Computer-Programs for Calculating Total from Specified Free or Free from Specified Total Ionic Concentrations in Aqueous-Solutions Containing Multiple Metals and Ligands

This chapter focuses on the computer programs for calculating total from specified free, or free from specified total ionic concentrations in aqueous solutions containing multiple metals and ligands. Many experiments in biology, biochemistry, biophysics, and physiology require aqueous solutions with concentrations of free cations, far below those obtainable by simply adding the corresponding salts to the solutions. Then metal buffers made up of the metallic ion (or cation) and the appropriate ligand (or anion) must be used. Similarly, living cells contain ligands, such as cation-binding proteins, that cause the total to differ from the free concentrations of metals. Ligands also bind hydrogen ions so that instead of a single complex between metal and ligand, several complexes form, corresponding to various degrees of protonation. Each has its own stability constant. Thus, apparent stability constants (Kapp) have to be calculated to characterize the multiple equilibria among one metal, one ligand, and the hydrogen ion at a given pH value. The main thrust of the present chapter is to describe a FORTRAN program named "SPECS" in such a way that it can be readily used by the largest number of investigators possible.