Sodium Sulfide (Na₂S) 1313-82-2

Sodium Sulfide (Na₂S) is a yellow to red-brown crystalline solid with the formula Na₂S and a molecular weight of 78.04 g/mol. It is highly soluble in water with a strongly alkaline solution. The 60% grade in flake form is the most common commercial product, widely used in leather dehairing and copper mining flotation.

Red flake sodium sulfide contains trace iron impurities that give it the reddish-brown color, while yellow flake sodium sulfide is more refined with lower iron content. Both grades contain approximately 60% Na₂S and offer comparable performance in most applications. Yellow flake is sometimes preferred for textile dyeing and applications where iron content must be minimized, while red flake is the standard choice for leather processing and mining.

In the leather industry, sodium sulfide is the primary chemical for the unhairing (dehairing) process. It works by hydrolyzing the disulfide bonds in keratin protein found in hair and epidermis. When applied to hides in a lime-sulfide bath, it breaks down the hair structure, allowing it to be easily removed. Sodium sulfide is preferred for its effectiveness and ability to penetrate the hide quickly.

In copper mining, sodium sulfide is used as a sulfidizing agent for the flotation of oxide copper minerals. It reacts with oxidized copper mineral surfaces to form a copper sulfide layer, allowing conventional sulfide collectors like xanthates to attach and float the copper minerals effectively. This process significantly improves the recovery of copper from oxide ores.

Sodium Sulfide requires careful handling. It is corrosive and can cause skin burns. When in contact with acids, it releases highly toxic hydrogen sulfide gas. It is also hygroscopic and will absorb moisture from the air. Store in a cool, dry, well-ventilated area in tightly sealed containers away from acids and moisture. Use appropriate PPE including gloves, goggles, and respiratory protection. Keep solutions strongly alkaline to minimize H₂S release.