2.1. This Recommendation deals with the calibration of conductivity cells by direct or indirect reference to standard solutions covered by the International Recommendation No. 56 « Standard solutions reproducing the conductivity of electrolytes ». The Recommendation determines the fundamental requirements for the calibration method based on the above formula (2). Other calibration methods are accepted provided that they give similar results. 2.2. Conductivity cells calibrated according to this Recommendation may be used for measuring the conductivity of aqueous and non-aqueous solutions within the range 0.1 S/m ? x ? 100 S/m.