Solution vapor pressure, regression

To use the ECES system, activity coefficient data for FeCl2 had to be developed. A recent paper by Susarev et al (15) presented experimental results of the vapor pressure of water over ferrous chloride solutions for temperatures from 25 to 100°C and concentrations of 1 to 4.84 molal. This data was entered into the ECES system in the Data Preparation Block with a routine VAPOR designed to regress such data and develop the interaction coefficients B, C, D of our model. These results replaced an earlier entry which was based on more limited data. All other data for studying the equilibria in the FeCl2-HCl-H20 system was already contained within the ECES system. 

The principal interests in this study are osmotic and activity coefficients of NaCl(ac ) and KCl(aq) solutions at temperatures to 350°C and up to saturation concentration. In the range 25-300 C and at 1 bar or saturation pressure, NaCl(aq) osmotic coefficients up to 4 m were taken from a comprehensive thermodynamic treatment of Pitzer et al. (9). Above 4 m, the values were taken from Liu and Lindsay (39). At temperatures above 300°C, osmotic coefficients were calculated from vapor pressure data of Wood et al. (4. Additional vapor pressure data are given in Refs. 41-47, but a critical evaluation of these data indicated that these are less precise measurements and were therefore given smaller weights in the regression. For KCl(aq), osmotic coefficients to 6 m at temperatures from 25-325 C at 1 bar or saturation pressure were taken from the ion interaction model of Pabalan and Pitzer (9). Additional values up to 350 C and saturation concentration were derived from Refs. 40,41, and 48. 

---