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Making Fe3O4 from Fe2O3? Answered

Does anybody know how to make Fe3O4 out of Fe2O3? I have a 50g batch of  Fe2O3 and I want to make Fe3O4 (magnetite) so I can make a ferrofluid. Any ideas?


Jack A Lopez

Best Answer 7 years ago

Magnetite contains Fe+3 and Fe+2 ions in the ratio 2:1
Fe3O4 = Fe2O3 + FeO

And the average oxidation state for Fe in magnetite is
(2*(-2) + 1*(-3)) /3 = -7/3 = -2.333

So I don't think you can get Fe3O4 from Fe2O3 just by roasting it in air.  The Fe2O3 has to lose oxygen for this to happen.

Supposedly you can make ferrofluid  by boiling Fe2O3 orange rust in oleic acid, and the reaction that does this is essentially reduction, the oleic acid stealing some of the oxygen atoms from Fe2O3. The following link shows how to make oleic acid from olive oil, and also ferrofluid by boiling orange rust in the resulting oleic acid.

Another way to make magnetite is by co-precipitating it from a solution that contains Fe+3 and Fe+2 ions in the ratio 2:1. And I have seen a recipe for this using iron-3 (ferric) and iron-2 (ferrous) chloride. Don't worry if you've only got the orange iron-3 chloride, you can mix it with steel wool to make the green iron-2 chloride. This is described (in several steps) here:

Jack A Lopezodvratno.zgodan

Answer 7 years ago

There was a pdf I should have linked to, here:

It's the same project as the opensourcenano one linked above, but the pdf has more detail.  From page 3 of that document:

Rust is obtained from rusted steel sources by shaving. Rust powder (1 g) is mixed with 20 g fatty acid mixture (FAM) and placed into the pan. Covered by a lid, the solution is boiled for 2 h, producing a thick smoke. This thick smoke diminishes in time, and the end product is a black gelatinous magnetic material.
The other recipe
used 30 mL of ferric chloride PCB etchant, plus 5 ml of oleic acid.  I'm not sure what that works out to in grams.  There's some "standard" molar concentration for the FeCl3 etchant; i.e. it comes mixed in some amount of water.  Guessing that the 5ml of oleic acid is pure oleic acid, at whatever its density is.

Jack A LopezJack A Lopez

Answer 7 years ago

Oops! I kinda screwed up that calculation for the oxidation state for Fe in magnetite.  First it's positive 3 and positve 2, and second:

(2*(3) + 1*(2)) /3 = 8/3 = 2.666

I'm just sayin': it's less than 3, which is what it is for Fe2O3.


5 years ago

Here is an oddity which I've observed that may have some bearing here.

In the course of my regular work (testing the drop size and spary partterns of atomizing nozzles for an aerospace company) sometimes we work with water instead of jet fuel. The water in Holland MI is very iron rich. We have to filter it lest particles distort our measurments. Some tests call for plain, tap water. Other tests call for deionized. In both cases I use the same type of clear-sided filter cartridge plus. During the course of several days testing, I can observe the plain, white, fine-pore, media filter change color.

Depending on whether or not my test employs a deioinizing thank the filter turns either rust red or black. With plain tap water, invariably the filter turns russet. But if the water has been first deionized, then instead the filter turn black.

Now, it is a fact that deionized water is far more caustic than plain tap water. It will dissolve brass and copper from the pipes in which it runs and plate these metals downstream onto stainless. For this reason we generally avoid to use deionized water. My assumption for the change in color of filter media has always been that it was from reducing hematite somehow into magnetite. But, being no chemist, I cannot state this for certain.


7 years ago

just simply fry it in the air