Corrosion and scale formation in water distribution systems are generally controlled by pH adjustment. The proper pH depends on the calcium and alkalinity concentrations, but is also affected by formation of certain complexes. If a portion of the calcium and a portion of the alkalinity or carbonate are complexed, this would reduce the concentrations of free ions effective at equilibrium, and make the true pHs higher than that calculated from the gross concentrations found by analysis. The specific objective of this project was to evaluate the dissociation constants for these complexes so that the optimum pH can be more accurately calculated. The dissociation constants of interest were those of the complexes formed by the calcium and magnesium ions with the carbonate, bicarbonate, and hydroxide anions.