Both the anhydrous and the hydrated salts in pure crystalline form are colorless solids, although technical grades of sodium sulfide are generally yellow to brick red owing to the presence of polysulfides and commonly supplied as a crystalline mass, in flake form, or as a fused solid.

It is used in other applications including ore flotation, oil recovery, making dyes, and detergent.

Alkylation of sodium sulfide give thioethers: Even aryl halides participate in this reaction.

[9] By a broadly similar process sodium sulfide can react with alkenes in the thiol-ene reaction to give thioethers.

[11] The reduction of nitro aromatic compounds to amines using sodium sulfide is known as the Zinin reaction in honor of its discoverer.

It reacts rapidly with acids to produce hydrogen sulfide, which is highly toxic.