Experimental measurement and modelling of KBr solubility in water, methanol, ethanol, and its binary mixed solvents at different temperatures

• Author(s): Pinho, Simão ; Macedo, Eugénia A.
• Date: 2002
• Persistent ID: http://hdl.handle.net/10198/1741
• Origin: Biblioteca Digital do IPB
• Subject(s): Salt; Solubility; Mixed solvent; UNIQUAC
• Document Type: Journal article
• Language: English
• Contributor(s): Biblioteca Digital do IPB

Description

A simple and accurate apparatus has been designed to measure the solubilities of potassium bromide by an analytical method. Salt solubility data have been measured in water, methanol, ethanol, (water + methanol), (water + ethanol), and (methanol + ethanol) solvents in the temperature range between 298.15 K and 353.15 K. A new formulation is presented for the calculation of salt solubility in pure and mixed solvents as a function of the temperature and solvent composition. This formulation is based on the symmetric convention for the normalization of the activity coefficients for all species in solution, and makes possible direct access to the solubility product of the salt in terms of its thermodynamic properties. The new solubility data measured in this work, as well as experimental information from the open literature, are used to estimate the interaction parameters of the two models proposed here. One model combines the original Universal Quasi Chemical (UNIQUAC) equation with a Pitzer–Debye–Huckel expression to take into account the long-range interaction forces; the other model only considers the short-range forces through the UNIQUAC equation with linear temperature dependent salt/solvent interaction parameters. Both models correlate satisfactorily the solubility data, although temperature and electrostatic effects are both very important in this type of equilibrium. Finally, some conclusions are drawn concerning the models versatility to represent other type of equilibrium data and prediction capabilities.