A compact computer code for ion speciation in aqueous solutions based on a robust algorithm

We developed a compact computer code for calculating ion speciation in aqueous solutions based on an algorithm reported by Leung et al. (Talanta, 35, 713– 718 (1988)). The program reads a set of analytical data of pH, total component concentrations, and the atmospheric CO₂pressure and iteratively calculates activities and concentrations of the components and complexes. In the present version of the program, only 14 components and 41 derived species are considered, but the number and kind of species can easily be changed simply by rewriting a file for inputting the number and names of species, stoichiometric coefficients of complexation reactions, and their equilibrium constants. The solution converged within a relative error of 0.01% usually after 8 iterations.