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{{Infobox lanthanum|block ref=d block}}
'''Lanthanum''' is a [[Chemistry:Chemical element|chemical element]]; it has [[Chemistry:Symbol|symbol]] '''La''' and [[Physics:Atomic number|atomic number]] 57. It is a [[Physics:Hardness|soft]], [[Physics:Ductility|ductile]], silvery-white [[Chemistry:Metal|metal]] that tarnishes slowly when exposed to air. It is the eponym of the [[Chemistry:Lanthanide|lanthanide]] series, a group of 15 similar elements between lanthanum and [[Chemistry:Lutetium|lutetium]] in the [[Chemistry:Periodic table|periodic table]], of which lanthanum is the first and the prototype. Lanthanum is traditionally counted among the rare earth elements. Like most other rare earth elements, the usual [[Chemistry:Oxidation state|oxidation state]] is +3, although some compounds are known with oxidation state +2. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity.

Lanthanum usually occurs together with [[Chemistry:Cerium|cerium]] and the other rare earth elements. Lanthanum was first found by the Swedish chemist [[Biography:Carl Gustaf Mosander|Carl Gustaf Mosander]] in 1839 as an impurity in [[Chemistry:Cerium nitrate|cerium nitrate]] – hence the name ''lanthanum'', from the [[Social:Ancient Greek|Ancient Greek]] {{lang|grc|λανθάνειν}} ({{transliteration|grc|lanthanein}}), meaning 'to lie hidden'. Although it is classified as a rare earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as [[Chemistry:Lead|lead]]. In minerals such as [[Chemistry:Monazite|monazite]] and [[Chemistry:Bastnäsite|bastnäsite]], lanthanum composes about a quarter of the lanthanide content.<ref>{{Cite web |title=Monazite-(Ce) Mineral Data |url=http://webmineral.com/data/Monazite-(Ce).shtml |access-date=10 July 2016 |website=Webmineral}}</ref> It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923.

Lanthanum compounds have numerous applications as [[Chemistry:Catalysis|catalysts]], additives in glass, carbon arc lamps for studio lights and projectors, ignition elements in [[Chemistry:Lighter|lighter]]s and torches, [[Physics:Hot cathode|electron cathodes]], [[Physics:Scintillator|scintillator]]s, [[Chemistry:Gas tungsten arc welding|gas tungsten arc welding]] electrodes, and other things. [[Chemistry:Lanthanum carbonate|Lanthanum carbonate]] is used as a phosphate binder in cases of [[Medicine:Hyperphosphatemia|high levels of phosphate in the blood]] seen with [[Medicine:Kidney failure|kidney failure]].

==Characteristics==

===Physical===
Lanthanum is the first element and prototype of the lanthanide series. In the periodic table, it appears to the right of the [[Chemistry:Alkaline earth metal|alkaline earth metal]] [[Chemistry:Barium|barium]] and to the left of the lanthanide cerium. Lanthanum is generally considered the first of the f-block elements by authors writing on the subject.<ref name="Fluck">{{Cite journal |last=Fluck |first=E. |year=1988 |title=New Notations in the Periodic Table |url=http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |url-status=live |journal=[[Chemistry:Pure and Applied Chemistry|Pure Appl. Chem.]] |volume=60 |issue=3 |pages=431–36 |doi=10.1351/pac198860030431 |archive-url=https://web.archive.org/web/20120325152951/http://www.iupac.org/publications/pac/1988/pdf/6003x0431.pdf |archive-date=25 March 2012 |access-date=24 March 2012 |s2cid=96704008}}</ref><ref>{{Cite book |last=[[Biography:Lev Landau|L. D. Landau]], [[Biography:Evgeny Lifshitz|E. M. Lifshitz]] |title=Quantum Mechanics: Non-Relativistic Theory |publisher=Pergamon Press |year=1958 |edition=1st |volume=3 |pages=256–7 }}</ref><ref name="Jensen1982">{{Cite journal |last=William B. Jensen |year=1982 |title=The Positions of Lanthanum (Actinium) and Lutetium (Lawrencium) in the Periodic Table |journal=J. Chem. Educ. |volume=59 |issue=8 |pages=634–636 |bibcode=1982JChEd..59..634J |doi=10.1021/ed059p634}}</ref><ref name="Jensen2015">{{Cite journal |last=Jensen |first=William B. |date=2015 |title=The positions of lanthanum (actinium) and lutetium (lawrencium) in the periodic table: an update |url=https://link.springer.com/article/10.1007/s10698-015-9216-1 |journal=Foundations of Chemistry |volume=17 |pages=23–31 |doi=10.1007/s10698-015-9216-1 |access-date=28 January 2021 |s2cid=98624395}}</ref><ref name="2021IUPAC">{{Cite journal |last=Scerri |first=Eric |date=18 January 2021 |title=Provisional Report on Discussions on Group 3 of the Periodic Table |journal=Chemistry International |volume=43 |issue=1 |pages=31–34 |doi=10.1515/ci-2021-0115 |s2cid=231694898|doi-access=free }}</ref> The 57 electrons of a lanthanum atom are arranged in the [[Physics:Electron configuration|configuration]] [Xe]5d<sup>1</sup>6s<sup>2</sup>, with three valence electrons outside the noble gas core. In chemical reactions, lanthanum almost always gives up these three valence electrons from the 5d and 6s [[Physics:Electron shell#Subshells|subshells]] to form the +3 oxidation state, achieving the stable configuration of the preceding noble gas [[Chemistry:Xenon|xenon]].<ref name="Greenwood1106">Greenwood and Earnshaw, p. 1106</ref> Some lanthanum(II) compounds are also known, but they are usually much less stable.<ref name="patnaik">{{Cite book |last=Patnaik |first=Pradyot |url={{Google books|plainurl=yes|id=Xqj-TTzkvTEC|page=243 }} |title=Handbook of Inorganic Chemical Compounds |date=2003 |publisher=McGraw-Hill |isbn=978-0-07-049439-8 |pages=444–446 |access-date=2009-06-06}}</ref><ref>{{cite journal |bibcode=2008AngCh.120.1510H |title=Lanthanum Does Form Stable Molecular Compounds in the +2 Oxidation State |last1=Hitchcock |first1=Peter B. |last2=Lappert |first2=Michael F. |last3=Maron |first3=Laurent |last4=Protchenko |first4=Andrey V. |journal=Angewandte Chemie |year=2008 |volume=120 |issue=8 |page=1510 |doi=10.1002/ange.200704887 }}</ref>  Lanthanum Monoxide (LaO) produces strong absorption bands in some stellar spectra.<ref>{{cite journal |bibcode=1928PPS....41..520J |title=The band spectrum of lanthanum monoxide |last1=Jevons |first1=W. |journal=Proceedings of the Physical Society |year=1928 |volume=41 |issue=1 |page=520 |doi=10.1088/0959-5309/41/1/355 }}</ref>

Among the lanthanides, lanthanum is exceptional as it has no 4f electrons as a single gas-phase atom. Thus it is only very weakly [[Physics:Paramagnetic|paramagnetic]], unlike the strongly paramagnetic later lanthanides (with the exceptions of the last two, [[Chemistry:Ytterbium|ytterbium]] and [[Chemistry:Lutetium|lutetium]], where the 4f shell is completely full).<ref>Cullity, B. D. and Graham, C. D. (2011) ''Introduction to Magnetic Materials'', John Wiley & Sons, {{ISBN|9781118211496}}</ref> However, the 4f shell of lanthanum can become partially occupied in chemical environments and participate in chemical bonding.<ref name="Wittig">{{Cite book |last=Wittig |first=Jörg |title=Festkörper Probleme: Plenary Lectures of the Divisions Semiconductor Physics, Surface Physics, Low Temperature Physics, High Polymers, Thermodynamics and Statistical Mechanics, of the German Physical Society, Münster, March 19–24, 1973 |date=1973 |publisher=Springer |isbn=978-3-528-08019-8 |editor-last=H. J. Queisser |series=Advances in Solid State Physics |volume=13 |location=Berlin, Heidelberg |pages=375–396 |chapter=The pressure variable in solid state physics: What about 4f-band superconductors? |doi=10.1007/BFb0108579}}</ref><ref>{{cite journal | last=Krinsky | first=Jamin L. | last2=Minasian | first2=Stefan G. | last3=Arnold | first3=John | title=Covalent Lanthanide Chemistry Near the Limit of Weak Bonding: Observation of (CpSiMe<sub>3</sub>)<sub>3</sub>Ce−ECp* and a Comprehensive Density Functional Theory Analysis of Cp<sub>3</sub>Ln−ECp (E = Al, Ga) | journal=Inorganic Chemistry | publisher=American Chemical Society (ACS) | volume=50 | issue=1 | date=2010-12-08 | issn=0020-1669 | doi=10.1021/ic102028d | pages=345–357}}</ref> For example, the melting points of the trivalent lanthanides (all but [[Chemistry:Europium|europium]] and ytterbium) are related to the extent of hybridisation of the 6s, 5d, and 4f electrons (lowering with increasing 4f involvement),<ref>{{Cite book |last=Gschneidner |first=Karl A. Jr. |title=Handbook on the Physics and Chemistry of Rare Earths |date=2016 |isbn=978-0-444-63851-9 |editor-last=Jean-Claude G. Bünzli |volume=50 |pages=12–16 |chapter=282. Systematics |editor-last2=Vitalij K. Pecharsky}}</ref> and lanthanum has the second-lowest melting point among them: 920&nbsp;°C. (Europium and ytterbium have lower melting points because they delocalise about two electrons per atom rather than three.)<ref>Krishnamurthy, Nagaiyar and Gupta, Chiranjib Kumar (2004) ''Extractive Metallurgy of Rare Earths'', CRC Press, {{ISBN|0-415-33340-7}}</ref> This chemical availability of f orbitals justifies lanthanum's placement in the f-block despite its anomalous ground-state configuration<ref name="Hamilton">{{Cite journal |last=Hamilton |first=David C. |date=1965 |title=Position of Lanthanum in the Periodic Table |journal=American Journal of Physics |volume=33 |issue=8 |pages=637–640 |bibcode=1965AmJPh..33..637H |doi=10.1119/1.1972042}}</ref><ref name="JensenLr">{{Cite web |last=Jensen |first=W. B. |date=2015 |title=Some Comments on the Position of Lawrencium in the Periodic Table |url=http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |url-status=dead |archive-url=https://web.archive.org/web/20151223091325/http://www.che.uc.edu/jensen/W.%20B.%20Jensen/Reprints/251.%20Lawrencium.pdf |archive-date=23 December 2015 |access-date=20 September 2015}}</ref> (which is merely the result of strong interelectronic repulsion making it less profitable to occupy the 4f shell, as it is small and close to the core electrons).<ref>{{Cite journal |last=Jørgensen |first=Christian |date=1973 |title=The Loose Connection between Electron Configuration and the Chemical Behavior of the Heavy Elements (Transuranics) |journal=Angewandte Chemie International Edition |volume=12 |issue=1 |pages=12–19 |doi=10.1002/anie.197300121}}</ref>

The lanthanides become harder as the series is traversed: as expected, lanthanum is a soft metal. Lanthanum has a relatively high resistivity of 615&nbsp;nΩm at room temperature; in comparison, the value for the good conductor aluminium is only 26.50&nbsp;nΩm.<ref name="Greenwood1429">Greenwood and Earnshaw, p. 1429</ref><ref name="CRC">{{RubberBible86th}}</ref> Lanthanum is the least volatile of the lanthanides.<ref name="radio">{{Cite web |title=The Radiochemistry of the Rare Earths, Scandium, Yttrium, and Actinium |url=http://library.lanl.gov/cgi-bin/getfile?rc000021.pdf |url-status=live |archive-url=https://web.archive.org/web/20210831203424/https://library.lanl.gov/cgi-bin/getfile?rc000021.pdf |archive-date=2021-08-31 |access-date=2016-06-23}}</ref> Like most of the lanthanides, lanthanum has a [[Physics:Hexagonal crystal system|hexagonal crystal structure]] at room temperature. At 310&nbsp;°C, lanthanum changes to a face-centered cubic structure, and at 865&nbsp;°C, it changes to a body-centered cubic structure.<ref name="CRC" />

===Chemical===
As expected from periodic trends, lanthanum has the largest [[Physics:Atomic radius|atomic radius]] of the lanthanides. Hence, it is the most reactive among them, tarnishing quite rapidly in air, turning completely dark after several hours and can readily burn to form lanthanum(III) oxide, La<sub>2</sub>O<sub>3</sub>, which is almost as basic as [[Chemistry:Calcium oxide|calcium oxide]].<ref name="Greenwood1105">Greenwood and Earnshaw, p. 1105–7</ref> A centimeter-sized sample of lanthanum will corrode completely in a year as its oxide [[Physics:Spallation|spalls]] off like iron [[Chemistry:Rust|rust]], instead of forming a protective oxide coating like [[Chemistry:Aluminium|aluminium]], scandium, yttrium, and lutetium.<ref>{{Cite web |title=Rare-Earth Metal Long Term Air Exposure Test |url=http://www.elementsales.com/re_exp/index.htm |access-date=2009-08-08}}</ref> Lanthanum reacts with the [[Chemistry:Halogen|halogen]]s at room temperature to form the trihalides, and upon warming will form binary compounds with the nonmetals nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic.<ref name="Greenwood1106" /><ref name="patnaik" /> Lanthanum reacts slowly with water to form [[Chemistry:Lanthanum hydroxide|lanthanum(III) hydroxide]], La(OH)<sub>3</sub>.<ref name="webelements">{{Cite web |title=Chemical reactions of Lanthanum |url=https://www.webelements.com/lanthanum/chemistry.html |access-date=2009-06-06 |publisher=Webelements}}</ref> In dilute [[Chemistry:Sulfuric acid|sulfuric acid]], lanthanum readily forms the aquated tripositive ion {{nowrap|[La(H<sub>2</sub>O)<sub>9</sub>]<sup>3+</sup>}}: this is colorless in aqueous solution since La<sup>3+</sup> has no d or f electrons.<ref name="webelements" /> Lanthanum is the strongest and [[Chemistry:HSAB theory|hardest]] base among the rare earth elements, which is again expected from its being the largest of them.<ref name="Greenwood1434">Greenwood and Earnshaw, p. 1434</ref>

Some lanthanum(II) compounds are also known, but they are much less stable.<ref name="patnaik" /><!-- Although mentioned in the section on physical properties, someone looking for chemical characteristics easily misses it their --> Therefore, in officially naming compounds of lanthanum its oxidation number always is to be mentioned.

===Isotopes===
[[File:Lanthanum stable nucleus.png|thumb|left|280px|Excerpt from the chart of nuclides showing stable isotopes (black) from barium ({{nobr|1=Z = 56}}) to neodymium ({{nobr|1=Z = 60}})]]
{{Main|Physics:Isotopes of lanthanum}}
Naturally occurring lanthanum is made up of two isotopes, the stable <sup>139</sup>La and the [[Chemistry:Primordial nuclide|primordial long-lived radioisotope]] <sup>138</sup>La. <sup>139</sup>La is by far the most abundant, making up 99.910% of natural lanthanum: it is produced in the [[Physics:S-process|s-process]] (slow [[Physics:Neutron|neutron]] capture, which occurs in low- to medium-mass stars) and the [[Physics:R-process|r-process]] (rapid neutron capture, which occurs in core-collapse [[Astronomy:Supernova|supernova]]e). It is the only stable isotope of lanthanum.<ref name="Audi">{{NUBASE 2003}}</ref> The very rare isotope <sup>138</sup>La is one of the few primordial odd–odd nuclei, with a long half-life of 1.05×10<sup>11</sup>&nbsp;years. It is one of the proton-rich [[Physics:P-nuclei|p-nuclei]] which cannot be produced in the [[Physics:S-process|s-]] or [[Physics:R-process|r-process]]es. <sup>138</sup>La, along with the even rarer [[Physics:Tantalum-180m|<sup>180m</sup>Ta]], is produced in the ν-process, where [[Physics:Neutrino|neutrino]]s interact with stable nuclei.<ref name="nu-process">{{Cite journal |last1=Woosley |first1=S. E. |last2=Hartmann |first2=D. H. |last3=Hoffman |first3=R. D. |last4=Haxton |first4=W. C. |year=1990 |title=The ν-process |journal=The Astrophysical Journal |volume=356 |pages=272–301 |bibcode=1990ApJ...356..272W |doi=10.1086/168839}}</ref> All other lanthanum isotopes are [[Physics:Synthetic radioisotope|synthetic]]: with the exception of <sup>137</sup>La with a half-life of about 60,000&nbsp;years, all of them have half-lives less than two days, and most have half-lives less than a minute. The isotopes <sup>139</sup>La and <sup>140</sup>La occur as fission products of uranium.<ref name="Audi" />

==Compounds==

[[Chemistry:Lanthanum oxide|Lanthanum oxide]] is a white solid that can be prepared by direct reaction of its constituent elements. Due to the large size of the La<sup>3+</sup> ion, La<sub>2</sub>O<sub>3</sub> adopts a hexagonal 7-coordinate structure that changes to the 6-coordinate structure of [[Chemistry:Scandium oxide|scandium oxide]] (Sc<sub>2</sub>O<sub>3</sub>) and [[Chemistry:Yttrium(III) oxide|yttrium oxide]] (Y<sub>2</sub>O<sub>3</sub>) at high temperature. When it reacts with water, [[Chemistry:Lanthanum hydroxide|lanthanum hydroxide]] is formed:<ref name="Shkolnikov2009">{{Cite journal |last=E.V. Shkolnikov |year=2009 |title=Thermodynamic Characterization of the Amphoterism of Hydroxides and Oxides of Scandium Subgroup Elements in Aqueous Media |journal=Russian Journal of Applied Chemistry |volume=82 |issue=2 |pages=2098–2104 |doi=10.1134/S1070427209120040 |s2cid=93220420}}</ref> a lot of heat is evolved in the reaction and a hissing sound is heard. Lanthanum hydroxide will react with atmospheric [[Chemistry:Carbon dioxide|carbon dioxide]] to form the basic carbonate.<ref name="Greenwood1107">Greenwood and Earnshaw, p. 1107–8</ref>

Lanthanum fluoride is insoluble in water and can be used as a [[Chemistry:Qualitative inorganic analysis|qualitative]] test for the presence of La<sup>3+</sup>. The heavier halides are all very soluble deliquescent compounds. The anhydrous halides are produced by direct reaction of their elements, as heating the hydrates causes hydrolysis: for example, heating hydrated LaCl<sub>3</sub> produces LaOCl.<ref name="Greenwood1107" />

Lanthanum reacts exothermically with hydrogen to produce the dihydride LaH<sub>2</sub>, a black, [[Chemistry:Pyrophoricity|pyrophoric]], brittle, conducting compound with the [[Chemistry:Calcium fluoride|calcium fluoride]] structure.<ref name="Fukai">{{Cite book |last=Fukai |first=Y. |title=The Metal-Hydrogen System, Basic Bulk Properties, 2d edition |publisher=Springer |year=2005 |isbn=978-3-540-00494-3}}</ref> This is a non-stoichiometric compound, and further absorption of hydrogen is possible, with a concomitant loss of electrical conductivity, until the more salt-like LaH<sub>3</sub> is reached.<ref name="Greenwood1107" /> Like LaI<sub>2</sub> and LaI, LaH<sub>2</sub> is probably an [[Physics:Electride|electride]] compound.<ref name="Greenwood1107" />

Due to the large ionic radius and great electropositivity of La<sup>3+</sup>, there is not much covalent contribution to its bonding and hence it has a limited coordination chemistry, like yttrium and the other lanthanides.<ref name="Greenwood1108">Greenwood and Earnshaw, pp. 1108–9</ref> [[Chemistry:Lanthanum oxalate|Lanthanum oxalate]] does not dissolve very much in alkali-metal oxalate solutions, and [La(acac)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>] decomposes around 500&nbsp;°C. Oxygen is the most common donor atom in lanthanum complexes, which are mostly ionic and often have high coordination numbers over 6: 8 is the most characteristic, forming [[Square antiprism|square antiprism]]atic and [[Snub disphenoid|dodecadeltahedral]] structures. These high-coordinate species, reaching up to coordination number 12 with the use of chelating ligands such as in La<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·9H<sub>2</sub>O, often have a low degree of symmetry because of stereo-chemical factors.<ref name="Greenwood1108" />

Lanthanum chemistry tends not to involve π bonding due to the electron configuration of the element: thus its organometallic chemistry is quite limited. The best characterized organolanthanum compounds are the [[Chemistry:Cyclopentadienyl complex|cyclopentadienyl complex]] La(C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>, which is produced by reacting anhydrous LaCl<sub>3</sub> with NaC<sub>5</sub>H<sub>5</sub> in [[Chemistry:Tetrahydrofuran|tetrahydrofuran]], and its methyl-substituted derivatives.<ref name="Greenwood1110">Greenwood and Earnshaw, p. 1110</ref>

==History==
[[File:Mosander Carl Gustav bw.jpg|thumb|right|Carl Gustaf Mosander, the scientist who discovered lanthanum as well as terbium and erbium]]
In 1751, the Swedish mineralogist [[Biography:Axel Fredrik Cronstedt|Axel Fredrik Cronstedt]] discovered a heavy mineral from the mine at Bastnäs, later named [[Chemistry:Cerite|cerite]]. Thirty years later, the fifteen-year-old [[Biography:Wilhelm Hisinger|Wilhelm Hisinger]], from the family owning the mine, sent a sample of it to Carl Scheele, who did not find any new elements within. In 1803, after Hisinger had become an ironmaster, he returned to the mineral with [[Biography:Jöns Jacob Berzelius|Jöns Jacob Berzelius]] and isolated a new oxide which they named ''ceria'' after the [[Astronomy:Dwarf planet|dwarf planet]] [[Astronomy:Ceres (dwarf planet)|Ceres]], which had been discovered two years earlier.<ref>{{Cite web |title=The Discovery and Naming of the Rare Earths |url=http://www.vanderkrogt.net/elements/rareearths.php |access-date=23 June 2016 |publisher=Elements.vanderkrogt.net}}</ref> Ceria was simultaneously independently isolated in Germany by [[Biography:Martin Heinrich Klaproth|Martin Heinrich Klaproth]].<ref name="Greenwood1424">Greenwood and Earnshaw, p. 1424</ref> Between 1839 and 1843, ceria was shown to be a mixture of oxides by the Swedish surgeon and chemist [[Biography:Carl Gustaf Mosander|Carl Gustaf Mosander]], who lived in the same house as Berzelius and studied under him: he separated out two other oxides which he named ''lanthana'' and ''[[Chemistry:Didymium|didymia]]''.<ref name="Weeks">{{Cite book |last=Weeks |first=Mary Elvira |url=https://archive.org/details/discoveryoftheel002045mbp |title=The discovery of the elements |date=1956 |publisher=Journal of Chemical Education |edition=6th |location=Easton, PA}}</ref><ref name="XI">{{Cite journal |last=Weeks |first=Mary Elvira |date=1932 |title=The Discovery of the Elements: XI. Some Elements Isolated with the Aid of Potassium and Sodium:Zirconium, Titanium, Cerium and Thorium |journal=The Journal of Chemical Education |volume=9 |issue=7 |pages=1231–1243 |bibcode=1932JChEd...9.1231W |doi=10.1021/ed009p1231}}</ref> He partially decomposed a sample of [[Chemistry:Cerium nitrate|cerium nitrate]] by roasting it in air and then treating the resulting oxide with dilute [[Chemistry:Nitric acid|nitric acid]].<ref>See:
* (Berzelius) (1839) [https://archive.org/stream/ComptesRendusAcademieDesSciences0008/ComptesRendusAcadmieDesSciences-Tome008-Janvier-juin1839#page/n361/mode/1up "Nouveau métal"] (New metal), ''Comptes rendus'', ''8'' : 356-357. From p. 356: ''"L'oxide de cérium, extrait de la cérite par la procédé ordinaire, contient à peu près les deux cinquièmes de son poids de l'oxide du nouveau métal qui ne change que peu les propriétés du cérium, et qui s'y tient pour ainsi dire caché. Cette raison a engagé M. Mosander à donner au nouveau métal le nom de ''Lantane''."'' (The oxide of cerium, extracted from cerite by the usual procedure, contains almost two fifths of its weight in the oxide of the new metal, which differs only slightly from the properties of cerium, and which is held in it so to speak "hidden". This reason motivated Mr. Mosander to give to the new metal the name ''Lantane''.)
* (Berzelius) (1839) [https://books.google.com/books?id=dF1KiX7MbSMC&pg=PA390 "Latanium — a new metal,"] {{Webarchive|url=https://web.archive.org/web/20221115194934/https://books.google.com/books?id=dF1KiX7MbSMC&pg=PA390 |date=2022-11-15 }} ''Philosophical Magazine'', new series, '''14''' : 390-391.</ref> That same year, Axel Erdmann, a student also at the Karolinska Institute, discovered lanthanum in a new mineral from Låven island located in a Norwegian fjord.

Finally, Mosander explained his delay, saying that he had extracted a second element from cerium, and this he called didymium. Although he didn't realise it, didymium too was a mixture, and in 1885 it was separated into praseodymium and neodymium.

Since lanthanum's properties differed only slightly from those of cerium, and occurred along with it in its salts, he named it from the [[Social:Ancient Greek|Ancient Greek]] ''λανθάνειν'' [lanthanein] (lit. ''to lie hidden'').<ref name="Greenwood1424" /> Relatively pure lanthanum metal was first isolated in 1923.<ref name="patnaik" />

==Occurrence and production==
Lanthanum is the third-most abundant of all the lanthanides, making up 39&nbsp;mg/kg of the Earth's crust, behind [[Chemistry:Neodymium|neodymium]] at 41.5&nbsp;mg/kg and cerium at 66.5&nbsp;mg/kg. It is almost three times as abundant as [[Chemistry:Lead|lead]] in the Earth's crust.<ref>{{Cite web |title=It's Elemental&nbsp;— The Periodic Table of Elements |url=http://education.jlab.org/itselemental/index.html |url-status=live |archive-url=https://web.archive.org/web/20070429032414/http://education.jlab.org/itselemental/index.html |archive-date=29 April 2007 |access-date=2007-04-14 |publisher=Jefferson Lab}}</ref> Despite being among the so-called "rare earth metals", lanthanum is thus not rare at all, but it is historically so named because it is rarer than "common earths" such as lime and magnesia, and historically only a few deposits were known. Lanthanum is considered a rare earth metal because the process to mine it is difficult, time-consuming, and expensive.<ref name="patnaik" /> Lanthanum is rarely the dominant lanthanide found in the rare earth minerals, and in their chemical formulae it is usually preceded by cerium. Rare examples of La-dominant minerals are monazite-(La) and lanthanite-(La).<ref>{{Cite web |last=Hudson Institute of Mineralogy |date=1993–2018 |title=Mindat.org |url=https://www.mindat.org/ |access-date=14 January 2018 |website=www.mindat.org}}</ref>

[[File:Monazite acid cracking process.svg|thumb|center|upright=3|Production of Lanthanum from Monazite sand]]
The La<sup>3+</sup> ion is similarly sized to the early lanthanides of the cerium group (those up to [[Chemistry:Samarium|samarium]] and [[Chemistry:Europium|europium]]) that immediately follow in the periodic table, and hence it tends to occur along with them in [[Chemistry:Phosphate|phosphate]], [[Chemistry:Silicate|silicate]] and [[Chemistry:Carbonate|carbonate]] minerals, such as [[Chemistry:Monazite|monazite]] (M<sup>III</sup>PO<sub>4</sub>) and [[Chemistry:Bastnäsite|bastnäsite]] (M<sup>III</sup>CO<sub>3</sub>F), where M refers to all the rare earth metals except scandium and the radioactive [[Chemistry:Promethium|promethium]] (mostly Ce, La, and Y).<ref name="Greenwood1103">Greenwood and Earnshaw, p. 1103</ref> Bastnäsite is usually lacking in [[Chemistry:Thorium|thorium]] and the heavy lanthanides, and the purification of the light lanthanides from it is less involved. The ore, after being crushed and ground, is first treated with hot concentrated sulfuric acid, evolving carbon dioxide, [[Chemistry:Hydrogen fluoride|hydrogen fluoride]], and [[Chemistry:Silicon tetrafluoride|silicon tetrafluoride]]: the product is then dried and leached with water, leaving the early lanthanide ions, including lanthanum, in solution.<ref name="Greenwood1426">Greenwood and Earnshaw, p. 1426–9</ref>

The procedure for monazite, which usually contains all the rare earths as well as thorium, is more involved. Monazite, because of its magnetic properties, can be separated by repeated electromagnetic separation. After separation, it is treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths. The acidic filtrates are partially neutralized with [[Chemistry:Sodium hydroxide|sodium hydroxide]] to pH 3–4. Thorium precipitates out of solution as hydroxide and is removed. After that, the solution is treated with [[Chemistry:Ammonium oxalate|ammonium oxalate]] to convert rare earths to their insoluble [[Chemistry:Oxalate|oxalate]]s. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, [[Chemistry:Cerium|cerium]], whose oxide is insoluble in HNO<sub>3</sub>. Lanthanum is separated as a double salt with ammonium nitrate by crystallization. This salt is relatively less soluble than other rare earth double salts and therefore stays in the residue.<ref name="patnaik" /> Care must be taken when handling some of the residues as they contain [[Physics:Radium-228|<sup>228</sup>Ra]], the daughter of <sup>232</sup>Th, which is a strong gamma emitter.<ref name="Greenwood1426" /> Lanthanum is relatively easy to extract as it has only one neighbouring lanthanide, cerium, which can be removed by making use of its ability to be oxidised to the +4 state; thereafter, lanthanum may be separated out by the historical method of [[Chemistry:Fractional crystallization|fractional crystallization]] of La(NO<sub>3</sub>)<sub>3</sub>·2NH<sub>4</sub>NO<sub>3</sub>·4H<sub>2</sub>O, or by ion-exchange techniques when higher purity is desired.<ref name="Greenwood1426" />

Lanthanum metal is obtained from its oxide by heating it with [[Chemistry:Ammonium chloride|ammonium chloride]] or fluoride and hydrofluoric acid at 300-400&nbsp;°C to produce the chloride or fluoride:<ref name="patnaik" />

:La<sub>2</sub>O<sub>3</sub> + 6 NH<sub>4</sub>Cl → 2 LaCl<sub>3</sub> + 6 NH<sub>3</sub> + 3 H<sub>2</sub>O

This is followed by reduction with alkali or alkaline earth metals in vacuum or argon atmosphere:<ref name="patnaik" />

:LaCl<sub>3</sub> + 3 Li → La + 3 LiCl

Also, pure lanthanum can be produced by electrolysis of molten mixture of anhydrous LaCl<sub>3</sub> and NaCl or KCl at elevated temperatures.<ref name="patnaik" />

==Applications==
[[Image:Glowing gas mantle.jpg|thumb|right|A Coleman white gas lantern mantle burning at full brightness]]
The first historical application of lanthanum was in gas lantern [[Physics:Gas mantle|mantles]]. [[Biography:Carl Auer von Welsbach|Carl Auer von Welsbach]] used a mixture of [[Chemistry:Lanthanum oxide|lanthanum oxide]] and [[Chemistry:Zirconium dioxide|zirconium oxide]], which he called ''Actinophor'' and patented in 1886. The original mantles gave a green-tinted light and were not very successful, and his first company, which established a factory in Atzgersdorf in 1887, failed in 1889.<ref>{{Cite book |url=https://books.google.com/books?id=EFzuCAAAQBAJ&q=Welsbach+Actinophor+Atzgersdorf&pg=PA122 |title=Episodes from the History of the Rare Earth Elements |date=2012-12-06 |publisher=Kluwer Academic Publishers |isbn=9789400902879 |editor-last=Evans |editor-first=C. H. |page=122}}</ref>

Modern uses of lanthanum include:
[[Image:LaB6HotCathode.jpg|thumb|{{chem|La|B|6}} hot cathode]]
[[File:Zblan transmit.jpg|thumb|Comparison of infrared transmittance of ZBLAN glass and silica]]
* One material used for anodic material of nickel-metal hydride batteries is {{chem|La|(Ni|3.6|Mn|0.4|Al|0.3|Co|0.7|)}}. Due to high cost to extract the other lanthanides, a [[Chemistry:Mischmetal|mischmetal]] with more than 50% of lanthanum is used instead of pure lanthanum. The compound is an intermetallic component of the {{chem|A|B|5}} type.<ref>{{Cite web |title=Inside the Nickel Metal Hydride Battery |url=http://www.cobasys.com/pdf/tutorial/inside_nimh_battery_technology.pdf |url-status=dead |archive-url=https://web.archive.org/web/20090227062546/http://www.cobasys.com/pdf/tutorial/inside_nimh_battery_technology.pdf |archive-date=2009-02-27 |access-date=2009-06-06}}</ref><ref>{{Cite journal |last1=Tliha |first1=M. |last2=Mathlouthi |first2=H. |last3=Lamloumi |first3=J. |last4=Percheronguegan |first4=A. |date=2007 |title=AB5-type hydrogen storage alloy used as anodic materials in Ni-MH batteries |journal=Journal of Alloys and Compounds |volume=436 |issue=1–2 |pages=221–225 |doi=10.1016/j.jallcom.2006.07.012}}</ref> NiMH batteries can be found in many models of the [[Engineering:Toyota Prius|Toyota Prius]] sold in the US.  These larger nickel-metal hydride batteries require massive quantities of lanthanum for the production. The 2008 [[Engineering:Toyota Prius|Toyota Prius]] NiMH battery requires {{convert|10|to|15|kg|lb}} of lanthanum. As engineers push the technology to increase fuel efficiency, twice that amount of lanthanum could be required per vehicle.<ref>{{Cite news |date=2009-08-31 |title=As hybrid cars gobble rare metals, shortage looms |publisher=Reuters 2009-08-31 |url=https://www.reuters.com/article/ousiv/idUSTRE57U02B20090831}}</ref><ref>{{Cite journal |last1=Bauerlein |first1=P. |last2=Antonius |first2=C. |last3=Loffler |first3=J. |last4=Kumpers |first4=J. |date=2008 |title=Progress in high-power nickel–metal hydride batteries |journal=Journal of Power Sources |volume=176 |issue=2 |pages=547 |bibcode=2008JPS...176..547B |doi=10.1016/j.jpowsour.2007.08.052}}</ref><ref>{{Cite web |date=19 November 2015 |title=Why Toyota offers 2 battery choices in next Prius |url=https://www.autonews.com/article/20151123/OEM06/311239986/why-toyota-offers-2-battery-choices-in-next-prius}}</ref>
* Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process. Heat energy is released every time they do so; therefore these alloys have possibilities in energy conservation systems.<ref name="CRC" /><ref>{{Cite journal |last=Uchida |first=H. |date=1999 |title=Hydrogen solubility in rare earth based hydrogen storage alloys |journal=International Journal of Hydrogen Energy |volume=24 |issue=9 |pages=871–877 |doi=10.1016/S0360-3199(98)00161-X}}</ref>
* [[Chemistry:Mischmetal|Mischmetal]], a pyrophoric alloy used in lighter flints, contains 25% to 45% lanthanum.<ref name="CRC2">{{Cite book |last=C. R. Hammond |title=The Elements, in Handbook of Chemistry and Physics |date=2000 |publisher=CRC press |isbn=978-0-8493-0481-1 |edition=81st}}</ref>
* [[Chemistry:Lanthanum oxide|Lanthanum oxide]] and the [[Chemistry:Lanthanum hexaboride|boride]] are used in electronic [[Physics:Vacuum tube|vacuum tube]]s as [[Physics:Hot cathode|hot cathode]] materials with strong emissivity of [[Physics:Electron|electron]]s. Crystals of {{chem| link = lanthanum hexaboride|La|B|6}} are used in high-brightness, extended-life, thermionic electron emission sources for [[Engineering:Electron microscope|electron microscope]]s and [[Physics:Hall-effect thruster|Hall-effect thruster]]s.<ref>{{Cite journal |last1=Jason D. Sommerville |last2=Lyon B. King |name-list-style=amp |title=Effect of Cathode Position on Hall-Effect Thruster Performance and Cathode Coupling Voltage |url=http://sgc.engin.umich.edu/erps/IEPC_2007/PAPERS/IEPC-2007-078.pdf |url-status=dead |journal=43rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 8–11 July 2007, Cincinnati, OH |archive-url=https://web.archive.org/web/20110720091007/http://sgc.engin.umich.edu/erps/IEPC_2007/PAPERS/IEPC-2007-078.pdf |archive-date=July 20, 2011 |access-date=2009-06-06}}</ref>
* [[Chemistry:Lanthanum trifluoride|Lanthanum trifluoride]] ({{chem|La|F|3}}) is an essential component of a heavy fluoride glass named [[Physics:ZBLAN|ZBLAN]]. This glass has superior transmittance in the infrared range and is therefore used for fiber-optical communication systems.<ref name="rutg">{{Cite web |last=Harrington, James A. |title=Infrared Fiber Optics |url=http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |archive-url=https://web.archive.org/web/20100802120432/http://irfibers.rutgers.edu/pdf_files/ir_fiber_review.pdf |archive-date=2010-08-02 |publisher=[[Organization:Rutgers University|Rutgers University]]}}</ref>
* Cerium-doped [[Chemistry:Lanthanum(III) bromide|lanthanum bromide]] and [[Chemistry:Lanthanum(III) chloride|lanthanum chloride]] are the recent inorganic [[Physics:Scintillator|scintillator]]s, which have a combination of high light yield, best energy resolution, and fast response. Their high yield converts into superior energy resolution; moreover, the light output is very stable and quite high over a very wide range of temperatures, making it particularly attractive for high-temperature applications. These scintillators are already widely used commercially in detectors of neutrons or<!-- "and"? --> gamma rays.<ref>{{Cite web |title=BrilLanCe-NxGen |url=http://www.oilandgas.saint-gobain.com/uploadedFiles/SGoilandgas/Documents/Detectors/Detectors-BrilLanCe-NxGen-Packaging.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110429014149/http://www.oilandgas.saint-gobain.com/uploadedFiles/SGoilandgas/Documents/Detectors/Detectors-BrilLanCe-NxGen-Packaging.pdf |archive-date=2011-04-29 |access-date=2009-06-06}}</ref>
* Carbon arc lamps use a mixture of rare earth elements to improve the light quality. This application, especially by the motion picture industry for studio lighting and projection, consumed about 25% of the rare-earth compounds produced until the phase out of carbon arc lamps.<ref name="CRC" /><ref>{{Cite report |url=https://digital.library.unt.edu/ark:/67531/metadc12817/ |title=Mineral Facts and Problems |last=Hendrick |first=James B. |date=1985 |publisher=Bureau of Mines |page=655 |id=Bulletin 675 |chapter-url=https://digital.library.unt.edu/ark:/67531/metadc12817/m1/663/?q=%22carbon%20arc%22 |chapter=Rare Earth Elements and Yttrium}}</ref>
* Lanthanum(III) oxide ({{chem|La|2|O|3}}) improves the alkali resistance of [[Chemistry:Glass|glass]] and is used in making special optical glasses, such as infrared-absorbing glass, as well as [[Physics:Camera|camera]] and [[Astronomy:Telescope|telescope]] [[Physics:Lens (optics)|lenses]], because of the high [[Physics:Refractive index|refractive index]] and low dispersion of rare-earth glasses.<ref name="CRC" /> Lanthanum oxide is also used as a grain-growth additive during the liquid-phase [[Earth:Sintering|sintering]] of [[Chemistry:Silicon nitride|silicon nitride]] and [[Chemistry:Zirconium diboride|zirconium diboride]].<ref>{{Cite journal |last1=Kim, K |last2=Shim |first2=Kwang Bo |date=2003 |title=The effect of lanthanum on the fabrication of ZrB2–ZrC composites by spark plasma sintering |journal=Materials Characterization |volume=50 |pages=31–37 |doi=10.1016/S1044-5803(03)00055-X}}</ref>
* Small amounts of lanthanum added to steel improves its malleability, resistance to impact, and [[Physics:Ductility|ductility]], whereas addition of lanthanum to [[Chemistry:Molybdenum|molybdenum]] decreases its hardness and sensitivity to temperature variations.<ref name="CRC" />
* Small amounts of lanthanum are present in many pool products to remove the phosphates that feed algae.<ref>{{Cite book |url={{Google books|plainurl=yes|id=Kr3NCY4GJaAC|page=25 }} |title=Pool Care Basics |pages=25–26}}</ref>
* Lanthanum oxide additive to tungsten is used in [[Chemistry:Gas tungsten arc welding|gas tungsten arc welding]] electrodes, as a substitute for [[Physics:Radioactive|radioactive]] thorium.<ref>{{Cite book |last=Howard B. Cary |url={{Google books|plainurl=yes|id=H3BgQGdTP_0C }} |title=Arc welding automation |date=1995 |publisher=CRC Press |isbn=978-0-8247-9645-7 |page=139}}</ref><ref>{{Cite book |last=Larry Jeffus. |title=Welding : principles and applications |date=2003 |publisher=Thomson/Delmar Learning |isbn=978-1-4018-1046-7 |location=Clifton Park, N.Y. |page=350 |chapter=Types of Tungsten |chapter-url={{Google books|plainurl=yes|id=zeRiW7en7HAC|page=RA1-PA750 }} |archive-url=https://web.archive.org/web/20100923150541/http://www.cmc.dk/ |archive-date=2010-09-23 |url-status=dead}}</ref>
* Various compounds of lanthanum and other rare-earth elements (oxides, chlorides, [[Chemistry:Lanthanide trifluoromethanesulfonates|triflates]], etc.) are components of various catalysis, such as petroleum cracking [[Chemistry:Catalyst|catalyst]]s.<ref>{{Cite book |last1=C. K. Gupta |url={{Google books|plainurl=yes|id=F0Bte_XhzoAC|page=441 }} |title=Extractive metallurgy of rare earths |last2=Nagaiyar Krishnamurthy |date=2004 |publisher=CRC Press |isbn=978-0-415-33340-5 |page=441}}</ref>
* Lanthanum-barium [[Physics:Radiometric dating|radiometric dating]] is used to estimate age of rocks and ores, though the technique has limited popularity.<ref>{{Cite journal |last1=S. Nakai |last2=A. Masuda |last3=B. Lehmann |date=1988 |title=La-Ba dating of bastnaesite |url=http://www.minsocam.org/ammin/AM73/AM73_1111.pdf |journal=American Mineralogist |volume=7 |issue=1–2 |page=1111 |bibcode=1988ChGeo..70...12N |doi=10.1016/0009-2541(88)90211-2}}</ref>
* [[Chemistry:Lanthanum carbonate|Lanthanum carbonate]] was approved as a medication (Fosrenol, Shire Pharmaceuticals) to absorb excess [[Chemistry:Phosphate|phosphate]] in cases of [[Medicine:Hyperphosphatemia|hyperphosphatemia]] seen in end-stage kidney disease.<ref name="fosrenol">{{Cite web |date=28 October 2004 |title=FDA approves Fosrenol(R) in end-stage renal disease (ESRD) patients |url=http://www.medicalnewstoday.com/articles/15538.php |url-status=dead |archive-url=https://web.archive.org/web/20090426054033/http://www.medicalnewstoday.com/articles/15538.php |archive-date=2009-04-26 |access-date=2009-06-06}}</ref>
* Lanthanum fluoride is used in phosphor lamp coatings. Mixed with europium fluoride, it is also applied in the crystal membrane of [[Physics:Fluoride selective electrode|fluoride ion-selective electrodes]].<ref name="patnaik" />
* Like [[Biology:Horseradish peroxidase|horseradish peroxidase]], lanthanum is used as an electron-dense tracer in [[Biology:Molecular biology|molecular biology]].<ref>{{Cite journal |last1=Chau YP |last2=Lu KS |date=1995 |title=Investigation of the blood-ganglion barrier properties in rat sympathetic ganglia by using lanthanum ion and horseradish peroxidase as tracers |journal=Acta Anatomica |volume=153 |issue=2 |pages=135–144 |doi=10.1159/000313647 |issn=0001-5180 |pmid=8560966}}</ref>
* Lanthanum-modified bentonite (or [[Earth:Phoslock|phoslock]]) is used to remove phosphates from water in lake treatments.<ref>{{Cite journal |last1=Hagheseresht |last2=Wang |first2=Shaobin |last3=Do |first3=D. D. |date=2009 |title=A novel lanthanum-modified bentonite, Phoslock, for phosphate removal from wastewaters |journal=Applied Clay Science |volume=46 |issue=4 |pages=369–375 |doi=10.1016/j.clay.2009.09.009|bibcode=2009ApCS...46..369H }}</ref>
* Lanthanum telluride (La<sub>3</sub>Te<sub>4</sub>) is considered to be applied in the field of radioisotope power system (nuclear power plant) due to its significant conversion capabilities. The transmuted elements and isotopes in the segment will not react with the material itself, thus presenting no harm to the safety of the power plant.  Though iodine, which can be generated during transmutation, is suspected to react with La<sub>3</sub>Te<sub>4</sub> segment, the quantity of iodine is small enough to pose no threat to the power system.<ref>{{Cite book |last1=R. Smith |first1=Michael B. |last2=Whiting |first2=Christopher |last3=Barklay |first3=Chad |title=2019 IEEE Aerospace Conference |chapter=Nuclear Considerations for the Application of Lanthanum Telluride in Future Radioisotope Power Systems |date=2019 |chapter-url=https://ieeexplore.ieee.org/document/8742136 |pages=1–11 |doi=10.1109/AERO.2019.8742136 |isbn=978-1-5386-6854-2 |osti=1542236 |s2cid=195221607}}</ref>

==Biological role==
Lanthanum has no known biological role in humans. The element is very poorly absorbed after oral administration and when injected its elimination is very slow. [[Chemistry:Lanthanum carbonate|Lanthanum carbonate]] (Fosrenol) was approved as a phosphate binder to absorb excess phosphate in cases of end stage renal disease.<ref name="fosrenol" />

While lanthanum has pharmacological effects on several receptors and ion channels, its specificity for the [[Chemistry:Gamma-Aminobutyric acid|GABA]] receptor is unique among trivalent cations. Lanthanum acts at the same modulatory site on the [[Biology:GABA receptor|GABA receptor]] as [[Chemistry:Zinc|zinc]], a known negative allosteric modulator. The lanthanum cation La<sup>3+</sup> is a positive allosteric modulator at native and recombinant GABA receptors, increasing open channel time and decreasing desensitization in a subunit configuration dependent manner.<ref>{{Cite journal |last=Boldyreva, A. A. |date=2005 |title=Lanthanum Potentiates GABA-Activated Currents in Rat Pyramidal Neurons of CA1 Hippocampal Field |journal=Bulletin of Experimental Biology and Medicine |volume=140 |issue=4 |pages=403–5 |doi=10.1007/s10517-005-0503-z |pmid=16671565 |s2cid=13179025}}</ref>

Lanthanum is an essential cofactor for the methanol dehydrogenase of the methanotrophic bacterium ''[[Biology:Methylacidiphilum fumariolicum|Methylacidiphilum fumariolicum]]'' SolV, although the great chemical similarity of the lanthanides means that it may be substituted with cerium, praseodymium, or neodymium without ill effects, and with the smaller samarium, europium, or gadolinium giving no side effects other than slower growth.<ref>{{Cite journal |last1=Pol |first1=Arjan |last2=Barends |first2=Thomas R. M. |last3=Dietl |first3=Andreas |last4=Khadem |first4=Ahmad F. |last5=Eygensteyn |first5=Jelle |last6=Jetten |first6=Mike S. M. |last7=Op Den Camp |first7=Huub J. M. |date=2013 |title=Rare earth metals are essential for methanotrophic life in volcanic mudpots |journal=Environmental Microbiology |volume=16 |issue=1 |pages=255–64 |doi=10.1111/1462-2920.12249 |pmid=24034209|url=https://repository.ubn.ru.nl//bitstream/handle/2066/128108/128108.pdf }}</ref>

==Precautions==
{{Chembox
| container_only = yes
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS02}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|260}}
| PPhrases = {{P-phrases|223|231+232|370+378|422}}<ref>{{Cite web |title=Lanthanum 261130 |url=https://www.sigmaaldrich.com/catalog/product/aldrich/261130 |website=Sigma-Aldrich}}</ref>
| NFPA-H = 0
| NFPA-F = 4
| NFPA-R = 2
| NFPA-S = w
| NFPA_ref = 
 }}
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Lanthanum has a low to moderate level of toxicity and should be handled with care. The injection of lanthanum solutions produces [[Medicine:Hyperglycemia|hyperglycemia]], low blood pressure, degeneration of the [[Biology:Spleen|spleen]] and [[Biology:Liver|hepatic]] alterations.{{citation needed|date=June 2019|reason=Cannot find book<!--<ref>{{Cite book |last=Pof. Dr. M. Zafar Iqbal |url={{Google books|plainurl=yes|id=vNcYAgAAQBAJ|page=23 }} |title=Elements in Health and Disease |publisher=Dr. Ahsan Iqbal |pages=23– |id=GGKEY:KEU6L0DDWZJ}}</ref>-->}} The application in carbon arc light led to the exposure of people to rare earth element oxides and fluorides, which sometimes led to pneumoconiosis.<ref>{{Cite journal |last1=Dufresne |first1=A. |last2=Krier |first2=G. |last3=Muller |first3=J. |last4=Case |first4=B. |last5=Perrault |first5=G. |date=1994 |title=Lanthanide particles in the lung of a printer |journal=Science of the Total Environment |volume=151 |issue=3 |pages=249–252 |bibcode=1994ScTEn.151..249D |doi=10.1016/0048-9697(94)90474-X |pmid=8085148}}</ref><ref>{{Cite journal |last1=Waring |first1=P. M. |last2=Watling |first2=R. J. |date=1990 |title=Rare earth deposits in a deceased movie projectionist. A new case of rare earth pneumoconiosis |journal=The Medical Journal of Australia |volume=153 |issue=11–12 |pages=726–30 |doi=10.5694/j.1326-5377.1990.tb126334.x |pmid=2247001 |s2cid=24985591}}</ref> As the La<sup>3+</sup> ion is similar in size to the Ca<sup>2+</sup> ion, it is sometimes used as an easily traced substitute for the latter in medical studies.<ref name="Emsley">{{Cite book |last=Emsley |first=John |title=Nature's building blocks: an A-Z guide to the elements |date=2011 |publisher=Oxford University Press |isbn=9780199605637 |pages=266–77}}</ref> Lanthanum, like the other lanthanides, is known to affect human metabolism, lowering cholesterol levels, blood pressure, appetite, and risk of blood coagulation. When injected into the brain, it acts as a painkiller, similarly to [[Biology:Morphine|morphine]] and other opiates, though the mechanism behind this is still unknown.<ref name="Emsley" />  Lanthanum meant for ingestion, typically as a chewable tablet or oral powder, can interfere with gastrointestinal imaging by creating opacities throughout the GI tract; if chewable tablets are swallowed whole, they will dissolve but present initially as coin-shaped opacities in the stomach, potentially confused with ingested metal objects such as coins or batteries.<ref>{{Cite journal |vauthors=Evans NS, Aronowitz P, Altertson TE |date=October 30, 2023 |title=Coin-Shaped Opacities in the Stomach |url=https://jamanetwork.com/journals/jama/fullarticle/2811509 |department=JAMA Clinical Challenge |journal=JAMA |volume=330 |issue=20 |pages=2016–2017 |doi=10.1001/jama.2023.19032 |pmid=37902730|s2cid=264589220 }}</ref>

==Prices==
The price for a (metric) ton [1000 kg] of ''Lanthanum oxide 99% (FOB China in USD/Mt)'' is given by the Institute of Rare Earths Elements and Strategic Metals as below $2,000 for most of the period from early 2001 to September 2010 (at $10,000 in the short term in 2008); it rose steeply to $140,000 in mid-2011 and fell back just as rapidly to $38,000 by early 2012.<ref>Specifications and notation: {{Cite web |title=lanthanum |url=https://en.institut-seltene-erden.de/seltene-erden-und-metalle/seltene-erden/lanthan/}}.access-date=27 October 2022.</ref> The average price for the last six months (April to September 2022) is given by the Institute as follows: ''Lanthanum Oxide - 99.9%min FOB China - 1308 EUR/mt'' and for ''Lanthanum Metal - 99%min FOB China - 3706 EUR/mt''.<ref>Information and notation: {{Cite web |title=ISE Metal-quotes |url=https://en.institut-seltene-erden.de/}}.access-date=27 October 2022.</ref>

==See also==
{{Subject bar
|portal=Chemistry
|book1=Lanthanum
|book2=Lanthanides
|book3=Period 6 elements
|book4=Group 3 elements
|book5=Chemical elements (sorted&nbsp;alphabetically)
|book6=Chemical elements (sorted by number)
}}

| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 7439-91-0
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 6I3K30563S

==References==
{{Reflist|30em}}

==Bibliography==

==Further reading==
* ''The Industrial Chemistry of the Lanthanons, Yttrium, Thorium and Uranium'', by R. J. Callow, Pergamon Press, 1967
* ''Extractive Metallurgy of Rare Earths'', by C. K. Gupta and N. Krishnamurthy, CRC Press, 2005
* ''Nouveau Traite de Chimie Minerale, Vol. VII. Scandium, Yttrium, Elements des Terres Rares, Actinium'', P. Pascal, Editor, Masson & Cie, 1959
* ''Chemistry of the Lanthanons'', by R. C. Vickery, Butterworths 1953

{{Periodic table (navbox)}}
{{Lanthanum compounds}}

[[Category:Lanthanum| ]]
[[Category:Chemical elements]]
[[Category:Lanthanides]]
[[Category:Reducing agents]]
[[Category:GABAA receptor positive allosteric modulators]]

{{Sourceattribution|Lanthanum}}