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How to do salt analysis

Find the anion and the cation. Write Experiment, Observation, Inference. Print if you need a file. This is the qualitative analysis scheme Class 12 CBSE students follow; ISC and other labs use the same tests.

Common salts

The salts that usually come up. Open one and copy the table.

Cation groups

GroupIonsReagent / note
0NH₄⁺NaOH, heat; Nessler’s reagent. Always first. Then stop if positive.
IPb²⁺ (also Ag⁺, Hg₂²⁺ in older lists)Dilute HCl. White ppt; PbCl₂ soluble in hot water.
IICu²⁺, As³⁺, …H₂S in dilute HCl. CuS is black.
IIIAl³⁺, Fe³⁺NH₄Cl + NH₄OH. White gelatinous Al(OH)₃ or reddish-brown Fe(OH)₃.
IVZn²⁺, Ni²⁺, Co²⁺, Mn²⁺H₂S in ammoniacal medium. ZnS is white.
VBa²⁺, Sr²⁺, Ca²⁺(NH₄)₂CO₃. Then flame + chromate / sulphate / oxalate.
VIMg²⁺Na₂HPO₄ after I-V are absent. Scratch the tube.

Anion tests

StepIonsWhat you see
Dilute H₂SO₄CO₃²⁻, S²⁻, SO₃²⁻, NO₂⁻, CH₃COO⁻CO₂ (lime water), H₂S (rotten eggs), SO₂, NO₂, vinegar.
Conc. H₂SO₄Cl⁻, Br⁻, I⁻, NO₃⁻, C₂O₄²⁻HCl fumes, Br₂ brown, I₂ violet, NO₂, CO + CO₂.
IndependentSO₄²⁻, PO₄³⁻BaCl₂ (acid-insoluble ppt); ammonium molybdate (canary yellow).

Order of tests

  1. Physical examination: colour, odour, state, solubility.
  2. Dry heating and flame test.
  3. Dilute H₂SO₄, then conc. H₂SO₄.
  4. Anion confirmatory (AgNO₃, BaCl₂, brown ring, lime water, …).
  5. Group 0 (NH₄⁺) on the original salt. If positive, stop cations.
  6. Original solution, then Groups I → VI until one cation is confirmed.
  7. Result, precautions, viva.

Viva: 40 questions. Quick practice: 15-question quiz.