What is "liver of sulfur"

Liver of Sulfur is a poorly defined mixture of potassium sulfide, potassium polysulfide, potassium thiosulfate, and probably potassium bisulfide. Synonyms include hepar sulfuris, sulfur''', '''sulfurated potash and sulfurated potassa.

Liver of sulfur is mainly used in metalworking to form a patina, turning copper alloys brown or black.

Typically liver of sulfur comes in a dry rock form which must be broken into smaller pieces and dissolved in hot water for use.