Iron(III) sulfate (or ferric sulfate), is the chemical compound with the formula Fe2(SO4)3. Usually yellow, it is a salt and soluble in water. A variety of hydrates are also known. Solutions are used in dyeing as a mordant, and as a coagulant for industrial wastes. It is also used in pigments, and in pickling baths for aluminum and steel.
Sulfuric acid, iron(3+) salt (3:2)
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||399.88 g/mol (anhydrous)|
489.96 g/mol (pentahydrate)
562.00 g/mol (nonahydrate)
|Density||3.097 g/cm3 (anhydrous) |
1.898 g/cm3 (pentahydrate)
|Melting point|| 480 °C (896 °F; 753 K) (anhydrous) |
175 °C (347 °F) (nonahydrate)
|Solubility||sparingly soluble in alcohol |
negligible in acetone, ethyl acetate
insoluble in sulfuric acid, ammonia
Refractive index (nD)
|1.814 (anhydrous) |
|NFPA 704 (fire diamond)|
|Lethal dose or concentration (LD, LC):|
LD50 (median dose)
|500 mg/kg (oral, rat)|
|NIOSH (US health exposure limits):|
|TWA 1 mg/m3|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Generally, ferric sulfate is used as a solution generated from iron wastes. The actual speciation is vague but its applications do not demand high purity materials.
Iron(III) sulfate is often generated as a solution rather than being isolated as a solid. It is produced on a large scale by treating sulfuric acid, a hot solution of ferrous sulfate, and an oxidizing agent. Typical oxidizing agents include chlorine, nitric acid and hydrogen peroxide.
- 2 FeSO4 + H2SO4 + H2O2 → Fe2(SO4)3 + 2 H2O
Mikasaite, a mixed iron-aluminium sulfate of chemical formula (Fe3+, Al3+)2(SO4)3 is the name of mineralogical form of iron(III) sulfate. This anhydrous form occurs very rarely and is connected with coal fires. The hydrates are more common, with coquimbite (nonahydrate) as probably the most often met among them. Paracoquimbite is the other, rarely met natural nonahydrate. Kornelite (heptahydrate) and quenstedtite (decahydrate) are rarely found. Lausenite (hexa- or pentahydrate) is a doubtful species. All the mentioned natural hydrates are unstable compounds connected with Fe-bearing primary minerals (mainly pyrite and marcasite) oxidation in ore beds. In the solutions of the ore beds oxidation zones the iron(III) sulfate is also an important oxidative agent.
- NIOSH Pocket Guide to Chemical Hazards. "#0346". National Institute for Occupational Safety and Health (NIOSH).
- Ferric sulfate. The Columbia Encyclopedia, Sixth Edition. Retrieved November, 2007.
- Wildermuth, Egon; Stark, Hans; Friedrich, Gabriele; Ebenhöch, Franz Ludwig; Kühborth, Brigitte; Silver, Jack; Rituper, Rafael (2000). "Iron Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a14_591.
- Iron compounds. Encyclopædia Britannica Article. Retrieved November, 2007