The influence of the pH at the electrode/solution interface on precipitation by means of electrochemistry was studied both theoretically and experimentally in pure calcocarbonic aqueous solutions. This interfacial pH was measured at the electrode by using a pH sensor-grid assembly in a submerged impinging cell. A model which takes into account the electrochemical oxygen reduction and the chemical dissociation of hydrogen carbonate and carbonic acid is proposed to calculate the pH at the electrode/solution interface. It can reproduce the data using values of adjustable parameters obtained from experiments. Hence, the local concentrations of and the supersaturation coefficient, β, were determined at the electrode. These data were used to interpret precipitation on a gold electrode.