Structure of aqueous solutions. A librational band study of hydration in solutions containing dipositive and tripositive metal ions

Abstract

The librational band of water has been studied in aqueous solutions of the nitrates and chlorides of Mg^II, Ca^II, Sr^II, Co^II, Ni^II, Cu^II, Zn^II, Pb^II, La^III, Al^III, Cr^III, Th^IV. The contribution due to coordinated water has been separated from the remainder of the band and the band frequency is found to be proportional to the hydrolysis constant (*K₁) for the reaction

                [M(OH₂)₆]ⁿ⁺ → [M(OH₂)₅OH]^(n-1)++H⁺

The metal-oxygen stretching frequency has also been identified and is found to show a similar relationship to *K₁. Changes noted between solutions containing nitrate and chloride anionic species are discussed in terms of solution structure.