[Jasim]

I wasn't sure where to stick this...

I'm attempting to make some ferrofluid, liquid magnet... I believe the general idea is to suspend magnetite in a liquid.
My problem is I have limited supplies and limited time. This is for a demonstration event.


Things I do have:

• Steel wool
• Iron (III) Chloride
• HCl (ACS)
• Citric Acid (ACS)

...and a variety of general stock chemicals in an organic and analytical laboratory.


I've seen several different recipes online and from what I understand the general procedure goes something like this: Using Fe(II) (substitute steel wool in 1M HCl) and Fe(III) in HCl solution to make magnetite. Can precipitate this with neutralization with ammonia solution.
Stick a group such as oleic acid (going to attempt citric) on the Fe (This step prevents the aggregation of the nanoparticles, other surfactant groups may be usable). Put this in a liquid to carry it, such as tetramethylammonumium hydroxide or kerosene.

I have tetrabutylammonium hydroxide...would this work in place of the tetramethylammonium? Or I have petroleum ether, heptane, toluene...Could I make something in place of the kerosene? Or is there some other alternative?

*** I know I'm getting confused here... I either go the route of addition of oelic (or citric? will that even work?) to make it soluble in kerosene (or similar) OR go the route of using the tetramethylammonium hydroxide (will the butyl work?) to make it soluble in water. ***


Do I have the general idea here? I really don't know what I'm doing...
I have a week to test this out and get a working demo, so if I need to order something, the sooner I know the better. Thank you for any input.


-----

For the precipitation of magnetite out of solution, I have this equation:

2FeCl₃ + FeCl₂ + 8NH₃ + 4H₂O  Fe₃O₄ + 8NH₄Cl

This looks like the easy part... I just need to figure out how to get it suspended in liquid....Meaning I need to figure out how to get the nanoparticles to not aggregate.

[Jasim]

I think one reason I'm having some difficulty, is there are a lot of methods online that produce a 'fake' ferrofluid, it's not really nanoparticles...You can't just dump a bunch of iron fillings into oil and it be a ferrofluid. The event is a child-friendly focus on nanotechnology, so having the real deal is important to me. It's going to remain contained and enclosed, so the safety of the components is not an issue.

[curiouscat]

It's going to remain contained and enclosed, so the safety of the components is not an issue.

Oh to think of the number of industrial accidents  predicated on exactly that assumption not staying true.

Not to deter you though; just as an observation.

I think the trick for you is to have small enough iron particles and plenty of surfactant.

[Jasim]

Well, I got to a dead-end...at least for now... Here is what I did and my observations....

I started by putting some steel wool into a large beaker with concentrated HCl. I stuck it on a stir/hot plate and heated gently with stirring. It took about half an hour or more, but the steel wool dissolved into solution, creating a light lime-green solution. I expect that this contains Iron (II).

I took some Iron (III) Chloride, reagent grade, weighed it out and put it into 1M HCl and mixed well. I took measured volumes of the green prepared solution and the Iron (III) Chloride and combined them into a large Erlenmeyer.

I proceeded to add, dropwise, ammonium hydroxide solution to the mixture. Upon each drop, the solution turned cloudy. I did this with the the flask on a vortexer being gently agitated. The agitation quickly dissipated the reddish-cloudiness seen after each drop addition of ammonium hydroxide.

Periodically, I attempted to test the pH for neutralization using 0-14 pH paper. This was a little difficult as the solution was a dark color from the Iron (III). I continued adding ammonium hydroxide until agitation no longer cause any change in the solution...The resulting solution was a cloudy, reddish-brown color.

I'm very certain I way over titrated as my solution when finished came up with an estimated pH around 10+. I'm concerned this may have been the cause of difficulty in the next step, but am uncertain.

I let the flask sit for a couple of hours. The solution separated. The dark reddish-brown precipitate separated from a clear liquid. The next step I was to carry out involved using a magnet to hold the precipitate in place while I decanted off the liquid...However, upon testing I found the precipitate to not be reactive to magnets. Both the steel wool and the Iron (III) Chloride was magnetic before attempting the synthesis of the magnetite.

I only had very weak magnets sitting around. I attempted to create a stronger magnet by stacking them...this did create a stronger magnetic force, but I can't be sure that the weakness of the magnet isn't to blame for the lack of reactivity from the precipitate. In addition, I fear the glass of the Erlenmeyer is a bit on the thick side.

I have placed an order for a neodymium magnet, rated with a 45-lb pull force. I should be receiving it today, but won't be able to test it until tomorrow.

I'm thinking I need to re-attempt the synthesis, actually using a burette this time and using more care.

Thoughts?

[Sircodekill]

I started by putting some steel wool into a large beaker with concentrated HCl. I stuck it on a stir/hot plate and heated gently with stirring. It took about half an hour or more, but the steel wool dissolved into solution, creating a light lime-green solution. I expect that this contains Iron (II).

I think one of the problems is the synthesis of Fe²⁺.

You attempt to make Fe(II) by reacting Feº with HCl, but this reaction may not stop there, being oxidized to Fe³⁺. If green colour means Fe²⁺, you know the composition but you don't know  anything about the concentration which is important. Maybe you have more Fe³⁺ than Fe²⁺ which explains very low yield.
Try to react it in some stoichiometryc way:

Fe + 2HCl  FeCl₂ + H₂

weight your iron and calculate the moles of acid you need. Maybe you only have Fe₂O₃ which is less magnetic.

[Sophia7X]

I've tried making ferrofluid before, except I didn't use the steel wool method. try iron fillings in HCl.
Something that's really important is to use dilute ammonia solution. Or else the magnetite particles you make will be too big (you want nano particles). Also, the precipitate should be black rather than a red brown, that seems to indicate problem with your iron (like the above poster mentioned). I suspect you have made iron(iii) oxide (reddish brown) since your ppt didn't respond to a magnet, rather than magnetite (Fe3O4) which is black.


Also, during the step where you added ammonium hydroxide, I don't think it matters how much you add, as long as you precipitate all of the Fe ions out. You'll have to boil off the ammonia later

[Jasim]

I abandoned this after making no progress. Here is some other notes...

It is now my belief that I would have obtained much better results had I started with Fe (II) Chloride, like I did with the Fe (III), instead of trying to use steel wool. I believe the steel wool had something else in it, as it was leaving a clear, crystalline precipitate after being digested with HCl.

I eventually attempted to account for the unknown concentration with regards to my prepared Fe (II) solution by adding enough steel wool until no more would be digested. I then considered this to be a saturated solution. I did likewise with my Fe (III) to make a saturated solution...I then combined at a ratio of 1 part Fe (II) solution to two parts Fe (III) solution.

This attempt yielded a more black solution, but I was running out of time and the solution failed to produce a precipitate. I had added a lot of water as a rinse during the procedure, not sure if that was the cause or something else.

After further investigation I agree that you can not over-titrate with ammonium hydroxide, so that is unlikely to be a cause of my difficulties.

I don't feel so bad about my failure, as I consulted with a much more experience nano-chemist regarding this. I was told that the synthesis is actually pretty difficult...something I had already surmised on my own.

Thank you for the input. Any further comments are appreciated.

[Sophia7X]

Haha, yes it is pretty difficult. My ferrofluid ended up flocculating after a week.