th The technologyoffroth flotation, invented in the early 20 century was first used for the concentration ofsulfide minerals. Since then it has been applied for the processing of many nonsulfide ores as well, including oxides, carbonates, silicates, soluble minerals like halite and sylvite and energy minerals like coal and bitumen. In recent years it has been used for several nonmineral applications, such as waste water treatment, deinking ofpaper for recycling and resource recovery from industrial wastes he technology continues to grow with new applications reportedevery year. Flotation is based on chemical phenomena occurring at the interfaces, solid/water and air/water. Surface Chemistry principles have played a significant role in the development of flotation technology. Knowledge ofaqueous solution chemistry and electrochemistry has added to our understanding ofthe reactions in flotation systems. ProfessorJan Leja's bookhas well served researchers and students as theytried to understand the chemistry of flotation, and it is a significant contribution to the advancement ofknowledge. However, since the book was first published, new research techniques and ever growing information have made an update necessary. The revised edition compiled by Dr. S. R. Rao has brought together fundamental aspects ofthe chemistryofflotation and how they apply to practical systems. It should serve all who are working in the area of flotation and interested inexploring new applications offlotation technology.