Cerium

<h2 id="characteristics">Characteristics</h2>
<h3>Physical</h3>
Cerium is the second element of the <a href="/facts/Lanthanide/rt3XIRCl">lanthanide</a> series. In the periodic table, it appears between the lanthanides <a href="/facts/Lanthanum/Uhmmy1sB">lanthanum</a> to its left and <a href="/facts/Praseodymium/2lnRJ9dH">praseodymium</a> to its right, and above the <a href="/facts/Actinide/kHC4lxJV">actinide</a> <a href="/facts/Thorium/ysdWH470">thorium</a>. It is a <a href="/facts/Ductile/SBJsahEk">ductile</a> metal with a hardness similar to that of <a href="/facts/Silver/xXe41BGg">silver</a>.<a class="footnote-ref" id="fnref:1" href="#fn:1">1</a> Its 58 electrons are arranged in the <a href="/facts/Electron_configuration/TQjRr22P">configuration</a> [Xe]4f15d16s2, of which the four outer electrons are <a href="/facts/Valence_electron/mXPA15VP">valence electrons</a>.<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a> The 4f, 5d, and 6s energy levels are very close to each other, and the transfer of one electron to the 5d shell is due to strong interelectronic repulsion in the compact 4f shell. This effect is overwhelmed when the atom is positively ionised; thus Ce2+ on its own has instead the regular configuration [Xe]4f2, although in some solid solutions it may be [Xe]4f15d1.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> Most lanthanides can use only three electrons as valence electrons, as afterwards the remaining 4f electrons are too strongly bound: cerium is an exception because of the stability of the empty f-shell in Ce4+ and the fact that it comes very early in the lanthanide series, where the nuclear charge is still low enough until <a href="/facts/Neodymium/GzDkTIoI">neodymium</a> to allow the removal of the fourth valence electron by chemical means.<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>
Cerium has a variable <a href="/facts/Electronic_structure/RuHwQWfp">electronic structure</a>. The energy of the 4f electron is nearly the same as that of the outer 5d and 6s electrons that are delocalized in the metallic state, and only a small amount of energy is required to change the relative occupancy of these electronic levels. This gives rise to dual valence states. For example, a volume change of about 10% occurs when cerium is subjected to high pressures or low temperatures. In its high pressure phase (α-Cerium), the 4f electrons are also delocalized and itinerate, as opposed to localized 4f electrons in low pressure phase (γ-Cerium).<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> It appears that the valence changes from about 3 to 4 when it is cooled or compressed.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>

<h3>Chemical properties of the element</h3>
Like the other lanthanides, cerium metal is a good <a href="/facts/Reducing_agent/CtfSGVXC">reducing agent</a>, having <a href="/facts/Reduction_potential/PqpNUgSl">standard reduction potential</a> of E⦵ = −2.34 V for the Ce3+/Ce couple.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> It tarnishes in air, forming a <a href="/facts/Passivation_(chemistry)/tPADJj5G">passivating</a> oxide layer like <a href="/facts/Iron/DkICCKIC">iron</a> rust. A centimeter-sized sample of cerium metal corrodes completely in about a year. More dramatically, metallic cerium can be highly <a href="/facts/Pyrophoric/1b8Sl2AJ">pyrophoric</a>:<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> 

Ce + O2 → CeO2
Being highly <a href="/facts/Electronegativity/H7Vq7Uah">electropositive</a>, cerium reacts with water. The reaction is slow with cold water but speeds up with increasing temperature, producing cerium(III) hydroxide and hydrogen gas:<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a>

2 Ce + 6 H2O → 2 Ce(OH)3 + 3 H2
<h3>Allotropes</h3>

Four <a href="/facts/Allotropy/2WUdHWxg">allotropic</a> forms of cerium are known to exist at standard pressure and are given the common labels of α to δ:<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a>

<ul><li>The high-temperature form, δ-cerium, has a bcc (<a href="/facts/Body-centered_cubic/92Co7BKM">body-centered cubic</a>) crystal structure and exists above 726 °C.</li>
<li>The stable form below 726 °C to approximately room temperature is γ-cerium, with an fcc (<a href="/facts/Face-centered_cubic/92Co7BKM">face-centered cubic</a>) crystal structure.</li>
<li>The DHCP (double <a href="/facts/Hexagonal_lattice_system/sSSok8wo">hexagonal close-packed</a>) form β-cerium is the equilibrium structure approximately from room temperature to −150 °C.</li>
<li>The fcc form α-cerium is stable below about −150 °C; it has a density of 8.16 g/cm3.</li>
<li>Other solid phases occurring only at high pressures are shown on the phase diagram.</li>
<li>Both γ and β forms are quite stable at room temperature, although the equilibrium transformation temperature is estimated at 75 °C.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a></li></ul>
At lower temperatures the behavior of cerium is complicated by the slow rates of transformation. Transformation temperatures are subject to substantial hysteresis and values quoted here are approximate. Upon cooling below −15 °C, γ-cerium starts to change to β-cerium, but the transformation involves a volume increase and, as more β forms, the internal stresses build up and suppress further transformation.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> Cooling below approximately −160 °C will start formation of α-cerium but this is only from remaining γ-cerium. β-cerium does not significantly transform to α-cerium except in the presence of stress or deformation.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> At atmospheric pressure, liquid cerium is more dense than its solid form at the melting
point.<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a><a class="footnote-ref" id="fnref:15" href="#fn:15">15</a><a class="footnote-ref" id="fnref:16" href="#fn:16">16</a>

<h3>Isotopes</h3>
Main article: <a href="/facts/Isotopes_of_cerium/n2LF751R">Isotopes of cerium</a>
Naturally occurring cerium is made up of four isotopes: 136Ce (0.19%), 138Ce (0.25%), 140Ce (88.4%), and 142Ce (11.1%). All four are <a href="/facts/Observationally_stable/vC0VVvqN">observationally stable</a>, though the light isotopes 136Ce and 138Ce are theoretically expected to undergo <a href="/facts/Double_electron_capture/aQ1ElH3c">double electron capture</a> to isotopes of <a href="/facts/Barium/IkL09XHQ">barium</a>, and the heaviest isotope 142Ce is expected to undergo double beta decay to 142Nd or alpha decay to 138Ba. Thus, 140Ce is the only theoretically <a href="/facts/Stable_isotope/vgcdxgjA">stable isotope</a>. None of these decay modes have yet been observed, though the double beta decay of 136Ce, 138Ce, and 142Ce have been experimentally searched for. The current experimental limits for their half-lives are:<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a>

136Ce: >3.8×1016 y
138Ce: >5.7×1016 y
142Ce: >5.0×1016 y
All other cerium isotopes are <a href="/facts/Synthetic_radioisotope/QfnUWAS6">synthetic</a> and <a href="/facts/Radioactivity/Ya6FVjt4">radioactive</a>. The most stable of them are 144Ce with a half-life of 284.9 days, 139Ce with a half-life of 137.6 days, and 141Ce with a half-life of 32.5 days. All other radioactive cerium isotopes have half-lives under four days, and most of them have half-lives under ten minutes.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> The isotopes between 140Ce and 144Ce inclusive occur as <a href="/facts/Fission_product/xJd9MXXH">fission products</a> of <a href="/facts/Uranium/n2sGWBzU">uranium</a>.<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a> The primary decay mode of the isotopes lighter than 140Ce is <a href="/facts/Beta_plus_decay/psWp4bJT">inverse beta decay</a> or <a href="/facts/Electron_capture/EIccoV1u">electron capture</a> to <a href="/facts/Isotopes_of_lanthanum/dT37muIv">isotopes of lanthanum</a>, while that of the heavier isotopes is <a href="/facts/Beta_decay/vxTBlckp">beta decay</a> to <a href="/facts/Isotopes_of_praseodymium/8J7u8hCJ">isotopes of praseodymium</a>.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> Some <a href="/facts/Isotopes_of_neodymium/ojKx8hWx">isotopes of neodymium</a> can <a href="/facts/Alpha_decay/rCsHNIUE">alpha decay</a> or are predicted to decay to isotopes of cerium.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a>
The rarity of the proton-rich 136Ce and 138Ce is explained by the fact that they cannot be made in the most common processes of <a href="/facts/Stellar_nucleosynthesis/qEQJdJe6">stellar nucleosynthesis</a> for elements beyond iron, the <a href="/facts/S-process/31HVkqkI">s-process</a> (slow <a href="/facts/Neutron_capture/elsFpM12">neutron capture</a>) and the <a href="/facts/R-process/wEDL01yc">r-process</a> (rapid neutron capture). This is so because they are bypassed by the reaction flow of the s-process, and the r-process nuclides are blocked from decaying to them by more neutron-rich stable nuclides. Such nuclei are called <a href="/facts/P-nuclei/LheR8EQW">p-nuclei</a>, and their origin is not yet well understood: some speculated mechanisms for their formation include <a href="/facts/Proton_capture/eLQDChDd">proton capture</a> as well as <a href="/facts/Photodisintegration/7TKyEJtc">photodisintegration</a>.<a class="footnote-ref" id="fnref:22" href="#fn:22">22</a> 140Ce is the most common isotope of cerium, as it can be produced in both the s- and r-processes, while 142Ce can only be produced in the r-process. Another reason for the abundance of 140Ce is that it is a <a href="/facts/Magic_nucleus/v9PwXFzQ">magic nucleus</a>, having a closed neutron shell (it has 82 neutrons), and hence it has a very low <a href="/facts/Cross_section_(physics)/lo014h2D">cross section</a> towards further neutron capture. Although its proton number of 58 is not magic, it is granted additional stability, as its eight additional protons past the magic number 50 enter and complete the 1g7/2 proton orbital.<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a> The abundances of the cerium isotopes may differ very slightly in natural sources, because 138Ce and 140Ce are the daughters of the long-lived <a href="/facts/Primordial_radionuclide/lFAUqHDv">primordial radionuclides</a> 138La and 144Nd, respectively.<a class="footnote-ref" id="fnref:24" href="#fn:24">24</a>

<h2 id="compounds">Compounds</h2>
Cerium exists in two main oxidation states, Ce(III) and Ce(IV). This pair of adjacent oxidation states dominates several aspects of the chemistry of this element. Cerium(IV) aqueous solutions may be prepared by reacting cerium(III) solutions with the strong oxidizing agents <a href="/facts/Peroxodisulfate/aCCrD5s2">peroxodisulfate</a> or <a href="/facts/Bismuthate/znSGlItd">bismuthate</a>. The value of E⦵(Ce4+/Ce3+) varies widely depending on conditions due to the relative ease of complexation and hydrolysis with various anions, although +1.72 V is representative. Cerium is the only lanthanide which has important aqueous and coordination chemistry in the +4 oxidation state.<a class="footnote-ref" id="fnref:25" href="#fn:25">25</a>

<h3>Halides</h3>
Cerium forms all four trihalides CeX3 (X = F, Cl, Br, I) usually by reaction of the oxides with the hydrogen halides. The anhydrous halides are pale-colored, paramagnetic, hygroscopic solids. Upon hydration, the trihalides convert to complexes containing aquo complexes [Ce(H2O)8-9]3+. Unlike most lanthanides, Ce forms a tetrafluoride, a white solid. It also forms a bronze-colored diiodide, which has metallic properties.<a class="footnote-ref" id="fnref:26" href="#fn:26">26</a> Aside from the binary halide phases, a number of anionic halide complexes are known. The fluoride gives the Ce(IV) derivatives CeF4−8 and CeF2−6. The chloride gives the orange CeCl2−6.<a class="footnote-ref" id="fnref:27" href="#fn:27">27</a>

<h3>Oxides and chalcogenides</h3>
<a href="/facts/Cerium(IV)_oxide/pqmIvGGc">Cerium(IV) oxide</a> ("ceria") has the <a href="/facts/Fluorite/y2G7C8zk">fluorite</a> structure, similarly to the dioxides of praseodymium and <a href="/facts/Terbium/ICF3PMED">terbium</a>. Ceria is a <a href="/facts/Nonstoichiometric_compound/DAssoN0e">nonstoichiometric compound</a>, meaning that the real formula is CeO2−x, where x is about 0.2. Thus, the material is not perfectly described as Ce(IV). Ceria reduces to <a href="/facts/Cerium(III)_oxide/SMr4rPnV">cerium(III) oxide</a> with hydrogen gas.<a class="footnote-ref" id="fnref:28" href="#fn:28">28</a> Many <a href="/facts/Nonstoichiometric/DAssoN0e">nonstoichiometric</a> <a href="/facts/Chalcogen/nXLGmnqL">chalcogenides</a> are also known, along with the trivalent Ce2Z3 (Z = <a href="/facts/Sulfur/IK0amTfM">S</a>, <a href="/facts/Selenium/k975NApC">Se</a>, <a href="/facts/Tellurium/v7QvfIvS">Te</a>). The monochalcogenides CeZ conduct electricity and would better be formulated as Ce3+Z2−e−. While CeZ2 are known, they are polychalcogenides with cerium(III): cerium(IV) derivatives of S, Se, and Te are unknown.<a class="footnote-ref" id="fnref:29" href="#fn:29">29</a>

<h3>Cerium(IV) complexes</h3>

The compound <a href="/facts/Ceric_ammonium_nitrate/PorTxSBS">ceric ammonium nitrate</a> (CAN) (NH4)2[Ce(NO3)6] is the most common cerium compound encountered in the laboratory. The six nitrate ligands bind as <a href="/facts/Bidentate_ligand/6etB3qeW">bidentate ligands</a>. The complex [Ce(NO3)6]2− is 12-coordinate, a high coordination number which emphasizes the large size of the Ce4+ ion. CAN is a popular oxidant in <a href="/facts/Organic_synthesis/WLFePEzH">organic synthesis</a>, both as a stoichiometric reagent<a class="footnote-ref" id="fnref:30" href="#fn:30">30</a> and as a catalyst.<a class="footnote-ref" id="fnref:31" href="#fn:31">31</a> It is inexpensive, stable in air, easily handled, and of low toxicity.<a class="footnote-ref" id="fnref:32" href="#fn:32">32</a> It operates by one-electron redox. Cerium nitrates also form 4:3 and 1:1 complexes with <a href="/facts/18-crown-6/DojoY5RF">18-crown-6</a> (the ratio referring to that between the nitrate and the <a href="/facts/Crown_ether/UNfhBQs5">crown ether</a>). Classically, CAN is a primary standard for quantitative analysis.<a class="footnote-ref" id="fnref:33" href="#fn:33">33</a><a class="footnote-ref" id="fnref:34" href="#fn:34">34</a> Cerium(IV) salts, especially <a href="/facts/Cerium(IV)_sulfate/eSagjum1">cerium(IV) sulfate</a>, are often used as standard reagents for <a href="/facts/Volumetric_analysis/gGUfvQcW">volumetric analysis</a> in <a href="/facts/Cerimetry/Au8fVmzv">cerimetric titrations</a>.<a class="footnote-ref" id="fnref:35" href="#fn:35">35</a>

Due to <a href="/facts/Charge-transfer_complex/hbIyNJlo">ligand-to-metal charge transfer</a>, aqueous cerium(IV) ions are orange-yellow.<a class="footnote-ref" id="fnref:36" href="#fn:36">36</a> Aqueous cerium(IV) is metastable in water<a class="footnote-ref" id="fnref:37" href="#fn:37">37</a> and is a strong oxidizing agent that oxidizes <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a> to give <a href="/facts/Chlorine/y27UwYBM">chlorine</a> gas.<a class="footnote-ref" id="fnref:38" href="#fn:38">38</a> In the <a href="/facts/Belousov%25E2%2580%2593Zhabotinsky_reaction/RHH660Iy">Belousov–Zhabotinsky reaction</a>, cerium oscillates between the +4 and +3 oxidation states to catalyze the reaction.<a class="footnote-ref" id="fnref:39" href="#fn:39">39</a>

<h3>Organocerium compounds</h3>
<a href="/facts/Organocerium_chemistry/bCW5qNQ6">Organocerium chemistry</a> is similar to that of the other <a href="/facts/Organolanthanide_chemistry/sRqPXTsD">lanthanides</a>, often involving complexes of <a href="/facts/Cyclopentadienyl/2cw59tjx">cyclopentadienyl</a> and <a href="/facts/Cyclooctatetraenide_anion/kkWW1bwk">cyclooctatetraenyl</a> ligands. <a href="/facts/Cerocene/Xb5KmCpQ">Cerocene</a> (Ce(C8H8)2) adopts the <a href="/facts/Uranocene/7cJHsK0X">uranocene</a> molecular structure.<a class="footnote-ref" id="fnref:40" href="#fn:40">40</a> The 4f electron in cerocene is poised ambiguously between being localized and delocalized and this compound is considered intermediate-valent.<a class="footnote-ref" id="fnref:41" href="#fn:41">41</a> 
<a href="/facts/Alkyl/vmEk8X4v">Alkyl</a>, <a href="/facts/Alkynyl/VHI4N5Wo">alkynyl</a>, and <a href="/facts/Alkenyl/RtYcS6kU">alkenyl</a> organocerium derivatives are prepared from the <a href="/facts/Transmetallation/Mm0hQzp3">transmetallation</a> of the respective <a href="/facts/Organolithium/xgYnjhP3">organolithium</a> or <a href="/facts/Grignard_reagent/0vkLtPo1">Grignard</a> reagents, and are more <a href="/facts/Nucleophile/xYccoaJQ">nucleophilic</a> but less basic than their precursors.<a class="footnote-ref" id="fnref:42" href="#fn:42">42</a><a class="footnote-ref" id="fnref:43" href="#fn:43">43</a>

<h2 id="history">History</h2>

Cerium was discovered in <a href="/facts/Bastn%25C3%25A4s/oVVqSJPW">Bastnäs</a> in Sweden by <a href="/facts/J%25C3%25B6ns_Jakob_Berzelius/HakSv3sP">Jöns Jakob Berzelius</a> and <a href="/facts/Wilhelm_Hisinger/09AEPVFQ">Wilhelm Hisinger</a>, and independently in Germany by <a href="/facts/Martin_Heinrich_Klaproth/5DAt7l6Q">Martin Heinrich Klaproth</a>, both in 1803.<a class="footnote-ref" id="fnref:44" href="#fn:44">44</a> Cerium was <a href="/facts/Ceres_(dwarf_planet)/yIVEMYtG">named</a> by Berzelius after the asteroid <a href="/facts/Ceres_(dwarf_planet)/yIVEMYtG">Ceres</a>, formally 1 Ceres, discovered two years earlier.<a class="footnote-ref" id="fnref:45" href="#fn:45">45</a><a class="footnote-ref" id="fnref:46" href="#fn:46">46</a> Ceres was <a href="/facts/List_of_former_planets/nPmSFFAl">initially considered to be a planet</a> at the time. The asteroid is itself named after the Roman goddess <a href="/facts/Ceres_(mythology)/z8aja7rQ">Ceres</a>, goddess of agriculture, grain crops, fertility and motherly relationships.<a class="footnote-ref" id="fnref:47" href="#fn:47">47</a>
Cerium was originally isolated in the form of its oxide, which was named ceria, a term that is still used. The metal itself was too electropositive to be isolated by then-current smelting technology, a characteristic of rare-earth metals in general. After the development of <a href="/facts/Electrochemistry/C0RUWpBH">electrochemistry</a> by <a href="/facts/Humphry_Davy/aDNRfNou">Humphry Davy</a> five years later, the earths soon yielded the metals they contained. Ceria, as isolated in 1803, contained all of the lanthanides present in the cerite ore from Bastnäs, Sweden, and thus only contained about 45% of what is now known to be pure ceria. It was not until <a href="/facts/Carl_Gustaf_Mosander/nlB4bhRp">Carl Gustaf Mosander</a> succeeded in removing lanthana and <a href="/facts/Didymium/qrefFWn8">"didymia"</a> in the late 1830s that ceria was obtained pure. Wilhelm Hisinger was a wealthy mine-owner and amateur scientist, and sponsor of Berzelius. He owned and controlled the mine at Bastnäs, and had been trying for years to find out the composition of the abundant heavy gangue rock (the "Tungsten of Bastnäs", which despite its name contained no <a href="/facts/Tungsten/WYwbNDYX">tungsten</a>), now known as cerite, that he had in his mine.<a class="footnote-ref" id="fnref:48" href="#fn:48">48</a> Mosander and his family lived for many years in the same house as Berzelius, and Mosander was undoubtedly persuaded by Berzelius to investigate ceria further.<a class="footnote-ref" id="fnref:49" href="#fn:49">49</a><a class="footnote-ref" id="fnref:50" href="#fn:50">50</a><a class="footnote-ref" id="fnref:51" href="#fn:51">51</a><a class="footnote-ref" id="fnref:52" href="#fn:52">52</a>
The element played a role in the <a href="/facts/Manhattan_Project/gtg8yRK2">Manhattan Project</a>, where cerium compounds were investigated in the <a href="/facts/Calutron/f58sCT1h">Berkeley</a> site as materials for <a href="/facts/Crucible/o7WrIqhu">crucibles</a> for <a href="/facts/Uranium/n2sGWBzU">uranium</a> and <a href="/facts/Plutonium/4bUw9zH3">plutonium</a> casting.<a class="footnote-ref" id="fnref:53" href="#fn:53">53</a> For this reason, <a href="/facts/Ames_Project/SUvswYqA">new methods</a> for the preparation and casting of cerium were developed within the scope of the <a href="/facts/Ames_Project/SUvswYqA">Ames</a> daughter project (now the <a href="/facts/Ames_Laboratory/zwwxY36t">Ames Laboratory</a>).<a class="footnote-ref" id="fnref:54" href="#fn:54">54</a> Production of extremely pure cerium in Ames commenced in mid-1944 and continued until August 1945.<a class="footnote-ref" id="fnref:55" href="#fn:55">55</a>

<h2 id="occurrence-and-production">Occurrence and production</h2>
Cerium is the most abundant of all the lanthanides and the 25th most abundant element, making up 68 <a href="/facts/Parts_per_million/PozRuoLM">ppm</a> of the Earth's crust.<a class="footnote-ref" id="fnref:56" href="#fn:56">56</a> This value is the same of <a href="/facts/Copper/I8PEE8oX">copper</a>, and cerium is even more abundant than common metals such as <a href="/facts/Lead/EYljasJN">lead</a> (13 ppm) and <a href="/facts/Tin/vxbbBgNz">tin</a> (2.1 ppm). Thus, despite its position as one of the so-called <a href="/facts/Rare-earth_metal/PQSUQumk">rare-earth metals</a>, cerium is actually not rare at all.<a class="footnote-ref" id="fnref:57" href="#fn:57">57</a> Cerium content in the soil varies between 2 and 150 ppm, with an average of 50 ppm; seawater contains 1.5 parts per trillion of cerium.<a class="footnote-ref" id="fnref:58" href="#fn:58">58</a> Cerium occurs in various minerals, but the most important commercial sources are the minerals of the <a href="/facts/Monazite/an71GkIH">monazite</a> and <a href="/facts/Bastn%25C3%25A4site/wSaG43h8">bastnäsite</a> groups, where it makes up about half of the lanthanide content. Monazite-(Ce) is the most common representative of the monazites, with "-Ce" being the Levinson suffix informing on the dominance of the particular REE element representative.<a class="footnote-ref" id="fnref:59" href="#fn:59">59</a><a class="footnote-ref" id="fnref:60" href="#fn:60">60</a><a class="footnote-ref" id="fnref:61" href="#fn:61">61</a> Also the cerium-dominant bastnäsite-(Ce) is the most important of the bastnäsites.<a class="footnote-ref" id="fnref:62" href="#fn:62">62</a><a class="footnote-ref" id="fnref:63" href="#fn:63">63</a> Cerium is the easiest lanthanide to extract from its minerals because it is the only one that can reach a stable +4 oxidation state in aqueous solution.<a class="footnote-ref" id="fnref:64" href="#fn:64">64</a> Because of the decreased solubility of cerium in the +4 oxidation state, cerium is sometimes depleted from rocks relative to the other rare-earth elements and is incorporated into <a href="/facts/Zircon/84APfbLt">zircon</a>, since Ce4+ and <a href="/facts/Zirconium/y7gsoQFz">Zr</a>4+ have the same charge and similar ionic radii.<a class="footnote-ref" id="fnref:65" href="#fn:65">65</a> In extreme cases, cerium(IV) can form its own minerals separated from the other rare-earth elements, such as <a href="/facts/Cerianite/c8wpAq63">cerianite</a>-(Ce)<a class="footnote-ref" id="fnref:66" href="#fn:66">66</a><a class="footnote-ref" id="fnref:67" href="#fn:67">67</a><a class="footnote-ref" id="fnref:68" href="#fn:68">68</a> and (Ce,Th)O2.<a class="footnote-ref" id="fnref:69" href="#fn:69">69</a>

Bastnäsite, LnIIICO3F, is usually lacking in <a href="/facts/Thorium/ysdWH470">thorium</a> and the heavy lanthanides beyond <a href="/facts/Samarium/09K3kl93">samarium</a> and <a href="/facts/Europium/dqmBm1vr">europium</a>, and hence the extraction of cerium from it is quite direct. First, the bastnäsite is purified, using dilute <a href="/facts/Hydrochloric_acid/HqItJlUT">hydrochloric acid</a> to remove <a href="/facts/Calcium_carbonate/UQ1wLFna">calcium carbonate</a> impurities. The ore is then roasted in the air to oxidize it to the lanthanide oxides: while most of the lanthanides will be oxidized to the sesquioxides Ln2O3, cerium will be oxidized to the dioxide CeO2. This is insoluble in water and can be leached out with 0.5 M hydrochloric acid, leaving the other lanthanides behind.<a class="footnote-ref" id="fnref:70" href="#fn:70">70</a>
The procedure for <a href="/facts/Monazite/an71GkIH">monazite</a>, (Ln,Th)PO4, 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 <a href="/facts/Sodium_hydroxide/xjtdYtq7">sodium hydroxide</a> to pH 3–4. Thorium precipitates out of solution as hydroxide and is removed. After that, the solution is treated with <a href="/facts/Ammonium_oxalate/63k4l9Nj">ammonium oxalate</a> to convert rare earths to their insoluble <a href="/facts/Oxalate/u0Gdem0A">oxalates</a>. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid, but cerium oxide is insoluble in HNO3 and hence precipitates out.<a class="footnote-ref" id="fnref:71" href="#fn:71">71</a> Care must be taken when handling some of the residues as they contain <a href="/facts/Radium-228/T0SlGtRH">228Ra</a>, the daughter of 232Th, which is a strong gamma emitter.<a class="footnote-ref" id="fnref:72" href="#fn:72">72</a>

<h2 id="applications">Applications</h2>

Cerium has two main applications, both of which use CeO2. The industrial application of ceria is for polishing, especially <a href="/facts/Chemical-mechanical_polishing/AmpHEfBD">chemical-mechanical planarization</a> (CMP). In its other main application, CeO2 is used to decolorize glass. It functions by converting green-tinted ferrous impurities to nearly colorless ferric oxides.<a class="footnote-ref" id="fnref:73" href="#fn:73">73</a> Ceria has also been used as a substitute for its radioactive congener <a href="/facts/Thorium_dioxide/wboPx2It">thoria</a>, for example in the manufacture of electrodes used in <a href="/facts/Gas_tungsten_arc_welding/EY7f43rh">gas tungsten arc welding</a>, where cerium as an alloying element improves arc stability and ease of starting while decreasing burn-off.<a class="footnote-ref" id="fnref:74" href="#fn:74">74</a>

<h3>Gas mantles and pyrophoric alloys</h3>
The first use of cerium was in <a href="/facts/Gas_mantle/d56ATf6b">gas mantles</a>, invented by Austrian chemist <a href="/facts/Carl_Auer_von_Welsbach/b1654JpC">Carl Auer von Welsbach</a>. In 1885, he had previously experimented with mixtures of <a href="/facts/Magnesium/XyIhd2FG">magnesium</a>, lanthanum, and yttrium oxides, but these gave green-tinted light and were unsuccessful.<a class="footnote-ref" id="fnref:75" href="#fn:75">75</a> Six years later, he discovered that pure <a href="/facts/Thorium_oxide/wboPx2It">thorium oxide</a> produced a much better, though blue, light, and that mixing it with cerium dioxide resulted in a bright white light.<a class="footnote-ref" id="fnref:76" href="#fn:76">76</a> Cerium dioxide also acts as a catalyst for the combustion of thorium oxide.
This resulted in commercial success for von Welsbach and his invention, and created great demand for thorium. Its production resulted in a large amount of lanthanides being simultaneously extracted as by-products.<a class="footnote-ref" id="fnref:77" href="#fn:77">77</a> Applications were soon found for them, especially in the pyrophoric alloy known as "<a href="/facts/Mischmetal/kCm2tjJ8">mischmetal</a>" composed of 50% cerium, 25% lanthanum, and the remainder being the other lanthanides, that is used widely for lighter flints.<a class="footnote-ref" id="fnref:78" href="#fn:78">78</a> Usually iron is added to form the alloy <a href="/facts/Ferrocerium/1Hp6Hmqw">ferrocerium</a>, also invented by von Welsbach.<a class="footnote-ref" id="fnref:79" href="#fn:79">79</a> Due to the chemical similarities of the lanthanides, chemical separation is not usually required for their applications, such as the addition of mischmetal to steel as an inclusion modifier to improve mechanical properties, or as catalysts for the cracking of petroleum.<a class="footnote-ref" id="fnref:80" href="#fn:80">80</a> This property of cerium saved the life of writer <a href="/facts/Primo_Levi/dIzLpHvz">Primo Levi</a> at the <a href="/facts/Auschwitz_concentration_camp/6o3xax0D">Auschwitz concentration camp</a>, when he found a supply of ferrocerium alloy and bartered it for food.<a class="footnote-ref" id="fnref:81" href="#fn:81">81</a>

<h3>Pigments and phosphors</h3>
The photostability of <a href="/facts/Pigment/I3clCYkF">pigments</a> can be enhanced by the addition of cerium, as it provides pigments with <a href="/facts/Lightfastness/5rJs3z6F">lightfastness</a> and prevents clear polymers from darkening in sunlight.<a class="footnote-ref" id="fnref:82" href="#fn:82">82</a> An example of a cerium compound used on its own as an <a href="/facts/List_of_inorganic_pigments/8Q9HC7AT">inorganic pigment</a> is the vivid red <a href="/facts/Cerium(III)_sulfide/vtmGBLkx">cerium(III) sulfide</a> (cerium sulfide red), which stays chemically inert up to very high temperatures. The pigment is a safer alternative to lightfast but toxic <a href="/facts/Cadmium_pigments/3NeFypNH">cadmium selenide-based pigments</a>.<a class="footnote-ref" id="fnref:83" href="#fn:83">83</a> The addition of cerium oxide to older <a href="/facts/Cathode-ray_tube/8NVGx5C7">cathode-ray tube</a> television glass plates was beneficial, as it suppresses the darkening effect from the creation of <a href="/facts/F-center/rsX640wh">F-center</a> defects due to the continuous electron bombardment during operation. Cerium is also an essential component as a <a href="/facts/Dopant/DvChmeRL">dopant</a> for <a href="/facts/Phosphor/vTLjrGDE">phosphors</a> used in CRT TV screens, fluorescent lamps, and later <a href="/facts/Light-emitting_diode/gE8x4MDb">white light-emitting diodes</a>.<a class="footnote-ref" id="fnref:84" href="#fn:84">84</a><a class="footnote-ref" id="fnref:85" href="#fn:85">85</a> The most commonly used example is <a href="/facts/Yttrium_aluminium_garnet/U6m3FjcR">cerium(III)-doped yttrium aluminium garnet</a> (Ce:YAG) which emits green to yellow-green light (550–530 nm) and also behaves as a <a href="/facts/Scintillator/vhxA1Ufo">scintillator</a>.<a class="footnote-ref" id="fnref:86" href="#fn:86">86</a>

<h3>Other uses</h3>
Cerium salts, such as the sulfides <a href="/facts/Cerium(III)_sulfide/vtmGBLkx">Ce2S3</a> and Ce3S4, were considered during the <a href="/facts/Manhattan_Project/gtg8yRK2">Manhattan Project</a> as advanced <a href="/facts/Refractory/LoKrzGkR">refractory materials</a> for the construction of crucibles which could withstand the high temperatures and strongly <a href="/facts/Redox/Pyd5RVcj">reducing</a> conditions when casting plutonium metal.<a class="footnote-ref" id="fnref:87" href="#fn:87">87</a><a class="footnote-ref" id="fnref:88" href="#fn:88">88</a> Despite desirable properties, these sulfides were never widely adopted due to practical issues with their synthesis.<a class="footnote-ref" id="fnref:89" href="#fn:89">89</a> Cerium is used as alloying element in aluminium to create castable eutectic <a href="/facts/Aluminium_alloys/1EzR3Y4t">aluminium alloys</a> with 6–16 wt.% Ce, to which other elements such as Mg, Ni, Fe and Mn can be added. These Al-Ce alloys have excellent high temperature strength and are suitable for automotive applications (e.g. in <a href="/facts/Cylinder_head/K0RJ8mxT">cylinder heads</a>).<a class="footnote-ref" id="fnref:90" href="#fn:90">90</a> Other alloys of cerium include Pu-Ce and Pu-Ce-Co <a href="/facts/Plutonium/4bUw9zH3">plutonium alloys</a>, which have been used as <a href="/facts/Nuclear_fuel/8RhAomlJ">nuclear fuel</a>.<a class="footnote-ref" id="fnref:91" href="#fn:91">91</a>
Other <a href="/facts/Automotive/fGFKUIlA">automotive</a> applications for the lower sesquioxide are as a <a href="/facts/Catalytic_converter/KsP1ecPY">catalytic converter</a> for the oxidation of CO and <a href="/facts/NOx/qd61Szdy">NOx</a> emissions in the exhaust gases from motor vehicles.<a class="footnote-ref" id="fnref:92" href="#fn:92">92</a><a class="footnote-ref" id="fnref:93" href="#fn:93">93</a>

<h2 id="biological-role-and-precautions">Biological role and precautions</h2>

The early lanthanides have been found to be essential to some <a href="/facts/Methanotrophic/fsFp7HDD">methanotrophic</a> bacteria living in <a href="/facts/Mudpot/EWLgfXhD">volcanic mudpots</a>, such as <a href="/facts/Methylacidiphilum_fumariolicum/b7HKSyHC">Methylacidiphilum fumariolicum</a>: <a href="/facts/Lanthanum/Uhmmy1sB">lanthanum</a>, cerium, <a href="/facts/Praseodymium/2lnRJ9dH">praseodymium</a>, and <a href="/facts/Neodymium/GzDkTIoI">neodymium</a> are about equally effective.<a class="footnote-ref" id="fnref:94" href="#fn:94">94</a><a class="footnote-ref" id="fnref:95" href="#fn:95">95</a> Cerium is otherwise not known to have biological role in any other organisms, but is not very toxic either; it does not accumulate in the food chain to any appreciable extent.<a class="footnote-ref" id="fnref:96" href="#fn:96">96</a><a class="footnote-ref" id="fnref:97" href="#fn:97">97</a><a class="footnote-ref" id="fnref:98" href="#fn:98">98</a> Because it often occurs together with calcium in <a href="/facts/Phosphate_mineral/WQylquz4">phosphate minerals</a>, and bones are primarily <a href="/facts/Calcium_phosphate/tn03xvdb">calcium phosphate</a>, cerium can accumulate in bones in small amounts that are not considered dangerous.<a class="footnote-ref" id="fnref:99" href="#fn:99">99</a>
<a href="/facts/Cerium_nitrate/gRf2asfI">Cerium nitrate</a> is an effective topical antimicrobial treatment for <a href="/facts/Third-degree_burn/EHdVoSxB">third-degree burns</a>,<a class="footnote-ref" id="fnref:100" href="#fn:100">100</a><a class="footnote-ref" id="fnref:101" href="#fn:101">101</a> although large doses can lead to cerium poisoning and <a href="/facts/Methemoglobinemia/UK2NhkuM">methemoglobinemia</a>.<a class="footnote-ref" id="fnref:102" href="#fn:102">102</a> 
Like all rare-earth metals, cerium is of low to moderate toxicity.<a class="footnote-ref" id="fnref:103" href="#fn:103">103</a> A strong reducing agent, it ignites spontaneously in air at 65 to 80 °C. Fumes from cerium fires are toxic.<a class="footnote-ref" id="fnref:104" href="#fn:104">104</a> Cerium reacts with water to produce hydrogen gas, and thus cerium fires can only be effectively extinguished using <a href="/facts/Fire_extinguisher/Lh96vD2x">class D dry powder</a> extinguishing media.<a class="footnote-ref" id="fnref:105" href="#fn:105">105</a> Workers exposed to cerium have experienced itching, sensitivity to heat, and skin lesions. Cerium is not toxic when eaten, but animals injected with large doses of cerium have died due to cardiovascular collapse. Cerium is more dangerous to aquatic organisms because it damages cell membranes; it is not very soluble in water and can cause environmental contamination.<a class="footnote-ref" id="fnref:106" href="#fn:106">106</a>
Cerium oxide, the most prevalent cerium compound in industrial applications, is not regulated in the United States by the <a href="/facts/Occupational_Safety_and_Health_Administration/dCGbW5Ax">Occupational Safety and Health Administration</a> (OSHA) as a hazardous substance.<a class="footnote-ref" id="fnref:107" href="#fn:107">107</a> In Russia, its <a href="/facts/Occupational_exposure_limit/chpTx5og">occupational exposure limit</a> is 5 mg/m3.<a class="footnote-ref" id="fnref:108" href="#fn:108">108</a> Elemental cerium has no established occupational or permissible exposure limits by the OSHA or <a href="/facts/American_Conference_of_Governmental_Industrial_Hygienists/xtRc73eQ">American Conference of Governmental Industrial Hygienists</a>, though it is classified as a flammable solid and regulated as such under the <a href="/facts/Globally_Harmonized_System_of_Classification_and_Labelling_of_Chemicals/zfNMjKPF">Globally Harmonized System of Classification and Labelling of Chemicals</a>.<a class="footnote-ref" id="fnref:109" href="#fn:109">109</a> Toxicological reports on cerium compounds have noted their <a href="/facts/Cytotoxicity/SQuTTLoL">cytotoxicity</a><a class="footnote-ref" id="fnref:110" href="#fn:110">110</a> and contributions to <a href="/facts/Interstitial_lung_disease/0LQEwsGc">pulmonary interstitial fibrosis</a> in workers.<a class="footnote-ref" id="fnref:111" href="#fn:111">111</a>

<h2 id="bibliography">Bibliography</h2>
<ul><li><a href="/facts/Norman_Greenwood/XRDmRE8L">Greenwood, Norman N.</a>; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). <a href="/facts/Butterworth-Heinemann/c9nUxIVF">Butterworth-Heinemann</a>. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-0-08-037941-8.</li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0486-5. <a href="0-8493-0486-5" target="_blank">0-8493-0486-5</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Greenwood & Earnshaw 1997, pp. 1232–5. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Jørgensen, Christian (1973). "The Loose Connection between Electron Configuration and the Chemical Behavior of the Heavy Elements (Transuranics)". Angewandte Chemie International Edition. 12 (1): 12–19. doi:10.1002/anie.197300121. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils (ed.), Inorganic Chemistry, translated by Eagleson, Mary; Brewer, William, San Diego/Berlin: Academic Press/De Gruyter, pp. 1703–5, ISBN 0-12-352651-5 <a href="0-12-352651-5" target="_blank">0-12-352651-5</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Wills, J. M.; Eriksson, Olle; Boring, A. M. (1991-10-14). "Theoretical studies of the high pressure phases in cerium". Physical Review Letters. 67 (16): 2215–2218. Bibcode:1991PhRvL..67.2215W. doi:10.1103/PhysRevLett.67.2215. ISSN 0031-9007. PMID 10044368. <a href="https://link.aps.org/doi/10.1103/PhysRevLett.67.2215" target="_blank">https://link.aps.org/doi/10.1103/PhysRevLett.67.2215</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Johansson, Börje; Luo, Wei; Li, Sa; Ahuja, Rajeev (17 September 2014). "Cerium; Crystal Structure and Position in The Periodic Table". Scientific Reports. 4: 6398. Bibcode:2014NatSR...4.6398J. doi:10.1038/srep06398. PMC 4165975. PMID 25227991. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4165975" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4165975</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Greenwood & Earnshaw 1997, pp. 1244–8. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Gray, Theodore (2010). The Elements. Black Dog & Leventhal Pub. ISBN 978-1-57912-895-1. <a href="978-1-57912-895-1" target="_blank">978-1-57912-895-1</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">"Chemical reactions of Cerium". Webelements. Retrieved 9 July 2016. <a href="https://www.webelements.com/cerium/chemistry.html" target="_blank">https://www.webelements.com/cerium/chemistry.html</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Koskimaki, D. C.; Gschneidner, K. A.; Panousis, N. T. (1974). "Preparation of single phase β and α cerium samples for low temperature measurements". Journal of Crystal Growth. 22 (3): 225–229. Bibcode:1974JCrGr..22..225K. doi:10.1016/0022-0248(74)90098-0. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Koskimaki, D. C.; Gschneidner, K. A.; Panousis, N. T. (1974). "Preparation of single phase β and α cerium samples for low temperature measurements". Journal of Crystal Growth. 22 (3): 225–229. Bibcode:1974JCrGr..22..225K. doi:10.1016/0022-0248(74)90098-0. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Koskimaki, D. C.; Gschneidner, K. A.; Panousis, N. T. (1974). "Preparation of single phase β and α cerium samples for low temperature measurements". Journal of Crystal Growth. 22 (3): 225–229. Bibcode:1974JCrGr..22..225K. doi:10.1016/0022-0248(74)90098-0. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Koskimaki, D. C.; Gschneidner, K. A.; Panousis, N. T. (1974). "Preparation of single phase β and α cerium samples for low temperature measurements". Journal of Crystal Growth. 22 (3): 225–229. Bibcode:1974JCrGr..22..225K. doi:10.1016/0022-0248(74)90098-0. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0486-5. <a href="0-8493-0486-5" target="_blank">0-8493-0486-5</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Stassis, C.; Gould, T.; McMasters, O.; Gschneidner, K.; Nicklow, R. (1979). "Lattice and spin dynamics of γ-Ce". Physical Review B. 19 (11): 5746–5753. Bibcode:1979PhRvB..19.5746S. doi:10.1103/PhysRevB.19.5746. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 199–200. ISBN 978-0-07-049439-8. <a href="978-0-07-049439-8" target="_blank">978-0-07-049439-8</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
 <a href="https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
 <a href="https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
 <a href="https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
 <a href="https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">Belli, P.; Bernabei, R.; Danevich, F. A.; Incicchitti, A.; Tretyak, V. I. (2019). "Experimental searches for rare alpha and beta decays". European Physical Journal A. 55 (140): 4–6. arXiv:1908.11458. Bibcode:2019EPJA...55..140B. doi:10.1140/epja/i2019-12823-2. S2CID 201664098. <a href="/wiki/European_Physical_Journal_A" target="_blank">/wiki/European_Physical_Journal_A</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
<li id="fn:22">Cameron, A. G. W. (1973). "Abundance of the Elements in the Solar System" (PDF). Space Science Reviews. 15 (1): 121–146. Bibcode:1973SSRv...15..121C. doi:10.1007/BF00172440. S2CID 120201972. <a href="https://pubs.giss.nasa.gov/docs/1973/1973_Cameron_ca06310p.pdf" target="_blank">https://pubs.giss.nasa.gov/docs/1973/1973_Cameron_ca06310p.pdf</a> <a href="#fnref:22" class="footnote-back-ref">↩</a></li>
<li id="fn:23">Cameron, A. G. W. (1973). "Abundance of the Elements in the Solar System" (PDF). Space Science Reviews. 15 (1): 121–146. Bibcode:1973SSRv...15..121C. doi:10.1007/BF00172440. S2CID 120201972. <a href="https://pubs.giss.nasa.gov/docs/1973/1973_Cameron_ca06310p.pdf" target="_blank">https://pubs.giss.nasa.gov/docs/1973/1973_Cameron_ca06310p.pdf</a> <a href="#fnref:23" class="footnote-back-ref">↩</a></li>
<li id="fn:24">Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
 <a href="https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf" target="_blank">https://www-nds.iaea.org/amdc/ame2016/NUBASE2016.pdf</a> <a href="#fnref:24" class="footnote-back-ref">↩</a></li>
<li id="fn:25">Greenwood & Earnshaw 1997, pp. 1244–8. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:25" class="footnote-back-ref">↩</a></li>
<li id="fn:26">Greenwood & Earnshaw 1997, pp. 1240–2. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:26" class="footnote-back-ref">↩</a></li>
<li id="fn:27">Greenwood & Earnshaw 1997, pp. 1244–8. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:27" class="footnote-back-ref">↩</a></li>
<li id="fn:28">Greenwood & Earnshaw 1997, pp. 1238–9. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:28" class="footnote-back-ref">↩</a></li>
<li id="fn:29">Greenwood & Earnshaw 1997, pp. 1238–9. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:29" class="footnote-back-ref">↩</a></li>
<li id="fn:30">Nair, Vijay; Deepthi, Ani (2007). "Cerium(IV) Ammonium Nitrate: A Versatile Single-Electron Oxidant". Chemical Reviews. 107 (5): 1862–1891. doi:10.1021/cr068408n. PMID 17432919. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:30" class="footnote-back-ref">↩</a></li>
<li id="fn:31">Sridharan, Vellaisamy; Menéndez, J. Carlos (2010). "Cerium(IV) Ammonium Nitrate as a Catalyst in Organic Synthesis". Chemical Reviews. 110 (6): 3805–3849. doi:10.1021/cr100004p. PMID 20359233. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:31" class="footnote-back-ref">↩</a></li>
<li id="fn:32">Sridharan, Vellaisamy; Menéndez, J. Carlos (2010). "Cerium(IV) Ammonium Nitrate as a Catalyst in Organic Synthesis". Chemical Reviews. 110 (6): 3805–3849. doi:10.1021/cr100004p. PMID 20359233. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:32" class="footnote-back-ref">↩</a></li>
<li id="fn:33">Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton, Florida: CRC Press. ISBN 0-8493-0486-5. <a href="0-8493-0486-5" target="_blank">0-8493-0486-5</a> <a href="#fnref:33" class="footnote-back-ref">↩</a></li>
<li id="fn:34">Gupta, C. K. & Krishnamurthy, Nagaiyar (2004). Extractive metallurgy of rare earths. CRC Press. p. 30. ISBN 978-0-415-33340-5. <a href="978-0-415-33340-5" target="_blank">978-0-415-33340-5</a> <a href="#fnref:34" class="footnote-back-ref">↩</a></li>
<li id="fn:35">Gschneidner K.A., ed. (2006). "Chapter 229: Applications of tetravalent cerium compounds". Handbook on the Physics and Chemistry of Rare Earths, Volume 36. The Netherlands: Elsevier. pp. 286–288. ISBN 978-0-444-52142-2. <a href="978-0-444-52142-2" target="_blank">978-0-444-52142-2</a> <a href="#fnref:35" class="footnote-back-ref">↩</a></li>
<li id="fn:36">Sroor, Farid M.A.; Edelmann, Frank T. (2012). "Lanthanides: Tetravalent Inorganic". Encyclopedia of Inorganic and Bioinorganic Chemistry. doi:10.1002/9781119951438.eibc2033. ISBN 978-1-119-95143-8. <a href="978-1-119-95143-8" target="_blank">978-1-119-95143-8</a> <a href="#fnref:36" class="footnote-back-ref">↩</a></li>
<li id="fn:37">McGill, Ian. "Rare Earth Elements". Ullmann's Encyclopedia of Industrial Chemistry. Vol. 31. Weinheim: Wiley-VCH. p. 190. doi:10.1002/14356007.a22_607. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:37" class="footnote-back-ref">↩</a></li>
<li id="fn:38">Greenwood & Earnshaw 1997, pp. 1244–8. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:38" class="footnote-back-ref">↩</a></li>
<li id="fn:39">B. P. Belousov (1959). "Периодически действующая реакция и ее механизм" [Periodically acting reaction and its mechanism]. Сборник рефератов по радиационной медицине (in Russian). 147: 145. <a href="#fnref:39" class="footnote-back-ref">↩</a></li>
<li id="fn:40">Greenwood & Earnshaw 1997, pp. 1248–9. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:40" class="footnote-back-ref">↩</a></li>
<li id="fn:41">Schelter, Eric J. (20 March 2013). "Cerium under the lens". Nature Chemistry. 5 (4): 348. Bibcode:2013NatCh...5..348S. doi:10.1038/nchem.1602. PMID 23511425. <a href="https://doi.org/10.1038%2Fnchem.1602" target="_blank">https://doi.org/10.1038%2Fnchem.1602</a> <a href="#fnref:41" class="footnote-back-ref">↩</a></li>
<li id="fn:42">Mikhail N. Bochkarev (2004). "Molecular compounds of "new" divalent lanthanides". Coordination Chemistry Reviews. 248 (9–10): 835–851. doi:10.1016/j.ccr.2004.04.004. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:42" class="footnote-back-ref">↩</a></li>
<li id="fn:43">M. Cristina Cassani; Yurii K. Gun'ko; Peter B. Hitchcock; Alexander G. Hulkes; Alexei V. Khvostov; Michael F. Lappert; Andrey V. Protchenko (2002). "Aspects of non-classical organolanthanide chemistry". Journal of Organometallic Chemistry. 647 (1–2): 71–83. doi:10.1016/s0022-328x(01)01484-x. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:43" class="footnote-back-ref">↩</a></li>
<li id="fn:44">"Visual Elements: Cerium". London: Royal Society of Chemistry. 1999–2012. Retrieved December 31, 2009. <a href="http://www.rsc.org/periodic-table/element/58/cerium" target="_blank">http://www.rsc.org/periodic-table/element/58/cerium</a> <a href="#fnref:44" class="footnote-back-ref">↩</a></li>
<li id="fn:45">"Visual Elements: Cerium". London: Royal Society of Chemistry. 1999–2012. Retrieved December 31, 2009. <a href="http://www.rsc.org/periodic-table/element/58/cerium" target="_blank">http://www.rsc.org/periodic-table/element/58/cerium</a> <a href="#fnref:45" class="footnote-back-ref">↩</a></li>
<li id="fn:46">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:46" class="footnote-back-ref">↩</a></li>
<li id="fn:47">"Visual Elements: Cerium". London: Royal Society of Chemistry. 1999–2012. Retrieved December 31, 2009. <a href="http://www.rsc.org/periodic-table/element/58/cerium" target="_blank">http://www.rsc.org/periodic-table/element/58/cerium</a> <a href="#fnref:47" class="footnote-back-ref">↩</a></li>
<li id="fn:48">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:48" class="footnote-back-ref">↩</a></li>
<li id="fn:49">Weeks, Mary Elvira (1956). The discovery of the elements (6th ed.). Easton, PA: Journal of Chemical Education. <a href="https://archive.org/details/discoveryoftheel002045mbp" target="_blank">https://archive.org/details/discoveryoftheel002045mbp</a> <a href="#fnref:49" class="footnote-back-ref">↩</a></li>
<li id="fn:50">Weeks, Mary Elvira (1932). "The Discovery of the Elements: XI. Some Elements Isolated with the Aid of Potassium and Sodium: Zirconium, Titanium, Cerium and Thorium". The Journal of Chemical Education. 9 (7): 1231–1243. Bibcode:1932JChEd...9.1231W. doi:10.1021/ed009p1231. <a href="/wiki/Mary_Elvira_Weeks" target="_blank">/wiki/Mary_Elvira_Weeks</a> <a href="#fnref:50" class="footnote-back-ref">↩</a></li>
<li id="fn:51">Marshall, James L. Marshall; Marshall, Virginia R. Marshall (2015). "Rediscovery of the elements: The Rare Earths–The Beginnings" (PDF). The Hexagon: 41–45. Retrieved 30 December 2019. <a href="http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20I.pdf" target="_blank">http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20I.pdf</a> <a href="#fnref:51" class="footnote-back-ref">↩</a></li>
<li id="fn:52">Marshall, James L. Marshall; Marshall, Virginia R. Marshall (2015). "Rediscovery of the elements: The Rare Earths–The Confusing Years" (PDF). The Hexagon: 72–77. Retrieved 30 December 2019. <a href="http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20II.pdf" target="_blank">http://www.chem.unt.edu/~jimm/REDISCOVERY%207-09-2018/Hexagon%20Articles/rare%20earths%20II.pdf</a> <a href="#fnref:52" class="footnote-back-ref">↩</a></li>
<li id="fn:53">Hirai, Shinji; Shimakage, Kazuyoshi; Saitou, Yasushi; Nishimura, Toshiyuki; Uemura, Yoichiro; Mitomo, Mamoru; Brewer, Leo (2005-01-21). "Synthesis and Sintering of Cerium(III) Sulfide Powders". Journal of the American Ceramic Society. 81 (1): 145–151. doi:10.1111/j.1151-2916.1998.tb02306.x. <a href="http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x" target="_blank">http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x</a> <a href="#fnref:53" class="footnote-back-ref">↩</a></li>
<li id="fn:54">Hadden, Gavin, ed. (1946). "Chapter 11 - Ames Project". Manhattan District History. Vol. 4. Washington, D.C.: United States Army Corps of Engineers. <a href="https://www.osti.gov/opennet/manhattan_district" target="_blank">https://www.osti.gov/opennet/manhattan_district</a> <a href="#fnref:54" class="footnote-back-ref">↩</a></li>
<li id="fn:55">Hadden, Gavin, ed. (1946). "Chapter 11 - Ames Project". Manhattan District History. Vol. 4. Washington, D.C.: United States Army Corps of Engineers. <a href="https://www.osti.gov/opennet/manhattan_district" target="_blank">https://www.osti.gov/opennet/manhattan_district</a> <a href="#fnref:55" class="footnote-back-ref">↩</a></li>
<li id="fn:56">Emsley, John (2003). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. ISBN 978-0-19-850340-8. <a href="978-0-19-850340-8" target="_blank">978-0-19-850340-8</a> <a href="#fnref:56" class="footnote-back-ref">↩</a></li>
<li id="fn:57">Greenwood & Earnshaw 1997, pp. 1294. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:57" class="footnote-back-ref">↩</a></li>
<li id="fn:58">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:58" class="footnote-back-ref">↩</a></li>
<li id="fn:59">Burke, Ernst A.J. (2008). "The use of suffixes in mineral names" (PDF). Elements. 4 (2): 96. Archived from the original (PDF) on 19 December 2019. Retrieved 7 December 2019. <a href="https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf" target="_blank">https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf</a> <a href="#fnref:59" class="footnote-back-ref">↩</a></li>
<li id="fn:60">"Monazite-(Ce): Mineral information, data and localities". www.mindat.org. <a href="https://www.mindat.org/min-2751.html" target="_blank">https://www.mindat.org/min-2751.html</a> <a href="#fnref:60" class="footnote-back-ref">↩</a></li>
<li id="fn:61">"CNMNC". nrmima.nrm.se. Archived from the original on 2019-08-10. Retrieved 2018-10-06. <a href="https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//" target="_blank">https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//</a> <a href="#fnref:61" class="footnote-back-ref">↩</a></li>
<li id="fn:62">"Bastnäsite-(Ce): Mineral information, data and localities". www.mindat.org. <a href="https://www.mindat.org/min-560.html" target="_blank">https://www.mindat.org/min-560.html</a> <a href="#fnref:62" class="footnote-back-ref">↩</a></li>
<li id="fn:63">Burke, Ernst A.J. (2008). "The use of suffixes in mineral names" (PDF). Elements. 4 (2): 96. Archived from the original (PDF) on 19 December 2019. Retrieved 7 December 2019. <a href="https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf" target="_blank">https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf</a> <a href="#fnref:63" class="footnote-back-ref">↩</a></li>
<li id="fn:64">Greenwood & Earnshaw 1997, pp. 1229–1232. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:64" class="footnote-back-ref">↩</a></li>
<li id="fn:65">Thomas, J. B.; Bodnar, R. J.; Shimizu, N.; Chesner, C. A. (2003). "Melt inclusions in zircon". Reviews in Mineralogy and Geochemistry. 53 (1): 63–87. Bibcode:2003RvMG...53...63T. doi:10.2113/0530063. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:65" class="footnote-back-ref">↩</a></li>
<li id="fn:66">"Cerianite-(Ce): Mineral information, data and localities". www.mindat.org. <a href="https://www.mindat.org/min-929.html" target="_blank">https://www.mindat.org/min-929.html</a> <a href="#fnref:66" class="footnote-back-ref">↩</a></li>
<li id="fn:67">"CNMNC". nrmima.nrm.se. Archived from the original on 2019-08-10. Retrieved 2018-10-06. <a href="https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//" target="_blank">https://web.archive.org/web/20190810195707/http://nrmima.nrm.se//</a> <a href="#fnref:67" class="footnote-back-ref">↩</a></li>
<li id="fn:68">Burke, Ernst A.J. (2008). "The use of suffixes in mineral names" (PDF). Elements. 4 (2): 96. Archived from the original (PDF) on 19 December 2019. Retrieved 7 December 2019. <a href="https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf" target="_blank">https://web.archive.org/web/20191219014458/http://elementsmagazine.org/archives/e4_2/e4_2_dep_mineralmatters.pdf</a> <a href="#fnref:68" class="footnote-back-ref">↩</a></li>
<li id="fn:69">Graham, A. R. (1955). "Cerianite CeO2: a new rare-earth oxide mineral". American Mineralogist. 40: 560–564. <a href="#fnref:69" class="footnote-back-ref">↩</a></li>
<li id="fn:70">Greenwood & Earnshaw 1997, pp. 1229–1232. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:70" class="footnote-back-ref">↩</a></li>
<li id="fn:71">Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. pp. 199–200. ISBN 978-0-07-049439-8. <a href="978-0-07-049439-8" target="_blank">978-0-07-049439-8</a> <a href="#fnref:71" class="footnote-back-ref">↩</a></li>
<li id="fn:72">Greenwood & Earnshaw 1997, pp. 1229–1232. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:72" class="footnote-back-ref">↩</a></li>
<li id="fn:73">Klaus Reinhardt; Herwig Winkler (2000). "Cerium Mischmetal, Cerium Alloys, and Cerium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a06_139. ISBN 978-3-527-30673-2.. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:73" class="footnote-back-ref">↩</a></li>
<li id="fn:74">AWS D10.11M/D10.11 - An American National Standard - Guide for Root Pass Welding of Pipe Without Backing. American Welding Society. 2007. <a href="#fnref:74" class="footnote-back-ref">↩</a></li>
<li id="fn:75">Lewes, Vivian Byam (1911). "Lighting" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. Vol. 16 (11th ed.). Cambridge University Press. p. 656. <a href="https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Lighting" target="_blank">https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Lighting</a> <a href="#fnref:75" class="footnote-back-ref">↩</a></li>
<li id="fn:76">Wickleder, Mathias S.; Fourest, Blandine; Dorhout, Peter K. (2006). "Thorium". In Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (PDF). Vol. 3 (3rd ed.). Dordrecht, the Netherlands: Springer. pp. 52–160. doi:10.1007/1-4020-3598-5_3. ISBN 978-1-4020-3555-5. Archived from the original (PDF) on 2016-03-07. <a href="978-1-4020-3555-5" target="_blank">978-1-4020-3555-5</a> <a href="#fnref:76" class="footnote-back-ref">↩</a></li>
<li id="fn:77">Greenwood & Earnshaw 1997, pp. 1228. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:77" class="footnote-back-ref">↩</a></li>
<li id="fn:78">Greenwood & Earnshaw 1997, pp. 1228. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:78" class="footnote-back-ref">↩</a></li>
<li id="fn:79">Klaus Reinhardt and Herwig Winkler in "Cerium Mischmetal, Cerium Alloys, and Cerium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2000, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_139 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:79" class="footnote-back-ref">↩</a></li>
<li id="fn:80">Greenwood & Earnshaw 1997, pp. 1229–1232. - Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 28. ISBN 978-0-08-037941-8.Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. <a href="#fnref:80" class="footnote-back-ref">↩</a></li>
<li id="fn:81">Wilkinson, Tom (6 November 2009). "Book Of A Lifetime: The Periodic Table, By Primo Levi". The Independent. Retrieved 25 October 2016. <a href="https://www.independent.co.uk/arts-entertainment/books/reviews/book-of-a-lifetime-the-periodic-table-by-primo-levi-1815315.html" target="_blank">https://www.independent.co.uk/arts-entertainment/books/reviews/book-of-a-lifetime-the-periodic-table-by-primo-levi-1815315.html</a> <a href="#fnref:81" class="footnote-back-ref">↩</a></li>
<li id="fn:82">Gleń, Marta; Grzmil, Barbara; Sreńscek-Nazzal, Joanna; Kic, Bogumił (2011-04-01). "Effect of CeO2 and Sb2O3 on the phase transformation and optical properties of photostable titanium dioxide". Chemical Papers. 65 (2): 203–212. doi:10.2478/s11696-010-0103-x. ISSN 1336-9075. S2CID 94458692. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:82" class="footnote-back-ref">↩</a></li>
<li id="fn:83">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:83" class="footnote-back-ref">↩</a></li>
<li id="fn:84">Cerium dioxide Archived 2013-03-02 at the Wayback Machine. nanopartikel.info (2011-02-02) <a href="http://www.nanopartikel.info/cms/lang/en/Wissensbasis/Cerdioxid" target="_blank">http://www.nanopartikel.info/cms/lang/en/Wissensbasis/Cerdioxid</a> <a href="#fnref:84" class="footnote-back-ref">↩</a></li>
<li id="fn:85">Trovarelli, Alessandro (2002). Catalysis by ceria and related materials. Imperial College Press. pp. 6–11. ISBN 978-1-86094-299-0. <a href="978-1-86094-299-0" target="_blank">978-1-86094-299-0</a> <a href="#fnref:85" class="footnote-back-ref">↩</a></li>
<li id="fn:86">Lu, Chung-Hsin; Hong, Hsin-Cheng; Jagannathan, R. (2002-01-01). "Sol–gel synthesis and photoluminescent properties of cerium-ion doped yttrium aluminium garnet powders". Journal of Materials Chemistry. 12 (8): 2525–2530. doi:10.1039/B200776M. ISSN 1364-5501. <a href="https://pubs.rsc.org/en/content/articlelanding/2002/jm/b200776m" target="_blank">https://pubs.rsc.org/en/content/articlelanding/2002/jm/b200776m</a> <a href="#fnref:86" class="footnote-back-ref">↩</a></li>
<li id="fn:87">Hirai, Shinji; Shimakage, Kazuyoshi; Saitou, Yasushi; Nishimura, Toshiyuki; Uemura, Yoichiro; Mitomo, Mamoru; Brewer, Leo (2005-01-21). "Synthesis and Sintering of Cerium(III) Sulfide Powders". Journal of the American Ceramic Society. 81 (1): 145–151. doi:10.1111/j.1151-2916.1998.tb02306.x. <a href="http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x" target="_blank">http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x</a> <a href="#fnref:87" class="footnote-back-ref">↩</a></li>
<li id="fn:88">Hadden, Gavin, ed. (1946). "Chapter 11 - Ames Project". Manhattan District History. Vol. 4. Washington, D.C.: United States Army Corps of Engineers. <a href="https://www.osti.gov/opennet/manhattan_district" target="_blank">https://www.osti.gov/opennet/manhattan_district</a> <a href="#fnref:88" class="footnote-back-ref">↩</a></li>
<li id="fn:89">Hirai, Shinji; Shimakage, Kazuyoshi; Saitou, Yasushi; Nishimura, Toshiyuki; Uemura, Yoichiro; Mitomo, Mamoru; Brewer, Leo (2005-01-21). "Synthesis and Sintering of Cerium(III) Sulfide Powders". Journal of the American Ceramic Society. 81 (1): 145–151. doi:10.1111/j.1151-2916.1998.tb02306.x. <a href="http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x" target="_blank">http://doi.wiley.com/10.1111/j.1151-2916.1998.tb02306.x</a> <a href="#fnref:89" class="footnote-back-ref">↩</a></li>
<li id="fn:90">Sims, Zachary (2016). "Cerium-Based, Intermetallic-Strengthened Aluminum Casting Alloy: High-Volume Co-product Development". JOM. 68 (7): 1940–1947. Bibcode:2016JOM....68g1940S. doi:10.1007/s11837-016-1943-9. OSTI 1346625. S2CID 138835874. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:90" class="footnote-back-ref">↩</a></li>
<li id="fn:91">Leary, J. A.; Mullins, L. J. (1964-11-01). PREPARATION OF TERNARY PLUTONIUM ALLOYS FOR CORE TEST FACILITY PROGRAM (Report). Los Alamos National Lab. (LANL), Los Alamos, NM (United States). OSTI 4650650. <a href="https://www.osti.gov/biblio/4650650" target="_blank">https://www.osti.gov/biblio/4650650</a> <a href="#fnref:91" class="footnote-back-ref">↩</a></li>
<li id="fn:92">Bleiwas, D.I. (2013). Potential for Recovery of Cerium Contained in Automotive Catalytic Converters. Reston, Va.: U.S. Department of the Interior, U.S. Geological Survey. <a href="https://purl.fdlp.gov/GPO/gpo36871" target="_blank">https://purl.fdlp.gov/GPO/gpo36871</a> <a href="#fnref:92" class="footnote-back-ref">↩</a></li>
<li id="fn:93">"Argonne's deNOx Catalyst Begins Extensive Diesel Engine Exhaust Testing". Argonne National Laboratory. Archived from the original on 2015-09-07. Retrieved 2014-06-02. <a href="https://web.archive.org/web/20150907191148/http://www.transportation.anl.gov/engines/cerium-oxide_catalyst.html" target="_blank">https://web.archive.org/web/20150907191148/http://www.transportation.anl.gov/engines/cerium-oxide_catalyst.html</a> <a href="#fnref:93" class="footnote-back-ref">↩</a></li>
<li id="fn:94">Pol, Arjan; Barends, Thomas R. M.; Dietl, Andreas; Khadem, Ahmad F.; Eygensteyn, Jelle; Jetten, Mike S. M.; Op Den Camp, Huub J. M. (2013). "Rare earth metals are essential for methanotrophic life in volcanic mudpots" (PDF). Environmental Microbiology. 16 (1): 255–64. doi:10.1111/1462-2920.12249. PMID 24034209. <a href="https://repository.ubn.ru.nl//bitstream/handle/2066/128108/128108.pdf" target="_blank">https://repository.ubn.ru.nl//bitstream/handle/2066/128108/128108.pdf</a> <a href="#fnref:94" class="footnote-back-ref">↩</a></li>
<li id="fn:95">Kang, L.; Shen, Z.; Jin, C. (April 2000). "Neodymium cations Nd3+ were transported to the interior of Euglena gracilis 277". Chin. Sci. Bull. 45 (7): 585–592. Bibcode:2000ChSBu..45..585K. doi:10.1007/BF02886032. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:95" class="footnote-back-ref">↩</a></li>
<li id="fn:96">Hawthorne, Joseph; De la Torre Roche, Roberto; Xing, Baoshan; Newman, Lee A.; Ma, Xingmao; Majumdar, Sanghamitra; Gardea-Torresdey, Jorge; White, Jason C. (2014-11-18). "Particle-Size Dependent Accumulation and Trophic Transfer of Cerium Oxide through a Terrestrial Food Chain". Environmental Science & Technology. 48 (22): 13102–13109. Bibcode:2014EnST...4813102H. doi:10.1021/es503792f. ISSN 0013-936X. PMID 25340623. <a href="https://pubs.acs.org/doi/10.1021/es503792f" target="_blank">https://pubs.acs.org/doi/10.1021/es503792f</a> <a href="#fnref:96" class="footnote-back-ref">↩</a></li>
<li id="fn:97">Majumdar, Sanghamitra; Trujillo-Reyes, Jesica; Hernandez-Viezcas, Jose A.; White, Jason C.; Peralta-Videa, Jose R.; Gardea-Torresdey, Jorge L. (2016-07-05). "Cerium Biomagnification in a Terrestrial Food Chain: Influence of Particle Size and Growth Stage". Environmental Science & Technology. 50 (13): 6782–6792. Bibcode:2016EnST...50.6782M. doi:10.1021/acs.est.5b04784. ISSN 0013-936X. PMID 26690677. <a href="https://pubs.acs.org/doi/10.1021/acs.est.5b04784" target="_blank">https://pubs.acs.org/doi/10.1021/acs.est.5b04784</a> <a href="#fnref:97" class="footnote-back-ref">↩</a></li>
<li id="fn:98">Gupta, Govind Sharan; Shanker, Rishi; Dhawan, Alok; Kumar, Ashutosh (2017), Ranjan, Shivendu; Dasgupta, Nandita; Lichtfouse, Eric (eds.), "Impact of Nanomaterials on the Aquatic Food Chain", Nanoscience in Food and Agriculture 5, Sustainable Agriculture Reviews, vol. 26, Cham: Springer International Publishing, pp. 309–333, doi:10.1007/978-3-319-58496-6_11, ISBN 978-3-319-58496-6, retrieved 2023-08-12 <a href="978-3-319-58496-6" target="_blank">978-3-319-58496-6</a> <a href="#fnref:98" class="footnote-back-ref">↩</a></li>
<li id="fn:99">Jakupec, M. A.; Unfried, P.; Keppler, B. K. (2005). "Pharmacological properties of cerium compunds". Reviews of Physiology, Biochemistry and Pharmacology. 153. Berlin, Heidelberg: Springer Berlin Heidelberg: 101–111. doi:10.1007/s10254-004-0024-6. ISBN 978-3-540-24012-9. PMID 15674649. Retrieved 2023-08-05. <a href="978-3-540-24012-9" target="_blank">978-3-540-24012-9</a> <a href="#fnref:99" class="footnote-back-ref">↩</a></li>
<li id="fn:100">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:100" class="footnote-back-ref">↩</a></li>
<li id="fn:101">Dai, Tianhong; Huang, Ying-Ying; Sharma, Sulbha K.; Hashmi, Javad T.; Kurup, Divya B.; Hamblin, Michael R. (2010). "Topical antimicrobials for burn wound infections". Recent Pat Anti-Infect Drug Discov. 5 (2): 124–151. doi:10.2174/157489110791233522. PMC 2935806. PMID 20429870. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2935806" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2935806</a> <a href="#fnref:101" class="footnote-back-ref">↩</a></li>
<li id="fn:102">Attof, Rachid; Magnin, Christophe; Bertin-Maghit, Marc; Olivier, Laure; Tissot, Sylvie; Petit, Paul (2007). "Methemoglobinemia by cerium nitrate poisoning". Burns. 32 (8): 1060–1061. doi:10.1016/j.burns.2006.04.005. PMID 17027160. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:102" class="footnote-back-ref">↩</a></li>
<li id="fn:103">Rim, Kyung Taek; Koo, Kwon Ho; Park, Jung Sun (March 2013). "Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review". Safety and Health at Work. 4 (1): 12–26. doi:10.5491/SHAW.2013.4.1.12. PMC 3601293. PMID 23516020. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293</a> <a href="#fnref:103" class="footnote-back-ref">↩</a></li>
<li id="fn:104">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:104" class="footnote-back-ref">↩</a></li>
<li id="fn:105">Spellman, Frank R. (2022-12-30). The Science of Rare Earth Elements: Concepts and Applications. CRC Press. pp. 104–105. ISBN 978-1-000-82129-1. <a href="978-1-000-82129-1" target="_blank">978-1-000-82129-1</a> <a href="#fnref:105" class="footnote-back-ref">↩</a></li>
<li id="fn:106">Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. Oxford University Press. pp. 120–125. ISBN 978-0-19-960563-7. <a href="978-0-19-960563-7" target="_blank">978-0-19-960563-7</a> <a href="#fnref:106" class="footnote-back-ref">↩</a></li>
<li id="fn:107">"Cerium(IV) oxide, REacton Safety Data Sheet". Fisher Scientific. March 27, 2024. Retrieved August 27, 2024. <a href="https://www.fishersci.com/store/msds?partNumber=AA4466236&productDescription=CERIUM+IV+OXIDE+500G&vendorId=VN00024248&countryCode=US&language=en" target="_blank">https://www.fishersci.com/store/msds?partNumber=AA4466236&productDescription=CERIUM+IV+OXIDE+500G&vendorId=VN00024248&countryCode=US&language=en</a> <a href="#fnref:107" class="footnote-back-ref">↩</a></li>
<li id="fn:108">Rim, Kyung Taek; Koo, Kwon Ho; Park, Jung Sun (March 2013). "Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review". Safety and Health at Work. 4 (1): 12–26. doi:10.5491/SHAW.2013.4.1.12. PMC 3601293. PMID 23516020. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293</a> <a href="#fnref:108" class="footnote-back-ref">↩</a></li>
<li id="fn:109">"Cerium Safety Data Sheet" (PDF). Ames Laboratory, U. S. Department of Energy. January 26, 2016. Retrieved August 27, 2024. <a href="https://www.ameslab.gov/sites/default/files/inline-files/58_Cerium_SDS.pdf" target="_blank">https://www.ameslab.gov/sites/default/files/inline-files/58_Cerium_SDS.pdf</a> <a href="#fnref:109" class="footnote-back-ref">↩</a></li>
<li id="fn:110">Rim, Kyung Taek; Koo, Kwon Ho; Park, Jung Sun (March 2013). "Toxicological Evaluations of Rare Earths and Their Health Impacts to Workers: A Literature Review". Safety and Health at Work. 4 (1): 12–26. doi:10.5491/SHAW.2013.4.1.12. PMC 3601293. PMID 23516020. <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293" target="_blank">https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3601293</a> <a href="#fnref:110" class="footnote-back-ref">↩</a></li>
<li id="fn:111">Environmental Protection Agency (September 2009). Toxicological Review of Cerium Oxide and Cerium Compounds (PDF) (Report). Washington, D.C. <a href="https://iris.epa.gov/static/pdfs/1018tr.pdf" target="_blank">https://iris.epa.gov/static/pdfs/1018tr.pdf</a> <a href="#fnref:111" class="footnote-back-ref">↩</a></li>
</ol>

Cerium open-in-new

Cerium