Electrical conductivity is a measure of the ability of a solution to carry a current. It is defined as the reciprocal or resistance, in ohms, of a 1 cm cube of liquid at a specified temperature which is expressed as siemens/cm. Current flow in liquids must be carried by ions. Ions are formed when a solid such as salt is dissolved in a liquid. For example, sodium chloride separates to form Na+ and Cl- ions. All ions present in the solutions contribute to the current that can flow through the sensor and therefore, contribute to the conductivity measurement. Electrical conductivity therefore is a measure of the concentration of ionizable solutes present in the sample.