.Vibrational spectra and 35Cl, 13C, 7Li and 1H n.m.r. spectra of anhydrous solutions of LiClO4 in diethyl ether have been studied. There is no evidence for the formation of free ions down to 0.1 M concentration of salt. Two salt species having concentration-dependent distributions are identified, these being contact ion pairs and ion aggregates. The salt species are solvated with one mole of solvent per mole of salt. The preferred conformation of the diethyl ether solvate molecule is trms-gauche. For pure dlethyl ether at 25°C the trans-trans → trans-gauche equilibrium has ΔH 5.85 kJ mol-1 and ΔS 19.5 J K-1 mol-1. The ΔH value is not influenced by the presence of salt, but ΔS increases as the salt concentration increases until at 4 M LiClO4 the value is 37.6 J K-1 mol-1.

Solutions of Mg(ClO4)2, Ca(ClO4)2 and Sr (ClO4)2 have been studied at a variety of concentrations up to saturation by means of infrared absorption, Raman scattering and multinuclear n.m.r. spectroscopy. For solutions of Mg(ClO4)2 there was little ion association up to saturation but for the other two salts association to both solvent shared anion- cation complexes and contact anion-cation complexes was identified. The nature of the association process was probed by using line broadening for the quadrupolar nuclei 17O, 35Cl and 43Ca . The extent of association to solvent shared anion-cation complexes was found to increase in the series Mg2+ < Ca2+ < Sr2+.

The variations of the infrared librational mode of water with concentration of added salt have been examined at 30�C for solutions of NH4F, NH4Cl, NH4Br, NH4I, LiCl, LiBr, NaCl, NaBr, NaI, KCl, KBr and KI. The data indicate that water in the primary hydration sheath can be distinguished from the remainder of the water and primary hydration numbers have been estimated. It is shown that in general the larger the ion the greater the change to the spectral band. The ammonium fluoride is shown to be unique in producing little disturbance of the water structure.

Anhydrous lithium perchlorate has been examined in the crystalline and molten state by infrared and Raman spectroscopy. In the crystalline phase all degenerate modes are split but the Raman and infrared spectra are essentially identical in the internal frequency region. In the molten state the spectra are more simple but no coincidences exist between infrared and Raman spectra. The spectra are interpreted in terms of a crystalline symmetry perturbation for both the solid and molten salts. The symmetry of the perturbing field is shown to change in going from the solid to the melt. An explanation of the melt spectra in terms of contact ion pairs is considered and dismissed. Observed vibrational frequencies and assignments are given.

Vibrational spectra of a series of halogeno-complex ions of antimony(III) and bismuth(III) are reported. Results of crystal spectra are discussed in terms of the structural environment and a comparative study of Raman solution and solid state spectra is given. Some force constants for hexahalogeno species on a modified Urey-Bradley force field have been calculated and their significance is discussed.