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Experiment No. N

Analysis of Arsenic(III) Iodide (As(I)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
Take 0.1 g of salt in a test tube and add conc. H₂SO₄Deep violet vapour with a pungent odour is evolvedI⁻ may be present
Confirmatory Tests
Layer Test
Take test solution or extract, add CHCl₃/CCl₄ and chlorine water dropwise, then shake vigorously		Violet colouration appears in the organic layerI⁻ is confirmed
Silver Nitrate Test
Acidify sodium carbonate extract with dilute HNO₃ and add AgNO₃		Yellow precipitate is obtained, insoluble in excess NH₄OHI⁻ 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 I⁻ ions as anion. The salt is As(I)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.