Lassaigne's Test (Sodium Fusion): Qualitative detection of N, S, halogens in organic compounds by sodium fusion + ionic tests. Key: blood-red = N+S; Prussian blue = N alone.

Tollens' Test (Silver Mirror Test): Ammoniacal AgNO3 + aldehyde → Ag0 (silver mirror). Developed by Bernhard Tollens. Distinguishes aldehyde from ketone.

Fehling's Test: Cu2+ tartrate/NaOH (alkaline) + aliphatic aldehyde → Cu2O (brick-red). Developed by Hermann von Fehling. Used for reducing sugars in food science.

Schiff's Test: Decolorized fuchsin (Schiff's reagent, fuchsin + SO2) + aldehyde → pink/magenta. Specific for aldehydes (not ketones). Developed by Hugo Schiff.

2,4-DNP Test: 2,4-Dinitrophenylhydrazine + C=O compound → orange/yellow 2,4-dinitrophenylhydrazone precipitate. Detects any carbonyl, cannot distinguish aldehyde from ketone.

Iodoform Test: I2/NaOH + methyl ketone $\frac{or ethanol}{acetaldehyde}$ → CHI3 (yellow iodoform crystals, SMILES: C(I)(I)I). Specific for CH3CO- group.

Carbylamine Test (Isocyanide Test): CHCl3 + KOH + primary amine (heat) → isocyanide (R-NC, foul smell). Specific for primary amines only.

FeCl3 Test for Phenol: Neutral FeCl3 + phenol → violet/blue/green iron-phenolate complex. Classic test for phenolic -OH.

Brown Ring Test for Nitrate: FeSO4 + dilute H2SO4 + conc. H2SO4 (layered) → brown ring [Fe(H2O)5(NO)]2+ at interface. Detects NO3-.

Azo Dye Test: Aromatic primary amine + NaNO2/HCl (0–5 °C) → diazonium salt + β-naphthol/NaOH → orange-red azo dye. Specific for aromatic 1° amines.

KMnO4/Oxalic Acid Titration: 5C2O42- + 2MnO4- + 16H+ → 10CO2 + 2Mn2+ + 8H2O. Self-indicating, 60–70 °C, acidic H2SO4 medium.