Qualitative analysis
How to do salt analysis · Viva · Quiz
To analyse the given inorganic salt for one acidic and one basic radical.
| Experiment | Observation | Inference |
|---|---|---|
| Take 0.1 g of salt and add conc. H₂SO₄ | A colourless gas is evolved which gives dense white fumes with ammonia | Cl⁻ may be present |
| Confirmatory Tests | ||
| Concentrated H₂SO₄ and MnO₂ Test Take a pinch of MnO₂ in salt solution and add 3–4 drops of conc. H₂SO₄, then heat | Greenish yellow chlorine gas is evolved | Presence of Cl⁻ is indicated |
| Silver Nitrate Test Acidify 1 mL of sodium carbonate extract with dilute HNO₃ (or use water extract) and add AgNO₃ solution | Curdy white precipitate soluble in NH₄OH | Cl⁻ is confirmed |
| Chromyl Chloride Test Take a little salt with solid K₂Cr₂O₇, add conc. H₂SO₄, heat. Pass the evolved gas through sodium hydroxide solution, divide into two parts. Acidify one part with acetic acid and add lead acetate solution | The sodium hydroxide solution becomes yellow; adding acetic acid and lead acetate gives yellow precipitate of lead chromate | Cl⁻ is confirmed |
| Experiment | Observation | Inference |
|---|---|---|
| Confirmatory Tests | ||
| If Group V is absent, add disodium hydrogen phosphate solution and scratch the inner walls with a glass rod | A white crystalline precipitate of magnesium ammonium phosphate is formed | Mg²⁺ may be present |
| Magneson Test To the alkaline solution add a drop of Magneson I reagent (p-nitrobenzeneazoresorcinol) | A blue precipitate / blue lake is formed | Mg²⁺ is confirmed |
The given salt contains Mg²⁺ as the cation (basic radical) and Cl⁻ as the anion (acidic radical). The salt is Magnesium Chloride (MgCl₂).