This book is part of a set of books which offers advanced students successive characterization tool phases, the study of all types of phase (liquid, gas and solid, pure or multi-component), process engineering, chemical and electrochemical equilibria, and the properties of surfaces and phases of small sizes. Macroscopic and microscopic models are in turn covered with a constant correlation between the two scales. Particular attention has been paid to the rigor of mathematical developments. This sixth volume is made up of two parts. The first part focuses on the study of ionic equilibria in water or non-aqueous solvents. The following are then discussed in succession: the dissociation of electrolytes, solvents and solvation, acid-base equilibria, formation of complexes, redox equilibria and the problems of precipitation. Part 2 discusses electrochemical thermodynamics, with the study of two groups: electrodes and electrochemical cells. The book concludes with the study of potential-pH diagrams and their generalization in an aqueous or non-aqueous medium.