- Thallium(I) iodide
Name = Thallium(I) iodide
ImageFile = Thallium-iodide-3D-vdW.png
ImageName = Thallium(I) iodide
OtherNames = thallium monoiodide
Section1 = Chembox Identifiers
CASNo = 7790-30-9
Section2 = Chembox Properties
Formula = TlI
MolarMass = 331.2878 g/mol
Appearance = yellow crystals
red crystals above 170 °C
Density = 7.29 g/cm3, solid
Solubility = insoluble
MeltingPt = 442°C
BoilingPt = 823°C
Section7 = Chembox Hazards
EUClass = not listed
Thallium(I) iodide (TlI) is a
chemical compoundof formula TlI. It is unusual in being one of the few water-insoluble metal iodides, along with AgI, PbI2 and HgI2.
TlI can be formed in aqueous solution by
metathesisof any soluble thallium salt with iodide ion. It is also formed as a by-product in thallium-promoted iodination of phenolswith thallium(I) acetate.
Attempts to oxidise TlI to thallium(III) iodide fail, since oxidation produces the thallium(I) triiodide, Tl+I3−.
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 believed to be caused by favourable thallium-thallium interactions, the closest Tl-Tl distance is 383pm. [cite journal
title = Thallium Halides - New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main-Group Elements
author = Anja-Verena Mudring
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. Under high pressure, 160kbar, it becomes a metallic conductor.
*Added to mercury arc lamps to improve their performance [G. H. Reiling, "Characteristics of Mercury Vapor-Metallic Iodide Arc Lamps," J. Opt. Soc. Am. 54, 532- (1964)] The light produced is 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]
*Used in trace amounts with NaI or CsI to produce a
scintillatorused in radiation scintillation detectors.
Thallium(I) iodide is, like all thallium compounds, highly toxic. Conditions/substances to avoid are:
* [http://www.webelements.com/ WebElements]
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