The use of chemical models is shown based on pair distribution functions (pdf) taking into account long and short-range interaction forces on the McMillan-Mayer (MM) level for the calculation of thermodynamic properties (association constant, activity coefficient, osmotic coefficient) and transport properties (conductivity) of electrolyte solutions from dilute to concentrated solutions. Extensions of the Debye-Huckel theory including ion association and solvation are used at low concentrations. High concentrations are treated by the use of the mean spherical approximation (MSA), the MSA-mass action law (MAL), and the associative MSA (AMSA) permitting one the access to systems with ion aggregation to trimers and tetramers. Comparison is made with experimental data.