The electric conductivities of aqueous solutions of sodium salts of benzoic acid, m-salicylic acid, and p-salicylic acid were measured in the temperature range from T = (278.15 to 313.15) K and in the concentration range c = (approximate to 2.10(-4) to approximate to 5.10(-3)) mol.dm(-3). The data were analyzed with Barthel's low-concentration chemical model yielding the limiting molar conductivity, Lambda(infinity) (T), and the association constant, K(A)(T). Using the known data of the limiting conductivities of sodium ion the limiting conductivities of the anions were evaluated, and their hydrodynamic radii in water were estimated. From Lambda(infinity)(T) the Eyring activation enthalpy of charge transport was determined and found to be higher than the corresponding value for viscous flow of water. Practically the total dissociation of the investigated salts in water is evident, and considerable differences in the anion mobilities are observed. They are discussed in terms of diffusivity and permeability of related acids at different carrier systems.