So I set out trying to make a large amount of FeCl2 via the reaction:
2FeCl3(aq) + Fe(s) --> 3FeCl2(aq)
I used PCB etching FeCl3, and fine steel wool. After dissolving and letting the steel wool completely react, the solution that resulted was a green
colour with a suspension of carbon particles. After filtering out all the carbon, I boiled off the water in a large evaporating dish, and the solution
changed from green to a dark brown, turning into a paste, and finally a brown-tan powder.
At the very bottom of the dish was a almost red-violet coloured residue underneeth all the dried product, and the rest of the product was varying
between a darker brown to a tan.
So I'm left wondering if I produced FeCl2 anhydrous, or the dihydrate, or if somehow oxygen in the air oxidized it back to Fe(III) and gave a mixture
of iron oxides, hydroxides, and chlorides. Does anyone have any idea of what happened?Polverone - 18-2-2010 at 18:54
Yes, it was oxidized by the air and you were left with a complex mixture of oxides and chlorides. The hydrated salt can be prepared by boiling down
the liquid while it is protected from the air, then letting it cool so crystals form. The anhydrous salt can be formed by passing dry hydrogen
chloride over heated iron or dry hydrogen over heated ferric chloride.aonomus - 18-2-2010 at 19:05
Hm, what about this method for saving the iron product and obtaining actual ferrous chloride:
- Transfer to large beaker, dissolve with HCl, and add more steel wool to reduce, then filter.
- Transfer to round bottom flask and distill under reduced pressure (reduced pressure should remove some of the oxygen, the rest should be displaced
by water and HCl vapour.
Edit: I only propose the above because I have no inert gas source, and additionally CO2 won't work (iron(II)carbonate is even more air sensitive!).
[Edited on 19-2-2010 by aonomus]IPN - 19-2-2010 at 01:27
Boiling the FeCl2 solution down while keeping pieces of iron in the solution should prevent oxidation. The solution should also be a bit acidic.
Any specific need for hydrated FeCl2? As if you only want a source of Fe2+ then preparing ammonium ferrous sulfate is highly recommended as that does
not suffer that bad from air oxidation. aonomus - 19-2-2010 at 05:03
I'm making ferrofluid and I want to create the magnetite particles in-situ instead of trying to buy some sort of magnetite powder and pray. I also
want to experiment with concentrations and amounts of ammonia to add to see if I can get particle size down.blogfast25 - 20-2-2010 at 12:38
There's a few good write-ups on ferrofluids. Here's one that worked for me:
So 2 months ago I started the process to get FeCl2 by using FeSO4 -> FeCO3 -> FeCl2, and then began to dry it in a sealed desiccator, this was
before Christmas. I started to take my other portion of mixed iron oxides, and reduce it all back to Fe(II) again, and decided to take the remaining
liquid from the desiccator and add it to the batch being crystallized. At the bottom of the beaker were 3 medium sized crystals, about sugar cube
size, of FeCl2!
So now I have to wonder, how can I store these big FeCl2 crystals without them oxidizing too much? I don't have any inert gas, so how can I store
these crystals - I pretty much have no intention of ever *using* them having waited 2 months for crystallization. Any thoughts?mr.crow - 26-2-2010 at 19:50
Congrats on the huge crystals! You could coat them with varnish or store them under a non-polar solvent in a little glass tube.aonomus - 26-2-2010 at 22:19
Some eye candy for everyone:
Side view of the crystals, they are still a little wet and drying off in the dessicator
Powdered FeCl2 on the right, FeCl2 crystals on the left, NaOH top left.
Eye candy, isn't it pretty?UnintentionalChaos - 27-2-2010 at 03:43
Ack! No dessicant! Those are hydrated crystals and you're going to ruin the surface! Once the surface is not damp looking, move them to a small,
airtight container with no dessicant to preserve them. They establish the appropriate humidity in there by themselves and then no more water is lost.
Stable temperature is good. Ideally, you have a small dessicator like setup, but use some of the powdered crystals instead of dessicant. Because of
the high surface area, they will absorb or release almost all the water to keep the humidity right, protecting much more from temp changes. As little
air space as possible is the way to go. A little nitrogen before sealing the container wouldn't hurt either.
You'll get better drying of the other solids if they're not packed. I use small glass baking dishes, "fluff" the solid and spread it on the bottom.
When dry, I move them to airtight containers and clean out the baking dishes.
[Edited on 2-27-10 by UnintentionalChaos]
[Edited on 2-27-10 by UnintentionalChaos]aonomus - 27-2-2010 at 06:41
Ah, oops. Well, moving to another container *now*
Edit: Ok, nothing bad happened to the crystals. They did however have a thin layer of FeCl3 that these crystals formed ontop of, so I scraped off the
FeCl3 and in the process, cracked a chunk into 2 smaller ones... oh well.
As for the powdered FeCl2, should I leave it in the desiccator? The desiccant is NaOH prills, so they will also react with HCl vapour.
[Edited on 27-2-2010 by aonomus]Sylis - 11-1-2011 at 19:25
I tried similar (almost exactly the same) instructions.
Though it didn't work out for me.
I'm assuming (since this is my first experiment, and I'm not really all that knowledgeable about chemistry, that I did a few things wrong.
First I added 5ml of Ferric Chloride to the Solution while it was heating instead of the oleic acid, which was just a personal mistake.
But also, I used a stainless steel pot and butane stove (heat source shouldn't be relevant I would think), perhaps the pot created an unwanted side
effect.
All my solution did was come out soupy, I did my best to stir it and mix it together, but with no luck.
Anyone have thoughts?
I'll be trying the experiment again shortly. Just want to know if I should change up how I heat the solution.
Basically all I got was a brown watery looking solution and a layer of brown, what can only be described as, muck at the bottom of the pot. blogfast25 - 12-1-2011 at 06:51
If you dissolve a large enough amount of Fe (I like fine steel wool for that) in hot (and enough), strong HCl and allow to cool you’ll get nice
crystals of FeCl2.4H2O. Mine weren’t as quite as large as that though. Very hard to preserve without at least some surface oxidation. Only Mohr’s
Salt (ammonium ferrous sulphate hydrate) keeps forever (and it makes very nice crystals too but not quite as emerald green as the FeCl2)
[Edited on 12-1-2011 by blogfast25]Arthur Dent - 12-1-2011 at 08:27
If you dissolve a large enough amount of Fe (I like fine steel wool for that) in hot (and enough), strong HCl and allow to cool you’ll get nice
crystals (...)
I recently used the method described above by blogfast25:
And succesfully produced some FeCl2 solution, however since it was for the purpose of creating FeCl3, I simply added a bit of concentrated hydrogen
peroxide and the solution rapidly turned from green to yellowish brown. After decanting and concentrating the liquor a bit, I have an endless supply
of PCB etchant for the cost of a bottle of hardware muriatic acid and some bulldog steel wool pads!
My goal was to avoid buying the factory bottled etchant because they sell it at criminally outrageous prices!
