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Analytical Methods

Chemical Analyses: Water: Electrical Conductivity

The electrical conductance (EC) of a solution is a measure of the ability of a solution to conduct a current. It is a property attributable to the ions in solution. Electrical current is transported through solutions via movement of ions, and conductivity increases as ion concentration increases. The conductivity of a solution is measured between two spatially fixed inert electrodes of known surface area. Conductance is directly proportional to the electrode surface area and inversely proportional to the distance between the electrodes. In the international system of units, conductivity is reported as decisiemens per meter (dS/m).

Conductivity can be used for a variety of applications at mine sites, including:

  • Comparing with other water quality parameters to show potential gross errors in analysis. For example, an increase or decrease in conductance of a particular water source will result in a similar increase or decrease in other water quality parameters such as total dissolved solids, sulfate, and metals. If this is not observed, analysis should be considered suspect and repeated;
  • Estimate the total dissolved solids in a sample by multiplying conductivity by an empirical factor determined from analysis.

Conductivity results given alone are very limiting as they do not measure individual contaminants nor the overall state of the water (MEND, 2001).

The common method for measuring conductance is described in Standard Methods, 1998, Section 2510. See below for a brief description of the method.

Conductivity method description

The conductivity of a sample is measured with a self-contained conductivity meter (Wheatstone bridge or equivalent). The instrument must be standardized with KCl solutions of known conductance before use. The cell is washed with 0.01 M KCl followed by one to two rinses with the sample prior to measurement. Temperature corrections are made if the sample is not analyzed at 25�C.

 

Chemical Analysis | Physical Properties

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