Potassium sulfide

Potassium sulfide is an inorganic compound with the formula K2S. The colourless solid is rarely encountered, because it reacts readily with water, a reaction that affords potassium hydrosulfide (KSH) and potassium hydroxide (KOH). Most commonly, the term potassium sulfide refers loosely to this mixture, not the anhydrous solid.

Potassium sulfide
Names
IUPAC name
Potassium sulfide
Other names
Dipotassium monosulfide,
Dipotassium sulfide,
Potassium monosulfide,
Potassium sulfide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.013.816
EC Number
  • 215-197-0
RTECS number
  • TT6000000
UNII
UN number 1847 1382
  • InChI=1S/2K.S/q2*+1;-2
    Key: DPLVEEXVKBWGHE-UHFFFAOYSA-N
  • [S-2].[K+].[K+]
Properties
K2S
Molar mass 110.262 g/mol
Appearance pure: colourless
impure: yellow-brown
Odor H2S
Density 1.74 g/cm3
Melting point 840 °C (1,540 °F; 1,110 K)
Boiling point 912 °C (1,674 °F; 1,185 K) (decomposes)
converts to KSH, KOH
Solubility in other solvents soluble in ethanol, glycerol
insoluble in ether
−60.0·10−6 cm3/mol
Structure
antiFluorite
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Causes skin burns. Dangerous for the environment
GHS labelling:
Danger
H314, H400
P260, P264, P273, P280, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P321, P363, P391, P405, P501
Related compounds
Other anions
 Potassium oxide
Potassium selenide
Potassium telluride
Potassium polonide
Other cations
 Lithium sulfide
Sodium sulfide
Rubidium sulfide
Caesium sulfide
Related compounds
 Potassium hydrosulfide
Potassium sulfite
Potassium sulfate
Iron(II) sulfide
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

Structure

It adopts "antifluorite structure," which means that the small K+ ions occupy the tetrahedral (F−) sites in fluorite, and the larger S2− centers occupy the eight-coordinate sites. Li2S, Na2S, and Rb2S crystallize similarly.[1]

Synthesis and reactions

It can be produced by heating K2SO4 with carbon (coke):

K2SO4 + 4 C → K2S + 4 CO

In the laboratory, pure K2S may be prepared by the reaction of potassium and sulfur in anhydrous ammonia. [2]

Sulfide is highly basic, consequently K2S completely and irreversibly 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 S2−. Other alkali metal sulfides behave similarly.[1]

Use in fireworks

Potassium sulfides are formed when black powder is burned and are important intermediates in many pyrotechnic effects, such as senko hanabi and some glitter formulations.[3]

See also

References
  1. Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 360.
  3. Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. ISBN 0-929388-05-4.
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