Potassium ferrioxalate

Last updated
Potassium ferrioxalate
Potassium ferrioxalate large crystals.jpg
Potassium-ferrioxalate-2D.png
Names
IUPAC name
Potassium iron(III) oxalate
Other names
potassium ferrioxalate
potassium trisoxalatoferrate(III)
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.035.398 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 238-954-7
PubChem CID
RTECS number
  • SZ3500000
UNII
UN number 3077
  • InChI=1S/3C2H2O4.Fe.K/c3*3-1(4)2(5)6;;/h3*(H,3,4)(H,5,6);;/q;;;+3;+1/p-2
    Key: VSRUWRBJHJVUDC-UHFFFAOYSA-L
  • [K+].o=c(-c(=o)o1)o[Fe-3]123(oc(-c(=o)o2)=o)oc(-c(=o)o3)=o.[K+].[K+]
Properties
K
3
[Fe(C
2
O
4
)
3
] (anhydrous)
K
3
[Fe( C
2
O
4
)3]·3H
2
O
(trihydrate)
Molar mass 437.20 g/mol (anhydrous)
491.25 g/mol (trihydrate)
Appearanceemerald green hydrated crystals
Density 2.13 g/cm3
Melting point 230 °C (446 °F; 503 K)the trihydrate loses 3H2O at 113 °C [1]
Structure
octahedral
0 D
Hazards [2]
Occupational safety and health (OHS/OSH):
Main hazards
Corrosive. Eye, respiratory and skin irritant.
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H302, H312
P280, P301+P330+P331, P302+P353, P312, P330, P363, P403, P501
Related compounds
Other anions
Sodium ferrioxalate
Related compounds
Iron(II) oxalate
Iron(III) oxalate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Potassium ferrioxalate, also called potassium trisoxalatoferrate or potassium tris(oxalato)ferrate(III) [3] is a chemical compound with the formula K
3
[Fe(C
2
O
4
)
3
]. It often occurs as the trihydrate K3[Fe(C2O4)3]·3H2O. Both are crystalline compounds, lime green in colour. [3]

Contents

The compound is a salt consisting of ferrioxalate anions, [Fe(C2O4)3]3−, and potassium cations K+. The anion 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. Potassium acts as a counterion, balancing the −3 charge of the complex. In solution, the salt dissociates to give the ferrioxalate anion, [Fe(C
2
O
4
)
3
]3−, which appears fluorescent green in color.

The ferrioxalate anion is quite stable in the dark, but is decomposed by light and high-energy electromagnetic radiation. This photo-sensitive property is used for chemical actinometry, the measure of luminous flux, and for preparation of blueprints.

Preparation

The complex can be synthesized by the reaction between iron(III) sulfate, barium oxalate and potassium oxalate: [4]

Fe
2
(SO
4
)
3
+ 3 BaC
2
O
4
+ 3 K
2
C
2
O
4
→ 2 K
3
[Fe(C
2
O
4
)
3
] + 3 BaSO
4

As can be read in the reference above, iron(III) sulfate, barium oxalate and potassium oxalate are combined in water and digested for several hours on a steam bath. Oxalate ions from barium oxalate will then replace the sulfate ions in solution, removing them as BaSO
4
which can then be filtered and the pure material can be crystallized.

Structure

The structures of the trihydrate and of the anhydrous salt have been extensively studied. [5] which indicates that the Fe(III) is high spin; as the low spin complex would display Jahn–Teller distortions. The ammonium and mixed sodium-potassium salts are isomorphous, as are related complexes with Al3+, Cr3+, and V3+.

The ferrioxalate complex displays helical chirality as it can form two non-superimposable geometries. 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). [6]

2-isomers-of-ferrioxalate.svg

Reactions

Photoreduction

The ferrioxalate anion is sensitive to light and to high-energy electromagnetic radiation, including X-rays and gamma rays. Absorption of a photon causes the decomposition of one oxalate ion to carbon dioxide CO2 and reduction of the iron(III) atom to iron(II). [7]

Thermal decomposition

The trihydrate loses the three water molecules at the same time when heated at 113 °C. [1]

At 296 °C, the anhydrous salt decomposes into the iron(II) complex potassium ferrioxalate, potassium oxalate, and carbon dioxide: [1]

2 K
3
[Fe(C
2
O
4
)
3
] → 2 K
2
[Fe(C
2
O
4
)
2
] + K
2
C
2
O
4
+ 2 CO
2

This light-catalyzed redox reaction once formed the basis of some photographic processes. However due to their insensitivity and ready availability of advanced digital photography, these processes have become obsolete.

Uses

Photometry and actinometry

The discovery of the efficient photolysis of the ferrioxalate anion was a landmark for chemical photochemistry and actinometry. The potassium salt was found to be over 1000 times more sensitive than uranyl oxalate, the compound previously used for these purposes. [7] [8]

Chemistry education

The synthesis and thermal decomposition of potassium ferrioxalate is a popular exercise for high school, college or undergraduate university students, since it involves the chemistry of transition metal complexes, visually observable photochemistry, and thermogravimetry. [9]

Blueprints

Before the ready availability of wide ink-jet and laser printers, large-size engineering drawings were commonly reproduced by the cyanotype method.

That was a simple contact-based photographic process that produced a "negative" white-on-blue copy of the original drawing—a blueprint. The process is based on the photolysis of an iron(III) complex which gets converted into an insoluble iron(II) version in areas of the paper that were exposed to light.

The complex used in cyanotype is mainly ammonium iron(III) citrate, but potassium ferrioxalate is also used. [10] [11]

See also

A number of other iron oxalates are known

Related Research Articles

Potassium ferrocyanide Chemical compound

Potassium ferrocyanide is the inorganic compound with formula K4[Fe(CN)6]·3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.

Actinometer

Actinometers are instruments used to measure the heating power of radiation. They are used in meteorology to measure solar radiation as pyranometers, pyrheliometers and net radiometers.

Potassium ferrate Chemical compound

Potassium ferrate is the chemical compound with the formula K2FeO4. This purple salt is paramagnetic, and is a rare example of an iron(VI) compound. In most of its compounds, iron has the oxidation state +2 or +3 (Fe2+ or Fe3+). Reflecting its high oxidation state, FeO2−4 is a powerful oxidizing agent.

Ferrate(VI) Ion

Ferrate(VI) is the inorganic anion with the chemical formula [FeO4]2−. It is photosensitive, contributes a pale violet colour to compounds and solutions containing it and is one of the strongest water-stable oxidizing species known. Although it is classified as a weak base, concentrated solutions containing ferrate(VI) are corrosive and attack the skin and are only stable at high pH.

Iron(III) fluoride Chemical compound

Iron(III) fluoride, also known as ferric fluoride, are inorganic compounds with the formula FeF3(H2O)x where x = 0 or 3. They are mainly of interest by researchers, unlike the related iron(III) chlorides. Anhydrous iron(III) fluoride is white, whereas the hydrated forms are light pink.

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.

Indium(III) sulfate (In2(SO4)3) is a sulfate salt of the metal indium. It is a sesquisulfate, meaning that the sulfate group occurs 11/2 times as much as the metal. It may be formed by the reaction of indium, its oxide, or its carbonate with sulfuric acid. An excess of strong acid is required, otherwise insoluble basic salts are formed. As a solid indium sulfate can be anhydrous, or take the form of a pentahydrate with five water molecules or a nonahydrate with nine molecules of water. Indium sulfate is used in the production of indium or indium containing substances. Indium sulfate also can be found in basic salts, acidic salts or double salts including indium alum.

Barium ferrate Chemical compound

Barium ferrate is the chemical compound of formula BaFeO4. This is a rare compound containing iron in the +6 oxidation state. The ferrate(VI) ion has two unpaired electrons, making it paramagnetic. It is isostructural with BaSO4, and contains the tetrahedral [FeO4]2− anion.

Rhodizonic acid Chemical compound

Rhodizonic acid is a chemical compound with formula C6H2O6 or (CO)4(COH)2. It can be seen as a twofold enol and fourfold ketone of cyclohexene, more precisely 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone.

Hydrogenoxalate Ion

Hydrogenoxalate or hydrogen oxalate is an anion with chemical formula HC
2
O
4
or HO
2
C–CO
2
, derived from oxalic acid by the loss of a single proton; or, alternatively, from the oxalate anion C
2
O2−
4
by addition of a proton. The name is also used for any salt containing this anion. Especially in older literature, hydrogenoxalates may also be referred to as bioxalates, acid oxalates, or monobasic oxalates. Hydrogenoxalate is amphoteric, in that it can react both as an acid or a base.

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.

Ferric oxalate Chemical compound

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.

Barium perchlorate is a powerful oxidizing agent, with the formula Ba(ClO4)2. It is used in the pyrotechnic industry.

Potassium ferrooxalate, also known as potassium bisoxalatoferrate(II), is a salt with the formula K
2
[Fe(C
2
O
4
)
2
], sometimes abbreviated K
2
FeOx
2
. The ferrooxalate anion [Fe(C
2
O
4
)
2
]2−
is a transition metal complex, consisting of an atom of iron in the +2 oxidation state bound to two bidentate oxalate ions C
2
O2−
4
. The anion charge is balanced by two cations of potassium K+
.

Caesium oxalate (standard IUPAC spelling) dicesium oxalate, or cesium oxalate (American spelling) is the oxalate of caesium. Caesium oxalate has the chemical formula of Cs2C2O4.

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.

Hydromelonic acid Chemical compound

Hydromelonic acid, is an elusive chemical compound with formula C
9
H
3
N
13
or (HNCN)
3
(C
6
N
7
)
, whose molecule would consist of a heptazine H3(C
6
N
7
)
molecule, with three cyanamido groups H–N=C=N– or N≡C–NH– substituted for the hydrogen atoms.

Transition metal oxalate complex

Transition metal oxalate complexes are coordination complexes with oxalate (C2O42−) ligands. Some are useful commercially, but the topic has attracted regular scholarly scrutiny. Oxalate (C2O42-) is a kind of dicarboxylate ligand. As a small, symmetrical dinegative ion, oxalate commonly forms five-membered MO2C2 chelate rings. Mixed ligand complexes are known, e.g., [Co(C2O4)(NH3)4]κ+.

References

  1. 1 2 3 J. Ladriere (1992): "Mössbauer study on the thermal decomposition of potassium tris (oxalato) ferrate(III) trihydrate and bis (oxalato) ferrate(II) dihydrate". Hyperfine Interactions, volume 70, issue 1, pages 1095–1098. doi : 10.1007/BF02397520
  2. "5936-11-8 - Potassium trioxalatoferrate(III) trihydrate - Potassium iron(III) oxalate - 31124 - Alfa Aesar". www.alfa.com.
  3. 1 2 A. Saritha, B. Raju, M. Ramachary, P. Raghavaiah, and K. A. Hussain (2012) "Synthesis, crystal structure and characterization of chiral, three-dimensional anhydrous potassium tris(oxalato)ferrate(III)", Physica B: Condensed Matter, volume 407, issue 21, pages 4208-4213. doi : 10.1016/j.physb.2012.07.005
  4. Bailar, Jr., John C.; Jones, Eldon M. (1939). Trioxalato Salts (Trioxalatoaluminiate, -ferriate, -chromiate, and -cobaltiate). Inorg. Synth. Inorganic Syntheses. Vol. 1. pp. 35–38. doi:10.1002/9780470132326.ch13. ISBN   9780470132326.
  5. Junk, Peter C. (2005). "Supramolecular interactions in the X-ray crystal structure of potassium tris(oxalato)ferrate(III) trihydrate". J. Coord. Chem. 58 (4): 355–361. doi:10.1080/00958970512331334250.
  6. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  7. 1 2 Hatchard, C. G.; Parker, C. A. (1956). "A new sensitive chemical actinometer. II. Potassium ferrioxalate as a standard chemical actinometer". Proceedings of the Royal Society of London. 235 (1203): 518–36. Bibcode:1956RSPSA.235..518H. doi:10.1098/rspa.1956.0102. S2CID   98652159.{{cite journal}}: CS1 maint: uses authors parameter (link)
  8. Pozdnyakov, Ivan P.; Kel, Oksana V.; Plyusnin, Victor F.; Grivin, Vyacheslav P.; Bazhin, Nikolai M. (2008). "New Insight into Photochemistry of Ferrioxalate". J. Phys. Chem. A. 112 (36): 8316–8322. Bibcode:2008JPCA..112.8316P. doi:10.1021/jp8040583. PMID   18707071.
  9. John Olmsted (1984): "Preparation and analysis of potassium tris(oxalato)ferrate(III)trihydrate: A general chemistry experiment". Journal of Chemical Education, volume 61, issue 12, page 1098. doi : 10.1021/ed061p1098
  10. Pablo Alejandro Fiorito and André Sarto Polo (2015): "A New Approach toward Cyanotype Photography Using Tris-(oxalato)ferrate(III): An Integrated Experiment". Journal of Chemical Education, volume 92, issue 10, pages 1721–1724. doi : 10.1021/ed500809n
  11. Mike Ware (2014): Cyanomicon - History, Science and Art of Cyanotype: photographic printing in Prussian blue . Online document at www.academia.edu, published by www.mikeware.co.uk, accessed on 2019-03-29.