AJKOER - 31-5-2017 at 12:54
Here is a simple experiment I performed which quickly produced a purple colored solution (opened attached pdf containing a picture). First, I secured
some thick aluminum foil (actually used an aluminum cover from take out food order) which I crunched down in a ball like shape. I then attempted to
filed this mass with an iron file producing a small amount of powder Al along with some scrapping, which undoubtedly where contaminated with Fe. I
added this product to 95% mixing alcohol (ethanol) to which I had previously added rock salt. That is it, with a possible formation of a very small,
but visible, amount of a ferrate salt.
I would argue my experiment is a possible related rediscovery of the original ferrate creation pathway, for in particular, Na2FeO4 (or Na2O.FeO3, a
Fe(VI) salt). Here is some history, to quote from Wikipedia on K2FeO4, link https://en.m.wikipedia.org/wiki/Potassium_ferrate :
"Edmond Frémy (1814 – 1894) later discovered that fusion of potassium hydroxide and iron(III) oxide in air produced a compound that was soluble in
water. The composition corresponded to that of potassium manganate. In the laboratory, K2FeO4 is prepared by oxidizing an alkaline solution of an
iron(III) salt with concentrated chlorine bleach.[1]"
My supposition is that the above path proceeds electrochemically with the likely creation of a battery cell (think iron-air battery) formed in the
presence of moisture and either a O2 or OH- reaction with the likes of Fe, FeO or Fe2O3.H2O .
My experiment may proceed also electrochemically via an Aluminium–Iron couple. For example, here is a recent article: "Galvanic Corrosion of the
Aluminium–Copper Couple in Uninhibited Aqueous Solutions of Glycols", by M. Tadjamoli, M. Tzinmann & C. Fiaud, Pages 36-40, 1984 and republished
online 20 Nov 2013, http://dx.doi.org/10.1179/000705984798273542 .
My rough take on the underlying chemistry in my experiment, first the anodic half cell reaction from the electric current created by an Aluminum/Iron
galvanic couple creating some solvated electrons in the ethanol mix further reacting as follows:
H2O + e- → OH- + .H
[ Note, as .H + .H → H2, this is akin to the reported half cell reaction: 2H2O(l) + 2e- → H2(g) + 2OH- with E= -0.42 V ]
Followed by, in one scenario, the reaction of .H with O2 creating the oxidizing hydroperoxyl radical:
•H + O2 → HO2 = H+ + O2•−
Finally, my suggested speculation on the formation of Na2FeO4 itself:
2 Na+ + 2 OH- + Fe(lll) + 2 (H+ + •O2-) → 2 H2O + Na2O.FeO3 + 3 e-
Note, I am just suggesting a product and pathway consistent with the observed colored solution. In any event, it is most likely not an efficient path
to sizable quantities of a ferrate salt.
Attachment: picb.pdf (2.4MB)
This file has been downloaded 241 times
AJKOER - 7-6-2017 at 07:56
OK, I have not been able to reproduce the above results.
Suspect that my metal file was contaminated with copper from using it to previously produce some copper powder. This means that the blue compound
could be a cuprate. With time, the aluminum replaces it with a lose of color in the solution.
Apparently, creating ferrate here was indeed too good to be true and I apologize for the possible contamination error.
There is at least one lesson here!
[Edited on 7-6-2017 by AJKOER]