Potassium sulfide

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Potassium sulfide

General
Systematic name	Potassium sulfide
Other names	Dipotassium monosulfide, Dipotassium sulfide, Potassium monosulfide
Molecular formula	K₂S
Molar mass	110.262 g/mol
Appearance	pure: colourless impure: yellow-brown
CAS number	[1312-73-8]
Properties
Density and phase	1.8 g/cm³
Solubility in water	converts to KSH, KOH
Other solvents
Melting point	840 °C
Boiling point	? °C
Basicity (pK_b)	?
Viscosity	? cP at ? °C
Structure
Crystal structure	antiFluorite
Hazards
MSDS	External MSDS
Main hazards	toxic
NFPA 704
R/S statement	R: 31-34 S: 26-45
RTECS number	TT6000000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	Na₂S
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Potassium sulfide is the chemical compound with the formula K₂S. It is an inorganic polymer with the so-called antifluorite structure, which means that the small K⁺ ions occupy the tetrahedral (F^-) site in fluorite]], and the large S^2- centers occupy the eight-coordinate (Ca²⁺) sites. Li₂S, Na₂S, Rb₂S crystallize similarly.^[1]

This salt contains the highly basic anion S^2-. As such it hydrolyzes in water according to the following equation:

K₂S + H₂O → KOH + KSH

For many purposes, this reaction is inconsequential since the mixture of SH^- and OH^- behaves as a source of S^2-. Other alkali metal sulfides behave similarly.^[1]

K₂S arises from the reaction of potassium and sulfur. In the laboratory, this synthesis is usually conducted in a solution of anhydrous ammonia.

[edit] Sulfurated potash (“Liver of Sulfur”)

Sulfurated potash is a poorly defined mixture of potassium sulfide, potassium polysulfide, potassium thiosulfate, and probably potassium bisulfide. Synonyms include hepar sulfuris, Liver of sulfur, sulfurated potash, sulfurated potassa.

Liver of sulfur is mainly used in metalworking to form a patina, turning copper alloys brown.

Liver of sulfur was once used in pharmaceutical preparations such as “white lotion”. At one time sulfurated potash was used to combat arthritis. It is not surprising that it fell into disfavor because sulfides and polysulfides are toxic. Sulfurated potash can also be used for the management of copper in Wilson's disease.^{[citation needed]}