Water And Aqueous Solutions At Subzero Temperatures

This Volume, the last of the series, is devoted to water in its metastable forms, especially at sub-zero temperatures. The past few years have wit nessed an increasing interest in supercooled water and amorphous ice. If the properties of liquid water in the normal temperature range are already eccentric, then they become exceedingly so below the normal freezing point, in the metastable temperature range. Water can be supercooled to -39°C without too much effort, and most of its physical properties show a re markable temperature dependence under these conditions. Although ade quate explanations are still lacking, the time has come to review available knowledge. The study of amorphous ice, that is, the solid formed when water vapor is condensed on a very cold surface, is of longer standing. It has achieved renewed interest because it may serve as a model for the liquid state. There is currently a debate whether or not a close structural relation ship exists between amorphous ice and supercooled water. The nucleation and growth of ice in supercooled water and aqueous solutions is also still one of those grey areas of research, although these topics have received considerable attention from chemists and physicists over the past two decades. Even now, the relationships between degree of supercooling, nucleation kinetics, crystal growth kinetics, cooling rate and solute concentration are somewhat obscure. Nevertheless, at the empirical level much progress has been made, because these topics are of considerable importance to biologists, technologists, atmospheric physicists and gla ciologists.

The International Association for the Properties of Water and Steam (IAPWS) has produced this book in order to provide an accessible, up-to-date overview of important aspects of the physical chemistry of aqueous systems at high temperatures and pressures. These systems are central to many areas of scientific study and industrial application, including electric power generation, industrial steam systems, hydrothermal processing of materials, geochemistry, and environmental applications. The authors’ goal is to present the material at a level that serves both the graduate student seeking to learn the state of the art, and also the industrial engineer or chemist seeking to develop additional expertise or to find the data needed to solve a specific problem. The wide range of people for whom this topic is important provides a challenge. Advanced work in this area is distributed among physical chemists, chemical engineers, geochemists, and other specialists, who may not be aware of parallel work by those outside their own specialty. The particular aspects of high-temperature aqueous physical chemistry of interest to one industry may be irrelevant to another; yet another industry might need the same basic information but in a very different form. To serve all these constituencies, the book includes several chapters that cover the foundational thermophysical properties (such as gas solubility, phase behavior, thermodynamic properties of solutes, and transport properties) that are of interest across numerous applications. The presentation of these topics is intended to be accessible to readers from a variety of backgrounds. Other chapters address fundamental areas of more specialized interest, such as critical phenomena and molecular-level solution structure. Several chapters are more application-oriented, addressing areas such as power-cycle chemistry and hydrothermal synthesis. As befits the variety of interests addressed, some chapters provide more theoretical guidance while others, such as those on acid/base equilibria and the solubilities of metal oxides and hydroxides, emphasize experimental techniques and data analysis. - Covers both the theory and applications of all Hydrothermal solutions - Provides an accessible, up-to-date overview of important aspects of the physical chemistry of aqueous systems at high temperatures and pressures - The presentation of the book is understandable to readers from a variety of backgrounds

The Definitive Reference for Food Scientists & EngineersThe Second Edition of the Encyclopedia of Agricultural, Food, and Biological Engineering focuses on the processes used to produce raw agricultural materials and convert the raw materials into consumer products for distribution. It provides an improved understanding of the processes used in

This report documents a FORTRAN version of the Spencer-Moller-Weare chemical thermodynamic model for aqueous electrolyte solutions at sub-zero temperatures (FREZCHEM). FREZCHEM is structured to predict the chemical composition and unfrozen water of aqueous solutions between -60 deg and +25 deg C at atmospheric pressure (0.101325 MPa). FREZCHEM includes two reaction pathways: freezing at variable temperature and fixed total water and evaporation at variable water and fixed temperature. Activity coefficients and the activity of water are calculated using the Pitzer equations, which are valid to high solution ionic strengths (approx. 20 mol k-1). Fifteen chloride and sulfate salts of sodium, potassium, calcium, and magnesium are included in the model. Predicted and experimental measurements of solute molalities and the unfrozen water fraction during sea water freezing are in good agreement. At -50 deg C, 0.3 % of sea water remains unfrozen with 99.7% of Na and 95.5% of Cl having precipitated into one of four salts. FREZCHEM should find many applications in physicochemical studies of aqueous solutions and freezing.