Several interesting results have emerged in studies of Aerosol-OT at the sapphire/solution interface that relate to effects of counter-ions, insensitivity to pH as well as the surface induced appearance of lamellar order at low concentrations. However a significant difference between phase behaviour in H2O and D2O precludes solvent contrast variation to elucidate the details of the structure, in particular the hydration of the head groups. This proposal is to perform experiments using a magnetic contrast layer and polarised neutrons and so provide an additional contrast set that will overcome this problem and provide specifically information about the hydration of head groups in the adsorbed layers at different concentrations.