Terbium(III,IV) oxide 2673142 210582923 2008-05-06T15:20:01Z Itub 426390 recat {{Chembox new | Name = Terbium(III,IV) oxide | ImageFile = Tetraterbium heptaoxide.jpg <!-- | ImageSize = 200px --> | ImageName = Terbium(III,IV) oxide | IUPACName = Tetraterbium heptaoxide | OtherNames = Terbium(III,IV) oxide,<br />Terbium peroxide | Section1 = {{Chembox Identifiers | CASNo = 12037-01-3 }} | Section2 = {{Chembox Properties | Formula = Tb<sub>4</sub>O<sub>7</sub> | MolarMass = 747.6972 g/mol | Appearance = Dark brown-black<br />hygroscopic solid. | Density = 7.3 g/cm<sup>3</sup>, solid. | Solubility = Insoluble. | MeltingPt = Decomposes to [[Terbium(III) oxide|Tb<sub>2</sub>O<sub>3</sub>]] | BoilingPt = '''See above''' }} | Section3 = {{Chembox Structure | MolShape = | Coordination = | CrystalStruct = | Dipole = }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = Oxidising agent. }} | Section8 = {{Chembox Related | OtherAnions = | OtherCations = [[Terbium(III) oxide]],<br />[[Terbium(IV) oxide]] | OtherCpds = [[Cerium(IV) oxide]],<br />[[Praseodymium(III,IV) oxide]] }} }} '''Terbium(III,IV) oxide''', occasionally called ''' tetraterbium heptaoxide''', has the formula Tb<sub>4</sub>O<sub>7</sub>, though some texts refer to it as TbO<sub>1.75</sub>. There is some debate as to whether it is a discrete compound, or simply one phase in an [[interstitial]] oxide system. Tb<sub>4</sub>O<sub>7</sub> is one of the main commercial [[terbium]] compounds, and the only such product containing at least some Tb(IV) (terbium in the +4 oxidation state), along with the more stable Tb(III). It is produced by heating the metal oxalate, and it is used in the preparation of other terbium compounds. Terbium forms three other major [[oxide]]s: [[Terbium(III) oxide|Tb<sub>2</sub>O<sub>3</sub>]], TbO<sub>2</sub>, and Tb<sub>6</sub>O<sub>11</sub>. ==Synthesis== Tb<sub>4</sub>O<sub>7</sub> is most often produced by ignition of the [[oxalate]] at or the [[sulfate]] in air.{{Ref|3}} The oxalate (at 1000 °C) is generally preferred, since the sulfate requires a higher temperature, and it produces an almost black product contaminated with Tb<sub>6</sub>O<sub>11</sub> or other oxygen-rich oxides. ==Chemical properties== Terbium(III,IV) oxide loses [[oxygen|O<sub>2</sub>]] when heated at high temperatures; at more moderate temperatures (ca. 350 °C) it reversibly loses oxygen, as shown by exchange with<sup>18</sup>O<sub>2</sub>. This property, also seen in Pr<sub>6</sub>O<sub>11</sub> and [[vanadium(V) oxide|V<sub>2</sub>O<sub>5</sub>]], allows it to work like V<sub>2</sub>O<sub>5</sub> as a [[redox]] [[catalyst]] in reactions involving oxygen. It was found as early as 1916 that hot Tb<sub>4</sub>O<sub>7</sub> catalyses the reaction of [[coal gas]] ([[Carbon monoxide|CO]] + [[Hydrogen|H<sub>2</sub>]]) with air, leading to incandescence and often the mixture catches fire.{{Ref|4}} Tb<sub>4</sub>O<sub>7</sub> reacts with atomic oxygen to produce TbO<sub>2</sub>, but a more convenient preparation of TbO<sub>2</sub> is by [[disproportionation]] of Tb<sub>4</sub>O<sub>7</sub>. This is performed by refluxing with an excess of an equal mixture of concentrated [[acetic acid]] and [[hydrochloric acid]]s for 30 minutes.{{Ref|5}} :Tb<sub>4</sub>O<sub>7</sub>([[Solid|s]]) + 6 [[Hydrochloric acid|HCl]]([[Aqueous|aq]]) → 2 TbO<sub>2</sub>(s) + 2 [[Terbium(III) chloride|TbCl<sub>3</sub>]](aq) + 3 [[Water (molecule)|H<sub>2</sub>O]]([[Liquid|l]]) Tb<sub>4</sub>O<sub>7</sub> reacts with other hot concentrated acids to produce terbium(III) salts, for example [[sulfuric acid]] gives [[terbium(III) sulfate]]. <!-- ==Applications== (to follow) --> ==References== {{Citationstyle|date=September 2007}} {{reflist}} #{{Note|1}} ''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990. # {{Note|2}} J. W. Mellor, ''A Comprehensive Treatise on Inorganic and Theoretical Chemistry'', pp 692-696, Longmans, Green & Co., London, 1967. # {{Note|3}}''Gmelin'' SE C 1 39, p 397. # {{Note|4}} D. W. Bissel, C. James, [[Journal of the American Chemical Society|''J. Am. Chem. Soc'']] '''38''', 873 (1916). # {{Note|5}} F. T. Edelmann, P. Poremba, in: ''Synthetic Methods of Organometallic and Inorganic Chemistry'', (W. A. Herrmann, ed.), Vol. 6, Georg Thieme Verlag, Stuttgart, 1997. ISBN 3-13-103071-2. [[Category:Terbium compounds]] [[Category:Mixed valence compounds]] [[Category:Oxides]]