Halogenated derivatives of simple hydrocarbons, like chloro-and fluoromethanes and -ethanes, are important chemicals in many industries for example as working media in organi~ Rankine cycles and refrigerating pro cesses. Although there are ecological reasons against using these substances, it is expected that they cannot be substituted in all cases. But optimizing the processes in which these substances have to be used can also contribute to minimizing the possible damage. This book summarizes the extensive experimental material available on the thermodynamic properties of 16 pure and mixed halogenated hydrocarbons, so that it can easily be used both by process and design engineers. The project was initiated by the late Professor Dr.-Ing. Eberhard Bender and Prof. Dr.-Ing. Dr.-Ing. E.h. H.D. Baehr. We would like to express our gratitude especially to Prof. Baehr for his continuing interest and to Springer-Verlag for their patience. Besides the authors, quite a large number of students contributed to the completion of the book. Among them we are most obliged to Mr. L. Hoffmann and Mr. F. Strepp for their assistance in preparing tables, diagrams and charts. We hope that this book will prove to be useful to many colleagues, and we welcome proposals, advice, and comments.