Conductometry

Conductometry is a measurement technique that determines the electrical conductance of an electrolyte solution to extract information about its ionic content and behavior. It relies on the fact that ions in solution carry charge and move under an electric field; the ease of this movement is quantified by conductance, the reciprocal of resistance. In dilute solutions, conductance depends on ion concentration, mobility, and temperature. The conductivity, denoted by κ, is the conductance of a solution per unit length and cross‑section and is related to the measured conductance G by κ = G × C, where C is the cell constant (a geometrical factor of the electrode arrangement). The molar or specific conductance (Λm or κ) provides standardized ways to compare solutions, with Λm defined as κ divided by the molar concentration.

Measurements are made with a conductivity meter using a conductivity cell equipped with electrodes. Common configurations include two-electrode and four-electrode cells; four-electrode setups minimize polarization effects. Calibration with standard solutions, typically potassium chloride (KCl), yields the cell constant. Temperature strongly influences conductance, so readings are either temperature‑controlled or temperature‑compensated, often reported at 25°C.

Applications of conductometry are diverse. In water analysis, it assesses total dissolved solids and salinity. In chemical processing, it monitors reaction progress, precipitation, and ion exchange. Conductometric titration uses changes in conductivity to locate equivalence points during acid–base or salt–base reactions. Limitations include interference by non‑electrolytes, very dilute or highly concentrated solutions, and electrode polarization, though AC excitation helps mitigate some effects.