Potassium ferrioxalate

Chembox new
Name = Potassium ferrioxalate
ImageFile = Potassium-ferrioxalate-2D.png ImageSize = 250px
ImageName = Potassium ferrioxalate
IUPACName = Potassium ferric(III) oxalate
OtherNames = Potassium ferrioxalatePotassium trioxalatoferrate (III)
Section1 = Chembox Identifiers
CASNo = 5936-11-8

Section2 = Chembox Properties
Formula = K3 [Fe(C2O4)3] K3 [Fe(C2O4)3] .3H2O
MolarMass = 437.20 g/mol
Appearance = emerald green hydrated crystals
Density = 2.13 g/cm3, solid
Solubility = ?M (20 °C)

MeltingPt = 230 °C (493.15 K)

Section3 = Chembox Structure
Coordination = octahedral
CrystalStruct =
Dipole = 0 D

Section7 = Chembox Hazards
ExternalMSDS =
MainHazards = Corrosive. Eye, respiratory and skin irritant.
RPhrases = R20 R21 R22 R34 R36 R37 R38
SPhrases =

Section8 = Chembox Related
OtherAnions =
OtherCations =
Function = compounds
OtherFunctn = Fe(C2O4)2

Potassium ferrioxalate, is a chemical compound with the formula K3 [Fe(C2O4)3] , where iron is in the +3 oxidation state. It is an octahedral transition metal complex in which three bidentate oxalate ions are bound to an iron centre. Potassium acts as a counterion, balancing the 3- charge of the complex. Crystals of the trihydrated form of the complex, K3 [Fe(C2O4)3] .3H2O, are emerald green in colour. In solution the complex dissociates to give the ferrioxalate anion, [Fe(C2O4)3] 3-, which appears fluorescent green in colour. Potassium ferrioxalate is often used in chemical actinometry.


The complex can be synthesised from the reaction between iron(III) sulfate, barium oxalate and potassium oxalate:

Fe2(SO4)3 + 3 Ba(C2O4) + 3 K2(C2O4) → 2 K3 [Fe(C2O4)3] + 3 BaSO4

The reactants are dissolved in water and heated for around 1.5 hours. BaSO4 precipitates out leaving behind the newly formed complex in solution. The complex can then be obtained by filtering off the BaSO4 and cooling the solution so that it crystallises out.


The ferrioxalate complex demonstrates optical activity since there are two non-superimposable stereoisomers of the complex. In accordance with the IUPAC convention, the isomer with the left handed screw axis is assigned the Greek symbol Λ (lambda). Its mirror image with the right handed screw axis is given the Greek symbol Δ (delta) [Greenwood&Earnshaw] .


In solution the ferrioxalate complex is decomposed by light. The complex reacts with a photon of light to form Fe(C2O4)22- and CO2. Iron is reduced (gains an electron) from the +3 oxidation state to +2. This process is called photoreduction:

2 [Fe(C2O4)3] 3- + "hν" → 2 [Fe(C2O4)2] 2- + C2O42- + 2 CO2

If a solution of green K3 [Fe(C2O4)3] is left in sunlight for a few hours it turns orange due to the formation of Fe(C2O4)22- ions.


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • ferrioxalate — noun The anion Fe(CO) or any salt containing this anion; potassium ferrioxalate is used as a standard in actinometry …   Wiktionary

  • Actinometer — Actinometers are instruments used to measure the heating power of radiation. They are used in meteorology to measure solar radiation as pyrheliometers.An actinometer is a chemical system or physical device which determines the number ofphotons in …   Wikipedia

  • Oxalate — The structure of the oxalate anion A ball and stick model of oxal …   Wikipedia

  • List of inorganic compounds — Tentative listing related to this page, inorganic compounds by element (presently under construction), as well as . This list is not necessarily complete or up to date ndash; if you see an article that should be here but isn t (or one that… …   Wikipedia

  • Complex (chemistry) — The term complex in chemistry is usually used to describe molecules or ensembles formed by the combination of ligands and metal ions. Originally, a complex implied a reversible association of molecules, atoms, or ions through weak chemical bonds …   Wikipedia

  • d electron count — The d electron count is a chemistry formalism used to describe the electron configuration of the valence electrons of a transition metal center in a coordination complex.[1][2] The d electron count is an effective way to understand the geometry… …   Wikipedia

  • actinometer — actinometric /ak tin oh me trik, ak teuh noh /, actinometrical, adj. actinometry, n. /ak teuh nom i teuhr/, n. a device for measuring intensity of radiation, esp. that of the sun. Cf. actinograph. [1825 35; ACTINO + METER] * * * ▪ chemistry    …   Universalium

Share the article and excerpts

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

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.