All Mesa Laboratories Conductivity Calibrator Solutions are laboratory quality, NIST-traceable, standard solutions used for the calibration of conductivity meters. Tolerance +/- 0.01 at 25° C Solution Specifications: Sodium Carbonate (CAS # 497-19-8)?Sodium Bicarbonate (CAS # 144-55-8)?Deionized Water (CAS # 7732-18-5)