Iron(II,III) oxide

Last updated
Iron(II,III) oxide
Fe3O4.JPG
Names
IUPAC name
iron(II) iron(III) oxide
Other names
ferrous ferric oxide, ferrosoferric oxide, iron(II,III) oxide, magnetite, black iron oxide, lodestone, rust, iron(II) diiron(III) oxide
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.013.889 OOjs UI icon edit-ltr-progressive.svg
PubChem CID
UNII
  • InChI=1S/3Fe.4O Yes check.svgY
    Key: SZVJSHCCFOBDDC-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/3Fe.4O/rFe3O4/c1-4-2-6-3(5-1)7-2
    Key: SZVJSHCCFOBDDC-QXRQKJBKAR
  • O1[Fe]2O[Fe]O[Fe]1O2
Properties
Fe3O4

FeO.Fe2O3

Molar mass 231.533 g/mol
Appearancesolid black powder
Density 5 g/cm3
Melting point 1,597 °C (2,907 °F; 1,870 K)
Boiling point 2,623 [1]  °C (4,753 °F; 2,896 K)
2.42 [2]
Hazards
NFPA 704 (fire diamond)
NFPA 704.svgHealth 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideFlammability 0: Will not burn. E.g. waterInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
0
0
1
OX
Thermochemistry
-1120.89 kJ·mol−1 [3]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Iron(II,III) oxide, or black iron oxide, is the chemical compound with formula Fe3O4. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (Fe2O3) which also occurs naturally as the mineral hematite. It contains both Fe2+ and Fe3+ ions and is sometimes formulated as FeO ∙ Fe2O3. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. [4] Its most extensive use is as a black pigment (see: Mars Black). For this purpose, it is synthesized rather than being extracted from the naturally occurring mineral as the particle size and shape can be varied by the method of production. [5]

Contents

Preparation

Heated iron metal interacts with steam to form iron oxide and hydrogen gas.

Under anaerobic conditions, ferrous hydroxide (Fe(OH)2) can be oxidized by water to form magnetite and molecular hydrogen. This process is described by the Schikorr reaction:

This works because crystalline magnetite (Fe3O4) is thermodynamically more stable than amorphous ferrous hydroxide (Fe(OH)2 ). [6]

The Massart method of preparation of magnetite as a ferrofluid, is convenient in the laboratory: mix iron(II) chloride and iron(III) chloride in the presence of sodium hydroxide. [7]

A more efficient method of preparing magnetite without troublesome residues of sodium, is to use ammonia to promote chemical co-precipitation from the iron chlorides: first mix solutions of 0.1 M FeCl3·6H2O and FeCl2·4H2O with vigorous stirring at about 2000 rpm. The molar ratio of the FeCl3:FeCl2 should be about 2:1. Heat the mix to 70 °C, then raise the speed of stirring to about 7500 rpm and quickly add a solution of NH4OH (10 volume %). A dark precipitate of nanoparticles of magnetite forms immediately. [8]

In both methods, the precipitation reaction relies on rapid transformation of acidic iron ions into the spinel iron oxide structure at pH 10 or higher.

Controlling the formation of magnetite nanoparticles presents challenges: the reactions and phase transformations necessary for the creation of the magnetite spinel structure are complex. [9] The subject is of practical importance because magnetite particles are of interest in bioscience applications such as magnetic resonance imaging (MRI), in which iron oxide magnetite nanoparticles potentially present a non-toxic alternative to the gadolinium-based contrast agents currently in use. However, difficulties in controlling the formation of the particles, still frustrate the preparation of superparamagnetic magnetite particles, that is to say: magnetite nanoparticles with a coercivity of 0 A/m, meaning that they completely lose their permanent magnetisation in the absence of an external magnetic field. The smallest values currently reported for nanosized magnetite particles is Hc = 8.5 A m−1, [10] whereas the largest reported magnetization value is 87 Am2 kg−1 for synthetic magnetite. [11] [12]

Pigment quality Fe3O4, so called synthetic magnetite, can be prepared using processes that use industrial wastes, scrap iron or solutions containing iron salts (e.g. those produced as by-products in industrial processes such as the acid vat treatment (pickling) of steel):

C6H5NO2 + 3 Fe + 2 H2O → C6H5NH2 + Fe3O4

Reduction of Fe2O3 with hydrogen: [13] [14]

3Fe2O3 + H2 → 2Fe3O4 +H2O

Reduction of Fe2O3 with CO: [15]

3Fe2O3 + CO → 2Fe3O4 + CO2

Production of nano-particles can be performed chemically by taking for example mixtures of FeII and FeIII salts and mixing them with alkali to precipitate colloidal Fe3O4. The reaction conditions are critical to the process and determine the particle size. [16]

Iron(II) carbonate can also be thermally decomposed into Iron(II,III): [17]

3FeCO3 → Fe3O4 + 2CO2 + CO

Reactions

Reduction of magnetite ore by CO in a blast furnace is used to produce iron as part of steel production process: [4]

Controlled oxidation of Fe3O4 is used to produce brown pigment quality γ-Fe2O3 (maghemite): [18]

More vigorous calcining (roasting in air) gives red pigment quality α-Fe2O3 (hematite): [18]

Structure

Fe3O4 has a cubic inverse spinel group structure which consists of a cubic close packed array of oxide ions where all of the Fe2+ ions occupy half of the octahedral sites and the Fe3+ are split evenly across the remaining octahedral sites and the tetrahedral sites.

Both FeO and γ-Fe2O3 have a similar cubic close packed array of oxide ions and this accounts for the ready interchangeability between the three compounds on oxidation and reduction as these reactions entail a relatively small change to the overall structure. [4] Fe3O4 samples can be non-stoichiometric. [4]

The ferrimagnetism of Fe3O4 arises because the electron spins of the FeII and FeIII ions in the octahedral sites are coupled and the spins of the FeIII ions in the tetrahedral sites are coupled but anti-parallel to the former. The net effect is that the magnetic contributions of both sets are not balanced and there is a permanent magnetism. [4]

In the molten state, experimentally constrained models show that the iron ions are coordinated to 5 oxygen ions on average. [19] There is a distribution of coordination sites in the liquid state, with the majority of both FeII and FeIII being 5-coordinated to oxygen and minority populations of both 4- and 6-fold coordinated iron.

Properties

Sample of magnetite, naturally occurring Fe3O4. Magnetite.jpg
Sample of magnetite, naturally occurring Fe3O4.

Fe3O4 is ferrimagnetic with a Curie temperature of 858 K (585 °C). There is a phase transition at 120 K (−153 °C), called Verwey transition where there is a discontinuity in the structure, conductivity and magnetic properties. [20] This effect has been extensively investigated and whilst various explanations have been proposed, it does not appear to be fully understood. [21]

While it has much higher electrical resistivity than iron metal (96.1 nΩ m), Fe3O4's electrical resistivity (0.3 mΩ m [22] ) is significantly lower than that of Fe2O3 (approx kΩ m). This is ascribed to electron exchange between the FeII and FeIII centres in Fe3O4. [4]

Uses

Ferumoxytol
Clinical data
Trade names Feraheme, Rienso
AHFS/Drugs.com Monograph
MedlinePlus a614023
License data
Routes of
administration 		Intravenous infusion
ATC code
  • None
Legal status
Legal status
Identifiers
  • iron(2+);iron(3+);oxygen(2-)
CAS Number
DrugBank
UNII
KEGG
ChEBI
CompTox Dashboard (EPA)
ECHA InfoCard 100.013.889 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula Fe3O4
Molar mass 231.531 g·mol−1
3D model (JSmol)
  • [O-2].[O-2].[O-2].[O-2].[Fe+2].[Fe+3].[Fe+3]
  • InChI=1S/3Fe.4O/q+2;2*+3;4*-2
  • Key:WTFXARWRTYJXII-UHFFFAOYSA-N

Fe3O4 is used as a black pigment and is known as C.I pigment black 11 (C.I. No.77499) or Mars Black. [18]

Fe3O4 is used as a catalyst in the Haber process and in the water-gas shift reaction. [25] The latter uses an HTS (high temperature shift catalyst) of iron oxide stabilised by chromium oxide. [25] This iron–chrome catalyst is reduced at reactor start up to generate Fe3O4 from α-Fe2O3 and Cr2O3 to CrO3. [25]

Bluing is a passivation process that produces a layer of Fe3O4 on the surface of steel to protect it from rust. Along with sulfur and aluminium, it is an ingredient in steel-cutting thermite.[ citation needed ]

Medical uses

Nano particles of Fe3O4 are used as contrast agents in MRI scanning. [26]

Ferumoxytol, sold under the brand names Feraheme and Rienso, is an intravenous Fe3O4 preparation for treatment of anemia resulting from chronic kidney disease. [23] [24] [27] [28] Ferumoxytol is manufactured and globally distributed by AMAG Pharmaceuticals. [23] [28]

Biological occurrence

Magnetite has been found as nano-crystals in magnetotactic bacteria (42–45 nm) [5] and in the beak tissue of homing pigeons. [29]

Related Research Articles

<span class="mw-page-title-main">Hematite</span> Common iron oxide mineral

Hematite, also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
2O
3. It has the same crystal structure as corundum (Al
2O
3) and ilmenite (FeTiO
3). With this it forms a complete solid solution at temperatures above 950 °C (1,740 °F).

<span class="mw-page-title-main">Iron(III) oxide</span> Chemical compound

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is readily attacked by acids. Iron(III) oxide is often called rust, since rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as hydrous ferric oxide.

<span class="mw-page-title-main">Iron oxide</span> Class of chemical compounds composed of iron and oxygen

Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of which is rust.

<span class="mw-page-title-main">Magnetite</span> Iron ore mineral

Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the exception of extremely rare native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.

<span class="mw-page-title-main">Wüstite</span> Iron(II) oxide mineral formed under reducing conditions

Wüstite is a mineral form of mostly iron(II) oxide found with meteorites and native iron. It has a grey colour with a greenish tint in reflected light. Wüstite crystallizes in the isometric-hexoctahedral crystal system in opaque to translucent metallic grains. It has a Mohs hardness of 5 to 5.5 and a specific gravity of 5.88. Wüstite is a typical example of a non-stoichiometric compound.

<span class="mw-page-title-main">Maghemite</span> Iron oxide with a spinel ferrite structure

Maghemite (Fe2O3, γ-Fe2O3) is a member of the family of iron oxides. It has the same formula as hematite, but the same spinel ferrite structure as magnetite (Fe3O4) and is also ferrimagnetic. It is sometimes spelled as "maghaemite".

<span class="mw-page-title-main">Magnetosome</span> Organelle in magnetotactic bacteria

Magnetosomes are membranous structures present in magnetotactic bacteria (MTB). They contain iron-rich magnetic particles that are enclosed within a lipid bilayer membrane. Each magnetosome can often contain 15 to 20 magnetite crystals that form a chain which acts like a compass needle to orient magnetotactic bacteria in geomagnetic fields, thereby simplifying their search for their preferred microaerophilic environments. Recent research has shown that magnetosomes are invaginations of the inner membrane and not freestanding vesicles. Magnetite-bearing magnetosomes have also been found in eukaryotic magnetotactic algae, with each cell containing several thousand crystals.

<span class="mw-page-title-main">Iron(II) hydroxide</span> Chemical compound

Iron(II) hydroxide or ferrous hydroxide is an inorganic compound with the formula Fe(OH)2. It is produced when iron(II) salts, from a compound such as iron(II) sulfate, are treated with hydroxide ions. Iron(II) hydroxide is a white solid, but even traces of oxygen impart a greenish tinge. The air-oxidised solid is sometimes known as "green rust".

<span class="mw-page-title-main">Ferrite (magnet)</span> Ferrimagnetic ceramic material composed of iron(III) oxide and a divalent metallic element

A ferrite is an iron oxide-containing magnetic ceramic material. They are ferrimagnetic, meaning they are attracted by magnetic fields and can be magnetized to become permanent magnets. Unlike many ferromagnetic materials, most ferrites are not electrically conductive, making them useful in applications like magnetic cores for transformers to suppress eddy currents.

<span class="mw-page-title-main">Direct reduced iron</span> Newly mined and refined type of metal

Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore into iron by a reducing gas which either contains elemental carbon or hydrogen. When hydrogen is used as the reducing gas there are no greenhouse gases produced. Many ores are suitable for direct reduction.

<span class="mw-page-title-main">Iron(III) oxide-hydroxide</span> Hydrous ferric oxide (HFO)

Iron(III) oxide-hydroxide or ferric oxyhydroxide is the chemical compound of iron, oxygen, and hydrogen with formula FeO(OH).

<span class="mw-page-title-main">Red beds</span> Sedimentary rocks with ferric oxides

Red beds are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain thin beds of conglomerate, marl, limestone, or some combination of these sedimentary rocks. The ferric oxides, which are responsible for the red color of red beds, typically occur as a coating on the grains of sediments comprising red beds. Classic examples of red beds are the Permian and Triassic strata of the western United States and the Devonian Old Red Sandstone facies of Europe.

<span class="mw-page-title-main">Mars surface color</span> Extraterrestrial geography

The surface color of the planet Mars appears reddish from a distance because of rusty atmospheric dust. From close up, it looks more of a butterscotch, and other common surface colors include golden, brown, tan, and greenish, depending on minerals.

Magnetic Nanorings are a form of magnetic nanoparticles, typically made of iron oxide in the shape of a ring. They have multiple applications in the medical field and computer engineering. In experimental trials, they provide a more localized form of cancer treatment by attacking individual cells instead of a general cancerous region of the body, as well as a clearer image of tumors by improving accuracy of cancer cell identification. They also allow for a more efficient and smaller, MRAM, which helps reduce the size of the technology houses it. Magnetic nanorings can be produced in various compositions, shapes, and sizes by using hematite nanorings as the base structure.

<span class="mw-page-title-main">Mill scale</span> Chemical compound produced in steel processing

Mill scale, often shortened to just scale, is the flaky surface of hot rolled steel, consisting of the mixed iron oxides iron(II) oxide, iron(III) oxide, and iron(II,III) oxide.

<span class="mw-page-title-main">Iron oxide nanoparticle</span>

Iron oxide nanoparticles are iron oxide particles with diameters between about 1 and 100 nanometers. The two main forms are composed of magnetite and its oxidized form maghemite. They have attracted extensive interest due to their superparamagnetic properties and their potential applications in many fields including molecular imaging.

<span class="mw-page-title-main">Schikorr reaction</span> Transformation of Fe(OH)2 into Fe3O4 with hydrogen release

The Schikorr reaction formally describes the conversion of the iron(II) hydroxide (Fe(OH)2) into iron(II,III) oxide (Fe3O4). This transformation reaction was first studied by Gerhard Schikorr. The global reaction follows:

Cuprospinel is a mineral. Cuprospinel is an inverse spinel with the chemical formula CuFe2O4, where copper substitutes some of the iron cations in the structure. Its structure is similar to that of magnetite, Fe3O4, yet with slightly different chemical and physical properties due to the presence of copper.

<span class="mw-page-title-main">Three-phase firing</span>

Three-phase firing or iron reduction technique is a firing technique used in ancient Greek pottery production, specifically for painted vases. Already vessels from the Bronze Age feature the colouring typical of the technique, with yellow, orange or red clay and brown or red decoration. By the 7th century BC, the process was perfected in mainland Greece enabling the production of extremely shiny black-slipped surfaces, which led to the development of the black-figure and red-figure techniques, which dominated Greek vase painting until about 300 BC.

<span class="mw-page-title-main">Iron(II) nitrate</span> Chemical compound

Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water serves as a ready source of ferrous ions.

References

  1. ↑ Magnetite (Fe3O4): Properties, Synthesis, and Applications Lee Blaney, Lehigh Review 15, 33-81 (2007). See Appendix A, p.77
  2. ↑ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN   0-07-049439-8
  3. ↑ Chase MW (1998). "NIST-JANAF Themochemical Tables". NIST (Fourth ed.): 1–1951.
  4. 1 2 3 4 5 6 Greenwood NN, Earnshaw A (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  5. 1 2 3 4 Cornell RM, Schwertmann U (2007). The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses. Wiley-VCH. ISBN   978-3-527-60644-3.
  6. ↑ Ma M, Zhang Y, Guo Z, Gu N (January 2013). "Facile synthesis of ultrathin magnetic iron oxide nanoplates by Schikorr reaction". Nanoscale Research Letters. 8 (1): 16. Bibcode:2013NRL.....8...16M. doi: 10.1186/1556-276X-8-16 . PMC   3598988 . PMID   23294626.
  7. ↑ Massart R (1981). "Preparation of aqueous magnetic liquids in alkaline and acidic media". IEEE Transactions on Magnetics. 17 (2): 1247–1248. Bibcode:1981ITM....17.1247M. doi:10.1109/TMAG.1981.1061188.
  8. ↑ Keshavarz S, Xu Y, Hrdy S, Lemley C, Mewes T, Bao Y (2010). "Relaxation of Polymer Coated Fe3O4 Magnetic Nanoparticles in Aqueous Solution". IEEE Transactions on Magnetics. 46 (6): 1541–1543. doi:10.1109/TMAG.2010.2040588. S2CID   35129018.
  9. ↑ Jolivet JP, Chanéac C, Tronc E (March 2004). "Iron oxide chemistry. From molecular clusters to extended solid networks". Chemical Communications (5): 481–7. doi:10.1039/B304532N. PMID   14973569.
  10. ↑ Ström V, Olsson RT, Rao KV (2010). "Real-time monitoring of the evolution of magnetism during precipitation of superparamagnetic nanoparticles for bioscience applications". Journal of Materials Chemistry. 20 (20): 4168. doi:10.1039/C0JM00043D.
  11. ↑ Fang M, Ström V, Olsson RT, Belova L, Rao KV (2011). "Rapid mixing: A route to synthesize magnetite nanoparticles with high moment". Applied Physics Letters. 99 (22): 222501. Bibcode:2011ApPhL..99v2501F. doi:10.1063/1.3662965.
  12. ↑ Fang M, Ström V, Olsson RT, Belova L, Rao KV (April 2012). "Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles". Nanotechnology. 23 (14): 145601. Bibcode:2012Nanot..23n5601F. doi:10.1088/0957-4484/23/14/145601. PMID   22433909. S2CID   34153665.
  13. ↑ US 2596954,Heath TD,"Process for reduction of iron ore to magnetite",issued 13 May 1952, assigned to Dorr Company
  14. ↑ Pineau A, Kanari N, Gaballah I (2006). "Kinetics of reduction of iron oxides by H2 Part I: Low temperature reduction of hematite". Thermochimica Acta . 447 (1): 89–100. doi:10.1016/j.tca.2005.10.004.
  15. ↑ Hayes PC, Grieveson P (1981). "The effects of nucleation and growth on the reduction of Fe2O3 to Fe3O4". Metallurgical and Materials Transactions B. 12 (2): 319–326. Bibcode:1981MTB....12..319H. doi:10.1007/BF02654465. S2CID   94274056.
  16. ↑ Arthur T. Hubbard (2002) Encyclopedia of Surface and Colloid Science CRC Press, ISBN   0-8247-0796-6
  17. ↑ "FeCO3 = Fe3O4 + CO2 + CO | The thermal decomposition of iron(II) carbonate". chemiday.com. Retrieved 2022-10-14.
  18. 1 2 3 Gunter Buxbaum, Gerhard Pfaff (2005) Industrial Inorganic Pigments 3d edition Wiley-VCH ISBN   3-527-30363-4
  19. ↑ Shi C, Alderman OL, Tamalonis A, Weber R, You J, Benmore CJ (2020). "Redox-structure dependence of molten iron oxides". Communications Materials. 1 (1): 80. Bibcode:2020CoMat...1...80S. doi: 10.1038/s43246-020-00080-4 . S2CID   226248368.
  20. ↑ Verwey EJ (1939). "Electronic Conduction of Magnetite (Fe3O4) and its Transition Point at Low Temperatures". Nature . 144 (3642): 327–328 (1939). Bibcode:1939Natur.144..327V. doi:10.1038/144327b0. S2CID   41925681.
  21. ↑ Walz F (2002). "The Verwey transition - a topical review". Journal of Physics: Condensed Matter. 14 (12): R285–R340. doi:10.1088/0953-8984/14/12/203. S2CID   250773238.
  22. ↑ Itai R (1971). "Electrical resistivity of Magnetite anodes". Journal of the Electrochemical Society. 118 (10): 1709. Bibcode:1971JElS..118.1709I. doi:10.1149/1.2407817.
  23. 1 2 3 "Feraheme- ferumoxytol injection". DailyMed. 9 July 2020. Retrieved 14 September 2020.
  24. 1 2 "Rienso EPAR". European Medicines Agency. 17 September 2018. Retrieved 14 September 2020.
  25. 1 2 3 Sunggyu Lee (2006) Encyclopedia of Chemical Processing CRC Press ISBN   0-8247-5563-4
  26. ↑ Babes L, Denizot B, Tanguy G, Jallet P (April 1999). "Synthesis of Iron Oxide Nanoparticles Used as MRI Contrast Agents: A Parametric Study". Journal of Colloid and Interface Science. 212 (2): 474–482. Bibcode:1999JCIS..212..474B. doi:10.1006/jcis.1998.6053. PMID   10092379.
  27. ↑ Schwenk MH (January 2010). "Ferumoxytol: a new intravenous iron preparation for the treatment of iron deficiency anemia in patients with chronic kidney disease". Pharmacotherapy. 30 (1): 70–79. doi:10.1592/phco.30.1.70. PMID   20030475. S2CID   7748714.
  28. 1 2 "Drug Approval Package: Feraheme (Ferumoxytol) Injection NDA #022180". U.S. Food and Drug Administration (FDA). Retrieved 14 September 2020.
    Rieves D (June 23, 2009). "Application Number: 22-180" (PDF) (Summary Review). Center for Drug Evaluation and Research.
  29. ↑ Hanzlik M, Heunemann C, Holtkamp-Rötzler E, Winklhofer M, Petersen N, Fleissner G (December 2000). "Superparamagnetic magnetite in the upper beak tissue of homing pigeons". Biometals. 13 (4): 325–31. doi:10.1023/A:1009214526685. PMID   11247039. S2CID   39216462.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.