Departures from ideality in electrolytes are described in the framework of the primitive model of ionic solutions in which the solvent is a dielectric continuum, using the mean spherical approximation (MSA). To include solvation and solvent concentration effects, we consider that the permittivity of the solvent and the sizes of the ions are concentration-dependent parameters. New expressions are derived for the activity coefficients and the osmotic coefficient. They are applied to pure ionic aqueous solutions of 18 salts, taking simple functions for the adjusted parameters. Good fittings are obtained in the concentration range 0-6 mol/kg.