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The conversion of conductivity (in μS/cm) to the total dissolved solids (in mg/kg) depends on the chemical composition of the sample and can vary between 0.54 and 0.96. Typically, the conversion is done assuming that the solid is sodium chloride; 1 μS/cm is then equivalent to about 0.64 mg of NaCl per kg of water.
Electrical conductivity of water samples is used as an indicator of how salt-free, ion-free, or impurity-free the sample is; the purer the water, the lower the conductivity (the higher the resistivity). Conductivity measurements in water are often reported as specific conductance, relative to the conductivity of pure water at 25 °C.
The standard is most often used as a comparative property in the specification of the conductivity of other metals. For example, the conductivity of a particular grade of titanium may be specified as 1.2 % IACS, meaning that its electrical conductivity is 1.2 % of the copper specified as the IACS standard. [2]
κ is the measured conductivity (formerly known as specific conductance), [3] c is the molar concentration of the electrolyte. The SI unit of molar conductivity is siemens metres squared per mole (S m 2 mol −1). [2] However, values are often quoted in S cm 2 mol −1. [4]
The siemens (symbol: S) is the unit of electric conductance, electric susceptance, and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and impedance respectively; hence one siemens is equal to the reciprocal of one ohm (Ω −1) and is also referred to as the mho.
The Bresle method uses the difference of conductivity of salts in water, each salt having a characteristic conductivity-versus-concentration relationship. The correlation between concentration and conductivity can be found in "Handbook of Chemistry and Physics". This relationship is useful only if the dissolved salt is known.
where TDS is expressed in mg/L and EC is the electrical conductivity in microsiemens per centimeter at 25 °C. The conversion factor k e varies between 0.55 and 0.8. [5] Some TDS meters use an electrical conductivity measurement to the ppm using the above formula. Regarding units, 1 ppm indicates 1 mg of dissolved solids per 1,000 g of water.
Let K 0 is the normal conductivity at one bar (10 5 N/m 2) pressure, K e is its conductivity at special pressure and/or length scale. Let d is a plate distance in meters, P is an air pressure in Pascals (N/m 2 ), T is temperature Kelvin, C is this Lasance constant 7.6 ⋅ 10 −5 m ⋅ K/N and PP is the product P ⋅ d/T .