The Study of Activity Coefficients on the Ternary System of NaCl-KCl-H2O at 35℃

That the activity coefficient of mixed electrolyte solution is determined using ISE has become a simple and practicable method. There are a lotofNa+、K+、Cl-、SO42-and a little Ca2+in the seawater and saline. The study of these ionic mean activity coefficients is very important in the designing and exploiting technology for the industry of producing salt, seawater desalinization and so on. The object of this text is the ternary system of NaCl-KCl-H2O at 35℃. The experiment device of determining the ionic average activity coefficients of electrolyte solutions has been set up. The electromotive force of pure NaCl and KCl aqueous solution has been determined using the ion selective electrode at 35℃. The electrode constants have been regressed. The mean relative error about the activity coefficient of KCl solution is 0.9% between the calculated value of Pitzer equation and the calculated value of regression. The mean relative error about the activity coefficient of NaCl solution is 1.5% between the calculated value of Pitzer equation and the calculated value of regression. The linearity connection of the electromotive force vs the logarithm value of activity is very good within the experiment concentration. This indicates the determination method and the experiment equipment are reliable and the determined data are believable. The ionic average activity coefficients of NaCl and KCl have been determined in the ternary mixture systemofNaCl-KCl-H2O at 35℃ using the ion selective electrode. The concentration of the mixed electrolyte solutions is 0.1~1.5 mmol/L in six groups altogether. The interaction parameters of the Pitzer equation have been regressed. The maximal relative error between the experiment value and the calculated value is 5.6% and the mean relative error is 2.3%.