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 |
|---|---|---|
| Universal Indicator | Solution turns blue or purple | OH⁻ may be present |
| Confirmatory Test | ||
| Phenolphthalein Test Add phenolphthalein indicator to salt solution | Solution turns pink | OH⁻ 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 OH⁻ as the anion (acidic radical). The salt is Aluminium Hydroxide (Al(OH)₃).