Measurement and Calculation of Solubilities in the Ternary System NaCH3COO + NaCl + H2O from 278 K to 323 K

Abstract

Solubility determinations in the ternary system NaCH3COO + NaCl + H2O were performed from 278.15 K to 323.15 K. The new measurements were combined with previous measurements of osmotic coefficients at 298.15 K and activity coefficients from 298.15 K to 318.15 K. The measurements were fitted with an extended Pitzer type model to generate equations for the prediction of solubilities and activities in mixed solutions of the ternary system. The model yields accurate representation of the experimental data. Although it was found that the values of the mixing parameters in the ion interaction equations are significantly different from zero, their influence is only small. Hence, extrapolation to temperatures outside of the fitted range appears to be possible. However, due to limitations of the binary model equations for NaCl (aq) and NaCH3COO (aq) there is an upper ionic strength limit of about (15 to 18) mol·kg-1. Hence, solubility calculations are limited to temperatures below about 328 K.