Potassium sulfide

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Potassium sulfide
Potassium sulfide
Identifiers
RTECS number TT6000000
Jmol-3D images Image 1
Properties
Molecular formula K2S
Molar mass 110.262 g/mol
Appearance pure: colourless
impure: yellow-brown
Odor HS
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)
Solubility in water converts to KSH, KOH
Solubility in other solvents soluble in ethanol, glycerol
insoluble in ether
Structure
Crystal structure antiFluorite
Hazards
R-phrases R17, R23, R25, R31, R34, R50
S-phrases S24, S26
Main hazards Dangerous for the environment (N)
Related compounds
Other cations Sodium sulfide, Iron(II) sulfide
Related compounds Potassium hydrosulfide, Potassium sulfite, Potassium sulfate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Potassium sulfide is the 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.

Structure[edit]

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[edit]

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[edit]

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[edit]

References[edit]

  1. ^ a b 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.