The binding mean spherical approximation theory is used to describe the thermodynamic properties of dicarboxylic acid salts by adding a chain term in the free energy. The dianions in these solutions are modeled as flexible charged chains composed of two, three, or four spheres. Five aqueous solutions of such salts are studied in different concentration ranges: dipotassium oxalate, disodium malonate, disodium succinate, potassium tartrate, and sodium tartrate. A description of the experimental deviations from ideality (osmotic and activity coefficients) for these salts is obtained. The model is compared with a previous one that does not include a chain contribution. It is found that the model with a chain contribution provides a more physically sound framework.