Solubility and Volatility of MoO3 in High-Temperature Aqueous Solutions

Abstract

The thermodynamic properties of the neutral molybdic acid H2MoO4 are evaluated at 273–623 K and the saturated water vapor pressure from our own solubility data at 563–623 K and literature results at lower temperatures. Combining the Gibbs energies of H2MoO4 in the state of the aqueous solution with those in the ideal gas state, we calculated Henry’s constants and the vapor–liquid distribution constants of H2MoO4 at 273–623 K, and with the use of the relevant asymptotic relations, extrapolated values of Henry’s constants, \(k_{\text{H}}\), and vapor–liquid distribution constants, \(K_{\text{D}}\), toward the critical point of pure water. Our results show that over the whole temperature range of the existence of the vapor–liquid equilibrium of water, the neutral molybdic acid H2MoO4 is somewhat less volatile compared with Si(OH)4, and the difference in volatility of these species decreases with the temperature.