Conductivity (electrolytic)

Conductivity or specific conductance of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter (S/m). Conductivity measurements are used routinely in many industrial and environmental applications as a fast, inexpensive and reliable way of measuring the ionic content in a solution. For example, the measurement of product conductivity is a typical way to monitor and continuously trend the performance of water purification systems. In many cases, conductivity is linked directly to the total dissolved solids (TDS). High-quality deionized water has a conductivity of κ = 0.05501 ± 0.0001 {\displaystyle \kappa =0.05501\pm 0.0001} μS/cm at 25 °C. This corresponds to a specific resistivity of ρ = 18.18 ± 0.03 {\displaystyle \rho =18.18\pm 0.03} MΩ⋅cm. The preparation of salt solutions often takes place in unsealed beakers. In this case the conductivity of purified water often is 10 to 20 times higher. A discussion can be found below. Typical drinking water is in the range of 200–800 μS/cm, while sea water is about 50 mS/cm (or 0.05 S/cm). Electrolytic conductivity varies from about 10E-10 S/m for purified toluene up to about 10 S/m for recently discovered highly concentrated “water-in-salt” solutions. Conductivity of aqueous and other polar solutions is traditionally determined by connecting the electrolyte in a Wheatstone bridge. Dilute solutions follow Kohlrausch's law of concentration dependence and additivity of ionic contributions. Lars Onsager gave a theoretical explanation of Kohlrausch's law by extending Debye–Hückel theory. Conductivity of low- and non-polar solutions is very low. It is also associated with motion of ions in electric field, but the nature and solvation of ions are different, as described on the page conductivity (non-aqueous). It is usually measured with probes having low cell constant and applying low frequency electric field. Notation is treacherous in this...