Date of Award
Master of Science in Chemical Engineering - (M.S.)
Chemical Engineering, Chemistry and Environmental Science
Dimitrios P. Tassios
Dana E. Knox
Vapor pressure depression data for CaCl2, NaI, LiBr, and LiCl were measured at a molality ranging between 0.2-7.5 depending on the solubility of the salt in ethanol. Data were also measured at 35° C for the LiCl. The apparatus used was a recirculation still of the Othmer type.
Osmotic coefficients were calculated from the total pressure of the system. The one parameter Bromley equation and the three parameter Pitzer equation were used to correlate the data. For all the systems, the Pitzer equation correlated the data better as one would expect. Mean activity coefficients were calculated graphically and from the equation parameters obtained from the nonlinear regression of the experimental osmotic coefficient data. Since experimental data were only taken to a molality of about 0.2, extrapolation to infinite dilution was necessary. This graphical technique can lead to errors of about 25% in the mean activity coefficient.
In order to determine if there was a temperature dependency in the parameters of the two equations, the literature was searched for data at other temperatures. Some data was found for the CaCl2 and NaI systems. Analysis of these data in conjunction with the data measured here indicate that: l) the Bromley "B" parameter could be represented by a simple first order polynomial in temperature and 2) no functionallity could be found between the three parameters in the Pitzer equation and temperature. This is in agreement with the findings of another study for strong electrolytes in methanol.
Czerwienski, Gregory J., "Osmotic and mean activity coefficients of CaCl2, NaI, LiBr and LiCl in ethanol at 50 degrees C" (1986). Theses. 1986.