Thallium(I) chloride

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Thallium(I) chloride
CsCl polyhedra.png
Thallium(I) chloride.jpg
IUPAC names
Thallium monochloride
Thallium(I) chloride
Other names
Thallous chloride
3D model (JSmol)
ECHA InfoCard 100.029.311 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 232-241-4
PubChem CID
UN number 2811 1707
  • InChI=1S/ClH.Tl/h1H;/q;+1/p-1 Yes check.svgY
  • InChI=1/ClH.Tl/h1H;/q;+1/p-1
  • Cl[Tl]
Molar mass 239.836 g/mol [1]
Appearancewhite, odorless crystalline solid [1]
Density 7.0 g/cm3 [1]
Melting point 431 °C (808 °F; 704 K) [1]
Boiling point 720 °C (1,328 °F; 993 K) [1]
3.3 g/L (25 °C) [1]
Solubility insoluble in alcohol [1]
57.8·10−6 cm3/mol [2]
2.247 (0.59 µm)
2.198 (0.75 µm)
2.145 (1 µm)
1.891 (5 µm)
2.193 (20 µm) [3]
CsCl, cP2
Pm3m, No. 221 [4]
a = 0.38416 nm
0.0567 nm3
Cubic (Tl+)
Cubic (Cl)
Safety data sheet (SDS)
GHS labelling:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
H300, H330, H373, H411
P260, P264, P270, P271, P273, P284, P301+P310, P304+P340, P310, P314, P320, P321, P330, P391, P403+P233, P405, P501
Lethal dose or concentration (LD, LC):
24 mg/kg, oral, mouse
Related compounds
Other anions
Thallium(I) fluoride
Thallium(I) bromide
Thallium(I) iodide
Other cations
Thallium(III) chloride
Silver(I) chloride
Lead(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Thallium(I) chloride, also known as thallous chloride, is a chemical compound with the formula TlCl. This colourless salt is an intermediate in the isolation of thallium from its ores. Typically, an acidic solution of thallium(I) sulfate is treated with hydrochloric acid to precipitate insoluble thallium(I) chloride. This solid crystallizes in the caesium chloride motif. [5]

The low solubility of TlCl is exploited in chemical synthesis: treatment of metal chloride complexes with TlPF6, gives the corresponding metal hexafluorophosphate derivative. The resulting TlCl precipitate is separated by filtration of the reaction mixture. The overall methodology is similar to the use of AgPF6, except that Tl+ is much less oxidizing.

The crystalline structure is of cubic caesium chloride type at room temperature, but it lowers to the orthorhombic thallium iodide type upon cooling, the transition temperature being likely affected by the impurities. [6] Nanometer-thin TlCl films grown on KBr substrates exhibit a rocksalt structure, while the films deposited on mica or NaCl are of the regular CsCl type. [7]

A very rare mineral lafossaite, Tl(Cl,Br), is a natural form of thallium(I) chloride. [8]

Thallium(I) chloride, like all thallium compounds, is highly toxic, although its low solubility limits its toxicity. [9]

Related Research Articles

Caesium Chemical element, symbol Cs and atomic number 55

Caesium is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of 28.5 °C (83.3 °F), which makes it one of only five elemental metals that are liquid at or near room temperature. Caesium has physical and chemical properties similar to those of rubidium and potassium. The most reactive of all metals, it is pyrophoric and reacts with water even at −116 °C (−177 °F). It is the least electronegative element, with a value of 0.79 on the Pauling scale. It has only one stable isotope, caesium-133. Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, a fission product, are extracted from waste produced by nuclear reactors.

Thallium Chemical element, symbol Tl and atomic number 81

Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861, in residues of sulfuric acid production. Both used the newly developed method of flame spectroscopy, in which thallium produces a notable green spectral line. Thallium, from Greek θαλλός, thallós, meaning "green shoot" or "twig", was named by Crookes. It was isolated by both Lamy and Crookes in 1862; Lamy by electrolysis, and Crookes by precipitation and melting of the resultant powder. Crookes exhibited it as a powder precipitated by zinc at the International exhibition, which opened on 1 May that year.

Zinc chloride Chemical compound

Zinc chloride is the name of chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This white salt is hygroscopic and even deliquescent. Samples should therefore be protected from sources of moisture, including the water vapor present in ambient air. Zinc chloride finds wide application in textile processing, metallurgical fluxes, and chemical synthesis. No mineral with this chemical composition is known aside from the very rare mineral simonkolleite, Zn5(OH)8Cl2·H2O.

Barium chloride Chemical compound

Barium chloride is an inorganic compound with the formula BaCl2. It is one of the most common water-soluble salts of barium. Like most other barium salts, it is white, toxic, and imparts a yellow-green coloration to a flame. It is also hygroscopic, converting first to the dihydrate BaCl2(H2O)2. It has limited use in the laboratory and industry.

Silver chloride Chemical compound with the formula AgCl

Silver chloride is a chemical compound with the chemical formula AgCl. This white crystalline solid is well known for its low solubility in water (this behavior being reminiscent of the chlorides of Tl+ and Pb2+). Upon illumination or heating, silver chloride converts to silver (and chlorine), which is signaled by grey to black or purplish coloration to some samples. AgCl occurs naturally as a mineral chlorargyrite.

Neodymium(III) chloride or neodymium trichloride is a chemical compound of neodymium and chlorine with the formula NdCl3. This anhydrous compound is a mauve-colored solid that rapidly absorbs water on exposure to air to form a purple-colored hexahydrate, NdCl3·6H2O. Neodymium(III) chloride is produced from minerals monazite and bastnäsite using a complex multistage extraction process. The chloride has several important applications as an intermediate chemical for production of neodymium metal and neodymium-based lasers and optical fibers. Other applications include a catalyst in organic synthesis and in decomposition of waste water contamination, corrosion protection of aluminium and its alloys, and fluorescent labeling of organic molecules (DNA).

Aluminium chloride Chemical compound

Aluminium chloride (AlCl3), also known as aluminium trichloride, describe compounds with the formula AlCl3(H2O)n (n = 0 or 6). They consist of aluminium and chlorine atoms in a 1:3 ratio, and one form also contains six waters of hydration. Both are white solids, but samples are often contaminated with iron(III) chloride, giving a yellow color.

Caesium fluoride Chemical compound

Caesium fluoride or cesium fluoride is an inorganic compound with the formula CsF and it is a hygroscopic white salt. Caesium fluoride can be used in organic synthesis as a source of the fluoride anion. Caesium also has the highest electropositivity of all non-radioactive elements and fluorine has the highest electronegativity of all elements.

Copper(I) chloride Chemical compound

Copper(I) chloride, commonly called cuprous chloride, is the lower chloride of copper, with the formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated hydrochloric acid. Impure samples appear green due to the presence of copper(II) chloride (CuCl2).

Caesium iodide Chemical compound

Caesium iodide or cesium iodide is the ionic compound of caesium and iodine. It is often used as the input phosphor of an X-ray image intensifier tube found in fluoroscopy equipment. Caesium iodide photocathodes are highly efficient at extreme ultraviolet wavelengths.

Caesium chloride Chemical compound

Caesium chloride or cesium chloride is the inorganic compound with the formula CsCl. This colorless salt is an important source of caesium ions in a variety of niche applications. Its crystal structure forms a major structural type where each caesium ion is coordinated by 8 chloride ions. Caesium chloride dissolves in water. CsCl changes to NaCl structure on heating. Caesium chloride occurs naturally as impurities in carnallite, sylvite and kainite. Less than 20 tonnes of CsCl is produced annually worldwide, mostly from a caesium-bearing mineral pollucite.

Sodium iodide Chemical compound

Sodium iodide (chemical formula NaI) is an ionic compound formed from the chemical reaction of sodium metal and iodine. Under standard conditions, it is a white, water-soluble solid comprising a 1:1 mix of sodium cations (Na+) and iodide anions (I) in a crystal lattice. It is used mainly as a nutritional supplement and in organic chemistry. It is produced industrially as the salt formed when acidic iodides react with sodium hydroxide. It is a chaotropic salt.

Thallium(I) bromide Chemical compound

Thallium(I) bromide is a chemical compound of thallium and bromine with a chemical formula TlBr. This salt is used in room-temperature detectors of X-rays, gamma-rays and blue light, as well as in near-infrared optics.

Thallium(I) iodide Chemical compound

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

Caesium bromide Chemical compound

Caesium bromide or cesium bromide is an ionic compound of caesium and bromine with the chemical formula CsBr. It is a white or transparent solid with melting point at 636 °C that readily dissolves in water. Its bulk crystals have the cubic CsCl structure, but the structure changes to the rocksalt type in nanometer-thin film grown on mica, LiF, KBr or NaCl substrates.

The thallium halides include monohalides, where thallium has oxidation state +1, trihalides in which thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. These materials find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 μm), whereas zinc selenide is opaque by 21.5 μm, and ZnSe optics are generally only usable to 650 cm−1 (15 μm).

There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.

Thallium(I) fluoride Chemical compound

Thallium(I) fluoride is the inorganic compound with the formula TlF. It is a white solid, forming orthorhombic crystals. The solid slightly deliquescent. It has a distorted sodium chloride (rock salt) crystal structure, due to the 6s2 inert pair on Tl+.

Metal halides

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.

Compounds of lead exist with lead in two main oxidation states: +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.


  1. 1 2 3 4 5 6 7 Haynes, p. 4.94
  2. Haynes, p. 4.135
  3. Haynes, p. 10.242
  4. Müürsepp, T.; Haav, A. (1974). "X-ray diffraction study of the systems TlI-CsI, TlI-RbI, and TlI-Tl Cl". Physica Status Solidi A. 21 (2): K81. Bibcode:1974PSSAR..21...81M. doi:10.1002/pssa.2210210251.
  5. Holleman, A. F.; Wiberg, E. Inorganic Chemistry. Academic Press: San Diego, 2001. ISBN   0-12-352651-5.
  6. Blackman, M; Khan, I H (1961). "The Polymorphism of Thallium and Other Halides at Low Temperatures". Proceedings of the Physical Society. 77 (2): 471. Bibcode:1961PPS....77..471B. doi:10.1088/0370-1328/77/2/331.
  7. Schulz, L. G. (1951). "Polymorphism of cesium and thallium halides". Acta Crystallographica. 4 (6): 487–489. doi:10.1107/S0365110X51001641.
  8. Lafossaite.
  9. Thallium Chloride Material Safety Data Sheet.

Cited sources