Modeling chemical equilibrium of target compounds is of interest when controlling the pH, alkalinity or corrosivity of drinking water. As part of this approach, one must determine the contribution rates of various components to mixtures which have given (known or prescribed) chemical characteristics. In the example presented, we want to determine the concentrations of several components of phosphoric acid such that the resulting pH value is equal to 8, and the total phosphate concentration is 0.1 mols. This worksheet requires that the Global Optimization Toolbox has been added to Maple.