Chapter 3 - Properties of Mixtures with Water

Abstract

Abstract Most of the applications of water at high temperatures use the interaction of water with other compounds, as in chemical reactions, extraction processes, hydrothermal processes, and others. Properties of mixtures of water with other compounds must be known for these processes. Water at ambient conditions readily dissolves salts and is not miscible with nonpolar components like hydrocarbons. At supercritical conditions, the solvent power of water for ionic species is dramatically reduced. On the other hand, supercritical water and hydrocarbons become completely miscible. This behavior of aqueous mixtures is discussed in this chapter for major groups of compounds, such as gases, hydrocarbons, volatile and nonvolatile electrolytes, and metal oxides. For aqueous mixtures, thermodynamic properties are discussed in general and for excess volumes. Influence of salts on dissociation of water is discussed. Transport properties like electric conductivity, diffusion, viscosity, and thermal conductivity of aqueous mixtures are important for designing hydrothermal processes and are reviewed. A major part of this chapter is the discussion of phase equilibria with water. A systematic classification of equilibrium behavior is presented. Modeling of phase behavior and solubility with simple equations of state is shown to describe the phase behavior of aqueous systems for a wide range of conditions. Solubility of gases in water is treated for many cases with Henry's law and its modifications. For the description of phase behavior with electrolytes, chemical reactions of ions with water are covered. Aqueous mixtures of inert gases and hydrocarbons with water, phase behavior and solubility of volatile electrolytes, nonvolatile electrolytes, metal oxides, and salts are treated in this chapter. The solubility of metal oxides in hydrothermal and supercritical water as the basis for hydrothermal processes leading to monocrystals and functional nanoparticles is also treated in this chapter.