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This is a collection of papers by Eli Ruckenstein devoted to the application of the Kirkwood-Buff theory of solutions to binary and multicomponent liquid mixtures. It is the first time ever these applications have been collected in book form.

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This book consists of a number of papers regarding the thermodynamics and structure of multicomponent systems that we have published during the last decade. Even though they involve different topics and different systems, they have something in common which can be considered as the "signature" of the present book. First, these papers are concerned with "difficult" or very nonideal systems, i. e. systems with very strong interactions (e. g. , hyd- gen bonding) between components or systems with large differences in the partial molar v- umes of the components (e. g. , the aqueous solutions of proteins), or systems that are far from "normal" conditions (e. g. , critical or near-critical mixtures). Second, the conventional th- modynamic methods are not sufficient for the accurate treatment of these mixtures. Last but not least, these systems are of interest for the pharmaceutical, biomedical, and related ind- tries. In order to meet the thermodynamic challenges involved in these complex mixtures, we employed a variety of traditional methods but also new methods, such as the fluctuation t- ory of Kirkwood and Buff and ab initio quantum mechanical techniques. The Kirkwood-Buff (KB) theory is a rigorous formalism which is free of any of the - proximations usually used in the thermodynamic treatment of multicomponent systems. This theory appears to be very fruitful when applied to the above mentioned "difficult" systems.

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The Kirkwood-Buff integrals and their applications to binary and ternary solutions.- Supercritical mixtures.- Solubility of gases in mixed solvents.- Solubility of pharmaceuticals and environmentally important compounds.- Aqueous solutions of biomolecules.- Water and dilute aqueous solutions.

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Eli Ruckenstein has won many notable awards, including the Foundes Award from the American Institue of Chemical Engineers, the National Academy of Engineering Founders Award, and the National Medal of Science.

His interests include transport phenomena, catalysis, colloids and interfces, phase transformations, thermodynamics, and materials.

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