SOLVENT ISOTOPE EFFECT ON THE VISCOSITY COEFFICIENT-B FOR MONOVALENT IONS IN WATER AT 25-DEGREES-C AND 40-DEGREES-C

For heavy water solutions of LiCl, NaCl, KCl and CsCl at 24 and KI at 25-degrees-C the values of B(M+) and B(X-) in the equation eta/eta-0 = 1 + A square-root c + [B(M+) + B(X-)] c were determined under the conventional assumption B(K+) = B(Cl-). Here eta-0 is the viscosity of the solvent and c the molarity. The solvent isotope effect on the B values was found to be small. The B values for the medium-sized ions K+, Cs+, Br-, and I- were systematically more negative in heavy water than in light water. This is consistent with the idea that negative B values indicate the ability of the ion to break the structure of the water, the structure of heavy water being more developed than that of light water. For the tetraalkylammonium ions, Me4N+, Pr4N+, and Bu4N+, on the other hand, the solvent isotope effect was small and random irrespective of the ion size. The temperature coefficients of B for the monatomic ions in heavy water were the same as for those in light water.