Measurement and Prediction of Physicochemical Properties of Liquors Relevant to the Sulfate Process for Titania Production. 1. Densities in the TiOSO4 + FeSO4 + H2SO4 + H2O System

No reliable model for the prediction of densities has been reported for the title system. Since this is partly due to conflicting experimental data available in the literature, densities in the title system have been measured by high-precision vibrating-tube densimetry over wide concentration ranges. Measurements comprise binary (single electrolyte) and mixed (ternary) acidic solutions of titanyl sulfate at (25 and 50) degrees C as well as binary, ternary, and quatemary mixtures containing iron(II) sulfate at 25 degrees C. We have found that a pro-rata additivity rule for densities applies to a series of aqueous metal sulfate + sulfuric acid mixtures at constant total sulfate concentration, based on hypothetical densities in the supersaturated concentration ranges of the binary metal sulfate subsystems. These hypothetical densities can be readily obtained by extrapolation of the properties of mixed solutions. When included in Masson-type density correlations for the binary metal sulfate systems, the resulting model resolves the reported inconsistencies in density predictions for the FeSO4 + H2SO4 + H2O system. This is the first density model that includes TiOSO4 as a component.