Built by Aabis
Notebook Theme

Experiment No. N

Analysis of Arsenic(III) Sulphite ((As)₂(SO₃)₃)

Aim

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

Preliminary Test

  • Odor: Odorless
  • Texture: Crystalline
  • Color: White
  • Solubility: Soluble in water

Test of Anion

ExperimentObservationInference
Warm 1 mL of water extract or sodium carbonate extract with dilute H₂SO₄Colourless gas with pungent smell of burning sulphur is evolvedSO₃²⁻ may be present
Confirmatory Tests
Barium Chloride Test
Add barium chloride to water extract or sodium carbonate extract		White precipitate dissolves on adding dilute HCl and SO₂ is evolvedSO₃²⁻ is confirmed
KMnO₄ Decolourisation Test
Add dilute H₂SO₄ to the barium sulphite precipitate and then very dilute KMnO₄ solution		Colour of potassium permanganate solution is dischargedSO₃²⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + H₂S gas in presence of dil. HCl and NH₄ClYellow precipitate is formedGroup-II-B (As³⁺) may be present
Confirmatory Test
Ammonium Molybdate Test
Treat the dissolved precipitate with concentrated nitric acid and ammonium molybdate solution		Canary yellow precipitate is formedPresence of As³⁺ is confirmed

Result

The given salt contains As³⁺ ions as cation and SO₃²⁻ ions as anion. The salt is (As)₂(SO₃)₃.

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.