Notebook Theme

Analysis of Iron(II) Carbonate (FeCO₃)

Qualitative analysis

Aim

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

Preliminary Test

  • Colour: Pale green
  • Odour: Odourless
  • State: Crystalline solid
  • Solubility: Insoluble in water

Test of Anion (CO₃²⁻)

ExperimentObservationInference
Take 0.1 g of salt, add 1–2 mL of dilute H₂SO₄Colourless odourless gas is evolved with brisk effervescence; lime water turns milkyCO₃²⁻ may be present
Confirmatory Test
Lime Water Test
Pass the gas through lime water
Lime water turns milky; milkiness disappears on passing excess gas (soluble calcium bicarbonate)CO₃²⁻ is confirmed

Test of Cation (Fe²⁺)

ExperimentObservationInference
Salt solution + NaOH solutionDirty green precipitateFe²⁺ may be present
Confirmatory Test
Potassium Ferricyanide Test
Add potassium ferricyanide solution
Dark blue precipitate (Turnbull's blue)Presence of Fe²⁺ is confirmed

Result

The given salt contains Fe²⁺ as the cation (basic radical) and CO₃²⁻ as the anion (acidic radical). The salt is Iron(II) Carbonate (FeCO₃).

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.