{{chembox | Reference = | Name = Thorium(IV) nitrate | ImageFile = | ImageFile1 = Thorium(IV) nitrate.jpg | ImageSize = | IUPACName = | OtherNames = | Section1 = {{Chembox Identifiers | CASNo = 13823-29-5 | index_label = (anhydrous) | CASNo_Ref = {{cascite|correct|CAS}} | CASNo2 = 87174-21-8 | index2_label = (trihydrate) | CASNo2_Ref = {{cascite|correct|CAS}} | CASNo3 = 13470-07-0 | index3_label = (tetrahydrate) | CASNo3_Ref = {{cascite|correct|CAS}} | CASNo4 = 14767-04-5 | index4_label = (pentahydrate) | CASNo4_Ref = {{cascite|correct|CAS}} | CASNo5 = 23739-44-8 | index5_label = (hexahydrate) | CASNo5_Ref = {{cascite|correct|CAS}} | ChemSpiderID = 24497 | EC_number = 237-514-1 | PubChem = 26293 | PubChem3 = 134672 | PubChem4 = 92043287 | PubChem5 = 129688133 | UNII_Ref = {{fdacite|correct|FDA}} | UNII = IF944P467K | UNII3_Ref = {{fdacite|correct|FDA}} | UNII3 = 66RXJ6ZF36 | InChI=1S/4NO3.Th/c4*2-1(3)4;/q4*-1;+4 | InChIKey = VGBPIHVLVSGJGR-UHFFFAOYSA-N | SMILES = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[Th+4] | InChI3=1S/4NO3.4H2O.Th/c4*2-1(3)4;;;;;/h;;;;4*1H2;/q4*-1;;;;;+4 | InChIKey3 = VAVIMIAZQDNXID-UHFFFAOYSA-N | SMILES3 = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.[Th+4] | InChI4=1S/4NO3.5H2O.Th/c4*2-1(3)4;;;;;;/h;;;;5*1H2;/q4*-1;;;;;;+4 | InChIKey4 = JFVMRMIHIHCMDY-UHFFFAOYSA-N | SMILES4 = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.[Th+4] | InChI5=1S/4NO3.6H2O.Th/c4*2-1(3)4;;;;;;;/h;;;;6*1H2;/q4*-1;;;;;;;+4 | InChIKey5 = HLGOSPFVTORIQZ-UHFFFAOYSA-N | SMILES5 = [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[N+](=O)([O-])[O-].O.O.O.O.O.O.[Th+4] }} | Section2 = {{Chembox Properties | Formula = {{chem2|Th(NO3)4}} | MolarMass = {{ubl |480.066 (anhydrous) |552.130 (tetrahydrate) |570.146 (pentahydrate) }} | Appearance = Colorless crystal<ref name=Ueki>{{cite journal|last1=Ueki|first1=T.|last2=Zalkin|first2=A.|last3=Templeton|first3=D. H.|title=Crystal structure of thorium nitrate pentahydrate by X-ray diffraction|journal=Acta Crystallographica|date=1 November 1966|volume=20|issue=6|pages=836–841|doi=10.1107/S0365110X66001944|s2cid=96633729 |url=http://www.escholarship.org/uc/item/4jv8n4vn|doi-access=free|bibcode=1966AcCry..20..836U }}</ref> | Density = {{val|2.8|u=g/cm3}}<ref name=herr>{{cite book|last1=Herrmann|first1=W. A.|last2=Edelmann|first2=Frank T.|last3=Poremba|first3=Peter|title=Synthetic Methods of Organometallic and Inorganic Chemistry, Volume 6, 1997: Volume 6: Lanthanides and Actinides|date=1999|publisher=Georg Thieme Verlag|isbn=9783131794611|page=210|url=https://books.google.com/books?id=oYyZAwAAQBAJ&pg=PT210|language=de}}</ref> | MeltingPtC = 55 | MeltingPt_ref = {{cn|date=August 2025}} | BoilingPt = Decomposes | Solubility = {{val|4.013|u=mol/L}} at ({{convert|25|C|F K}})<ref>{{cite journal|last1=Kalinkin|first1=A. M.|title=Calculation of Phase Equilibria in the Th(NO3)4-HNO3-H2O System at 25&nbsp;°C|journal=Radiochemistry|date=2001|volume=43|issue=6|pages=553–557|doi=10.1023/A:1014847506077|bibcode=2001Radch..43..553K |s2cid=92858856}}</ref> | SolubleOther = alcohols, ketones, esters and ethers | VaporPressure = {{ubl |{{convert|0.7|torr|Pa}} ({{convert|25|C|F K}}) |{{convert|1.2|torr|Pa}} ({{convert|42|C|F K}}) |{{convert|10.7|torr|kPa}} ({{convert|68|C|F K}})<ref name=Cheda>{{cite journal|last1=Cheda|first1=J.A.R.|last2=Westrum|first2=Edgar F.|last3=Morss|first3=Lester R.|title=Heat capacity of Th(NO3)4·5H2O from 5 to 350 K|journal=The Journal of Chemical Thermodynamics|date=January 1976|volume=8|issue=1|pages=25–29|doi=10.1016/0021-9614(76)90146-4|url=https://deepblue.lib.umich.edu/bitstream/2027.42/21859/1/0000263.pdf|hdl=2027.42/21859|hdl-access=free}}</ref> }} }} | Section3 = {{Chembox Structure | Structure_ref = <ref name=dbrown>{{cite book|last1=Brown|first1=D.|editor1-last=Bailar|editor1-first=J.C.|title=Comprehensive inorganic chemistry|date=1973|publisher=Pergamon Press|location=Oxford [u.a.]|isbn=008017275X|pages=286–292|edition=1.|chapter=Carbonates, nitrates, sulphates, sulfites, selenates, selenites, tellurates and tellurites}}</ref> | CrystalStruct = orthorhombic | SpaceGroup = | PointGroup = | LattConst_a = {{val|1.1191|u=nm}} | LattConst_b = {{val|2.2889|u=nm}} | LattConst_c = {{val|1.0579|u=nm}} | LattConst_alpha = | LattConst_beta = | LattConst_gamma = | LattConst_ref = | LattConst_Comment = (pentahydrate) | UnitCellVolume = | UnitCellFormulas = | Coordination = | MolShape = | OrbitalHybridisation = | Dipole = }} | Section4 = {{Chembox Thermochemistry | Thermochemistry_ref = <ref name=Cheda /> | HeatCapacity = {{val|480.83|u=J|up=(K·mol)}} | Entropy = | DeltaHform = {{val|-2.29|u=kJ|up=(K·mol)}} | DeltaGfree = | DeltaHcombust = | DeltaHfus = | DeltaHvap = | DeltaHsublim = | HHV = | LHV = }} | Section5 = {{Chembox Hazards | Hazards_ref = {{cn|date=August 2025}} | GHSPictograms = {{GHS03}}{{GHS07}}{{GHS08}}{{GHS09}} | GHSSignalWord = Warning | HPhrases = {{H-phrases|272|302|315|319|335|373|411}} | PPhrases = {{P-phrases|210|220|221|260|261|264|270|271|273|280|301+312|302+352|304+340|305+351+338|312|314|321|330|332+313|337+313|362|370+378|391|403+233|405|501}} }} }} '''Thorium(IV) nitrate''' is a chemical compound, a salt of thorium and nitric acid with the formula {{chem2|Th(NO3)4}}. A white solid in its anhydrous form, it can form tetra- and pentahydrates. As a salt of thorium it is weakly radioactive.

==Preparation== Thorium(IV) nitrate hydrate can be prepared by the reaction of thorium(IV) hydroxide and nitric acid: :{{chem2 | Th(OH)4 + 4 HNO3 + 3 H2O -> Th(NO3)4 + 5 H2O }} Different hydrates are produced by crystallizing in different conditions. When a solution is very dilute, the nitrate is hydrolysed. Although various hydrates have been reported over the years, and some suppliers even claim to stock them, only the tetrahydrate and pentahydrate actually exist.<ref name=benz />{{efn|Bogus hydrates include 12, 6, 5.5, 2 and 1 water molecules{{cn|date=August 2025}} }} What is called a hexahydrate, crystallized from a neutral solution, is probably a basic salt.<ref name=katz>{{cite book|last1=Katz|first1=Joseph j.|last2=Seaborg|first2=Glenn t.|title=The Chemistry of the Actinide and Lanthanide Elements|date=2008|publisher=Springer|isbn=978-1-4020-3598-2|pages=106–108|chapter=Thorium}}</ref>

The pentahydrate is the most common form. It is crystallized from dilute nitric acid solution.<ref name=herr/>

The tetrahydrate, {{chem2|Th(NO3)4*4H2O}} is formed by crystallizing from a stronger nitric acid solution. Concentrations of nitric acid from 4 to 59% result in the tetrahydrate forming.<ref name=benz>{{cite book|last1=Benz|first1=R.|last2=Naoumidis|first2=A.|last3=Brown|first3=D.|title=Th Thorium: Supplement Volume C 3 Compounds with Nitrogen|publisher=Springer Science & Business Media|isbn=9783662063309|pages=70–79|url=https://books.google.com/books?id=iVzxCAAAQBAJ&pg=PA70|language=en|date=2013-11-11}}</ref> The thorium atom has 12-coordination, with four bidentate nitrate groups and four water molecules attached to each thorium atom.<ref name=katz/>

To obtain the anhydrous thorium(IV) nitrate, thermal decomposition of {{chem2|Th(NO3)4*2N2O5}} is required. The decomposition occurs at {{convert|150-160|C|F}}.<ref>{{cite journal |last1=Ferraro |first1=John R. |last2=Katzin |first2=Leonard I. |last3=Gibson |first3=George |title=The Reaction of Thorium Nitrate Tetrahydrate with Nitrogen Oxides. Anhydrous Thorium Nitrate 1 |journal=Journal of the American Chemical Society |date=January 1955 |volume=77 |issue=2 |pages=327–329 |doi=10.1021/ja01607a023}}</ref>

==Properties== Anhydrous thorium nitrate is a white substance. It is covalently bound with low melting point of {{convert|55|C|F}}.<ref name=benz/>

The pentahydrate {{chem2|Th(NO3)4*5H2O}} crystallizes with clear colourless crystals<ref name=Ueki/> in the orthorhombic system. Each thorium atom is connected twice to each of four bidentate nitrate groups, and to three water molecules via their oxygen atoms. In total the thorium is eleven-coordinated. There are also two other water molecules in the crystal structure.The water is hydrogen bonded to other water, or to nitrate groups.<ref name=dbrown/>

Thorium nitrate can dissolve in several different organic solvents<ref name=dbrown/> including alcohols, ketones, esters and ethers.<ref name=katz/> This can be used to separate different metals such as the lanthanides. With ammonium nitrate in the aqueous phase, thorium nitrate prefers the organic liquid, and the lanthanides stay with the water.<ref name=katz/>

Thorium nitrate dissolved in water lowers it freezing point. The maximum freezing point depression is {{convert|−37|C|F}} with a concentration of {{val|2.9|u=mol/kg}}.<ref>{{cite journal|last1=Apelblat|first1=Alexander|last2=Azoulay|first2=David|last3=Sahar|first3=Ayala|title=Properties of aqueous thorium nitrate solutions. Part 1.—Densities, viscosities, conductivities, pH, solubility and activities at freezing point|journal=Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases|date=1973|volume=69|pages=1618|doi=10.1039/F19736901618}}</ref>

==Reactions== left|thumb|300px|Thorium(IV) nitrate used in a lamp. When thorium nitrate pentahydrate is heated, nitrates with less water are produced, however the compounds also lose some nitrate. At {{convert|140|C|F}} a basic nitrate, {{chem2|ThO(NO3)2}} is produced. When strongly heated thorium dioxide is produced.<ref name=dbrown/>

A polymeric peroxynitrate is precipitated when hydrogen peroxide combines with thorium nitrate in solution with dilute nitric acid. Its formula is {{chem2|Th6(O2)10(NO3)4*10H2O}}.<ref name=dbrown/> thumb|left|Th<sub>6</sub>(OO)<sub>10</sub>(NO<sub>3</sub>)<sub>4</sub>·10H<sub>2</sub>O is precipitated by the reaction of thorium nitrate aqueous solution with hydrogen peroxide The hydrolysis of thorium nitrate solutions produces basic nitrates {{chem2|Th2(OH)4(NO3)4*''x''H2O}} and {{chem2|Th2(OH)2(NO3)6*8H2O}}. In crystals of {{chem2|Th2(OH)2(NO3)6*8H2O}} a pair of thorium atoms are connected by two bridging oxygen atoms. Each thorium atom is surrounded by three bidentate nitrate groups and three water molecules, bringing the coordination number to 11.<ref name=dbrown/>

When oxalic acid is added to a thorium nitrate solution, insoluble thorium oxalate precipitates.<ref>{{cite book|last1=Bagnall|first1=Kenneth W.|title=Th Thorium: Compounds with Carbon: Carbonates, Thiocyanates, Alkoxides, Carboxylates|publisher=Springer Science & Business Media|isbn=9783662063156|page=82|url=https://books.google.com/books?id=ZUTtCAAAQBAJ&pg=PA82|language=en|date=2013-12-12}}</ref> Other organic acids added to thorium nitrate solution produce precipitates of organic salts with citric acid; basic salts, such as tartaric acid, adipic acid, malic acid, gluconic acid, phenylacetic acid, valeric acid.<ref>{{cite book|last1=Bagnall|first1=Kenneth W.|title=Th Thorium: Compounds with Carbon: Carbonates, Thiocyanates, Alkoxides, Carboxylates|publisher=Springer Science & Business Media|isbn=9783662063156|pages=66,73,74,105,107,113,122|url=https://books.google.com/books?id=ZUTtCAAAQBAJ&pg=PA82|language=en|date=2013-12-12}}</ref> Other precipitates are also formed from sebacic acid and azelaic acid

==Double salts== Hexanitratothorates with the generic formula {{chem2|M2^{I}Th(NO3)6}} or {{chem2|M^{II}Th(NO3)6*8H2O}} are made by mixing other metal nitrates with thorium nitrate in dilute nitric acid solution. {{chem2|M^{II} }} can be Mg, Mn, Co, Ni, or Zn. {{chem2|M^{I} }} can be Cs, {{chem2|(NO)+}} or {{chem2|(NO2)+}}.<ref name=dbrown/> Crystals of the divalent metal thorium hexanitrate octahydrate have a monoclinic form with similar unit cell dimensions: β=97°, a=9.08 b=8.75-8 c=12.61-3.<ref>{{cite journal|last1=Šćavničar|first1=S.|last2=Prodić|first2=B.|title=The crystal structure of double nitrate octahydrates of thorium and bivalent metals|journal=Acta Crystallographica|date=1 April 1965|volume=18|issue=4|pages=698–702|doi=10.1107/S0365110X65001603|doi-access=free|bibcode=1965AcCry..18..698S }}</ref> Pentanitratothorates with the generic formula {{chem2|M^{I}Th(NO3)5*''x''H2O}} are known for {{chem2|M^{I} }} being Na or K.<ref name=dbrown/>

{{chem2|K3Th(NO3)7}} and {{chem2|K3H3Th(NO3)10*4H2O}} are also known.<ref name=katz/>

==Complexed salts== Thorium nitrate also crystallizes with other ligands and organic solvates including ethylene glycol diethyl ether, tri(n-butyl)phosphate, butylamine, dimethylamine, and trimethylphosphine oxide.<ref name=katz/>

==References== {{reflist}}

==Notes== {{notelist}}

{{Thorium compounds}} {{Nitrates}}

Category:Thorium(IV) compounds Category:Nitrates Category:Deliquescent materials