thallium(I) iodide
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 476998979
| ImageFile = TlI_structure.png
| ImageName = Thallium(I) iodide
| IUPACName =
| OtherNames = Thallium monoiodide
Thallous iodide
|Section1={{Chembox Identifiers
| CASNo = 7790-30-9
| CASNo_Ref = {{cascite|correct|CAS}}
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 56430
| EC_number = 232-199-7
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 98W17EMO3C
| PubChem = 62679
| InChI = 1/HI.Tl/h1H;/q;+1/p-1
| InChIKey = CMJCEVKJYRZMIA-REWHXWOFAG
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/HI.Tl/h1H;/q;+1/p-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = CMJCEVKJYRZMIA-UHFFFAOYSA-M
| SMILES = I[Tl]
}}
|Section2={{Chembox Properties
| Formula = {{math|TlI}}
| MolarMass = 331.287 g/molHaynes, p. 4.94
| Appearance = yellow crystals
| Solubility = 0.085 g/L (25 °C)
| SolubleOther = insoluble in alcohol
| MeltingPtC = 441.7
| BoilingPtC = 824
| MagSus = −82.2·10−6 cm3/molHaynes, p. 4.136
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| GHSPictograms = {{GHS06}}{{GHS08}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|300|330|373|411}}
| PPhrases = {{P-phrases|260|264|270|271|273|284|301+310|304+340|310|314|320|321|330|391|403+233|405|501}}
| NFPA-H =
| NFPA-F =
| NFPA-R =
| NFPA-S =
| FlashPt = Non-flammable
}}
|Section8={{Chembox Related
| OtherAnions = Thallium(I) fluoride
Thallium(I) chloride
Thallium(I) bromide
| OtherCations = Gallium(I) iodide
Indium(I) iodide
| OtherCompounds = Mercury(II) iodide
Lead(II) iodide
}}
}}
Thallium(I) iodide is a chemical compound with the formula {{math|{{chem2|TlI|auto=yes}}}}. It is exists as both a solid and high temperature red polymorph. Thallium(I) iodide is one of several water-insoluble metal iodides, along with AgI, CuI, SnI2, SnI4, PbI2, and HgI2.
Synthesis and reactions
TlI can be formed in aqueous solution by metathesis of soluble thallium salt with iodide ion.{{cite book|author=E. Dönges|chapter=Thallium(l) Chloride, Bromide and Iodide T1C1, TIBr, TiI|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=2|pages=869-870}} Alternatively, it has been prepared from the elements:{{cite book |doi=10.1002/14356007.a26_607 |chapter=Thallium and Thallium Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Micke |first1=Heinrich |last2=Wolf |first2=Hans Uwe |isbn=3-527-30673-0 }}
:{{math|{{chem2|2 Tl + I2 -> 2TlI}}}}
An excess of iodine produces thallium(I) triiodide, {{math|Tl+I3−}}.
Physical properties
The room temperature form of TlI is yellow and has an orthorhombic structure {{cite journal|doi=10.1063/1.1678917|title=Molecular structure and anharmonicity in thallium iodide|journal=The Journal of Chemical Physics|volume=58|pages=271–278|year=1973|last1=Lowndes|first1=R. P.|last2=Perry|first2=C. H.|issue=1|bibcode=1973JChPh..58..271L}} which can be considered to be a distorted NaCl structure. The distorted structure is may be caused by favorable thallium-thallium interactions, the closest Tl-Tl distance is 383 pm.{{cite journal
| title = Thallium Halides – New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main-Group Elements
| author = Mudring, Anja-Verena
| journal = European Journal of Inorganic Chemistry
| volume = 2007
| issue = 6
| pages = 882–890
| doi = 10.1002/ejic.200600975
| year = 2007
}} At 175 °C the yellow form transforms to a red CsCl form. This phase transition is accompanied by about two orders of magnitude jump in electrical conductivity. The CsI structure can be stabilized down to room temperature by doping {{math|TlI}} with other halides such as RbI, CsI, KI, AgI, TlBr and TlCl.{{cite journal|doi=10.1016/j.physb.2008.10.002|title=Electrical conductivity in TlI–TiO2 composite solid electrolyte|journal=Physica B: Condensed Matter|volume=404|pages=36–40|year=2009|last1=Sultana|first1=Saima|last2=Rafiuddin|issue=1|bibcode=2009PhyB..404...36S}} Thus, presence of impurities might be responsible for coexistence of the cubic and orthorhombic {{math|TlI}} phases at ambient conditions. Under high pressure, 160 kbar, {{math|TlI}} becomes a metallic conductor. Nanometer-thin {{math|TlI}} films grown on LiF, NaCl or KBr substrates exhibit the cubic rocksalt structure.{{cite journal|doi=10.1107/S0365110X51001641|title=Polymorphism of cesium and thallium halides|journal=Acta Crystallographica|volume=4|issue=6|pages=487–489|year=1951|last1=Schulz|first1=L. G.|bibcode=1951AcCry...4..487S }}
Applications
Thallium(I) iodide was initially added to mercury arc lamps to improve their performance{{cite journal|doi=10.1364/JOSA.54.000532|title=Characteristics of Mercury Vapor–Metallic Iodide Arc Lamps|journal=Journal of the Optical Society of America|volume=54|issue=4|pages=532|year=1964|last1=Reiling|first1=Gilbert H.|bibcode=1964JOSA...54..532R}} The light produced was mainly in the blue green part of the visible light spectrum least absorbed by water, so these have been used for underwater lighting.Underwater Journal and information bulletin, IPC Science and Technology Press, (1973), p 245 In modern times, it is added to quartz and ceramic metal halide lamps that uses rare-earth halides like dysprosium, to increase their efficiency and to get the light color more close to the blackbody locus. Thallium iodide alone can be used to produces green colored metal halide lamps. Thallium(I) iodide is also used in trace amounts with NaI or CsI to produce scintillators used in radiation detectors.
Natural occurrence
Thallium(I) iodide is a rare mineral called nataliyamalikite. Small grains were found embedded in mascagnite sourced from fumaroles at Avachinsky, a volcano in Russia's Kamchatka Peninsula that can reach temperatures of {{convert|640|C|F}}.{{Cite web|url=https://www.mindat.org/min-47920.html|title=Nataliyamalikite: Mineral information, data and localities.|website=www.mindat.org}}{{cite news|last=Anderson |first=Natali |title=New Mineral Discovered: Nataliyamalikite |url=http://www.sci-news.com/geology/new-mineral-nataliyamalikite-05017.html |work=Sci News |date=July 6, 2017 |accessdate=March 16, 2022}}
Safety
Like all thallium compounds, thallium(I) iodide is highly toxic with an LD50 of 24.1mg/kg in rats.{{cite web | title=SAFETY DATA SHEET - Thallium(I) iodide | url=https://www.fishersci.com/store/msds?partNumber=AA43001&productDescription=keyword&vendorId=VN00024248&countryCode=US&language=en | access-date=2024-12-13}}
References
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