# How to Make Ferrofluid in a Bottle

I am trying to accomplish the very famous magnetic Ferrofluid in a bottle aka office desk toy.

Before anyone suggest to buy online, I would like to make it myself and learn the whole process VS store bought item.

here is a short video of it

Grade 11 chemistry was the last time I studied chemistry.

I would like to create the similar/same toy

My first question is: is ferrofliud thick liquid you can just buy online or do you have to make it yourself using ink toner or magnetic powder etc

I tried making it using ink toner powder mixing it with vegetable oil. The results were not the best but worth a shot, it ended up thick blob and alot of particles it was not clear at all and very hard to see through it.

for the clear liquid I used 50% cleaning alcohol, i tried using water before and it just ended up making the whole glass black. So in short this is the measurements I used and once again I apologize if I forgot to mention anything. I used black ink toner mixed it with vegetable oil, ink toner 10 grams vegetable oil 20ml, and 100ml was cleaning alcohol

Alot of people suggest use magnetic powder instead of ink toner what do you recommend? What different liquids should I be using so it does not mix and stays clear. Some people suggest online make sure you only use water without minerals and iron and many other liquids

• – Mithoron Jul 9 '16 at 11:56

## 3 Answers

It is always easier to buy ferrofluid than to make it. Some of the steps don't work well unless the conditions are just right and it is hard to get them right on your first attempt. Luckily there are plenty of suppliers (this UK supplier is top of my Google search for "ferrofluid sales" and they also supply lots of cool magnets).

Ferrofluid is a suspension of small magnetic particles (often magnetite, the magnetic oxide of iron) in a fluid. To avoid the heavy and magnetic particles clumping together or precipitating, they need to be coated in a surfactant. And this only works if the particles are the right size (very small) and you have the right mix of surfactant that works in the carrier fluid (the fluid is usually mineral oil or vegetable oil; alcohols will be a poor choice).

Laserprinter toner isn't usually a mix of suspended magnetic particles: only specialty toner inks are (the ones used for machine readable printing). If you can get the right sort, it will save a lot of effort, but the wrong toner won't work at all and will just make a mess.

There are quite a few recipes on places such as Youtube, but some of them don't work well or don't explain some of the important details. So, if you don't want to spend a lot of time experimenting to get the synthesis right, just buy the ferrofluid.

You have to be sure to use the type of toner powder that is made to print "machine readable type" like on checks. It is magnetic, the regular toner powder is not magnetic and does not work. It makes a mess.

I have not yet tried it but there is a youtuber who has made excellent ferrofluid at home. The broad steps are as follows :

1. Making the magnetic nanoparticles (Fe3O4)
2. Coating them with a surfactant (Oleic acid)
3. Dissolving in suitable carrier solution (petrol/kerosene)

Making the magnetic nanoparticles

Add FeCl2 and FeCl3 solution in 1:2 ratio in a beaker and continue mixing it while adding NH3 drop wise. First the solution will turn brown. Keep adding until the solution turns black

$$3NH_3+3H_2O+FeCl_3→3NH_4Cl+Fe(OH)_3$$

$$2NH_3+2H_2O+FeCl_2→2NH_4Cl+Fe(OH)_2$$

$$Fe(OH)_2+2Fe(OH)_3→4H_2O+Fe_3O_4$$

This leaves us with Fe3O4 in NH4Cl solution.

You can also heat the solution for sometime at about 80 ℃

Note - some people suggest adding the iron solution to ammonia and not he other way around.

Separating out the Fe3O4 from the solution

To the solution add small amount of Oleic acid and some excess of ammonia which will form ammonium oleate which binds to the magnetic particles and is soluble

$$OleicAcid+NH_3→AmmoniumOleate$$

heat the solution to about 80 ℃ – 90 ℃ . The ammonium oleate will decompose to again form oleic acid (which is hydrophobic) and it will separate out the magnetic particles from the solution.

Purification

We don't want

1. Particles that are too big
2. Particles that are not properly coated with Oleic acid

To deal with them follow these steps

• Dissolve the Oleic acid coated particles in petrol/kerosene and then keep the beaker over a big magnet to precipitate the unwanted big particles. Then Decant the useful Oleic acid coated particles which stayed in the solution

• Now add double the volume of Acetone to extract these particle out of the solution. They stay coated with Oleic acid.

This was the purification process. Note that you can also use paint thinner in place of petrol and isopropyl alcohol in place of Acetone.

Dissolving in carrier fluid

Now let the particles dry out and then add a few drops of kerosene/petrol to make a concentrated solution. The ferrofluid should be ready now.

Additional information

If you don't have oleic acid then you can obtain it by saponification of olive oil.

$$OliveOil+CausticSoda/NaOH \xrightarrow{\text{boil}} soap$$

Dissolve the soap in water with some acid (sulphuric). The oily substance collected at the top is mostly Oleic acid with stearic acid and linoleic acid. This can be further purified by refrigeration.

Melting point of oleic acid is 13–14℃ while that of stearic acid is 68℃ and linoleic acid is -12℃

You can also make ferrous chloride from ferric chloride by adding irin nails to it.