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Experiment No. N

Analysis of Ammonium Sulphide ((NH₄)₂S)

Aim

To determine the presence of anion and cation in the given salt

Preliminary Test

  • Odor: Odor of rotten eggs
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Warm the salt with dilute H₂SO₄Colourless gas with smell of rotten eggs is evolvedS²⁻ may be present
Confirmatory Tests
Lead Acetate Test
Pass gas through filter paper dipped in lead acetate solution		Paper turns blackS²⁻ is confirmed
Sodium Nitroprusside Test
Make solution alkaline with NH₄OH (or sodium carbonate extract) and add sodium nitroprusside solution		Purple/violet colouration is producedS²⁻ is confirmed

Test of Cation

ExperimentObservationInference
Take 0.1 g of salt and add 1–2 mL of NaOH solution, then heatA smell of ammonia is evolvedNH₄⁺ may be present
Bring a glass rod dipped in hydrochloric acid near the mouth of the test tubeDense white fumes are observedNH₄⁺ may be present
Confirmatory Test
Nessler's Reagent Test
Pass the evolved gas through Nessler’s reagent		Brown colouration or a brown precipitate of basic mercury(II) amido-iodide is obtainedPresence of NH₄⁺ is confirmed

Result

The given salt contains NH₄⁺ ions as cation and S²⁻ ions as anion. The salt is (NH₄)₂S.

Precautions

  1. Handle the chemicals with care.
  2. Don't use excess of chemicals.
  3. Keep the mouth of the test tube away from the face.