Thallium(I) iodide

Synthesis and reactions

TlI can be formed in aqueous solution by metathesis of soluble thallium salt with iodide ion. Alternatively, it has been prepared from the elements: : An excess of iodine produces thallium(I) triiodide, Tl+I3−.

Physical properties

The room temperature form of TlI is yellow and has an orthorhombic structure 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

Applications

Thallium(I) iodide was initially added to mercury arc lamps to improve their performance 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. 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 640 C.

Safety

Like all thallium compounds, thallium(I) iodide is highly toxic with an LD50 of 24.1mg/kg in rats.

References

Cited sources

References

1. Haynes, p. 4.94
2. Haynes, p. 4.136
3. E. Dönges. (1963). "Handbook of Preparative Inorganic Chemistry, 2nd Ed.". Academic Press.
4. (2000). "Ullmann's Encyclopedia of Industrial Chemistry".
5. (1973). "Molecular structure and anharmonicity in thallium iodide". The Journal of Chemical Physics.
6. (2009). "Electrical conductivity in TlI–TiO2 composite solid electrolyte". Physica B: Condensed Matter.
7. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica.
8. (1964). "Characteristics of Mercury Vapor–Metallic Iodide Arc Lamps". Journal of the Optical Society of America.
9. Underwater Journal and information bulletin, IPC Science and Technology Press, (1973), p 245
10. "Nataliyamalikite: Mineral information, data and localities.".
11. Anderson, Natali. (July 6, 2017). "New Mineral Discovered: Nataliyamalikite". Sci News.
12. "SAFETY DATA SHEET - Thallium(I) iodide".