Making Fe3O4/Magnetite: Tips & Suggestions

[mrizzo29]

I know that this has already been a topic of discussion in another forum a few years ago, but I've been having some trouble and I thought that I would make a new forum.

I've tried multiple ways of making it, yet nothing seems to work for me.

I've tried dissolving steel wool in hydrochloric acid to give me FeCl2 then adding etching solution (FeCl3) and NaOH which should precipitate out the Fe3O4, but all it gives me is a reddish/brown solution with a lot of mushy gunk in it. I tried filtering this then putting a magnet next to it, but it did nothing.
I think this is the equation for this reaction
FeCl2 + 2FeCl3 + 8NaOH --> Fe3O4 + 8NaCl + 4H2O

Another way I tried was dissolving some steel wool in the etching solution which should have given me FeCl2 then mixing that in a 1:2 ratio with more etching solution and adding ammonia to that. I got the same reddish/brown stuff.
the equation for this one i think is
FeCl2 + 2FeCl3 + 8NH3 + 4H2O --> Fe3O4 + 8NH4Cl

any suggestions?

 

[Borek]

I suppose you need to precisely control concentrations and conditions - pH, temperature, agitation. Otherwise Fe(OH)₃ seems to be most likely product.

 

[mrizzo29]

I think I read somewhere that if the solution is too basic, it will yield ferrihydrite not Fe₃O₄. I only wish I could find something that said at what pH it must be at to form the magnetite.

 

[mrizzo29]

here i think it says that the pH should be 7.

http://answers.yahoo.com/question/i...bq1a6DYjzKIX;_ylv=3?qid=20080327034534AA13OJK

if not it forms ferrihydrite which is what I think I got.

 

[Borek]

Try these:

http://www.google.com/search?q=Massart+method+magnetite

 

[mrizzo29]

ok thanks. btw what is the Massart Method? I've tried finding what it was, but my search yielded no results.

 

[Borek]

I think it was published in 1981, that's all I know. I suppose you should be able to find a reference in the articles googled.

 

[mrjeffy321]

I used to make Fe3O4 too (as a matter of fact, I even made a thread about it on this forum to discuss it….back when such things were not so demonized).

The way I made it was….

Prepare an Fe+2 / Fe+3 (aq) solution in a 1 : 2 mole ratio.
One may do this by dissolving some steel wool in Hydrochloride acid to make Iron(II) Chloride. Iron(III) Chloride may be obtained was PCB board etchant (which is, or used to be, sold at Ratio shack and Fry’s electronics stores).

Precipitate out the (hydroxide /) oxide by adding Sodium Hydroxide to the Fe+2/Fe+3 solution. I would add solid NaOH to the Iron solution (carefully of course), since I do not think that NaOH (aq) worked as well…having to due with the heat of dissolution perhaps. I have had success using NH4OH solutions to cause the precipitation.

As I recall, after doing the above, I obtained a black, magnetic precipitate. Filter it, and allow it to dry. One can even dry it in an oven to make sure to convert any Iron Hydroxide into Iron Oxide on the process.

 

[mrizzo29]

thanks. just one more quick question, do you think adding sodium bicarbonate would work in substitution for the solid NaOH? I have a high concentrated solution of NaOH but not the crystals (though I guess I could boil off the water to get them).

 

[Borek]

thanks. just one more quick question, do you think adding sodium bicarbonate would work in substitution for the solid NaOH?

Doubtfull. Not so high pH and you are adding other anion that can precipitate with iron.

I have a high concentrated solution of NaOH but not the crystals (though I guess I could boil off the water to get them).

Beware! Heating this solution can be dangerous, it has very high boiling point and is very corrosive. Main problem is that it may splatter everything around, that's the way it behaves.

 

[mrizzo29]

mrjeffy321,

how much of each reactant did you use? I know the 1:2 ration of FeCl2:FeCl3 but what was the molarity of them and the ammonia you used (I don't have any NaOH crystals handy)? because I think one of the problems that went wrong with my trials was that the solution was too basic yielding ferrihydrite instead of magnetite.

 

[mrjeffy321]

I did this several years ago, so I am recalling all this from memory.

I do not remember the concentrations of the Iron solutions, but perhaps they might have been on the order of a few molar.

The ammonia I used was the standard stuff one would buy as a cleaning solution (but without soap additives), so it was fairly dilute, perhaps around 5%, or less, by weight. I never was successful in my few attempts using NH4OH, though.

Solid Sodium Hydroxide may be obtained in the form of solid drain cleaner crystals (the classic example would be “Red Devil Lye”, which is now impossible to find in stores, but Drain-O also contains solid NaOH along with a lot of other junk). Other, liquid, drain-cleaners might also work as a substitute since they would be very concentrated NaOH solutions (with other stuff mixed in); just make sure it is the NaOH drain cleaner, not the liquid H2SO4 type drain cleaners.

I think I added NaOH well in excess of what was required to precipitate out all the Iron. Any excess NaOH will just stay in solution; adding too much should not hurt.



I would not advise trying to boil down NaOH solutions to dryness to obtain solid NaOH. Aside from the potential hazards associated with boiling concentrated NaOH solutions, the solution can also be quite corrosive / damaging to several types of containers (such as glass) which one might want to use for the process.

 

[mrizzo29]

ok thanks. I'll post how it goes once I find the time to try it again.

 

[mrizzo29]

alright I got it to work with ammonia. After initially adding some ammonia to iron (II/II) chloride solution, it turned the weird reddish/brown color, then I added more until it turned black. after it settled on the bottom I tried to see if it moved with a magnet and it did. thanks for all the help