A recently proposed model which describes the thermodynamic properties of aqueous 1:1 halides in terms of (i) Coulombic interaction via a Debye-Huckel contribution and of (ii) the thermodynamics of the hydration of the ions has been extended to include incomplete dissociation. It is applied to aqueous CsCl (273 less than or equal to T/K less than or equal to 523), its mixtures with NaCl and HCl, to aqueous CsI (298 less than or equal to T/K less than or equal to 378) and to aqueous HCl (520 less than or equal to T/K less than or equal to 638). The dissociation equilibrium constants derived do agree well with values estimated from other sources. The prediction of the thermodynamics of the ternary solutions of CsCl with NaCl and HCl is improved.