Potassium sulfide

Potassium sulfide
Potassium sulphide
IUPAC name
Potassium sulfide
Other names
Dipotassium monosulfide,
Dipotassium sulfide,
Potassium monosulfide,
Potassium sulphide
Identifiers
CAS number 1312-73-8 YesY
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
 YesY sulfide (verify) (what is: YesY/N?)
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).

Contents

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, 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]

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

  • Liver of sulfur

References

  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. 200.
  3. ^ Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. ISBN 0-929388-05-4.