Thallium(I) sulfide

Thallium(I) sulfide, Tl₂S, is a chemical compound of thallium and sulfur.

Thallium(I) sulfide

Unit cell of thallium sulfide.
Names
IUPAC name Thallium(I) sulfide
Other names thallous sulfide, thallous sulphide
Identifiers
CAS Number	1314-97-2 Y
3D model (JSmol)	Interactive image
ChemSpider	140161 Y
ECHA InfoCard	100.013.865
EC Number	215-250-8
PubChem CID	16683485
UNII	W63QXT8PYG Y
CompTox Dashboard (EPA)	DTXSID801027166
InChI InChI=1S/S.2Tl/q-2;2*+1 Y Key: BXJGLLKRUQQYTC-UHFFFAOYSA-N Y
SMILES S([Tl])[Tl]
Properties
Chemical formula	Tl2S
Molar mass	440.833 g/mol
Appearance	black crystalline solid
Density	8.390 g/cm3
Melting point	448 °C (838 °F; 721 K)
Boiling point	1,367 °C (2,493 °F; 1,640 K)
Magnetic susceptibility (χ)	−88.8·10−6 cm3/mol
Structure
Crystal structure	Trigonal, hR81
Space group	R3, No. 146
Lattice constant	a = 12.150(2) Å, c = 18.190(4) Å[1]
Lattice volume (V)	2325.57 Å3
Formula units (Z)	27
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

Occurrence

Tl₂S is found in nature as the mineral carlinite^[2] which has the distinction of being the only sulfide mineral of thallium that does not contain at least two metals. Tl₂S has a distorted anti-CdI₂ structure.^[3]

Synthesis

Tl₂S can be prepared from the elements or by precipitating the sulfide from a solution of thallium(I), e.g. the sulfate or nitrate. Thin films have been deposited, produced from a mixture of citratothallium complex and thiourea. Heating the film in nitrogen at 300°C converts all the product into Tl₂S ^[4]

History and applications

This salt was used in some of the earliest photo-electric detectors by Theodore Case who developed the so-called thalofide (sometimes spelt thallofide) cell, used in early film projectors. Case described the detector material as consisting of thallium, oxygen and sulfur,^[5] and this was incorrectly described by others as being thallium oxysulfide, which incidentally is a compound that is not known. Case's work was then built on by R.J. Cashman who recognised that the controlled oxidation of the Tl₂S film was key to the operation of the cell.^[6] Cashman's work culminated in the development of long wave infrared detectors used during the Second World War.^[7] Reliable Tl₂S detectors were also developed in Germany at the same time.^[6]