Apparent molar volumes V-phi and apparent molar heat capacities C-p,C-phi have been determined for aqueous citric acid and its mono-, di, and tri-sodium salts at the pressure p = 0.35 MPa and at temperatures 278.15 less than or equal to T/K less than or equal to 393.15. Densities were measured using a vibrating-tube densimeter (DMA 512, Anton Paar, Austria) at the pressure p = 0.35 MPa and at temperatures 278.15 less than or equal to T/K less than or equal to 368.15. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.01 less than or equal to m/(mol . kg(-1)) less than or equal to 1.0. Heat capacities of these same solutions were measured using a twin fixed-cell, differential-output, power-compensation, temperature-scanning calorimeter (NanoDSC model 6100, Calorimetry Sciences Corporation, Spanish Fork, UT, U.S.A.) at the pressure p = 0.35 MPa and at temperatures 278.15 less than or equal to T/K less than or equal to 393. Equations to describe the (m, T, V-phi) and (m, T, C-p,C-phi) surfaces of each solute were obtained by regression. Using these equations we calculated the surfaces (in, T, Delta(r)V(m)), (m, T, Delta(r)C(p,m)), (m, T, Delta(r)H(m)), (m, T, pQ(a)), and (m, T, Delta(r)S(m)) for each of the three-proton dissociation reactions of aqueous citric acid. The Delta(r)H(m) and pQ(a) surfaces were calculated for each proton dissociation reaction by integration using our (m, T, Delta(r)C(p,m)) results with the molality dependence of Delta(r)H(m), and pQ(a) for each reaction at T = 298.15 K obtained from the literature. Corrections for the partial dissociation and/or hydrolysis of each citrate species were applied in these calculations.