Test for Bismuth(III) ion

Test for Bismuth(III) ion

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

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