Abstract: ~(23)Na~+ chemical shifts of NaBPh_4 in mixed solvents of CH_3OH-CH_3COCH_3, CH_3OH-CH_3CN, DMSO-DMF, DMSO-HCONH_2 were measured. By means of isosolvation point the solvating abilities were compared. Meanwhile the data were treated quantitatively to obtain a geometric equilibrium constant, K~1/n, and the free energy of preferential solvation, △G/n, as outlined by Covington. According to the results, the relative solvating abilities of the solvents were found to be: CH_3OH>CH_3COCH_3>CH_3CN, DMSO=HCONH_2>DMF by iso-solvation point and DMSO>HCONH_2>DMF by ΔG/n.
The order indicates that the solvating ability of one solvent in binary mixture depends not only on its own nature, but also on character of cosolvent and structure of binary mixture.