Within the last two decades, the experimental technology for the study of high temperature solid-vapor and liquid-vapor equilibria has mushroomed so fast that· both academic and industrial research­ ers desirous of working in this field — be they physical chemists, metallurgists, ceramists, petrologists, crystal chemists, or mem­ bers of any of the several branches of materials science — find themselves in the situation that in order to learn the art of the latest techniques, a period of apprenticeship or residency needs be spent at an institution or laboratory currently engaged in this type of solid-vapor or liquid-vapor research. The tech­ niques for control of the vapor phase at total pressures of one atmosphere or greater have not been well defined in the literature. Therefore, the purpose of this volume will be to serve as a labora­ tory manual for the control, calibration, and measurement of high temperature-high pressure equilibria. The avowed aims of this treatment of experimental techniques are: (1) to give, in terms understandable at the graduate student level, the laboratory procedures necessary to the design and utilization of good experimental technique, (2) to list the limitations, dangers, and technical pitfalls inherent or intrinsic to the described techniques, (3) to give theory and specific data only where they are essential to the experimental design, (4) to give with each chapter references that are extensive enough to serve as a bibliography of the state-of-the-art of technique development within the last decade.