Potassium pentasulfide

Potassium pentasulfide is the inorganic compound with the formulaK₂S₅. It is a red-orange solid that dissolves in water. The salt decomposes rapidly in air. It is one of several polysulfide salts with the general formulaM₂S_n, where M = Li, Na, K and n = 2, 3, 4, 5, 6. The polysulfide salts of potassium and sodium are similar.

The salt is prepared by the addition of elemental sulfur to potassium sulfide. An idealized equation is shown for potassium hydrosulfide:

4KSH +S₈ → 2K₂S₅ + 2H₂S

The structure consists of zigzag chains ofS2−5 paired withK⁺ ions.

Various polysulfidesK₂S₂ -K₂S₆ are components of liver of sulfur. Polysulfides, like sulfides, can induce stress corrosion cracking in carbon steel and stainless steel.