Calculation of chemical equilibrium concentrations of complexing ligands and metals A flexible computer programme taking account of uncertainty in formation constant values

Metal complexes often act as substrates in enzymic reactions. Because their concentrations cannot be measured directly, they must be calculated from the formation constants and the total concentrations of the different metal and ligand species. An iteration algorithm devised by Sayce has been used to formulate a FORTRAN (ICT 1900) programme, which meets the following requirements. (1) The programme may be made to calculate the total concentrations for the parent species if the free concentration of any metal or ligand species is known, or to calculate the free concentrations of all species for which the total concentrations are known. This feature of the programme is useful for calculation of the total amounts which must be put into a solution in order to achieve prescribed free concentrations. (2) To allow for the uncertainty in the formation constants of the complex species the programme permits the input values of the formation constants to be varied automatically and the resulting variation of the calculated concentrations to be evaluated.