On the Partitioning of the NMR B′-Coefficient. The Evaluation of Single Ion B′-Coefficients by a New Method and the Correlation with the Viscosity B-Coefficient, Partial Molal Volume and Electrostatic Entropy of Solvation of Ions in Aqueous and Nonaqueous Systems

Abstract

Abstract A new method of division used for the viscosity B-coefficient has now been extended to the partitioning of the NMR B′-coefficient both in aqueous and various nonaqueous systems. The derived set of Bi′-values, unlike those obtained by other methods in water are found to be quantitatively related to the ionic molal volumes obtained by the UVP method. The usual assumption of equal contributions of K+ and Cl− ions has been discarded. Abraham et al.’s electrostatic entropy of solvation of ions has also been found to give excellent linear correlation with the derived NMR Bi′-values in different solvents. The striking feature is that the NMR Bi′-values as derived by Abraham and coworkers by a different method are almost identical to the present values in all the nonaqueous solvents studied. The slight disagreement observed for the aqueous system has been discussed as being due to encroaching of the disordered second layer to the first layer of solvation, thereby making the absolute entropy estimates less certain. Both the cationic and anionic Bi′-values are represented by a single smooth parabolic curve against the crystal ionic radii as predicted by the theory. The hydration number for Cl− ion as derived from this work agrees excellently with the widely accepted value.