Data base on ionization and Henry's law constants up to 673 K are presented by temperature dependent equations for volatile, weak electrolyte water pollutants; ammonia, carbon dioxide, hydrogen sulfide, sulfur dioxide and hydrogen cyanide. In the fitting of ionization constants, various recent sources of experimental isothermal data are mainly utilized, however, Henry's constants are correlated by two steps : first the vapor pressures, the partial molar volumes at infinite dilution, and the vapor and liquid phase nonidealities based on the vapor-liquid equilibrium conditions are calculated from P-T-x data. And then the calculated Henry's constants at different isotherms are treated as a function of temperature. Both correlations reproduce actual data accurately up to high temperatures for reliable phase equilibrium calculations.