Ferric oxalate, also known as iron(III) oxalate, refers to
inorganic compound
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''.
Inorgan ...
s with the formula (H
2O)
x but could also refer to salts of
3-. (H
2O)
x are
coordination polymers with varying degrees of hydration. The
coordination complex
A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of chemical bond, bound molecules or ions, that are in turn known as ' ...
with the formula
3- forms a variety of salts, a well-known example being
potassium ferrioxalate. This article emphasizes the coordination polymers.
Structure
Tetrahydrate
According to
X-ray crystallography
X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...
of the tetrahydrate , iron is octahedral. The oxalate ligands are
bridging. Some through all four oxygen atoms, some with two oxygen atoms. Half of the water is
lattice water, being situated between chains of Fe oxalates. Mössbauer spectrum of exhibits an
isomer shift of 0.38 mm/s and a
quadrupole splitting of 0.40 mm/s, suggesting a high spin in octahedral coordination.
Production
Ferric oxalate may be produced by reaction of iron(III) hydroxide and solution of
oxalic acid:
:
Uses
Dentistry
Like many oxalates, ferric oxalate has been investigated as a short-term treatment for
dentin hypersensitivity. It is used in certain toothpaste formulations; however, its effectiveness has been questioned.
Photography
Ferric oxalate is used as the light-sensitive element in the
Kallitype photographic printing process; and the platinotype process Platinum/Palladium Printing.
Batteries
Ferric oxalate tetrahydrate has been investigated as a possible cheap material for the positive electrode of
lithium-iron batteries. It can intercalate
lithium
Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...
ions at an average potential of 3.35 V, and has shown a sustainable capacity of 98 mAh/g.
[
]
Organic synthesis
Ferric oxalate hexahydrate is used with sodium borohydride for radical Markovnikov hydrofunctionalization reactions of alkenes.
See also
A number of other iron oxalates are known:-
* Iron(II) oxalate
* Potassium ferrioxalate
* Sodium ferrioxalate
References
{{Oxalates
Oxalates
Iron(III) compounds