Two-dimensional phase transitions as displayed by adsorption isotherms on graphite and other lamellar solids

An introductory review is given to the study of two-dimensional phase transitions, as most easily observed on lamellar solids. Two examples have been chosen, namely the xenon-graphite and krypton-graphite couples, which have been the subject of the most extensive and detailed studies. These illustrate the development of research in the field, providing significant and typical results leading to fundamental questions on the nature of two-dimensional phases and their transitions.