Autoprotolysis constants and standardization of pH measurements in tetrahydrofuran-water mixtures

Standard emf for the cell Pt/Ag/AgCl/HCl in THF-water/GE (glass electrode) in tetrahydrofuran-water mixtures containing 0-70% (w/w) of tetrahydrofuran and values of the autoprotolysis constants, K-ap, of these media were obta ined. The influence of variations in the solvent composition on pK(ap) valu es was evaluated. The resulting equations enables us to determine pK(ap) va lues in any tetrahydrofuran-water mixture, and thus permit one to establish the pH scale in these mixtures. The quasilattice quasichemical (QLQC) theo ry of preferential solvation was applied to obtain the degree of preferenti al solvation of hydrogen ions in these media, in order to explain the varia tion of the pK(ap) values obtained in the tetrahydrofuran-water mixtures st udied.