Isopiestic studies of thermodynamic properties of solutions of ampicillin sodium and penicillin sodium in water at T = 298.15 K

Osmotic coefficients of the solutions of ampicillin sodium and penicillin sodium in water at T = 298.15 K were measured using the isopiestic technique. The experimental osmotic coefficients have been correlated using the ion interaction model of Pitzer, e-NRTL model of Chen, NRF and a fourth-order polynomial in terms of molality. The vapor pressures of the solutions and the solvent activities have been calculated from the osmotic coefficients. Reliability of the models in expression of the osmotic coefficients were compared on the basis of standard deviation of the fittings.

► The osmotic coefficients of the solutions of ampicillin sodium and penicillin sodium in water have been measured.
► Measured osmotic coefficients were correlated using Pitzer, e-NRTL, NRF models and polynomial equation.
► Vapour pressures were evaluated from the correlated osmotic coefficients.