Electrical conductivity is a measure of the
ability of a solution to carry a current. Current
flow in liquids differs from that in metal
conductors in that electrons cannot flow
freely, but must be carried by ions. Ions are
formed when a solid such as salt is dissolved
in a liquid to form electrical components
having opposite electrical charges. For
example, sodium chloride separates to form
Na+
and Cl
-
ions. All ions present in the
solutions contribute to the current flowing
through the sensor and therefore, contribute to
the conductivity measurement. Electrical
conductivity can therefore be used as a
measure of the concentration of ionizable
solutes present in the sample.