The ionic strength of a solution is the concentration of ions in a solution.

$I\; =\; \backslash begin\{matrix\}\backslash frac\{1\}\{2\}\backslash end\{matrix\}\backslash sum\_\{i=1\}^\{n\}\; c\_\{i\}z\_\{i\}^\{2\}$

where $c\_i$ is the molarity concentration of ion $i$, $z\_i$ is the charge of that ion, and the sum is taken over all ions in the solution. For a 1:1 electrolyte such as sodium chloride, the ionic strength is equal to the concentration. For multivalent ions, the ionic strength is greater than the concentration.

analytical chemistry

Ionenstärke | Siła jonowa