Mean activity coefficients in the NaCl-NH4HCO3-H2O system at 293.15-308.15K

The mean activity coefficients of NaCl in the NaCl-NH4HCO3-H2O system, meas ured by an electrochemical cell using ion-selective electrodes, were used t o calculate the mean activity coefficients of NH4HCO3 in the system through a thermodynamic model. The measurements were made at four temperatures fro m 293.15 to 308.15 K up to 1.8 mol kg(-1), at NH4HCO3 molality fractions of 0.2 and 0.4. Both sets of values agree with those obtained from Pitzer equ ation incorporated with chemical reactions. This observation supports the a pplicability of the existing parameters for calculating mean activity coeff icients of this system. (C) 2001 Elsevier Science B.V. All rights reserved.