What is the conductivity of seawater in general?

The conductivity per unit length of seawater column with cross-sectional area of 1 cm2 is called "seawater conductivity". This is a method to measure the salinity of seawater by electrical conductivity. The conductivity of seawater varies with the temperature, pressure and salinity of seawater. At the same temperature and pressure, the conductivity of seawater with the same ion composition is only related to salinity. If this relationship can be solved, the salinity value can be obtained according to the conductivity. For convenience, "relative conductivity" is often used, that is, the ratio of the conductivity of water samples to that of seawater with salinity of 35‰ at the same temperature and standard atmospheric pressure.

The conductivity (reciprocal of resistivity) of seawater is usually represented by the symbol σ, which is generally 3-5 ohms/meter. When the temperature is 17℃, the conductivity of standard seawater is 4.54-4.8 1ω/m, which is 7 times that of copper and 2 times that of glass. The conductivity of seawater is more than 1000 times that of ordinary lakes and rivers. 1964, Weyl established the empirical formula τ = 25-T℃ (T℃ is the temperature of seawater): log σ =-0.42373+0.892 log Cl (‰)-10-4 τ [ The range of Cl(‰) is 17 ‰-20 ‰, and the range of tC is that the current density j of the conductor is directly proportional to the applied electric field intensity e and jocE, that is, j=σE, where σ is a proportional constant and σ = j/e, that is, the current density per unit electric field intensity.