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Experiment No. N

Analysis of Cobalt(II) Sulfate (CoSO₄)

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
Confirmatory Tests
If no earlier anion test is positive, acidify the extract with dilute HCl and add BaCl₂ solutionWhite precipitate of barium sulphate, insoluble in conc. HCl or conc. HNO₃ is obtainedSO₄²⁻ may be present
Lead Acetate Test
Acidify the solution with acetic acid and add lead acetate solution		White precipitate appearsPresence of SO₄²⁻ is confirmed

Test of Cation

ExperimentObservationInference
Original solution + H₂S gas in presence of NH₄OHBlack precipitate is formedGroup IV cation may be present
Dissolve the black sulphide precipitate in aqua regia and heatResidue remains in solution after evaporationCo²⁺ may be present
Confirmatory Test
Potassium Hexanitritocobaltate(III) Test
Neutralise with NH₄OH, acidify with dilute acetic acid and add strong potassium nitrite solution		Yellow precipitate is formedPresence of Co²⁺ is confirmed

Result

The given salt contains Co²⁺ ions as cation and SO₄²⁻ ions as anion. The salt is CoSO₄.

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.