Uranium tetrafluoride: Difference between revisions

| Verifiedfields = changed

| Watchedfields = changed

| verifiedrevid = 451188952

| Name = Uranium tetrafluoride

| ImageFile = Uranium_tetrafluoride.jpg

| ImageFile1 = Kristallstruktur Uran(IV)-fluorid.png

| ImageSize1 =

| IUPACName = Uranium(IV) fluoride<br />Uranium tetrafluoride

| OtherNames =

| SystematicName =

| Section1 = {{Chembox Identifiers

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| CASNo = 10049-14-6

| CASNo_Ref = {{cascite|correct|CAS}}

| EINECS = 233-170-1

| PubChem = 61461

| UNII_Ref = {{fdacite|correct|FDA}}

| UNII = PJ46VTD8B2

| SMILES = F[U](F)(F)F

| Section2 = {{Chembox Properties

| Formula = UF₄

| MolarMass = 314.02 g/mol

| Appearance = Green crystalline solid

| Density = 6.70 g/cm³, solid

| Solubility = Insoluble

| MeltingPtC = 1036

| BoilingPtC = 1417

| pKa =

| Section3 = {{Chembox Structure

| CrystalStruct = [[Monoclinic]], [[Pearson symbol|mS60]]

| SpaceGroup = C2/c, No. 15

| Section4 =

| Section5 =

| Section6 =

| Section7 = {{Chembox Hazards

| ExternalSDS = [http://physchem.ox.ac.uk/MSDS/UR/uranium_tetrafluoride.html External MSDS]

| GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}

| GHSSignalWord = Danger

| HPhrases = {{H-phrases|300|330|373|411}}

| PPhrases = {{P-phrases|}}

| FlashPt = Non-flammable

| Section8 = {{Chembox Related

| OtherAnions = [[Uranium(IV) chloride]]<br />[[Uranium(IV) bromide]]<br />[[Uranium(IV) iodide]]<br />[[Uranium dioxide]]

| OtherCations = [[Praseodymium(IV) fluoride]]<br />[[Thorium(IV) fluoride]]<br />[[Protactinium(IV) fluoride]]<br />[[Neptunium(IV) fluoride]]<br />[[Plutonium(IV) fluoride]]

| OtherCompounds = [[Uranium hexafluoride]]

{{redirect|Green salt|the salt substitute|Salicornia#Culinary use}}

'''Uranium tetrafluoride''' is the [[inorganic compound]] with the [[Chemical formula|formula]] UF₄. It is a green solid with an insignificant [[vapor pressure]] and low [[solubility]] in [[water]]. Uranium in its tetravalent ([[uranous]]) state is important in various technological processes. In the uranium refining industry it is known as '''green salt'''.<ref name=Ullmann/>

==Production==

UF₄ is prepared from [[Uranium dioxide|UO₂]] in a fluidized bed by reaction with [[Hydrogen fluoride|HF]]. The UO₂ is derived from mining operations. Around 60,000 tonnes per year are prepared in this way annually. A common impurity is [[Uranyl fluoride|UO₂F₂]]. UF4 is susceptible to [[hydrolysis]] as well.<ref name=Ullmann>{{Ullmann |doi=10.1002/14356007.a27_281.pub2|title=Uranium, Uranium Alloys, and Uranium Compounds|year=2007|last1=Peehs|first1=Martin|last2=Walter|first2=Thomas|last3=Walter|first3=Sabine|last4=Zemek|first4=Martin}}</ref>

UF₄ is formed by the reaction of [[Uranium hexafluoride|UF₆]] with hydrogen gas in a vertical tube-type reactor.

UF₄ is less stable than the uranium oxides and reacts slowly with moisture at ambient temperature, forming UO₂ and HF, the latter of which is very [[Corrosive substance|corrosive]] and [[Toxicity|toxic]]; it is thus less favourable for long-term disposal. The bulk [[density]] of UF₄ varies from about 2.0 g/cm³ to about 4.5 g/cm³ depending on the production process and the properties of the starting uranium compounds.

A [[molten salt reactor]] design, a type of [[nuclear reactor]] where the working fluid is a [[molten salt]], would use UF₄ as the core material. UF₄ is generally chosen over other salts because of the usefulness of the elements without [[isotope separation]], better neutron economy and moderating efficiency, lower [[vapor pressure]] and better chemical stability.

==Reactions==

Uranium tetrafluoride reacts with fluorine, first to give [[uranium pentafluoride]] and then [[Volatility (chemistry)|volatile]] UF₆:

:2{{nbsp}}UF₄ + F₂ → 2{{nbsp}}UF₅

:2{{nbsp}}UF₅ + F₂ → 2{{nbsp}}UF₆

UF₄ is reduced by [[magnesium]] to give the metal:<ref name=G&E>{{Greenwood&Earnshaw2nd}} </ref>

:UF₄ + 2{{nbsp}}Mg → U + 2{{nbsp}}MgF₂

It is oxidized to UF₅ at room temperature and then, at 100{{nbsp}}°C, to the [[hexafluoride]].

==Structure==

Like most metal fluorides, UF₄ is a dense highly crosslinked [[inorganic polymer]]. As established by [[X-ray crystallography]], the U centres are eight-coordinate with square antiprismatic coordination spheres. The fluoride centres are doubly bridging.<ref name=G&E/><ref>{{Cite journal | last1 = Kern | first1 = S. | last2 = Hayward | first2 = J. | last3 = Roberts | first3 = S. | last4 = Richardson | first4 = J. W. | last5 = Rotella | first5 = F. J. | last6 = Soderholm | first6 = L. | last7 = Cort | first7 = B. | last8 = Tinkle | first8 = M. | last9 = West | first9 = M. | last10 = Hoisington | first10 = D.| last11 = Lander | first11 = G. A.| doi = 10.1063/1.467963 | title = Temperature Variation of the Structural Parameters in Actinide Tetrafluorides | journal = The Journal of Chemical Physics | volume = 101 | issue = 11 | pages = 9333–9337 | year = 1994 | bibcode = 1994JChPh.101.9333K| url = https://zenodo.org/record/1232099 }}</ref>

==Safety==

Like all uranium salts, UF₄ is [[toxic]] and thus harmful by inhalation, ingestion, and through skin contact.

==See also==

* [[Praseodymium(IV) fluoride]] which has the same crystal structure

==References of historical interest==

* {{Cite journal | last1 = Booth | first1 = H. S. | last2 = Krasny-Ergen | first2 = W. | last3 = Heath | first3 = R. E. | journal = Journal of the American Chemical Society | volume = 68 | issue = 10 | pages = 1969 |title=Uranium Tetrafluoride| year = 1946 | doi = 10.1021/ja01214a028 }}

* {{cite web|url= http://web.ead.anl.gov/uranium/guide/ucompound/propertiesu/tetrafluoride.cfm|title= Uranium Tetrafluoride|work= Appendix A of the PEIS (DOE/EIS-0269)|publisher= Argonne National Laboratory|access-date= 22 November 2011|archive-date= 30 January 2016|archive-url= https://web.archive.org/web/20160130021820/http://web.ead.anl.gov/uranium/guide/ucompound/propertiesu/tetrafluoride.cfm|url-status= dead}}

{{fluorides}}

{{Actinide halides}}

[[Category:Uranium(IV) compounds]]

[[Category:Actinide halides]]