Na2S6

Sodium hexasulfide, with the chemical formula Na2S6, is an inorganic compound belonging to the class of alkali metal polysulfides. It is formed by the reaction of sodium sulfide with elemental sulfur. Na2S6 typically exists as a crystalline solid, often appearing as bright yellow to orange needles. Its solubility in water is notable, readily dissolving to form a solution that is alkaline due to hydrolysis. These aqueous solutions are often referred to as "sulfur dyes" or "sulfur inks" and are used in textile dyeing processes, particularly for cotton, imparting dark shades of black, blue, and brown. The hexasulfide anion, S6^2-, is a cyclic structure. Na2S6 is an oxidizing agent and can react with acids to release hydrogen sulfide gas. It is also sensitive to air and moisture, which can lead to decomposition. Commercial production often involves heating sodium sulfide and sulfur together in specific ratios. Beyond its application in dyeing, Na2S6 has found limited use in some laboratory syntheses and has been explored for potential applications in battery technology.