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Homemade Ferrofluid

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Nik

Mon Mar 27 2006, 07:26AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

"stuck a magnet at each end to keep the magnet inside moving"
"The result is a system that turns random motion into electricity"

Those lines are the ones that strike me as not quite science. If some one has a diagram it might clear things up a bit.

ragnar

Mon Mar 27 2006, 08:18AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

I think the implication is that the magnet at each end of the tube is oriented so its poles are alike to the mobile one in between.

--------           ---------            ---------
|N......S|  ====   |S.......N|   ====   |N.......S|
 --------           ---------            ---------

Random motion causes magnet in the middle to start gliding on its little ferrofluid blob to one or other end of the tube. "Boink" - since like poles repel, the magnet is returned in the other direction. Induced currents / Lenz's law / magnetic braking, whichever way you want to say it, charges up the capacitor and also slows down the movement of the magnet. "Boink."

Chris

Mon Mar 27 2006, 01:21PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Wow, and none of that has anything to do with the process of making ferrofluid at home, which is what this thread is about. Let's keep on topic and see if anyone has anything more to add which is productive to this thread.

Part Scavenger

Tue Mar 28 2006, 05:13AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

That's great heidi! I'm back from out of town, and I have the rest of the week off (sort of)! Yea! I'll make a batch this week while I'm finishing my DRSSTC. HV and ferrofluid!

Part Scavenger

Fri Mar 31 2006, 02:35PM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

I tried it again last night. I was able to make a beautiful batch of magnetite, but the oleic acid thing didn't work.

A was afraid at first becuase it was doing that red mud thing again even though I was adding ammonia slowly. So, looking at Heidi's previous post, I thought I might add more. About 80mL's later, the red completely went away and all I had was magnetite which was extremely responsive to a magnet. After evaporating all the ammonia out, which took about 40 min, I added my *oleic acid* It didn't work right at all. I guess I'll just have to get some as I have no way of knowing whether or not I actually got oleic or not. I tried both ways, BC's soapmaking, and the stuff I've had sitting on the counter for a month. Neither seemed to work.

BTW, why *near boiling*? Why not just boil it?

Heiders

Fri Mar 31 2006, 02:45PM

Registered Member #268 Joined: Tue Feb 28 2006, 02:44AM
Location: Ontario, Canada
Posts: 48

Aren't you supposed to add the oleic before or during the first couple minutes of cooking? I have been... What happens (according to Andrew) is the oleic reacts with the ammonia to form ammonium oleate, which breaks down in the heat, the ammonium leaves the solution as a gas and the oleate ion (which you want) is left in solution. Eventually the oleate is reconverted to oleic acid and surrounds the magnetite particles.

It is the oleic that dissolves in the kerosene, not the magnetite. Both are insuluble in water, but oleic is soluble in kerosene, so you have a carrier and a surfactant, respectively.

Mine boiled a couple times when I wasn't looking, it didn't seem to make much difference, but I tried to keep it below boiling as much as I could.

Good to have you back!

Part Scavenger

Sat Apr 01 2006, 01:30AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

Oh.

Man. And I just got all my glassware clean too. I just thought the oleic was supposed to get hot. Not that it had something to do with the ammonia. I'll have more time around sunday, maybe I'll give it another whirl. Thanks for the correction. I'll try adding ammonia to the batch of magnetite I have already and see if that works, if not, I'll make another batch. How's it coming with you?

Heiders

Sun Apr 02 2006, 04:55PM

Registered Member #268 Joined: Tue Feb 28 2006, 02:44AM
Location: Ontario, Canada
Posts: 48

Ugh, I am getting so frustrated. No matter how much extra ammonia I add, it won't fully react anymore. I dont know what else to do! I am almost out of ammonia (ie don't have enough for another batch) so I am going to get a different brand and see if that works. Any other ideas?

Chris

Sun Apr 02 2006, 06:05PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

You could try mixing up some NaOH solution, probably with similar concentration to the ammonia. I got it to precipitate once with that, but didn't have the supply to continue experimenting.

Heiders

Thu Apr 06 2006, 04:13AM

Registered Member #268 Joined: Tue Feb 28 2006, 02:44AM
Location: Ontario, Canada
Posts: 48

Semi-success, I at least can now get the magnetite fully reacted. I used a fresh, filtered (whereas last one was just settled) solution of FeCl2 and new, no scent/colour ammonia. I think having fresh reactants really helped, and I needed far less of the new ammonia than the lemon stuff. Before, I needed ~250mL. Now, I need ~190mL.

When I cooked it however, it didn't fully "blob" the way it did before, so I couldn't pour off the water without losing magnetite. After adding kerosene, I had a thick layer of responsive ferrofluid on top of some water, but it's too thin. I think by leaving it overnight uncovered in a ventilated area, enough kerosene might evaporate to increase the viscosity to a point where spikes can be supported. More on that in a couple days.

There is still a small black blob in the bottom that wont dissolve into the kerosene, not too sure why. Contaminants perhaps?

Any news Part Scavenger?

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