Adsorbed layers of H2O and HClO4 on Au(111) are prepared at various temperatures under vacuum conditions and analyzed by X-ray photoelectron spectroscopy (XPS). Total coverages are in the range of(1-3) x 10(15) cm(-2). Nonequilibrated layers obtained at 80 K by a sequential adsorption of H2O and HClO4 (or vice versa) exhibit different O1s and C12p binding energies and desorption characteristics ("layering"). Low Ols binding energies indicate direct interaction of oxygen lone pair orbitals of ClO4- with surface orbitals of Au. In light of these O1s binding energies, ClO4 ions interacting with the Au(111) surface are likely to exist for equilibrated mixed layers with molecule-ratios [H2O]/[HClO4] below 7.