Physical Chemistry: An Advanced Treatise, Volume I: Thermodynamics deals with the applications of thermodynamics to mixtures, fluids, and solid systems at high pressures and temperatures, critical phenomena, practical handling of coupled gas equilibriums, and matter in electric, magnetic, and gravitational fields. This book begins with a survey of basic laws, followed by discussions on questions of stability, irreversible processes, surfaces, the third law, and a short introduction to Caratheodory's axiomatic foundation. The zeroth law of thermodynamics, gaseous mixtures, internal equilibrium in solids, thermodynamic properties of the mixture, and theory of linear differential forms are also elaborated. This publication presents a comprehensive treatment of physical chemistry for advanced students and researchers.