A Method for Numerical Calculation of Equilibrium Composition in Multicomponent Aqueous Solutions

A numerical method for the calculation of equilibrium composition in multicomponent aqueous solutions has been developed. With this method the independent components are parted from the total equilibrium components in the system and the equilibrium relations of the dependent components are experessed by the independent components only. Combining the equilibrium relations with the mass and charge balance equations, the fundamental equations for calculating the equilibrium composition are reduced to the number of independent components. These non-linear simultaneous equations can be solved easily by the Newton-Raphson technique. The H-Na-Cl-PO4 aqueous system was chosen as an example. The calculated values of the pH and electric conductivity of the aqueous solutions are compared with the experimental values. The features of this method can be expressed as follows. 1) The method is applicable to a wide range of multicomponent aqueous systems. 2) Concentrations of all components at equilibrium can be easily obtained. 3) Physical properties, such as ionic strength and electric conductivity, can be calculated effectively.