In redox reactions learned in school, the exchange of electrons determines how substances behave. In polarography, developed by Heyrovský, a dropping mercury electrode is polarized while the current is measured. The resulting S-shaped curve shows at which potential ions are reduced or oxidized. The half-wave potential identifies the substance, and the diffusion current height reveals its concentration. Because fresh mercury drops form every second, the electrode surface is always clean, giving highly reproducible data. The method became essential for monitoring heavy-metal pollution, controlling pharmaceutical quality, and studying metal ions in biology.

Polarography is an electrochemical current-potential technique distinguished by its use of the dropping mercury electrode (DME). Because mercury exhibits a large hydrogen overpotential, a wide cathodic potential window is accessible, minimizing interference from hydrogen evolution. The measured current is diffusion-controlled and can be quantified through the Ilković equation i_d = 607 n D^{1/2} m^{2/3} t^{1/6} C. The half-wave potential E_1/2 follows the Nernst equation, allowing qualitative identification even in complex mixtures. Continuous renewal of the DME surface prevents adsorption of reaction products and enables trace (ppm to ppb) metal determination. Later innovations such as pulse modes and electrochemical preconcentration expanded the field into modern voltammetry, yet the conceptual foundation traces back directly to Heyrovský’s pioneering work.

By elucidating diffusion-controlled currents at the DME, Heyrovský established a quantitative paradigm for electroanalytical chemistry. Empirical characterization of drop weight m and lifetime t distributions, coupled with Ilković’s theoretical expression i_d ∝ D^{1/2} m^{2/3} t^{1/6} C (proportionality constant 607), quantified DME dissolvability. Subsequent differentiation of adsorption-controlled cathodic waves via prereduction steps, and exploration of isotope effects in acidic media, all relied on Heyrovský’s methodology. Exploiting E_1/2 shifts to derive formation constants of metal-ligand complexes provided inorganic coordination chemistry with a powerful tool. His groundwork paved the way for differential-pulse, square-wave, and stripping voltammetries, techniques still ubiquitous in environmental monitoring, bioanalysis, and nanomaterial characterization.