The structure of ionic liquid (IL)-gas interfaces is currently a hot topic in the field and our understanding of pure ILs is improving. However, very little is known about the surface structure and dynamics of mixtures of ILs. In recent work, which we plan to publish soon, we have used neutron reflectometry (NR) to investigate the ILs [C2MIM][Tf2N] and [C12MIM][Tf2N] and have found significant surface ordering in [C12MIM][Tf2N]. In addition, we have preliminary evidence, from NR experiments, of surface enrichment of the [C12MIM]+ ions in a mixture of these two ILs containing 24 mol % [C12MIM][Tf2N]. This proposal aims to investigate the effects of composition on the surface structure of these IL mixtures by measuring the reflectivity of two additional compositions containing 8 and 63 mol % [C12MIM][Tf2N]. This is crucial for our understanding of the gas-liquid interface in this system.