Thallium(I) iodide

Thallium(I) iodide
Names
	Other names Thallium monoiodide; Thallous iodide
Identifiers
CAS Number	7790-30-9 ;
3D model (JSmol)	Interactive image;
ChemSpider	56430 ;
ECHA InfoCard	100.029.272
EC Number	232-199-7;
PubChem CID	62679;
UNII	98W17EMO3C ;
CompTox Dashboard (EPA)	DTXSID10894795 ;
	InChI InChI=1S/HI.Tl/h1H;/q;+1/p-1 Key: CMJCEVKJYRZMIA-UHFFFAOYSA-M ; InChI=1/HI.Tl/h1H;/q;+1/p-1 Key: CMJCEVKJYRZMIA-REWHXWOFAG;
	SMILES I[Tl];
Properties
Chemical formula	TlI
Molar mass	331.287 g/mol
Appearance	yellow crystals
Density	7.1 g/cm3
Melting point	441.7 °C (827.1 °F; 714.8 K)
Boiling point	824 °C (1,515 °F; 1,097 K)
Solubility in water	0.085 g/L (25 °C)
Solubility	insoluble in alcohol
Magnetic susceptibility (χ)	−82.2·10−6 cm3/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H330, H373, H411
Precautionary statements	P260, P264, P270, P271, P273, P284, P301+P310, P304+P340, P310, P314, P320, P321, P330, P391, P403+P233, P405, P501
Flash point	Non-flammable
Related compounds
Other anions	Thallium(I) fluoride; Thallium(I) chloride; Thallium(I) bromide
Other cations	Gallium(I) iodide; Indium(I) iodide
Related compounds	Mercury(II) iodide; Lead(II) iodide
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Thallium(I) iodide is a chemical compound with the formula ${\ce {TlI}}$ . It is unusual in being one of the few water-insoluble metal iodides, along with ${\ce {AgI}}$ , ${\ce {CuI}}$ , ${\ce {SnI2}}$ , ${\ce {SnI4}}$ , ${\ce {PbI2}}$ and ${\ce {HgI2}}$ .

Chemistry

TlI can be formed in aqueous solution by metathesis of any soluble thallium salt with iodide ion. It is also formed as a by-product in thallium-promoted iodination of phenols with thallium(I) acetate.

Attempts to oxidise TlI to thallium(III) iodide fail, since oxidation produces thallium(I) triiodide, $Tl + I 3 -$ .

Physical properties

The room temperature form of TlI is yellow and has an orthorhombic structure ^[3] which can be considered to be a distorted NaCl structure. The distorted structure is believed to be caused by favourable thallium-thallium interactions, the closest Tl-Tl distance is 383 pm.^[4] 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 $TlI$ with other halides such as RbI, CsI, KI, AgI, TlBr and TlCl.^[5] Thus, presence of impurities might be responsible for coexistence of the cubic and orthorhombic $TlI$ phases at ambient conditions.^[3] Under high pressure, 160 kbar, $TlI$ becomes a metallic conductor. Nanometer-thin $TlI$ films grown on LiF, NaCl or KBr substrates exhibit the cubic rocksalt structure.^[6]

Applications

Thallium(I) iodide was initially added to mercury arc lamps to improve their performance^[7] 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.^[8] 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

Natural thallium(I) iodide was first discovered in a naturally occurring setting in 2017 as a orthorhombic polymorph 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 640 °C (1,184 °F). The geologists that discovered it speculate that further research into this mineral is likely to add to the understanding of the geochemical evolution of the planet^[9]^[10]

Safety

Like all thallium compounds, thallium(I) iodide is highly toxic.

References

^ ^a ^b ^c ^d ^e ^f ^g Haynes, p. 4.94
^ Haynes, p. 4.136
^ ^a ^b Lowndes, R. P.; Perry, C. H. (1973). "Molecular structure and anharmonicity in thallium iodide". The Journal of Chemical Physics. 58 (1): 271–278. Bibcode:1973JChPh..58..271L. doi:10.1063/1.1678917.
^ Mudring, Anja-Verena (2007). "Thallium Halides – New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main-Group Elements". European Journal of Inorganic Chemistry. 2007 (6): 882–890. doi:10.1002/ejic.200600975.
^ Sultana, Saima; Rafiuddin (2009). "Electrical conductivity in TlI–TiO2 composite solid electrolyte". Physica B: Condensed Matter. 404 (1): 36–40. Bibcode:2009PhyB..404...36S. doi:10.1016/j.physb.2008.10.002.
^ Schulz, L. G. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica. 4 (6): 487–489. Bibcode:1951AcCry...4..487S. doi:10.1107/S0365110X51001641.
^ Reiling, Gilbert H. (1964). "Characteristics of Mercury Vapor–Metallic Iodide Arc Lamps". Journal of the Optical Society of America. 54 (4): 532. Bibcode:1964JOSA...54..532R. doi:10.1364/JOSA.54.000532.
^ Underwater Journal and information bulletin, IPC Science and Technology Press, (1973), p 245
^ "Nataliyamalikite: Mineral information, data and localities". www.mindat.org.
^ Anderson, Natali (July 6, 2017). "New Mineral Discovered: Nataliyamalikite". Sci News. Retrieved March 16, 2022.

Cited sources

Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. ISBN 1-4398-5511-0.

[r1-1] ^ ^a ^b ^c ^d ^e ^f ^g Haynes, p. 4.94

[2] Haynes, p. 4.136

[low-3] Lowndes, R. P.; Perry, C. H. (1973). "Molecular structure and anharmonicity in thallium iodide". The Journal of Chemical Physics. 58 (1): 271–278. Bibcode:1973JChPh..58..271L. doi:10.1063/1.1678917.

[4] Mudring, Anja-Verena (2007). "Thallium Halides – New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main-Group Elements". European Journal of Inorganic Chemistry. 2007 (6): 882–890. doi:10.1002/ejic.200600975.

[5] Sultana, Saima; Rafiuddin (2009). "Electrical conductivity in TlI–TiO2 composite solid electrolyte". Physica B: Condensed Matter. 404 (1): 36–40. Bibcode:2009PhyB..404...36S. doi:10.1016/j.physb.2008.10.002.

[str-6] Schulz, L. G. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica. 4 (6): 487–489. Bibcode:1951AcCry...4..487S. doi:10.1107/S0365110X51001641.

[7] Reiling, Gilbert H. (1964). "Characteristics of Mercury Vapor–Metallic Iodide Arc Lamps". Journal of the Optical Society of America. 54 (4): 532. Bibcode:1964JOSA...54..532R. doi:10.1364/JOSA.54.000532.

[8] Underwater Journal and information bulletin, IPC Science and Technology Press, (1973), p 245

[9] "Nataliyamalikite: Mineral information, data and localities". www.mindat.org.

[10] Anderson, Natali (July 6, 2017). "New Mineral Discovered: Nataliyamalikite". Sci News. Retrieved March 16, 2022.

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