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Potassium sulfide

Names
IUPAC name Potassium sulfide
Other names Dipotassium monosulfide, Dipotassium sulfide, Potassium monosulfide, Potassium sulphide
Identifiers
CAS Number	1312-73-8
ECHA InfoCard	100.013.816
RTECS number	TT6000000
CompTox Dashboard (EPA)	DTXSID70909738
Properties
Chemical formula	K2S
Molar mass	110.262 g/mol
Appearance	pure: colourless impure: yellow-brown
Density	1.8 g/cm
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
Occupational safety and health (OHS/OSH):
Main hazards	Dangerous for the environment (N)
Related compounds
Other cations	Sodium sulfide, Iron(II) sulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Y verify (what is  ?) Infobox references

Potassium sulfide is the inorganic compound with the formula K₂S. The colourless solid is rarely encountered, because it reacts readily and irreversibly with water, a reaction that affords potassium bisulfide (KSH) and potassium hydroxide (KOH).

Structure

It adopts "antifluorite structure," which means that the small K ions occupy the tetrahedral (F) sites in fluorite, and the larger S centers occupy the eight-coordinate (Ca) sites. Li₂S, Na₂S, and Rb₂S crystallize similarly.

Synthesis and reactions

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.

It can also be produced by heating K₂SO₄ with coal: K₂SO₄ + 2C = K₂S + 2 CO₂

K₂SO₄ + 4C = K₂S + 4 CO

This salt contains the highly basic anion S, which completely 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 S. Other alkali metal sulfides behave similarly.

An other method of making K₂S in lab is burning the 50:50 mixture of fine crushed potassium permanganate and elemental sulfur powder. The mixture can be ignited simply by a matchstick or adding a single drop of glycerol on the mixture. The products after burning are manganese dioxide and potassium sulfide. Potassium sulfide can be tested by adding few drops of concentrated sulfuric acid on burnt mixture. Because it produces H₂S gas, which smells like rotten eggs. The reactions are as follow:

2KMnO₄ + S → K₂S + 2MnO₂ + 2O₂

K₂S + 2H₂SO₄ → H₂S + 2KHSO₄

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.

See also

• Liver of sulfur

References

1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
2. Shimizu, Takeo. "Fireworks: the Art, Science, and Technique." Pyrotechnica Publications: Austin, 1981. ISBN 0-929388-05-4.

• Potassium compounds
• Sulfides
• Inorganic compounds