Potassium sulfide is an
inorganic compound with the formula
K2 S. The colourless solid is rarely encountered, because it reacts readily with water, a reaction that affords
potassium hydrosulfide
Potassium hydrosulfide is the inorganic compound with the formula KSH. This colourless salt consists of the cation and the bisulfide anion . It is the product of the half-neutralization of hydrogen sulfide with potassium hydroxide. The compound ...
(KSH) and potassium hydroxide (KOH). Most commonly, the term potassium sulfide refers loosely to this mixture, not the anhydrous solid.
Structure
It adopts "antifluorite structure," which means that the small K
+ ions occupy the tetrahedral (F
−) sites in
fluorite, and the larger S
2− centers occupy the eight-coordinate sites.
Li2S,
Na2S, and Rb
2S crystallize similarly.
[Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. .]
Synthesis and reactions
It can be produced by
heating K
2SO
4 with carbon (
coke):
:K
2SO
4 + 4 C → K
2S + 4 CO
In the laboratory, pure K
2S may be prepared by the reaction of potassium and sulfur in anhydrous ammonia.
[Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 360.]
Sulfide is highly basic, consequently K
2S completely and irreversibly
hydrolyzes
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis ...
in water according to the following equation:
:K
2S + H
2O → 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.
[
]
Use in fireworks
Potassium sulfides are formed when black powder
Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
is burned and are important intermediates in many pyrotechnic effects, such as senko hanabi
Senko hanabi ( 線香花火 ''senkō hanabi'' ) (sparkler - literally: incense-stick fireworks) is a traditional Japanese firework. Essays about them date back to at least 1927.
They are a thin shaft of twisted tissue paper about 20 centimete ...
and some glitter
Glitter is an assortment of small, reflective particles that come in a variety of shapes, sizes, and colors. Glitter particles reflect light at different angles, causing the surface to sparkle or shimmer. Glitter is similar to confetti, sparkle ...
formulations.[Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. .]
See also
* Liver of sulfur
References
{{Sulfides
Potassium compounds
Sulfides
Inorganic compounds
Fluorite crystal structure