Density model for sodium hydroxide–sodium aluminate solutions

The purpose of this paper is to develop a model of the densities of multi-component aqueous electrolyte solutions containing NaOH and NaAl(OH)4. Coefficients for the Laliberte–Cooper model of multi-component electrolyte solutions were developed from published density data for the NaOH–NaAl(OH)4–H2O system. The density data were split into two groups, data for parameterization and data for validation. The model was able to predict the validation data well, with an R2 greater than 0.99 for five of seven datasets and greater than 0.95 for all datasets. The model was shown to extrapolate to temperature and composition ranges outside those used for model parameterization. Similarly, using coefficients derived here for NaAl(OH)4 and published coefficients for NaOH and NaNO2, the model was shown to accurately predict the density of solutions that contain NaNO2 in addition to NaOH–NaAl(OH)4 (R2 = 0.993). This indicates that the model coefficients developed here can be incorporated into models of diverse multi-component electrolyte solutions.