Sodium sulfide - Na2S

What is Sodium sulfide?

Sodium sulfide is an inorganic chemical compound with the formula Na2S that has attained an important position in the organic chemical industry. It is a strong alkaline solution when exposed to moist air it smells like rotten eggs. Although the solid state is yellow in colour in solution it is colourless. Usually it comes in the grades as “sodium sulfide flakes”.

IUPAC name – disodium sulfanide

Na2S Sodium sulfide
Density 1.86 g/cm³
Molecular Weight/ Molar Mass 78.0452 g/mol
Autoignition temperature > 480 °C (896 °F; 753 K)
Melting Point 1,176° C (2,149° F)
Chemical Formula Na2S

Sodium sulfide Structure – Na2S

Sodium sulfide

Physical Properties of Sodium sulfide – Na2S

Odour Odor of rotten eggs
Appearance Anhydrous yellow crystalline solids
Storage temp‎ 2-8°C
pH 10.4
Oxidation number -2
Solubility Insoluble in ether; slightly soluble in alcohol

Chemical Properties of Sodium sulfide – Na2S

    • Sodium sulfide dissolves in water to form its corresponding ions. The reaction is as below.

Na2S + H2O → 2Na+ + HS + OH

    • It can be easily oxidised when heated it forms sodium carbonate and sulfur dioxide.

2Na2S + 3O2 + 2CO2 → 2Na2CO3 + 2SO2

    • It reacts with sulphur forming polysulfides.

2Na2S + S8 → 2Na2S5

Uses of Sodium sulfide – Na2S

  • Used in water treatment as an oxygen scavenger agent and also used as a metal precipitant.
  • Used in photographic industry to protect developer solutions from oxidation in textile industry sa bleaching.
  • Utilized in the production of elastic synthetic materials, sulfur colors and other substances.
  • Used primarily in pulp and paper industry in the hraft process.It increase the selectivity of the sulfate cooking process and increase the rate of delignification.
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