Ferric oxalate

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Ferric oxalate
Ferric oxalate.svg
Systematic IUPAC name
iron(3+) ethanedioate (2:3)
Other names
Iron(III) oxalate
3D model (JSmol)
ECHA InfoCard 100.019.047 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 220-951-7
PubChem CID
  • InChI=1S/3C2H2O4.2Fe/c3*3-1(4)2(5)6;;/h3*(H,3,4)(H,5,6);;/q;;;2*+3/p-6
  • [Fe+3].[Fe+3].O=C([O-])C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O
Molar mass 375.747 g/mol
AppearancePale yellow solid (anhydrous)
Lime green solid (hexahydrate)
Odor odorless
Melting point 365.1 °C (689.2 °F)
slightly soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Ferric oxalate, also known as iron(III) oxalate, is a chemical compound composed of ferric ions and oxalate ligands; it may also be regarded as the ferric salt of oxalic acid. The anhydrous material is pale yellow; however, it may be hydrated to form several hydrates, such as potassium ferrioxalate, or Fe2(C2O4)3 · 6 H2O , which is bright green in colour.




Room temperature Mossbauer spectrum of
Fe2(C2O4)3*4H2O Mossbauer spectrum.jpg
Room temperature Mössbauer spectrum of Fe2(C2O4)3·4H2O

The crystal structure of the tetrahydrate Fe2(C2O4)3· 4 H2O was determined in 2015. It has a triclinic unit cell containing two iron atoms. Each iron atom has octahedral coordination bonds to the oxygen atoms of three oxalate molecules and one water molecule. Two of those three oxalates, lying in approximately perpendicular planes, are tetradentate, and connect the iron atoms into zigzag chains. The third oxalate molecule is bidentate, and connects iron atoms of adjacent chains, creating an open-layered structure. Half of the water molecules lie, unbound, between those chains. Mössbauer spectrum of Fe2(C2O4)3· 4 H2O indicates that iron is present in a unique environment with an isomer shift of 0.38 mm/s and a quadrupole splitting of 0.40 mm/s, suggesting a high spin Fe3+ in octahedral coordination. [1]



Like many oxalates, ferric oxalate has been investigated as a short-term treatment for dentin hypersensitivity. [2] It is used in certain toothpaste formulations; however, its effectiveness has been questioned. [3]


Ferric oxalate is used as the light-sensitive element in the Kallitype photographic printing process; and the platinotype process Platinum/Palladium Printing.


Ferric oxalate tetrahydrate has been investigated as a possible cheap material for the positive electrode of lithium-iron batteries. It can intercalate lithium ions at an average potential of 3.35 V, and has shown a sustainable capacity of 98 mAh/g. [1]

Organic synthesis

Ferric oxalate hexahydrate is used with sodium borohydride for radical Markovnikov hydrofunctionalization reactions of alkenes. [4]

See also

A number of other iron oxalates are known:-

Related Research Articles

Alkali metal Group of highly-reactive chemical elements

The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Together with hydrogen they constitute group 1, which lies in the s-block of the periodic table. All alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour. This family of elements is also known as the lithium family after its leading element.

Coordination complex Molecule or ion containing ligands datively bonded to a central metallic atom

A coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals, are coordination complexes.

Oxide Chemical compound with at least one oxygen atom attached to the central atom

An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion. Certain elements can form multiple oxides, differing in the amounts of the element combining with the oxygen. Examples are carbon, iron, nitrogen (see nitrogen oxide), silicon, titanium, lithium, and aluminium. In such cases the oxides are distinguished by specifying the numbers of atoms involved, as in carbon monoxide and carbon dioxide, or by specifying the element's oxidation number, as in iron(II) oxide and iron(III) oxide.

Iron(III) chloride Inorganic compound

Iron(III) chloride is the inorganic compound with the formula FeCl3. Also called ferric chloride, it is a common compound of iron in the +3 oxidation state. The anhydrous compound is a crystalline solid with a melting point of 307.6 °C. The color depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red.

Oxalate Any derivative of oxalic acid; chemical compound containing oxalate moiety

Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl oxalate (C2O4(CH3)2). It is a conjugate base of oxalic acid. At neutral pH in aqueous solution, oxalic acid converts completely to oxalate.

In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.

In chemical nomenclature, the IUPAC nomenclature of inorganic chemistry is a systematic method of naming inorganic chemical compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It is published in Nomenclature of Inorganic Chemistry. Ideally, every inorganic compound should have a name from which an unambiguous formula can be determined. There is also an IUPAC nomenclature of organic chemistry.

Double salt

A double salt is a salt that contains more than one different cation or anion. Examples of double salts include alums (with the general formula MIMIII[SO4]2·12H2O) and Tutton's salts (with the general formula [MI]2MII[SO4]2·6H2O). Other examples include potassium sodium tartrate, ammonium iron(II) sulfate (Mohr's salt), and bromlite BaCa(CO3)2. The fluorocarbonates contain fluoride and carbonate anions. Many coordination complexes form double salts.

Iron(III) nitrate Chemical compound

Iron(III) nitrate, or ferric nitrate, is the name used for a series of inorganic compounds with the formula Fe(NO3)3.(H2O)n. Most common is the nonahydrate Fe(NO3)3.(H2O)9. The hydrates are all pale colored, water-soluble paramagnetic salts.

Nickel(II) nitrate Chemical compound

Nickel nitrate is the inorganic compound Ni(NO3)2 or any hydrate thereof. The anhydrous form is not commonly encountered, thus "nickel nitrate" usually refers to nickel(II) nitrate hexahydrate. The formula for this species is written in two ways: Ni(NO3)2.6H2O and, more descriptively [Ni(H2O)6](NO3)2. The latter formula indicates that the nickel(II) center is surrounded by six water molecules in this hydrated salt. In the hexahydrate, the nitrate anions are not bonded to nickel. Also known are three other hydrates: Ni(NO3)2.9H2O, Ni(NO3)2.4H2O, and Ni(NO3)2.2H2O. Anhydrous Ni(NO3)2 is also known.

In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals.

Potassium ferrioxalate Chemical compound

Potassium ferrioxalate, also called potassium trisoxalatoferrate or potassium tris(oxalato)ferrate(III) is a chemical compound with the formula K
]. It often occurs as the trihydrate K3[Fe(C2O4)3]·3H2O. Both are crystalline compounds, lime green in colour.

Croconic acid Chemical compound

Croconic acid or 4,5-dihydroxycyclopentenetrione is a chemical compound with formula C5H2O5 or (C=O)3(COH)2. It has a cyclopentene backbone with two hydroxyl groups adjacent to the double bond and three ketone groups on the remaining carbon atoms. It is sensitive to light, soluble in water and ethanol and forms yellow crystals that decompose at 212 °C.

Iron(II) oxalate Chemical compound

Ferrous oxalate, or iron(II) oxalate, is an inorganic compound with the formula FeC2O4 · xH2O where x is typically 2. These are orange compounds, poorly soluble in water.

Sodium ferrioxalate Chemical compound

Sodium ferrioxalate is a chemical compound with the formula Na3Fe(C2O4)3. It is also called sodium oxalatoferrate or sodium trisoxalatoferrate.

A metal ion in aqueous solution or aqua ion is a cation, dissolved in water, of chemical formula [M(H2O)n]z+. The solvation number, n, determined by a variety of experimental methods is 4 for Li+ and Be2+ and 6 for elements in periods 3 and 4 of the periodic table. Lanthanide and actinide aqua ions have a solvation number of 8 or 9. The strength of the bonds between the metal ion and water molecules in the primary solvation shell increases with the electrical charge, z, on the metal ion and decreases as its ionic radius, r, increases. Aqua ions are subject to hydrolysis. The logarithm of the first hydrolysis constant is proportional to z2/r for most aqua ions.

Thorium(IV) nitrate Chemical compound

Thorium(IV) nitrate is a chemical compound with the formula Th(NO3)4. A white solid in its anhydrous form, it can form tetra- and pentahydrates. As a salt of thorium it is weakly radioactive.

Potassium ferrooxalate, also known as potassium bisoxalatoferrate(II), is a salt with the formula K
], sometimes abbreviated K
. The ferrooxalate anion [Fe(C
is a transition metal complex, consisting of an atom of iron in the +2 oxidation state bound to two bidentate oxalate ions C
. The anion charge is balanced by two cations of potassium K+

The nickel organic acid salts are organic acid salts of nickel. In many of these the ionised organic acid acts as a ligand.

Ferrioxalate Ion

Ferrioxalate or trisoxalatoferrate(III) is a trivalent anion with formula [Fe(C2O4)3]3−. It is a transition metal complex consisting of an iron atom in the +3 oxidation state and three bidentate oxalate ions C2O2−4 anions acting as ligands.


  1. 1 2 Ahouari, Hania; Rousse, Gwenaëlle; Rodríguez-Carvajal, Juan; Sougrati, Moulay-Tahar; Saubanère, Matthieu; Courty, Matthieu; Recham, Nadir; Tarascon, Jean-Marie (2015). "Unraveling the Structure of Iron(III) Oxalate Tetrahydrate and Its Reversible Li Insertion Capability". Chemistry of Materials. 27 (5): 1631–1639. doi:10.1021/cm5043149.
  2. Gillam, D. G.; Newman, H. N.; Davies, E. H.; Bulman, J. S.; Troullos, E. S.; Curro, F. A. (2004). "Clinical evaluation of ferric oxalate in relieving dentine hypersensitivity". Journal of Oral Rehabilitation. 31 (3): 245–250. doi:10.1046/j.0305-182X.2003.01230.x. PMID   15025657.
  3. Cunha-Cruz, J.; Stout, J. R.; Heaton, L. J.; Wataha, J. C. (29 December 2010). "Dentin Hypersensitivity and Oxalates: a Systematic Review". Journal of Dental Research. 90 (3): 304–310. doi:10.1177/0022034510389179. PMC   3144108 . PMID   21191127.
  4. Barker, Timothy (2001-04-15). "Ferric Oxalate Hexahydrate". Encyclopedia of Reagents for Organic Synthesis (1 ed.). Wiley. pp. 1–4. doi:10.1002/047084289X.rn02346. ISBN   978-0-471-93623-7. S2CID   225482606.