Sodium sulfide

Lore & Background

Sodium sulfide is produced industrially by carbothermic reduction of sodium sulfate with coal, yielding Na2S and carbon dioxide. In the laboratory, it can be prepared by reducing sulfur with sodium in anhydrous ammonia or in dry THF with a catalytic amount of naphthalene. The anhydrous form adopts an antifluorite structure, while the nonahydrate features sulfide ions hydrogen-bonded to twelve water molecules.

Reader's Guide

Sodium sulfide is significant primarily for its dominant use in the kraft process for pulp and paper, where it aids delignification to produce cellulose. It also serves in water treatment as an oxygen scavenger and metals precipitant, in chemical photography for toning, in textiles as a bleaching and dechlorinating agent, and in leather processing as an unhairing agent. In organic chemistry, it acts as a nucleophile to form thioethers and as a reducing agent, notably converting nitro groups to amines in the Zinin reaction. Its strongly alkaline nature requires careful handling, as it can cause chemical burns and reacts with acids to produce toxic and explosive hydrogen sulfide.

Did You Know?

• Sodium sulfide is immediately hydrolyzed to sodium hydrosulfide when exposed to moisture.
• The nonahydrate features S2- hydrogen-bonded to 12 water molecules.
• It is used in the Zinin reaction to reduce nitro aromatic compounds to amines.
• Oxidation with hydrogen peroxide gives sodium sulfate.