Data processing for the determination of stability constants

In the process of extracting values for stability constants from experimental measurements, two types of variables, logarithmic (such as log[X] and log K) and linear (such as [X] and CX), must be handled in the chemical speciation calculation. This makes it difficult for us to assess the reliability of complex speciation distribution and to evaluate errors in the stability constants propagated from the errors in the measurements. To overcome this difficulty, two calculation tools, (i) non-linear least-squares program and (ii) tableau-solver formulation, were developed and implemented in commercial spread sheet software. The former directly correlates the random and statistical errors in the data with those in the estimated stability constants, whereas the latter simulates the equilibrium for a set of given total concentrations of the metal and ligand with the values of stability constants. (authors)