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Fig 3.21. Conductivity meter with probe. 

Photo courtesy of Nuno Nogueira from Wikimedia.

Conductivity is a measure of a solution’s ability to conduct electricity. Since electricity needs charged particles in order to flow, there is generally a positive relationship between the concentration of ions and the ability of a solution to conduct electricity. 

Scientists use conductivity meters (see Fig. 3-22) to determine the salinity content of sea water (remember that salinity refers to the amount of dissolved salts in a solution). Conductivity meters are also used in industry to measure ionic content in public water supplies, hospitals and even breweries.
Ions and Conductivity
The conductivity of a solution is directly related to the concentration of ions in a solution. The interesting thing about conductivity is that it is non-ion specific. This means that 1000 sodium ions (Na+) result in the same amount of conductivity as 1000 potassium ions (K+). In fact, if the type of dissolved substance is known, you can use the conductivity to estimate the total amount of dissolved ions, and therefore dissolved solids. In other words, we can use conductivity as a way to measure of ion solubility.


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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.