Densities and speed of sound of dilute aqueous solutions of three sodium sulfonamides structurallyrelated, namely, sodium sulfadiazine (NaSD), sodium sulfamerazine (NaSMR) and sodium sulfamethazine (NaSMT) were measured as a function of molal concentration at various temperatures (278.15-308.15) K. Standard molar quantities and related properties were calculated and the results were interpreted in terms of structural effects, and solute-solvent interactions. Results suggest that these sulfonamides are acting as structure makers of the water-structure. (C) 2017 Elsevier Ltd.