Potassium sulfide
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2008-06-14T11:46:36Z
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{{Chembox new
| Name = Potassium sulfide
| ImageFile = Potassium-sulfide-unit-cell-3D-ionic.png
<!-- | ImageSize = 200px -->
| ImageName = Potassium sulfide
| IUPACName = Potassium sulfide
| OtherNames = Dipotassium monosulfide,<br />Dipotassium sulfide,<br />Potassium monosulfide
| Section1 = {{Chembox Identifiers
| CASNo = 1312-73-8
| RTECS = TT6000000
}}
| Section2 = {{Chembox Properties
| Formula = K<sub>2</sub>S
| MolarMass = 110.262 g/mol
| Appearance = pure: colourless<br />impure: yellow-brown
| Density = 1.8 g/cm<sup>3</sup>
| Solubility = converts to KSH, KOH
| Solvent = other solvents
| SolubleOther = soluble in [[ethanol]] and [[glycerol]]
| MeltingPt = 840 °C
}}<!--
|[[Boiling point]]
| ? °C
|-
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| Section3 = {{Chembox Structure
| CrystalStruct = anti[[Fluorite]]
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| MainHazards = toxic
| RPhrases = 31-34
| SPhrases = 26-45
}}
| Section8 = {{Chembox Related
| OtherCpds = [[Sodium sulfide|Na<sub>2</sub>S]]
}}
}}
'''Potassium sulfide''' is the [[chemical compound]] with the formula K<sub>2</sub>S. It is an inorganic polymer with the "antifluorite structure," which means that the small K<sup>+</sup> ions occupy the tetrahedral (F<sup>−</sup>) sites in [[fluorite]], and the larger S<sup>2−</sup> centers occupy the eight-coordinate (Ca<sup>2+</sup>) sites. [[lithium sulfide|Li<sub>2</sub>S]], [[sodium sulfide|Na<sub>2</sub>S]], and Rb<sub>2</sub>S crystallize similarly.<ref name=Holleman>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref>
This salt contains the highly basic anion S<sup>2−</sup>, which completely [[hydrolysis|hydrolyzes]] in water according to the following equation:
:K<sub>2</sub>S + H<sub>2</sub>O → KOH + KSH
For many purposes, this reaction is inconsequential since the mixture of SH<sup>−</sup> and OH<sup>−</sup> behaves as a source of S<sup>2−</sup>. Other alkali metal sulfides behave similarly.<ref name=Holleman/>
K<sub>2</sub>S arises from the reaction of potassium and sulfur. In the laboratory, this synthesis is usually conducted in a solution of anhydrous ammonia.
==Sulfurated potash (“Liver of Sulfur”)==
'''Sulfurated potash''' is a poorly defined mixture of potassium sulfide, potassium [[polysulfide]], [[thiosulfate|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.
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. The compound is not added directly to the fireworks but rather forms during their combustion<ref name=Shimizu>Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. ISBN 0-929388-05-4.</ref>.
==References==
{{reflist}}
[[Category:Potassium compounds]]
[[Category:Sulfides]]
[[Category:Inorganic compounds]]
[[ar:كبريتيد بوتاسيوم]]
[[ca:Sulfur de potassi]]
[[de:Kaliumsulfid]]
[[pl:Siarczek potasu]]
[[zh:硫化钾]]