The enthalpies of solution of NaBPh4 in mixtures of water and methanol, sec-butanol or dimethyl sulphoxide, and those of Ph4AsCl in mixtures of water and sec-butanol or acetonitrile, as well the density of sec-butanol-water mixed solvent, have been measured at a temperature of 298.15 K. Enthalpic pair interaction coefficients of the organic salt-cosolvent have been calculated (h(xy)). The relationships h(xy) = f(v(PHI22)) for the salts under investigation have been plotted and discussed. It has been confirmed that the interactions of both salts with the mixed solvent, and particularly with water, are different.