Electrical conductivity meter

Louvain-La-Neuve

Conductimetry is a dosing method based on the conductive properties of an ionic solution, called an electrolyte, which conducts electricity. This technique makes it possible to determine the concentration of the ions present but also the kinetics of a reaction or to carry out titrations.
The principle consists in measuring the resistance of a solution located between two electrodes; plates covered with platinum black face to face and supplied by an alternating voltage. Once the cell is immersed in the ionic solution, the voltage across its terminals is varied and the intensity of the current flowing through it is measured.

Depending on the concentration of ions present, the solution will have a greater or lesser conductivity. Before making a measurement, the conductivity meter must be calibrated which consists of determining the cell constant using standard solutions (usually a KCl solution).

Tables provide information on the conductivity of the ions and that of the standard solution as a function of the temperature which has a strong influence on the measurement.

The conductivity meter is based on Ohm's law: U = R*I where U represents the voltage (volts), I the intensity (amps) and R the resistance (ohms). It then gives a value of the conductance G, expressed in siemens, knowing that: G = 1/R.

The conductivity depends on the concentration of the ions, the nature of the ionic solution and the temperature of the solution.