the gouging rods and not the SS cathodes. It tends to form a "coca-cola" coloured liquid and is difficult to remove. I precipitate it with alum but
even this doesn't remove it all.
A strong colloidal ferric hydroxide solution is a dark red colour. If a strong colloidal solution of ferric hydroxide is allowed to stand for a week
or so in a glass vessel, a gelatinous solid is precipitated. Perhaps the chlorate is acting as a catalyst to speed up this process in your case. You
should be able to evaporate the water from it, it reportedly behaves like silica-gel.
Regards, Xenoid
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12AX7
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My chlorate cell has gone through large amounts of graphite, never seeing any iron in suspension. I don't know how I could tell, since the graphite
is so much blacker than anything else. I have precipitated it, noting a brown precipitate in the solution after filtering and adjusting pH. The
biggest source of soluble iron probably comes from the acid, which is muriatic acid diluted 1:5 or so and sometimes used to remove iron stains from
vessels (since I have it laying around on hand, ready to use for...whatever).
I've dealt with Fe(OH)3 and Si(OH)4 gels before. I don't recall exactly what produced them. One gel I believe came from a chromate experiment, so
was red from acid dichromate ions. I do recall having a suspension of these things sitting over a glass wool filter, taking weeks to filter some
water. I never waited for it to run colorless. Eventually, the silica gel dried to a hard, deep red translucent solid with conchoidial fracture,
and the iron gel to an opaque drab orange to brown solid.
Tim
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12AX7
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Another day of sitting and it appears the Fe(OH)3 colloid is seperating very slowly. Probably, boiling would help force it into crystallinity.
Slowly, a red solution is appearing above, which should be a solution of Fe(III) ions.
Tim
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