The one-stage multilinear regression method previously applied to the analysis of emf data for aqueous electrochemical cells as a function of temperature and solute concentration has been extended to the analysis of emf data for the cell: Pt|H 2|HCl ( m), CH 3OH( x), H 2O (1 − x) | AgCl|Ag as a function of methanol mole fraction ( x) as well as solute molality ( m) and temperature. In this way discrepancies between various sets of data are revealed and the consistent set of data for the standard potential of the cell so obtained can be used for the evaluation of thermodynamic acid dissociation constants and standard reference pH values in this important, much studied mixed aqueous solvent system.