Molten salts, slag and glasses comprise an interesting class of high temperature ionic melts of enormous theoretical as well as practical importance. Molten salts are of primary interest to high temperature chemists whereas process metallurgists are often interested in pyrometallurgical slags. The glassmaking industry needs to understand molten glasses. Unfortunately, experts in any one of these areas are often unfamiliar with concepts developed in other areas which may be of great relevance. The present text is an attempt to bridge the gap. Theories concerning the nature and properties of these liquids, structure property relations, basic thermodynamics and its application are discussed. A second feature of the book relates to brief discussions on various physic-chemical experimental techniques employed to study these systems. The third feature of the book is discussion of some industrial processes that employ these systems. It will be of interest to students of chemistry and metallurgy and as reference material for persons in industry, particularly those interested in process metallurgy and glassmaking.