Sodium Sulfide

Sodium sulfide is the chemical compound with the formula Na2S, or more commonly its hydrate Na2S·9H2O. Both are colorless water-soluble salts that give strongly alkaline solutions.

Physical Properties:

Chemical formula：Na2S

Molar mass： 78.0452 g/mol (anhydrous)/240.18 g/mol (nonahydrate)

Appearance：colorless, hygroscopic solid

Odor：rotten eggs

Density：1.856 g/cm3 (anhydrous)/1.58 g/cm3 (pentahydrate)/1.43 g/cm3 (nonohydrate)

Melting point：1,176 °C (2,149 °F; 1,449 K) (anhydrous)/100 °C (pentahydrate)/50 °C (nonahydrate)

Solubility in water：12.4 g/100 mL (0 °C)/18.6 g/100 mL (20 °C)/39 g/100 mL (50 °C) (hydrolyses)

Applications:

Leather Processing: Used to remove hair and other unwanted proteins from animal hides during leather production.

Pulp and Paper Industry: Employed in kraft paper manufacturing to break down lignin in wood pulp, making the pulp easier to process.

Chemical Production: Acts as a precursor for other chemicals, including dyes, sulfur-containing compounds, and sulfur-based flotation agents in mining.

Water Treatment: Sodium sulfide used to remove heavy metals from wastewater by precipitating metal sulfides, which can be filtered out of the solution.

Photographic Industry: Sodium sulfide used in the manufacture of photographic developers and sulfur toning solutions.

Handling and Storage:

Handling: Must be handled with protective gear, including gloves, goggles, and masks, as it is highly alkaline and emits toxic hydrogen sulfide.

Storage: Store in a cool, dry, and well-ventilated area away from moisture, acids, and oxidizing agents.

Spillage: In case of spills, sodium sulfide should be contained and neutralized with diluted acid under controlled conditions, with proper ventilation to avoid H₂S buildup.