A practical potentiometric method was applied successfully to experimental electrochemical data in order to determine the autoprotolysis constants (pKap) of water + dimethyl sulfoxide mixtures containing 0-90 % of DMSO by volume at 25° C and 0.1 M ionic strength was maintained in each mixture by NaClO4 solution. The results indicated that water-DMSO mixtures are more basic media than pure water...