Conductivity is the ability of a solution to conduct electricity. It is dependent on the presence of ions in the solution. Ions are derived from ionic compounds that dissolve in water, such as sodium chloride.
The more concentrated a solution is, the higher the conductivity is. In most cases it is a proportional relationship. As the ion concentration increases, the conductivity increases.
Some solutions have a limit to how conductive it can be. Once that point is reached, increasing the solution concentration will actually lower conductivity. This is observed in sulfuric acid solutions.
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Conductivity is measured by placing two plates into a sample and applying a potential across the plate. This will read the current, which is then used to calculate conductivity using Ohm's Law.
Influence of Temperature
Conductivity is temperature dependent. Conductivity meters compensate for temperature effects by referencing a standard temperature.
Conductivity meters should be calibrated to a standard solution to ensure accurate measurements. Standard solutions should have a conductivity close to that of the samples to be measured.