Potassium sulfide
Potassium sulfide is the chemical compound with the formula K2S. It is an inorganic polymer with the "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 (Ca2+) sites. Li2S, Na2S, and Rb2S crystallize similarly.[1]
This salt contains the highly basic anion S2−, 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 S2−. Other alkali metal sulfides behave similarly.[1]
K2S 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, 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[2].