Notebook Theme

Analysis of Manganese(II) Iodide (MnI₂)

Qualitative analysis

Aim

To analyse the given inorganic salt for one acidic and one basic radical.

Preliminary Test

  • Colour: Pale pink
  • Odour: Odourless
  • State: Crystalline solid
  • Solubility: Soluble in water

Test of Anion (I⁻)

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 (Mn²⁺)

ExperimentObservationInference
Original solution + H₂S gas in presence of NH₄OHBlack or flesh-coloured precipitate is formedGroup IV cation may be present
Confirmatory Test
Sodium Hydroxide Test
Dissolve the precipitate in dilute HCl by boiling and add NaOH in excess
White precipitate forms first, then turns brown on standingPresence of Mn²⁺ is confirmed

Result

The given salt contains Mn²⁺ as the cation (basic radical) and I⁻ as the anion (acidic radical). The salt is Manganese(II) Iodide (MnI₂).

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.