FTP, name this dimensionless value, a thermodynamic correction for mole fraction, symbolized a.
This parameter's change with temperature is given by the difference in the molar enthalpy of the pure substance and its partial specific enthalpy in solution divided by the square of the kinetic temperature.  For solutions of high ionic strength, expressions like the Pitzer and Meissner equations may be used to estimate the values of the namesake coefficient that enables its calculation, though at lower concentrations the Debye-H?ckel equation is more useful.  For ideal gases, it is defined as the exponential of the standard-reference potential divided by the kinetic temperature, and for pure condensed phases it is unity.  FTP, name this dimensionless value, a thermodynamic correction for mole fraction, symbolized a.
This parameter's change with temperature is given by the difference in the molar enthalpy of the pure substance and its partial specific enthalpy in solution divided by the square of the kinetic temperature.  
chemical activity