1. Hydrogen Sulphide test:
When H2S is passed, a black ppt is formed. The ppt is insoluble in dilute cold acids and in (NH4)2S. But dissolves in boiling concentrated HCl.
2Bi3+ + 3H2S → Bi2S3 + 6H+
2. Ammonia test:
A white ppt is formed when ammonium hydroxide solution is added to the sample solution. The ppt is insoluble in excess ammonium hydroxide solution.
Bi3+ + NO3– + 2NH3 + 2H2O → Bi(OH)2NO3 ↓ + 2NH4+
3. Sodium hydroxide test:
When sodium hydroxide solution is added, a white ppt is obtained. The ppt is soluble in acids.
Bi3+ + 3OH– → Bi(OH)3 ↓
Bi(OH)3 + 3H+ → Bi3+ + 3H2O
When boiled, the ppt loses water and turns yellowish-white. When the yellowish-white ppt is treated with concentrated hydrogen peroxide, a yellowish-brown ion is formed.
Bi(OH)3 → BiO.OH↓ + H2O
BiO.OH + H2O2 → BiO3– + H+ + H2O
4. Potassium iodide test:
When potassium iodide solution is added dropwise, a black ppt is obtained.
Bi3+ + 3I– → BiI3 ↓
When excess of the reagent is added, the ppt dissolves to form orange coloured tetraiodobismuthate ion.
BiI3 + I– → [BiI4]–
5. Sodium tetrahydroxostannate(II) test:
When freshly prepared sodium tetrahydroxostannate is added, a black ppt is obtained.
Bi3+ + 3OH– → Bi(OH)3 ↓
2Bi(OH)3 + 3[Sn(OH)4]2- → 2Bi↓ + 3[Sn(OH)6]2-
6. Water test:
When a solution of a bismuth salt is poured into a large volume of water, a white ppt is obtained, which is soluble in dilute mineral acid but insoluble in tartaric acid and NaOH solution.
Bi3+ + NO3– + H2O → BiO(NO3) ↓ + 2H+
Bi3+ + Cl– + H2O → BiOCl ↓ + 2H+
7. Disodium hydrogen phosphate test:
When disodium hydrogen phosphate solution is added, a white crystalline ppt is obtained.
Bi3+ + HPO4– → BiPO4 ↓ + H+
8. Pyrogallol test:
When freshly prepared pyrogallol solution is added in slight excess to a hot, faintly acidic solution of bismuth ions, a yellow ppt is obtained.
Bi + C6H3(OH)3 → Bi(C6H3O3)↓ +3H+
9. Cinchonine-potassium iodide test:
When Cinchonine-potassium iodide solution is added, orange-red colouration or ppt is obtained in acidic solution.
10. Thiourea test:
In presence of dilute nitric acid, an intense yellow ppt is formed with thiourea solution.
11. 8-Hydroxyquinoline test:
In acidic medium when treated with 8-Hydroxyquinoline and KI solution, a red ppt is obtained.
Bi3+ + C9H7ON + H+ + 4I– → C9H7ON.HBiI4↓
