We believe this to be the first monograph devoted to the physicochemical properties of solutions in organic solvent systems. Although there have 1 been a number of books on the subject of non-aqueous solvents - 4, they have been devoted, almost entirely, to inorganic solvents such as liquid ammonia, liquid sulphur dioxide, etc. A variety of new solvents such as dimethylformamide, dimethylsulphoxide and propylene carbonate have become commercially available over the last twenty years. Solutions in these solvents are of technological interest in connection with novel battery systems and chemical synthesis, while studies of ion solvation and transport properties have fostered academic interest. This monograph is primarily concerned with electrolytic solutions although discussion of non-electrolyte solutions has not been excluded. We have deliberately omitted consideration of the important area of solvent extraction, since this has been adequately covered elsewhere. Our contributors were asked to review and discuss their respective areas with particular reference to differences in technique necessitated by use of non-aqueous solvents while not reiterating facts well-known from experience with aqueous solutions. We have striven to build their contributions into a coherent and consistent whole. We thank our con tributors for following our suggestions so ably and for their forebearance in the face of our editorial impositions.