Conductometrie

Conductometry is a method used to measure the electrical conductivity of a liquid in order to assess its ionic content and to monitor chemical processes. A conductometer applies a small electrical signal between electrodes immersed in the solution and records the resulting conductance, which depends on the concentration and mobility of ions present.

Conductivity, denoted by κ, describes a solution’s ability to conduct electric current and is influenced by ion concentrations and mobilities. It can be expressed as κ = sum ci λi, where ci is the molar concentration and λi is the molar ionic conductivity. At infinite dilution, κ approaches Λm0 c. In practice, a conductance meter provides a measured conductance G that relates to conductivity through the cell constant K: G = κ × K. The conductivity value is then derived as κ = G / K. Temperature compensation is commonly employed, and results are often reported at a reference temperature such as 25 °C.

Instrumentation typically involves a conductometer with a two-electrode conductivity cell (frequently made of platinum or graphite) connected to a meter. Modern instruments include temperature sensors (thermistor or Pt100) and automatic temperature compensation. Some setups use four-electrode cells to reduce polarization errors.

Applications include assessing total dissolved solids in water, monitoring chemical reactions (notably conductometric titrations) and reaction progress, evaluating ionic strength and solution purity, and supporting process control in chemical manufacturing and food and beverage industries.

Advantages of conductometry are its speed, non-destructive nature, and simplicity, with minimal sample preparation. Limitations include non-specific measurements (no speciation), sensitivity to temperature and ionic strength, need for careful calibration, and potential deviations at high ionic strengths or in non-ionic systems.