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 |
|---|---|---|
| Warm the solid salt with dilute H₂SO₄ | Brown fumes of NO₂ are evolved | NO₂⁻ may be present |
| Confirmatory Tests | ||
| Potassium Iodide Starch Test Take evolved gas and add KI + starch solution acidified with acetic acid | Blue colour appears | NO₂⁻ 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 formed | NO₂⁻ 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 NO₂⁻ as the anion (acidic radical). The salt is Magnesium Nitrite (Mg(NO₂)₂).