Activity Coefficient Determination for the Ternary Systems CsCl in N-Methylformamide or Urea plus Water Mixtures at T=298.15 K

The mean activity coefficients for CsCl in N-methylformamide or urea (w) + H2O (1 - w) systems were determined in this work by potentiometry, using ion-selective electrodes at 298.15 K. The value of mass fraction w was varied between 0.00 and 0.40 in five unit-steps and the molality of CsCl was between 0.0020 and 1.4009 mol center dot kg(-1). The experimental data have been correlated with the Pitzer, modified Pitzer and the extended Debye-Huckel equations. The resulting values of the mean activity coefficients, the osmotic coefficients and the standard Gibbs energy of transfer, together with the Pitzer ion-interaction parameters (beta ((0)), beta ((1)) and C (phi)), extended Debye-Huckel parameters (a, c and d), and modified Pitzer parameters (b, B (MX), C (MX)) are reported for the investigated systems.