L Yousefi - Islamic Azad University, branch of Islamshahr.

In this work, calculation of saturation molality in saline solutions was used in calculating of the mean ionic activity coefficients (MIAC) of electrolytes for a number of single salt electrolyte solutions at atmospheric pressure, and temperatures in the range of 20 and 80 °C. MIAC wascomposed of two parts: a) the long - range electrostatic interaction contribution. b) The short -range electrostatic interaction contribution. Long range (MIAC), was represented by Pitzer-Debye - Hückel, model and pitzer interaction parameters. Modified UNIFAC Dortmund model was used for calculation of short range (MIAC), interaction parameters between solvent group (H2O) and ions groups (Na+,Ca+2,Cl ,SO4 2) have been estimated.

Electrolyte solutions; Activity coefficients; Saturation molality; Adjustable parameters