Non-Aqueous Solutions is a collection of papers presented at the Fourth International Conference on the same subject. One paper presents the application of far- and mid-infra-red, Raman, alkali metal n.m.r. and 35C1 n.m.r. techniques to the study of electrolyte solutions in non-aqueous solvents. The paper notes that spectroscopic techniques can be very useful in the elucidation of the structure of electrolyte solutions. Both the vibrational spectroscopy and particularly the alkali metal n.m.r. are very sensitive probes of the immediate chemical environment of ions in solutions. Another paper points out that the energy change associated with the solvation of ions can be represented as the sum of two energy terms; firstly, from the dielectric polarization of the solvent molecules in the continuous dielectric medium; and secondly, due to specific ion-solvent interactions in the inner solvation shells of the ions. The energy contribution of the latter is minimal but can show comparatively large differences in various types of solvents. Another paper describes the chemistry of solutions in highly associated strong protonic acid solvents, including sulphuric acid, oleums, fluorosulfuric acid, and hydrogen fluoride. Organic chemists, analytical chemists, investigators, and scientists whose works involve physical or inorganic chemistry will find the collection truly beneficial.