I have recently put in a few of my own attempts at making ferrofluid, and here's some things I learned and my reinterpretation of the guide.
http://chemistry.about.com/od/demonstrationsexperiments/ss/liquidmagnet_2.htm
That site goes step by step with words on how to make a ferrofluid including making the magnetite nanoparticles, but after doing it 4 times I found it was a bit vague at alot of parts.
So here is my own step by step guide for making the ferrofluid.
Materials:
A: Unscented or uncolored ammonia: Got mine from walmart
http://www.walmart.com/ip/Great-Value-Ammonia-64-oz/13023511
B: Steel/Iron Wool: Any hardware store, don't get an SOS pad with soap in it
http://www.homedepot.com/buy/paint/paint-tools/homax-products/no-10120000-steel-wool-12-pad-pk-grade-0000-66130.html
C: PBC Etchant (aka Ferric Chloride Solution: Got mine at Radio Shack
http://www.radioshack.com/product/index.jsp?productId=2102868
D: Distilled Water: Walmart? Really many places carry this.
E. 2 small class containers in which you can measure out milliliter volumes (I got mine off amazon)
http://www.amazon.com/Corning-Graduated-Griffin-Beaker-Assortment/dp/B004DGIITC
F: 1 larger glass container to mix things in, half to full liter in volume
G. Coffee Filters
H: Something to stir with that isn't metal (I used a wooden doll rod)
I: Rubber Gloves/Saftey Glasses (optional): Better safe than sorry? Can be bought again at most hardware stores.
J: Portable Heat source: Electric stove burner or kerosine camping grill
K: Ice
L: Small plastic tub to put make an ice bath in
Procedure:
1. Set up in a ventilated area (outside) cause this stuff stinks. (alot)
2. Pour 20 milliliters PBC etchant and 20 milliliters distilled water into your glass measuring container.
3. Stuff in a cotton swab sized chunk of steel wool, and using your stirring rod to smash it down in.
4. The steel wool should start dissolving and the solution should start turning a greenish color.
5. Keep adding cottonball size pieces of steel wool and stirring until it stops dissolving. (probably 2-5 pieces depending on how fine the wool is and how tightly balled they are)
6. Pour 20ml PBC etchant into a separate measuring container.
7. Take your solution in which you added steel wool and pour it through a coffee filter into the fresh 20 ml of PBC etchant until it reaches 40 mL. (half straight etchant and half wool-dissolved solution)
8. Pour this new 40 mL of solution into your larger mixing container.
9. Make an ice bath in your plastic tub and chill the solution as well as about 250ml-750ml ammonia(depending on it's concentration) in its own container.
*note cooling the solution and ammonia was recommend to me by the person who made this stuff at his home www.youtube.com/watch?v=PhJms4r1IzU
*I have not yet tried it to see if it makes a difference
10. While stirring slowly(extremely slowly, ideally drop by drop) pour ammonia into this solution. At first it will turn a muddy red-brown and then as you keep adding ammonia it will turn a jet black. Once it goes completely black you have precipitated magnetite.
*This is a long and tedious process
11. Now you have a mixture of water, ammonia, and magnetite. Heat this up to just below boiling for about 15 min.
12. While this is heating (or after it is heated) create a mix of ammonia and oleic acid by heating about 300ml ammonia (mine was weak stuff) and mixing in oleic acid until it starts to form soaps
13. Add this mixture to the magnetite precipitate and stir for a long time to try and fully coat all of the particles present
***WARNING***
This last step has a high chance to boil over your container if you heat it too high or rapidly, covering your heater in jet black rust and ammonia that is hard to get off. Err on the side of caution when heating. You have been warned.
And finally after step 13, let the mixture cool and add kerosine and mix. Let the kerosine and water layers separate and suck the top kerosine layer off (this is the ferro fluid.)
