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]

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Thallium(I) chloride

Names
IUPAC names Thallium monochloride Thallium(I) chloride
Other names Thallous chloride
Identifiers
CAS Number	7791-12-0 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:37117 Y
ChemSpider	23044 Y
DrugBank	DB09316
ECHA InfoCard	100.029.311
EC Number	232-241-4
PubChem CID	24642
UNII	37CB58V15B Y
UN number	2811 1707
CompTox Dashboard (EPA)	DTXSID6024333
InChI InChI=1S/ClH.Tl/h1H;/q;+1/p-1 Y Key: GBECUEIQVRDUKB-UHFFFAOYSA-M Y InChI=1/ClH.Tl/h1H;/q;+1/p-1 Key: GBECUEIQVRDUKB-REWHXWOFAE
SMILES Cl[Tl]
Properties
Chemical formula	TlCl
Molar mass	239.836 g/mol[1]
Appearance	white, 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]
Solubility in water	3.3 g/L (25 °C)[1]
Solubility	insoluble in alcohol[1]
Magnetic susceptibility (χ)	−57.8·10−6 cm3/mol[2]
Refractive index (nD)	2.247 (0.59 µm) 2.198 (0.75 µm) 2.145 (1 µm) 1.891 (5 µm) 2.193 (20 µm)[3]
Structure
Crystal structure	CsCl, cP2
Space group	Pm3m, No. 221[4]
Lattice constant	a = 0.38416 nm
Lattice volume (V)	0.0567 nm3
Formula units (Z)	1
Coordination geometry	Cubic (Tl+) Cubic (Cl−)
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
Lethal dose or concentration (LD, LC):
LD50 (median dose)	24 mg/kg, oral, mouse
Safety data sheet (SDS)	http://www.crystran.co.uk/uploads/files/178.pdf
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). N verify (what is YN ?) Infobox references

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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]