Osmotic coefficient data for NaOH–NaCl–NaAl(OH)4–H2O system measured by an isopiestic method and modeled using Pitzerʹs model at 298.15 K

Osmotic coefficient data were obtained for the aqueous solutions of NaOH–NaCl–NaAl(OH)4. The solutions were prepared by dissolving AlCl3·6H2O in aqueous NaOH solutions. The osmotic coefficients of the solutions were measured by an isopiestic method at 25°C. The osmotic coefficient data were used to evaluate the unknown binary and mixing parameters of Pitzerʹs model for the aqueous NaOH–NaCl–NaAl(OH)4–H2O system. The binary Pitzerʹs parameters, β(0), β(1), and Cφ, for NaAl(OH)4 were found to be −0.0083, 0.0710, and 0.00184 respectively. These binary parameters were obtained from the data on the ternary system. This was necessary since it was not possible to prepare a single (NaAl(OH)4) solution. The mixing parameters, ΘOH−Al(OH)−4, ΘCl−Al(OH)−4, ΨNa+OH−Al(OH)−4, and ΨNa+Cl−Al(OH)−4 were found to be −0.2255, −0.2430, −0.0388, and 0.2377 respectively. The experimental osmotic coefficient data were correlated well with Pitzerʹs model using the parameters obtained.