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Experiment No. N

Analysis of Potassium Nitrite (KNO₂)

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
Warm the solid salt with dilute H₂SO₄Brown fumes of NO₂ are evolvedNO₂⁻ may be present
Confirmatory Tests
Potassium Iodide Starch Test
Take evolved gas and add KI + starch solution acidified with acetic acid		Blue colour appearsNO₂⁻ is confirmed
Sulphanilic Acid / 1-Naphthylamine Test
Acidify 1 mL of water extract with acetic acid and add sulphanilic acid solution followed by 1-naphthylamine reagent		Red colour is formedNO₂⁻ 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 NO₂⁻ ions as anion. The salt is KNO₂.

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.