Activity coefficient of aqueous sodium bicarbonate

Abstract

The determination of the activity coefficient and related properties of sodium bicarbonate presents special problems because of the appreciable vapor pressure of CO₂ above such solutions. With the development of reliable equations for the thermodynamic properties of mixed electrolytes, it is possible to determine the parameters for NaHCO₃ from cell measurements or NaCl-NaHCO₃ mixtures. Literature data are analyzed to illustrate the method and provide interim values, hoever it is noted that further measurements over a wider range of concentrations would yield more definitive results. Lastly, an estimate is also given for the activity coefficient of KHCO₃.