Making ferrofluid from scratch
Why Chemistry Stack Exchange recommends it
Chemistry Stack Exchange answerers point people to it as a worked example of magnetite co-precipitation and oleate-stabilised ferrofluid synthesis when they discuss Fe3O4 preparation.
Recommended by 3 people across 4 different months, 2020 to 2025.
What it is
NileRed documents his months-long effort to synthesize ferrofluid from scratch. He precipitates magnetite nanoparticles from ferrous and ferric chloride, coats them with oleic acid, and suspends them in kerosene. The video walks through the failures, the lab steps and the final working method.
What people said
Recommends uhoh · 2020-02 · Chemistry Stack Exchange · on “Estimating maximum size of magnetite particles in this Nile Red ferrofluid video?”
In the Nile Red video Making ferrofluid from scratch [this video] a suspension of small magnetite [LINK] ( $\ce{Fe^{2+}Fe_2^{3+}O_4^{2−}}$ ) particles is produced from a combination of ferrous chloride and ferric chloride. The nanoparticles are then given a coating of oleic acid ( $\ce{CH3(CH2)7CH=CH(CH2)7COOH}$ ) to provide steric stabilization [LINK] to prevent aggregation, then dissolved in kerosene. After about 23:20 : …the magnetite isn’t truly dissolving, it’s going into suspension . This is because the nanoparticles aren’t soluble in the solvent, but they’re small enough that they can still easily get dispersed. The oleic acid coating that helps with this, by preventing two particles from
Recommends D. Liew · 2022-09 · Chemistry Stack Exchange · on “Can I make Ferrofluid without evaporating Ammonium?”
To answer your first question, I believe that the ammonium oleate already being a relatively soluble salt allows its deprotonation such that the resulting oleate ions are able to bond to the magnetite in suspension (both by electrostatic attraction and hydrophobic interactions). Subsequent heating is done simply to remove dissociated $\ce{NH4Cl}$ from the water in the form of $\ce{NH3}$ and $\ce{HCl}$ gas. Might be worth noting that your initial addition of aqueous $\ce{NH3}$ (aka $\ce{NH4OH}$ ) for the co-precipitation is in excess. A video by NileRed [this video] suggests neutralising this excess ammonium (hydroxide) instead with the use of hydrochloric acid, instead of using high heat which wo
Recommends Poutnik · 2024-04 · Chemistry Stack Exchange · on “Fe3O4 as a mixed oxide”
Iron(II,III) oxide [LINK] $\ce{Fe3O4}$ : ... has a cubic inverse spinel group structure which consists of a cubic close packed array of oxide ions where all of the $\ce{Fe^2+}$ ions occupy half of the octahedral sites and the $\ce{Fe^3+}$ are split evenly across the remaining octahedral sites and the tetrahedral sites. The Massart method of preparation of magnetite as a ferrofluid, is convenient in the laboratory: mix iron(II) chloride and iron(III) chloride in the presence of sodium hydroxide. \begin{align} \ce{FeCl2(aq) + 2 FeCl3(aq) + 8 NaOH(aq) &-> Fe(OH)2(s) + 2 Fe(OH)3(s) + 8 NaCl(aq)}\\ \ce{Fe(OH)2(s) + 2 Fe(OH)3(s) &-> 4 H2O(l) + Fe3O4(s)} \end{align} (For more, see this Ferrofluid p
Recommends Poutnik · 2025-10 · Chemistry Stack Exchange · on “Roasting pyrite - product magnetite”
Depending on purpose, magnetite can be formed by alkalization of mixture of Fe(II) + Fe(III) salts in stoichiometric ratio 1 : 2 - See NileRed's Youtube video [this video] of preparation of magnetic liquid (stabilised suspension of Fe3O4). In case or reproducing the fluid preparation, there is high level of experience needed, as the complex procedure has some critical points.
Cites user144956 · 2024-04 · Chemistry Stack Exchange · on “Need help with synthesis of iron (II,III) oxide (Fe₃O₄) nanoparticles”
What you need to do is create a solution with both $\ce{Fe^{2+}}$ and $\ce{Fe^{3+}}$ present in the right proportion. Buy a water solution of iron (III) chloride (easy to obtain as a circuit board etchant) -- there you have your source of $\ce{Fe^{3+}}$ ions. Next, take some of that etchant and mix it with fine grade steel wool -- the wool will dissolve away, reducing $\ce{Fe^{3+}}$ to $\ce{Fe^{2+}}$ in the process: $$\ce{2FeCl3 + Fe -> 3FeCl2}$$ Now, you need to mix the proper amounts of iron (III) chloride with iron (II) chloride solutions: two to one is the stochiometric ratio, but some of iron (II) is going to be oxidized by air during the stirring process, so it's better to use around 1