A chemical compound having the formula Na2S, Sodium Sulfide is commonly available in its hydrate form (Na2s.9H2o). The colorless chemical compounds are highly soluble in water and form highly alkaline solutions. Na2S emits hydrogen sulfide when exposed to moist air that has a smell of rotten eggs. A few of the commercially available samples of the compound have been specified as Na2S.xH2O wherein the amount of Na2S has not been mentioned. More commonly available grade contains roughly 60% Na2S by weight, implying that the value of x is close to 3. These grades of sodium have a yellow color due to the presence of polysulfides. Marketed as ‘sodium sulfide flakes’, these grades are red solids but form colorless solutions.Structure:
Sodium sulfide has an antifluorite structure, meaning that the Na+ ion occupies fluoride sites within the caF2 framework while the larger S2- occupies sites meant for Ca2+. Produced industrially by the carbothermic reduction of sulfates by using coal (Na2SO4 + 2 C → Na2S + 2 CO2), sodium sulfide is used for a variety of applications across sectors. In laboratories, the compound is produced by reducing sulfur using sodium in anhydrous ammonia or by sodium in dry THF along with a catalytic amount of naphthalene (forming sodium naphthalenide) 2 Na + S → Na2S.Usage:
- Tanning Industry: It is used to destroy hair on hides or skins during processing.
- Dyeing Industry: It is an essential raw material used for the production sulfur black and as a reductant for sulfur dyestuff.
- Textile Industry: It is used for destroying nitration.
- Mining industry: Used for sulphide ore flotation, smelting nonferrous metals and waste water removal from heavy metals.