Sodium Sulphide (Na2S)

Sodium sulfide (Na₂S) is an inorganic compound typically encountered as a yellow to brick-red solid due to polysulfide impurities.  Sodium sulfide is widely used in industrial processes, including: Leather tanning (dehairing hides), Ore flotation in mining (sulfide mineral separation), pulp and paper manufacturing (as part of the kraft process), textile dyeing (as a reducing agent for sulfur dyes) and chemical synthesis of thiols, thioethers, and other sulfur-containing compounds. 

It acts as a strong nucleophile and reducing agent, reacting readily with alkyl halides, metal salts, and oxidizing agents.