A study of ion-solvent interaction in aqueous Al(III), Y(III) and La(III) nitrate solutions

Abstract

The apparent molar compressibility j_K of aqueous solutions of aluminum, yttrium and lanthanum nitrates have been determined from ultrasound velocity and density measurement at 200^oC. The values of jK have been extrapolated to infinite dilution and from the data j_K⁰ the total hydration numbers Z₀ for investigated solutions were obtained. The variation of apparent molar compressibility at concentration 0.4 mol/l versus parameter z²/r (z-valency of metal, r-radius of cation) is presented. This dependence is nonlinear, so the ion-solvent interaction cannot be explained simply by the electrostatic field theory. That may be due to individual chemical nature of the investigated cations. The partial molar volumes `V⁰_Me(III) were calculated for individual cations. The volume change DV⁰_Me(III) for water causes by ion - solvent interactions are discussed. The assumption is made that nonlinear dependence of the values DV⁰_Me(III) against an atomic number is conditioned by the different water exchange mechanism for individual cations.