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 salt with dilute H₂SO₄ | Colourless gas with smell of rotten eggs is evolved | S²⁻ may be present |
| Confirmatory Tests | ||
| Lead Acetate Test Pass gas through filter paper dipped in lead acetate solution | Paper turns black | S²⁻ is confirmed |
| Sodium Nitroprusside Test Make solution alkaline with NH₄OH (or sodium carbonate extract) and add sodium nitroprusside solution | Purple/violet colouration is produced | S²⁻ is confirmed |
| Experiment | Observation | Inference |
|---|---|---|
| Original solution + Dil. HCl + NH₄Cl solid + NH₄OH | White gelatinous precipitate | Al³⁺ may be present |
| Confirmatory Tests | ||
| Dissolve white precipitate in dilute HCl and divide into two parts | To the first part, add sodium hydroxide and warm. A white gelatinous precipitate dissolves in excess sodium hydroxide solution | Aluminium is confirmed |
| Blue Lake Test To the second part, add few drops of blue litmus solution and then NH₄OH dropwise along the sides of the test tube | A blue floating mass appears in colourless solution | Presence of Al³⁺ is confirmed |
The given salt contains Al³⁺ as the cation (basic radical) and S²⁻ as the anion (acidic radical). The salt is Aluminium Sulphide (Al₂S₃).