Potassium sulfide
| Potassium sulphide | |
|---|---|
 |
|
|
Potassium sulfide |
|
|
Other names
Dipotassium monosulfide, |
|
| Identifiers | |
| CAS number | 1312-73-8  |
| RTECS number | TT6000000 |
| Properties | |
| Molecular formula | K2S |
| Molar mass | 110.262 g/mol |
| Appearance | pure: colourless impure: yellow-brown |
| Density | 1.8 g/cm3 |
| Melting point |
840 °C |
| Boiling point |
decomposes |
| Solubility in water | converts to KSH, KOH |
| Solubility in other solvents | soluble in ethanol and glycerol |
| 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 sulfite, Potassium sulfate |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
|
| 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 bisulfide (KSH) and potassium hydroxide (KOH). Most commonly, the term potassium sulfide refers loosely to this mixture, not the anhydrous solid.
Contents |
[edit] 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]
[edit] Synthesis and reactions
It can be produced by heating K2SO4 with carbon (coke):
- K2SO4 + 4 C → K2S + 4 CO
In the laboratory, a number of methods exist.[2] K2S arises from the reaction of potassium and sulfur. In the laboratory, this synthesis is usually conducted by combining a solution of potassium in anhydrous ammonia with elemental sulfur. Another method of making K2S in laboratory involves the reaction of potassium permanganate and elemental sulfur:
- 2 KMnO4 + S → K2S + 2 MnO2 + 2 O2
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]
[edit] 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]
[edit] See also
[edit] References
- ^ a b Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 200.
- ^ Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. ISBN 0-929388-05-4.
