Notebook Theme

Experiment No. N

Analysis of Potassium Nitrate (KNO₃)

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
Add conc. H₂SO₄ to the solution and boil with a few copper turnings/chipsOn heating, brown fumes (NO₂) are evolved in excess and the solution becomes blueNO₃⁻ may be present
Confirmatory Test
Brown Ring Test
Take 1 mL of salt solution, add 2 mL conc. H₂SO₄, cool, then add freshly prepared ferrous sulphate solution along the sides
Brown ring is formed at the junction of the two solutionsNO₃⁻ is confirmed

Test of Cation

ExperimentObservationInference
Flame test in a clean non-luminous flameLilac flameK⁺ may be present
Confirmatory Test
Sodium Cobaltinitrite Test
Salt solution + sodium cobaltinitrite reagent
Yellow precipitateK⁺ is confirmed

Result

The given salt contains K⁺ ions as cation and NO₃⁻ ions as anion. The salt is KNO₃.

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.