Thallium(I) chloride, also known as thallous chloride, is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula TlCl. This colourless salt is an intermediate in the isolation of

thallium Thallium is a chemical element with the Symbol (chemistry), 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 W ...

from its ores. Typically, an acidic solution of

thallium(I) sulfate Thallium(I) sulfate (Tl2SO4) or thallous sulfate is the sulfate salt of thallium in the common +1 oxidation state, as indicated by the Roman numeral I. It is often referred to as simply thallium sulfate. Uses During the last two centuries, Tl2SO4 ...

is treated with

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

to precipitate insoluble thallium(I)

chloride The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...

. This solid crystallizes in the

caesium chloride Caesium chloride or cesium chloride is the inorganic compound with the formula Cs Cl. 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 ...

motif. The low solubility of TlCl is exploited in chemical synthesis: treatment of metal chloride complexes with TlPF₆, gives the corresponding metal

hexafluorophosphate Hexafluorophosphate is an anion with chemical formula of . It is an octahedral species that imparts no color to its salts. is isoelectronic with sulfur hexafluoride, , and the hexafluorosilicate dianion, , and hexafluoroantimonate . In this anio ...

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 In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

thallium iodide type upon cooling, the transition temperature being likely affected by the impurities. Nanometer-thin TlCl films grown on KBr substrates exhibit a

rocksalt Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

structure, while the films deposited on

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

or NaCl are of the regular CsCl type. A very rare mineral lafossaite, , is a natural form of thallium(I) chloride. Thallium(I) chloride, like all thallium compounds, is highly toxic, although its low solubility limits its toxicity.Thallium Chloride Material Safety Data Sheet
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References

Cited sources

* Chlorides Thallium(I) compounds Metal halides Caesium chloride crystal structure {{inorganic-compound-stub