In this study, a new estimation of the standard state partial molar heat capacity (Cp(0)) of three binary systems [NaCl(aq), HCl(aq), and NaOH(aq)] for temperatures ranging from (298.15 to 493.15) K is performed. From experimental data (available in the literature to date) corresponding to the apparent molar heat capacities of the above-mentioned electrolytes, a procedure based on the assumption of Pitzer's ion interaction model was applied to calculate these important Cp(0) values at a given temperature. Results obtained for each electrolyte (or ion) were correlated as functions of temperature by commonly used polynomial equations. Use of the hydrogen ion convention enabled estimates of the temperature-dependent values of Cp(0) of the individual ions Na(+)(aq), Cl(-)(aq), and OH(-)(aq). When used to calculate the temperature-dependent values of the Gibbs free energy of formation of OH-(aq), the formula for Cp(0)(7) of OH(-)(aq) given herein provides good agreement with values derived from independent measurements of the ion constant of water at elevated temperatures. In the specific case of NaCl, a considerable disagreement was observed between the estimations performed using Archer's model (Archer, D. G. J. Phys. Chem. Ref. Data 1992, 793-829) and some experimental data published years later. This fact call be explained, among other factors, by the dependence of the model parameters on the experimental uncertainty and systematic errors, which call be incurred during calorimetric experiments. For this reason, continuous revisions and updating of the proposed correlations are required when new experimental data become available.