Sciencemadness Discussion Board

Preparation of Ferrate solution.

moonfisher - 23-3-2016 at 14:45

Iron is almost always on the cationic part of the ionic substance. However, using strong oxidants, Iron can be brought into the VI oxidation state, [FeO₄]2− Rather easily, despite being the strong known water-stable oxidizer.

Woelen posed a very fun experiment involving this, but that involves such scarce things like "equipment" and "clean reagents".

So, I present you: The Half-assed Synthesis of the Ferrate Anion!
This is as OTC as I can make it. Making Iron acetate via peroxide and cleaning vinegar raises it's own issues- as Ferrate is stable only in alkaline conditions.

Materials:
1- Lye
2- Bleach
3- Iron Nails
4- Some Wire
5- Batteries, 9V
6- Borax
7- Isopropyl Achohol
8- A Matchbox
9- 2 ceramic containers, one much smaller than the other
10- Glass container, for admiring
11- Water

Iron (III) Hydroxide via electrolysis
Attach the 9V batteries into a series, then wire the screws to opposite terminals of the series
Produce a saturated solution of borax and water. Borax seems to prevent formation of iron (II) hydroxide, as well as not releasing toxic Cl gas or something. Baking soda should work, but borax is usually closer to the bleach any way whatevs.
Stick the nails into the solution, leave for a long while. A heavy foamy orange precipitate will result. Be aware that H2 gas is evolved.
Pour off excess electrolytic fluid.

Ferrate precursor solution
Pour the hydroxide suspension into the small ceramic container. Add a little lye. Pour enough bleach to dissolve the lye, and then some more- completely submerging the hydroxide. DO NOT DRINK THIS!

Place the ceramic container into another ceramic container. Pour a 1/2 cm layer of isopropyl alcohol into the outer one, then ignite. Do not place face into fire. Leave until the isopropyl burns off, and the container cools enough to be handled

Pour the corrosive, extremely oxidizing, toxic, but porple into a glass container to admire. It has a distinct, light purple-grey tint, especially under light. The yield is pitiful, pathetic really but you just made the world's most potent oxidizer practically by accident!

moonfisher - 23-3-2016 at 14:47

Forgot to add the reaction:


2 Fe(OH)3 + 3 OCl− + 4 OH− → 2 [FeO4]2− + 5 H2O + 3 Cl−


[Edited on 23-3-2016 by moonfisher]

ave369 - 23-3-2016 at 21:59

A little question: what is the isopropyl flame for? Ferrate synthesis via the hypochlorite method proceeds better in ice-cold temperatures. Heat is ferrate's worst enemy. If you want a little heat, you can simply put some dry KOH into the solution, but it's a common mistake!

Try to do this without heat. The yield will be better, and the purple color more pronounced.

Also you can try to crystallize the ferrate by displacing it from the solution by adding a saturated solution of KOH. Or precipitate barium ferrate.


Another tip: iron hydroxide can be whipped up real fast through concentrated nitric acid. You need nitric acid of ~60-70% concentration, it eats through iron nails amazingly fast (caution, NO2!). After NO2 stops to evolve, add alkali, and you will have a solution of NaNO3 and a thick, voluminous, chokolate-like precipitate of Fe(OH)3.

moonfisher - 24-3-2016 at 05:07

Quote: Originally posted by ave369  
A little question: what is the isopropyl flame for? Ferrate synthesis via the hypochlorite method proceeds better in ice-cold temperatures. Heat is ferrate's worst enemy. If you want a little heat, you can simply put some dry KOH into the solution, but it's a common mistake!

Try to do this without heat. The yield will be better, and the purple color more pronounced.

Also you can try to crystallize the ferrate by displacing it from the solution by adding a saturated solution of KOH. Or precipitate barium ferrate.


Another tip: iron hydroxide can be whipped up real fast through concentrated nitric acid. You need nitric acid of ~60-70% concentration, it eats through iron nails amazingly fast (caution, NO2!). After NO2 stops to evolve, add alkali, and you will have a solution of NaNO3 and a thick, voluminous, chokolate-like precipitate of Fe(OH)3.


Thanks for the nitric acid method of producing iron III hydroxide, but the point of this was to be as simplistic as possible. I could try boiling down the bleach, then chilling it, then pouring it into the hydroxide. The boiling was because Ferrate would not form at 25C and heat makes the hypochlorite in the bleach a-working. I'll post an update once I get home.

I didn't try precipitation of the Ferrate!

[Edited on 24-3-2016 by moonfisher]

ave369 - 24-3-2016 at 23:02

Do not boil down the bleach! It disproportionates when hot, producing chlorate and chloride, which are useless for ferrate synthesis!

You should make strong bleach yourself, by electrolyzing a cold alkaline chloride solution with good cooling of the cell. Preferably it should be potassium bleach.

And NO heating at any point of the synthesis! The hypochlorite works well even when ice-cold! The reaction proceeds slower, you need patience for the Fe(OH)3 to dissolve, and a lot of stirring. But you do not lose any product to "The Fizz" (decomposition with evolution of oxygen, which yields Fe(OH)3 - essentially, decomposition of hypochlorite catalyzed by Fe(OH)3). "The Fizz", the scourge of ferrate synthesis, dramatically decreases yield.



[Edited on 25-3-2016 by ave369]