1817 — Jean Louis Lassaigne (French chemist) develops the sodium fusion test for detecting nitrogen, sulfur, and halogens in organic compounds. Originally described as fusing with metallic potassium (later standardized to sodium).

1820s–1830s — Systematic qualitative analysis of inorganic cations developed by various European analytical chemists. The systematic group-based precipitation scheme (using H2S, NH4OH, etc.) is formalized.

1834 — Justus von Liebig develops elemental combustion analysis for carbon and hydrogen in organic compounds, complementing the Lassaigne test for other elements.

1869 — Hugo Schiff develops Schiff's test (decolorized fuchsin) for detecting aldehydes.

1880s — Fehling's solution (developed by Hermann von Fehling, 1848) gains widespread use for distinguishing reducing sugars and aliphatic aldehydes from ketones.

1886 — Acetanilide (antifebrin) introduced as the first synthetic analgesic — demonstrating the practical importance of N-acylation of aniline.

1888 — Tollens' reagent standardized by Bernhard Tollens for aldehyde detection (silver mirror test).

1910s — 2,4-Dinitrophenylhydrazine (2,4-DNP) introduced as a carbonyl-detecting reagent, giving characteristic crystalline hydrazones useful for characterizing unknown carbonyls.

1914 — KMnO4 titration of oxalic acid established as a standard method for standardizing permanganate solutions in analytical laboratories.

Present (NEET context) — All these tests remain core practical chemistry topics in CBSE Class 11–12 and are directly tested in NEET, JEE, and other entrance exams.