Computation of physicochemical parameters, inter alia, pH, in complex (bio)chemical systems

Generic equations and algorithms are derived to compute, in complex (bio)chemical systems at equilibrium, the following physicochemical parameters: pH (or the concentration of any chemical species), partitions between acid and base forms, global charge, molar mean charges, ionic strength, and molar mean contributions to ionic strength. The model only requires the knowledge of existing thermodynamic constants and of the composition of the system in chemical species as the sum of the different forms other than the species under examination. It takes ionic strength aspects into consideration. Several innovations simplify the computation process: use of polyacidity constants, generalized expression of molar parameters, computation of global parameters from molar mean contributions, simplified corrections for activity, and easy iterative process for pH determination. The model always elicites a unique equilibrium state, namely, it always yields a unique pH value. Computed values always agreed with experimental measurements, thereby validating the model. Digital computer programs were prepared to use the proposed algorithms, which are also a very simple and easy way, compared to the available mathematical descriptions, to solve the problem “manually” without computer facilities.