Equilibria phenomena are of central importance to solvent-extraction science. Such phenomena have been investigated for many decades. Two primary methods are employed in studying solvent-extraction equilibria-graphical methods (slope analysis) and numerical methods (computer modeling). Despite the widespread availability of computers, graphical methods are still extensively used. A few years ago, we introduced a Visual Basic Application for Microsoft Excel (registered) designed for analyzing solvent-extraction equilibria (Lumetta et al. 1999). This program was named the SX Solver. The SX Solver program takes advantage of the graphical user-interface of Excel(registered), so it is designed to be user-friendly. However, the initial version of the SX Solver had several limitations. The program has been upgraded to overcome many of these. The latest version contains the following enhancements: Activity coefficients for mixed electrolyte systems can be calculated; the coextraction of acid with the metal ion can be included in the model; aqueous-phase metal complexation can be incorporated into the model; and in addition, minor enhancements to the user interface have been introduced.