Sciencemadness Discussion Board

Ferric Chloride and Sodium Metabisulfite

Eric Slighton - 9-6-2016 at 22:47

I was trying to make magnetite (Fe3O4) from Ferric Chloride Fe(iii)Cl.

Reaction with a base (NaOH) produces a slow-settling mud that looks like red rust (Fe2O3), but from web search is probably FeO(OH), or Iron(iii) oxide-hydroxide.

Thinking that Iron(ii) would get me what I wanted, I added a solution of Sodium Metabisulfite. The product is a faster settling black grain that looks like Magnetite, but from reading I am guessing that it is some kind of oxide-hydroxide as well...

Is there any way to figure out what this is?

myristicinaldehyde - 10-6-2016 at 04:16

Well, is it magnetic?

morsagh - 10-6-2016 at 06:00

Easy way to produce Fe(OH)2 is to react your Fe3+ solution with ascorbic acid and than add NaOH... but be careful when filltring, iron(II) hydroxide oxidise very fast

blogfast25 - 10-6-2016 at 06:18
Quote:
Pour 10 ml of PCB etchant and 10 ml of distilled water in a glass cup.

Add a piece of steel wool to the solution. Mix the liquid until you get a color change. The solution should become bright green (green is the FeCl2).

Filter the liquid through filter paper or a coffee filter. Keep the liquid; discard the filter.

Precipitate the magnetite out of the solution. Add 20 ml of PCB etchant (FeCl3) to the green solution (FeCl2). If you are using stock solutions of ferric and ferrous chloride, keep in mind FeCl3 and FeCl2 react in a 2:1 ratio.

Stir in 150 ml of ammonia. The magnetite, Fe3O4, will fall out of solution. This is the product you want to collect.


http://chemistry.about.com/od/demonstrationsexperiments/ss/l...

DraconicAcid - 10-6-2016 at 07:40

Doesn't heating the muddy iron(III) hydroxide cause it to convert to magnetite?

Eric Slighton - 10-6-2016 at 23:17

Yes it is magnetic. I think it is FeO.

AJKOER - 19-6-2016 at 05:58

First, an electrochemical based preparation, referred to by the cited reference as a corrosion reaction, that proceeds spontaneously over time in the presence of a NaCl electrolyte, so one could claim it to be an iron/water (absence oxygen) battery cell. Interestingly, one can fairly quickly visibly produce Fe3O4 as a black solid coating (see my attached picture) for the construction of a magnetite electrode, by first boiling iron in distilled water (previously recently boiled to remove oxygen) in a microwave for 30 seconds containing some sea salt with a plastic wrap to seal off oxygen and after 5 minutes, reheating in the microwave for 30 seconds (see photo, some 7 hours into the reaction). To quote Wikipedia, https://en.m.wikipedia.org/wiki/Schikorr_reaction :

"Anaerobic corrosion of metallic iron to give iron(II) hydroxide and hydrogen:

3 (Fe + 2 H2O → Fe(OH)2 + H2)

followed by the Schikorr reaction:

3 Fe(OH)2 → Fe3O4 + 2 H2O + H2

give the following global reaction:

3 Fe + 6 H2O → Fe3O4 + 2 H2O + 4 H2
3 Fe + 4 H2O → Fe3O4 + 4 H2 "

Per another source, "Corrosion of carbon steel under sequential aerobic–anaerobic environmental conditions", link: https://www.google.com/url?sa=t&source=web&rct=j&... , the half reactions are given as:

Reduction of water: 2 H2O + 2 e- → H2 + 2 OH-
Oxidation of iron: Fe + 2 OH- → Fe(OH)2 + 2 e-

followed by the Schikorr reaction as detailed above. Note, sea salt, in my opinion, provides an excellent electrolyte which accelerates the electrochemical half reactions. To quote a source https://www.google.com/url?sa=t&source=web&rct=j&... :

"A laboratory simulation study of the impact of pH and chloride content on the corrosion of cast iron and mild steel was conducted. There was a linear relationship between the corrosion rate of cast iron and the log of chloride ion concentration in the pH range 7.8< pH >5.5 with only a small pH effect noted for the given range of conditions. Studies on a 19th century mild steel sample indicated that the corrosion rate was linearly dependent on the square root of the chloride ion concentration and the corrosion rate fell in a linear fashion as the pH was increased to strongly alkaline solutions of sodium hydroxide. "

I further suspect that the combination of using a microwave (particularly kinetically active on iron rapidly raising the solution's temperature to boiling, source of radicals,..) and the minerals/impurities in sea salt itself (ranging from bacteria to sulfates, iodides..), may contribute to the reaction speed as well as the normal expectation at RT is otherwise slow.

[Edit] One may be able to apply mechanical abrasion to the surface of the iron (best as a metal sheet) to remove FeO.H2O that could further lead (via a Schikorr reaction) to Fe3O4 as a powder. This would parallel a recent citation on a published article I made at http://www.sciencemadness.org/talk/viewthread.php?tid=52&... on buffing a Pb electrode.
-----------------------------

In a non-electrical purview, Fe3O4, Magnetite, is after all Fe(II,III) oxide, FeO.Fe2O3, a mixed salt!

In this regard, here is a previously cited preparation courtesy of Esplosivo that highlights the general technique involved in a mixed salt prep wich generally requires attention to concentration, temperature and stirring speed.
Quote: Originally posted by Esplosivo  
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:

Quote:

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 75 degC 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]


Link: http://www.sciencemadness.org/talk/viewthread.php?tid=2262

Some of my prior comments, same thread:
Quote: Originally posted by AJKOER  
Here is one of the lower temperature paths, to quote from Atomisty.com on Triferric tetroxide, Fe3O4 (link: http://iron.atomistry.com/triferric_tetroxide.html ):
"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 http://bse.sci-lib.com/article005843.html )

Other interestingly comments from Atomistry.com 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]


Finally, Magnetite, FeO.Fe2O3, is more precisely paramagnetite. To quote Franklyn on this forum on the topic of magnetism:

"I'm by no means expert in the field, it is highly specialized and the
subject of an endless presentation of papers in physics journals.
There are a few variations on the theme of permanent magnetism
all of it related to the physical structure and atomic organization of
the materials involved. Most any textbook on the subject will explain
at length the differences. Basically there is ferro magnetism, para
magnetism, ferrimagnetism, anti-ferri magnetism, diamagnetism, and
a host of effects manifesting aspects of these alone or in combination."

Link: http://www.sciencemadness.org/talk/viewthread.php?tid=5389#p...

[Edited on 19-6-2016 by AJKOER]

20150621_165253_resized.jpg-thumb.jpg - 6kB

[Edited on 19-6-2016 by AJKOER]