Sciencemadness Discussion Board


Saerynide - 4-7-2004 at 21:11

How do you make Fe3O4?

A Google search yeilds zippo, and the board has discussed many ways to make Fe2O3, but Fe3O4 seems be all have been made by accident. Does anyone have a sure fire way to make it? :o

The_Davster - 4-7-2004 at 22:32

I think I have made Fe3O4. I was trying to make Fe2O3 but I obtained a black powder instead of a rust one. I simply placed a piece of steel wool half submerged in water and waited several weeks. This was done a while ago so I probally have forgotten details.

guy - 4-7-2004 at 23:38

In my chemistry dictionary, it says that FeO decomposes to Fe and Fe3O4 below 570 C.

darkflame89 - 5-7-2004 at 02:14

Isn't that magnetite?

Saerynide - 5-7-2004 at 02:18


sanity gone - 5-7-2004 at 08:49

Try bruning dry steel wool in air and see if that results in the magnetite.

I am a fish - 5-7-2004 at 10:38

You really need to find a pottery supplier. Are you absolutely certain there are none where you live?

Fe3O4 is produced by digging it out of the ground. The reason you can't find methods of synthesising it, is probably due to the fact that there is no need to.

Cyrus - 5-7-2004 at 21:46

I read some method on the internet where small pieces of steel wool were shoved into a copper pipe taped to a vacuum cleaner-reversed? Because of the extra air flow, the steel wool will burn better. You could try burning steel wool or maybe even steel turnings
in a pure O2 atmosphere, this one is really fun, but it makes fumes.
Get the O2 any way you want, I like 2H2O2 --MnO2 --> 2H2O + O2.

Honestly, none of these methods are very practical though. You have got to find a pottery supplier in your area or online.

sanity gone - 5-7-2004 at 22:41

I don't think you need a pure O2 atmosphere. I'm pretty sure you make rust by oxidation in water, you make magneite by oxidation in air... but I could be wrong.

DirtyDan - 6-7-2004 at 06:56

Ive seen tons of info of obtaining Fe2O3 and Fe3O4 from electralysis, tried it to the product just depends on the voltage/amperage if i remember right although i have no specifics for you. Just get a ~10v ~5a power supply, some water (salt? or does that contaminate it?) and a nail. When i did it it made a greenish brownish slurry, once filtered and dried it turned brown on the filter and black as a powder.

unionised - 6-7-2004 at 14:51

What do you get if you
mix FeCl3 solution with FeSO4 solution (in the right proportions);
add NaOH;
filter off the precipitated mixed Fe(III) and Fe(II) oxides/ hydroxides and
heat the stuff to drive off water?

guy - 6-7-2004 at 16:24

Nevermind. It just looked like it because the Hydrogen peroxide oxidezed the remaining Fe+2 ions to Fe+3 and it turned dark red.

[Edited on 7-7-2004 by guy]

Theoretic - 13-9-2004 at 09:49

I once took a gob of fine steel wool and put a burning match to it. Then I blew hard, and a kind of glowing "combustion" area appeared and spread. It was like a burning area spreading on a large chunk of charcoal. You had to blow all the time, but it looked very nice, and I was left with black stuff I'm sure is Fe3O4.

Esplosivo - 13-9-2004 at 10:23

The reaction quoted below was found in my 'collection' and I don't know from where I got it. I was going to use this reaction to produce Fe3O4 for a chlorate cell next summer. Anyway here it is:


Procedure for preparation of magnetite

Fe2+ + OH- + NO3 --> Fe3O4 + NH3 + H2O

Dissolve 6.95g of Ferrous sulfate in 100 mL of water. In another container dissolve 0.018g sodium nitrate and 3.75g potassium hydroxide in 50 mL of water. Each solution is heated to about 75degC and the two solutions are mixed with vigorous stirring. A thick gelatinous green precipitate forms. After being stirred at 90 to 100 degC for 10 min, the precipitate turns to a finely divided dense black substance. The mixture is cooled to room temperature and is made acidic with a little 6M HCl. The precipitated magnetite is centrifuged or filtered on a medium or fine porosity sintered glass filter and washed with water until the wash water gives no test for sulfate with barium chloride. The product is dried at 110 degC for 1 or 2 hours. The yield is about 1.75 g of magnetite.

Quite a low yield but the product should be pure.

Edit: On reading unionised post again I've noticed that such a reaction could lead to the formation of Fe3O4, since Fe3O4 is actually a mixture - FeO.Fe2O3 . Instead of NaOH as a base I would used some milder bases, such as NH3(aq). With strong bases the formation of ferrates could result in loss in yield. Correct me if I'm wrong, this is just a guess.

[Edited on 13-9-2004 by Esplosivo]

guy - 13-9-2004 at 20:16

I don't know for sure but you could take wo pieces of steel wool and attach to a battery and touch it together for a short time. It will glow and burn and have Fe3O4.

BrAiNFeVeR - 13-9-2004 at 22:58

I'm very interested in this product too.
I made it by accident some time ago while producing FeSO4 by Fe + H2SO4.
It appeared to be a by-product at a certain pH / temperature, because I only got about 0.5 grams of it.

I have it in a vial with parafin oil and it's extremely fun to play with when a strong magnet is near :)
It's cool to actually see the magnetic field in full 3D.

Esplosivo - 14-9-2004 at 06:11

Originally posted by BrAiNFeVeR
I'm very interested in this product too.
I made it by accident some time ago while producing FeSO4 by Fe + H2SO4.
It appeared to be a by-product at a certain pH / temperature, because I only got about 0.5 grams of it.

What was the concentration of the acid you used? I cannot immagine any possible way in which Fe3O4 could have formed by such a rxn. Could it be that your Fe was already contaminated?

Edit: Yesterday I set up a simple electrolysis setup, using an iron anode and a graphite cathode. As the electrolyte I used a solution of NaCl. The set up was run for >24hrs using a car battery charger as a power supply. A brown-black precipitate was present which seems Fe3O4. The pic I have taken do not show the real colour of the precipitate. I'll try testing the ppt later on. If this works out then the Fe3O4 required for a chlorate cell can easily be produced.

[Edited on 14-9-2004 by Esplosivo]

guy - 14-9-2004 at 15:49

How could that cell produce Fe3O4?

Wouldn't it make FeCl2 and NaOH which would react to form Fe(OH)2?

The black precipitate could be iron errosion which is both magnetic.

Esplosivo - 14-9-2004 at 21:37

Actually the NaCl soln was very dilute, just to increase the conductivity that's all. And from the amount of ppt collected it is actually impossible to be erosion, quite a lot of ppt was formed. The solution is colourless, completely. Therefore there are no iron salts in there.

I've also 'tested' the solution by adding dilute NaOH. A cloudy soln resulted which was not thick, therefore showing only a low conc of iron salts.

markgollum - 15-9-2004 at 15:14

Way back, when I was experimenting with thermit, I made Fe2O3 by electrolysis of salt water with an iron anode as you describe. The ppt you describe is Fe(OH)3 (grey 'cloudy' suspension, to black sludge, depending on concentration) and it IS formed by erosion of the Fe anode. Fe(OH)3 dehydrates easily to Fe2O3 (red) in the oven.

Useful for H2 as well...

Al Koholic - 18-9-2004 at 05:24

This method hasn't been mentioned yet unfortunately. By packing a pyrex tube full of steel wool and leading steam through the tube one can prepare Fe3O4. Simply heat the pyrex tube with a bunsen burner while the steam is passing through to accelerate the reaction of H2O with Fe.

Hydrogen can then be passed through whatever cleaning situation you have in mind or simply vented off at a safe distance from the flame.

3Fe + 4H2O(g) + heat --> Fe3O4 + 4H2(g)

The process also works with Mg to produce MgO and H2.

Mg + H2O(g) + heat --> MgO + H2(g) just as an interesting side note.

This would be extremely simple.

mick - 18-9-2004 at 09:02

I have got to be wrong here but I will mention it having done a bit of welding and own an old car.
If you strip some old thick rusty metal down you go through all the layers of paint, iron 2 and 3 oxides. When you get to what looks like metal if you start taping it with a welding hammer then stuff will start breaking up from the pitting in the iron and it is magnetic. I thought it was Fe3O4 which is very stable and fairly strong, as long as not too much oxygen and water can get to it, other wise you end up with an electrolytic cell across it to the iron underneath.
If you clean that stuff of and do not seal the iron properly it will rust faster than anything
If you have got an old iron structure that has been regularly painted there should be a layer of Fe3O4 next to the iron

I clean every thing else off now but leave what I think is Fe3O4 and just put a few coats of good quality paint, from the primer up and cover the thing in waxy stuff.

I think the electrolytic cell only happens when there are lower oxidation levels of iron around.

[Edited on 18-9-2004 by mick]

[Edited on 18-9-2004 by mick]

elementcollector1 - 22-11-2013 at 18:34

Quote: Originally posted by Amos Backstrom  
Fe3O4 can be made by passing H2O (g) over hot Fe. ;)

Red-hot, finely powdered Fe, that is. Not something one can do on the hotplate.

blogfast25 - 23-11-2013 at 07:30

Simplest way BY FAR:

Prepare solution of a ferric salt. Split it into two parts, one of two parts (by volume), one of one part (by volume).

To the one part, add some steel wool. The steel wool reduces the Fe(III) to Fe(II):

Fe(III) + Fe === > 2 Fe(II). Filter off the steel wool. This solution will now be green.

To it, add the two parts of Fe(III) solution. Now you have Fe(II) and Fe(III) in the right ratio.

Precipitate the Magnetite with ammonia. It's a black precipitate and definitely responds to strong magnets (Nd, e.g.)

This is how magnetite for ferrofluids is prepared, usually starting from PCB etchant solution.

[Edited on 23-11-2013 by blogfast25]

AJKOER - 24-12-2013 at 20:25

Here is one of the lower temperature paths, to quote from on Triferric tetroxide, Fe3O4 (link: ):

"ferric oxide is heated to 400° C. in a current of hydrogen saturated with water vapour at 30° to 50° C. At higher temperatures products increasingly rich in ferrous oxide are obtained."

I would avoid an excess of H2 due to the following possible reaction (temperature not specified):

Fe3O4 + 4 H2 ---> 3 Fe + 4 H2O (see )

Other interestingly comments from include:

"According to Moissan, magnetic oxide of iron exists in two polymorphic forms, according to its method of preparation. The one form, obtained by high temperature methods, such as the combustion of iron in oxygen, the action of steam on iron at red heat, and the calcination of ferric oxide at bright red heat, is characterised by its insolubility in concentrated boiling nitric acid, by its high density (5 to 5.09), and by its resistance to further oxidation when heated in air.

The second variety resembles the former in its black appearance and magnetic properties, but differs from it in density (4.86), in its solubility in nitric acid, and in its tendency to oxidise to ferric oxide when calcined in air. It is converted into the other variety when raised to white heat in nitrogen. As explained in the case of ferrous oxide, however, these differences may simply be due to variations in the states of aggregation of the oxide, according to its method of preparation."

[Edited on 25-12-2013 by AJKOER]

Zyklon-A - 25-12-2013 at 12:17

Here are some ways to make Fe3O4:
C6H5NO2 + 3 Fe + 2 H2O → C6H5NH2 + Fe3O4.

3Fe2O3 + H2 → 2Fe3O4 +H2O.

3Fe2O3 + CO → 2Fe3O4 + CO2, however with that last one, there's also this: Fe3O4 + 4CO → 3Fe + 4CO2. So, if you use to much CO you'll end up with metallic iron, (I think that reaction happens only at very high temps).

[Edited on 25-12-2013 by Zyklonb]

Zyklon-A - 25-12-2013 at 12:24

Quote: Originally posted by I am a fish  
You really need to find a pottery supplier. Are you absolutely certain there are none where you live?

Fe3O4 is produced by digging it out of the ground. The reason you can't find methods of synthesising it, is probably due to the fact that there is no need to.

Fe3O4 is so cheap that it is used in the production of Fe2O3: 2Fe3O4 + ½ O2 → 3(α-Fe2O3)

Boron Trioxide - 3-1-2014 at 14:19

I have tried making Fe3O4 by the method described in this pdf, iron (II) sulfate is heated then reacted with a mixture of potassium nitrate and sodium hydroxide.
This is supposed to convert the iron sulfate to green iron (II) hydroxide that would be then oxidized to Fe3O4.

However when trying this myself the mixed solution turns the color of tea and then slowly precipitates Fe2O3, any ideas on what I did wrong.
Note: I used a solution of iron sulfate produced by reacting copper sulfate with iron. This produced a nice green solution, also the hydroxide was in solution and was produced through the electrolysis of sodium chloride, its pH was checked to be around pH 13-14.

Sorry I didn't think to take any pictures of the reaction.
Also I did this reaction a few days ago, and when I rechecked the pH on my sodium hydroxide it was neutral after being stored in glass for a day any idea why?

If anyone else succeeds with this method let us know.

IMG_0774.JPG - 78kB

Attachment: magnetite_Synthesis.pdf (124kB)
This file has been downloaded 738 times

Zyklon-A - 3-1-2014 at 14:39

NaOH(aq) with only 13-14 Ph is not very much NaOH in solution, did you use a salt bridge to make it from NaCl? Otherwise it will have the Cl- ion which may be responsible for the green color, I don't know why it made Fe2O3, maybe because there was not an adequate amount of NaOH? Find out how pure your NaOH is, I tried to make NaOH that way, and I could never get it to work right.
Edit: It is no longer high PH because ferrous sulfate is the product of ferrous hydroxide and sulfuric acid.
Ferrous hydroxide is a weak base, and sulfuric acid is a strong acid, so you would expect ferrous sulfate to be acidic.

[Edited on 3-1-2014 by Zyklonb]

Boron Trioxide - 3-1-2014 at 15:02

That is a good point, I didn't use a salt bridge to produce the NaOH, I had thought the excess Cl ions wouldn't effect it. I will try again when I am able and will use a salt bridge.

By the way I should have specified the picture I posted was of the Fe(II)SO4 in solution. I also have a more concentrated solution of this though it is more of a yellowish color more representing the pdf's pictures.

[Edited on 3-1-2014 by Boron Trioxide]

Make a salt bridge.

Zyklon-A - 3-1-2014 at 15:12

Make a simple salt bridge.

It says use KNO3, but if you don't have any, NaCl will also work. (Although not as well.)

[Edited on 3-1-2014 by Zyklonb]

Zyklon-A - 3-1-2014 at 16:51

I copied this exactly and it worked except, I couldn't get a power supply that worked well enough to be effective.
Be careful as chlorine gas is given off, however it won't get so bad that you'll be poisoned, if you can't smell it you'er fine, if you can, just put it outside and don't inhale it.

[Edited on 4-1-2014 by Zyklonb]