Comparison of Models for the Prediction of the Electrical Conductivity of Electrolyte Solutions

It has been almost one century since Onsager developed the limiting law of equivalent conductivity of electrolyte solutions. Thenceforth, many models have been developed; however, they have not been assessed thoroughly and systematically. This paper comprehensively investigates the accuracy and reliability of six equivalent conductivity models, namely, the Debye-Hückel-Onsager limiting law (DHOLL), extended law (DHOEE), smaller ion shell (DHOSiS), along with the simplified and full mean spherical approximation (MSA, MSA-Simple), and Quint-Viallard (QV). To this aim, we have prepared a database of experimental data for 126 electrolytes. The accuracy of the models is examined with the help of graphical methods and error analysis over a wide range of concentrations ([0, 18] mol/L) and temperatures ([0, 100]°C). Moreover, the origin of possible errors of models is inspected with a term-by-term analysis of relaxation and electrophoretic effects. It is shown that the absolute average deviation of models depends highly on the electrolyte type, and it is generally smaller for 1:1 salts, especially at low concentrations (less than 5%). The error evolution with concentration also reveals that MSA-Simple and DHOEE are more reliable over a wide range of concentration and electrolyte types. It is concluded that MSA-Simple predicts the equivalent conductivity at lower temperatures and the trend of versus T more satisfactorily than the other models.