Differential capacitance measurements are reported for solutions of LiClO4 and LiAsF6 in highly purified tetraethylene glycol dimethylether ("tetramer") et an HMDE. The solvent forms part of a homologous series of molecules which range from low molar mass liquids to high molar mass solids. It was necessary to allow for ion association when interpreting the behaviour of the diffuse double layer because of the low relative permittivity of the tetramer. No significant specific adsorption of the anions was detected, although adsorption of ClO4- at high positive charge on the electrode appeared greater than that of AsF6-. The inner layer capacitance behaved in the manner of Parsons’ "Group 1" and "Group 2" solvents, and the values were fitted to a four state model.