The textbook (Volume 2 of the standard work by Stephan/Mayinger) presents the material in a scientifically rigorous yet always very illustrative manner. Numerous practical exercises facilitate understanding. P. Stephan and K. Schaber have revised and updated the 15th edition. To enhance the understanding of the phenomena of phase behavior, the phase diagrams have been placed before the calculation methods of mixture thermodynamics. Additionally new: thermodynamic fundamentals of spontaneous phase transitions and a chapter on electrolyte solutions.