Iron(III) phosphate

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Iron(III) phosphate
A-quartz.png
Iron(III) phosphate pentahydrate
Identifiers
CAS number 10045-86-0 (anhydrous), 13463-10-0 (dihydrate)
PubChem 24861
Jmol-3D images Image 1
Properties
Molecular formula FeO4P
Molar mass 150.82 g mol−1
Appearance yellow-brown solid
Density 3.056 g/cm3 (anhydrous)
2.87 g/cm3 (20 °C, dihydrate)
Melting point 250 °C (482 °F; 523 K)
(dihydrate) decomposes[1]
Solubility in water anhydrous:
insoluble
dihydrate:
0.642 g/100 mL (100 °C)[1]
Thermochemistry
Specific
heat capacity
C
180.5 J/mol·K (dihydrate)[1]
Std molar
entropy
So298
171.3 J/mol·K (dihydrate)[1]
Std enthalpy of
formation
ΔfHo298
-1888 kJ/mol (dihydrate)[1]
Hazards
GHS pictograms The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)[2]
GHS signal word Warning
GHS hazard statements H315, H319, H335[2]
GHS precautionary statements P261, P305+351+338[2]
EU classification Irritant Xi
R-phrases R36/37/38
S-phrases S26, S36
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Iron(III) phosphate is the inorganic compound with the formula FePO4. Several related materials are known, including four polymorphs of FePO4 and two polymorphs of the dihydrate FePO4·(H2O)2. These materials find several technical applications as well as occurring in the mineral kingdom.[3]

Structure[edit]

The most common form of FePO4 adopts the structure of α-quartz. As such the P and Fe have tetrahedral molecular geometry. At high pressures, a phase change occurs to a more dense structure with octahedral Fe centres. Two orthorhombic structures and a monoclinic phase are also known. In the two polymorphs of the dihydrate, the Fe center is octahedral with two mutually cis water ligands.[4]

Uses[edit]

Iron(III) phosphate is one of the few molluscicides approved for use in the practice of organic farming.[5] Unlike the older metaldehyde, it is non-toxic to pets and wildlife.

It can be used in steel and metal manufacturing processes. When bonded to a metal surface, iron phosphate prevents further oxidation of the metal. Its presence is partially responsible for the corrosion resistance of the Iron pillar of Delhi.

Iron phosphate coatings are also primarily used as base coatings for paint in order to increase adhesion to the iron or steel substrate, and is often used in rustproofing as well. It can also be used for bonding fabrics, wood, and other materials to these surfaces as well. Iron phosphate coatings are usually applied as part of a painting or powder coating process.

Iron phosphate can also be used as an intercalation electrode in a lithium-ion battery despite having low electronic conductivity. However, in recent years its use as an electrode material has been increasingly more common as materials engineers have overcome the electronic conductivity issue. FePO4 is an ideal electrode material for batteries in electric vehicles due to its thermal stability and generally good cyclability.

Legislation[edit]

Iron(III) phosphate is not allowed as food additive in European Union. It was withdrawn from the list of allowed substances in the directive 2002/46/EC in 2007.

Safety[edit]

Can cause eye, skin, and respiratory tract irritation. May be harmful if swallowed. Avoid inhalation of dusts.

See also[edit]

References[edit]

  1. ^ a b c d e "iron(III) phosphate dihydrate". chemister.ru. Retrieved 3 July 2014. 
  2. ^ a b c Sigma-Aldrich Co., Iron(III) phosphate dihydrate. Retrieved on 2014-05-03.
  3. ^ Song, Y.; Zavalij, P. Y.; Suzuki, M.; Whittingham, M. S. (2002). "New Iron(III) Phosphate Phases: Crystal Structure and Electrochemical and Magnetic Properties". Inorganic Chemistry 41: 5778–5786. doi:10.1021/ic025688q. Retrieved 3 July 2014. 
  4. ^ Zaghib, K.; Julien, C. M. (2005-01). "Structure and electrochemistry of FePO4·2H2O hydrate". Journal of Power Sources 142: 279–284. doi:10.1016/j.jpowsour.2004.09.042. Retrieved 3 July 2014. 
  5. ^ "COMMISSION REGULATION (EC) No 889/2008". European Union law. Retrieved 3 July 2014. 

External links[edit]