This book is the first part of a course on “Thermodynamics and Statistical Physics” held at present in physical and physicomathe- matical faculties of our universities. In comparison with existing courses of thermodynamics the book has the following distinctive features:1. Greater attention than in other books is devoted to a dis­ cussion of the initial propositions of thermodynamics, which en­ ables us to establish both the limitations of thermodynamics and its organic connexion with statistical physics.2. The content of the second law of thermodynamics is analysed logically and with greater consistency, by taking into account theof negative absolute temperatures.methods of thermodynamics are considered and discussedtheory of critical phenomena is expounded according to Gibbs, which enables us to establish the connexion of these pheno­ mena with phase transitions of the second kind.5. The thermodynamics of systems with negative absolute tem­ peratures is treated.6. The fundamentals of the thermodynamics of irreversible pro­ cesses are given.7. The large number of problems included in the book form an integral part of the course. Many are devoted to certain additional questions that are not always treated in the course and do not enter in the main text of the book. For these reasons the solutions of the problems are set out in as much detail as possible.