Iron(II) hydroxide

Iron(II) hydroxide

Chembox new
Name = Iron(II) hydroxide
ImageFile = Iron(II) hydroxide.jpg
ImageName =
OtherNames =
Section1 = Chembox Identifiers

Section2 = Chembox Properties
Formula = Fe(OH)2
MolarMass = 89.86 g/mol
Density =
Solvent =
SolubleOther =
MeltingPt =
BoilingPt =

Iron(II) hydroxide or ferrous hydroxide is a compound produced when iron(II) ions, from a compound such as iron (II) sulfate react with hydroxide ions. Iron(II) hydroxide itself is practically white, but even traces of oxygen impart it with a greenish tinge. If the solution was not deoxygenated and the iron reduced, the precipitate can vary in color starting from green to reddish brown depending on the iron(III) content. This precipitate is also known as "green rust" in the crystal lattice of which Fe2+ ions are easily substituted by Fe3+ ions produced by its progressive oxidation. In the presence of oxygen the color changes quickly. Green rust is a powerful reducing agent and also a layer double hydroxides (LDH) capable to sorb anions because of the presence of positive electrical charges borne on its surface. The mineralogical form of green rust is a recently discovered fougerite. All forms of green rust (including fougerite) does not correspond the ideal Fe(OH)2 compound, as their structure is more complex and variable. The natural analogue of Fe(OH)2 compound is a very rare mineral amakinite, (Fe,Mg)(OH)2.

Iron(II) hydroxide is poorly soluble (1.43 × 10−3 g/L). It precipitates from from the reaction of iron(II) sulfate and hydroxide ions (from a soluble compound containing hydroxide ion):

:FeSO4 + 2OH → Fe(OH)2 + SO42−

It is also easily formed as an undesirable by-product of other reactions, a.o., in the synthesis of siderite, an iron carbonate (FeCO3), if the crystal growth conditions are poorly controlled (reagent concentrations, addition rate, addition order, pH, pCO2, T, ageing time, ...).


Anions such as selenite and selenate can be easily adsorbed on the positively charged surface of green rust where they are subsequently reduced by Fe2+. The resulting products being poorly soluble (Se0, FeSe, or FeSe2).

Ferrous hydroxide has also been investigated as an agent for the removal of toxic selenate and selenite ions from water systems such as wetlands. The ferrous hydroxide reduces these ions to elemental selenium, which is insoluble in water and precipitates out. [cite journal
last = Zingaro
first = Ralph A.
coauthors = "et al."
year = 1997
title = Reduction of oxoselenium anions by iron(II) hydroxide
journal = Environment International
volume = 23
issue = 3
pages = 299–304
doi = 10.1016/S0160-4120(97)00032-9

Note: pKsp = 15.097 where p is the -log and Ksp is the Solubility Product Constant. This means it has a low tendency to dissolve, but is not entirely insoluble. An acidic solution would allow this to disassociate more because the H+ would react with the OH- in the compound.

In a basic solution (potassium hydroxide), ferrous hydroxide is the electrochemically active material of the negative electrode of the Nickel-iron battery.

ee also

* Rust
* Green rust
* Layered double hydroxides
* Periodic table


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • iron(III) hydroxide — geležies(III) hidroksidas statusas T sritis chemija formulė Fe(OH)₃ atitikmenys: angl. ferric hydroxide; ironic hydroxide; iron(III) hydroxide rus. железа гидроокись; железа(III) гидроксид …   Chemijos terminų aiškinamasis žodynas

  • iron(II) hydroxide — geležies(II) hidroksidas statusas T sritis chemija formulė Fe(OH)₂ atitikmenys: angl. ferrous hydroxide; iron(II) hydroxide rus. железа гидрозакись; железа(II) гидроксид …   Chemijos terminų aiškinamasis žodynas

  • Magnesium iron silicate hydroxide — may refer to: Anthophyllite Cummingtonite Serpentine group This disambiguation page lists articles associated with the same title. If an …   Wikipedia

  • Iron supplements — are supplements that can be prescribed by a doctor for a medical reason. Iron can also be a dietary supplement, which can be purchased in supermarkets etc. These two categories should not be confused. The first iron pills were commonly known as… …   Wikipedia

  • Iron(III) chloride — Iron(III) chloride …   Wikipedia

  • Iron oxide — pigment Role of iron oxides …   Wikipedia

  • Iron(III) oxide-hydroxide — A number of species are dubbed iron(III) oxide hydroxide. These chemicals are oxide hydroxides of iron, and may occur in anhydrous (IronOxygen(Hydroxide)) or hydrated (IronOxygen(Hydroxide)·nH2O) forms. The monohydrate(IronOxygen(Hydroxide)·H2O)… …   Wikipedia

  • Iron oxide adsorption — is a water treatment process that is used to remove arsenic from drinking water. Arsenic is a common natural contaminant of well water and is highly carcinogenic. Iron oxide adsorption treatment for arsenic in groundwater is a commonly practiced… …   Wikipedia

  • Iron(III) oxide — Iron(III) oxide …   Wikipedia

  • Hydroxide — Lewis structure of the hydroxide ion showing three lone pairs on the oxygen atom …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”