In-situ IR reflection spectroscopy has been used to probe the structure of the double layer on an Au(111) electrode in solutions containing specifically adsorbed nitrate ions. The adsorbed nitrate ion is found to be bonded to the gold surface through one of its oxygen atoms. Both adsorbed nitrate ions, as well as those in the solution are found to possess C-2v symmetry. Nitrate ions in the double layer form contact ion-pairs with hydronium ions, possibly with an extra water molecule incorporated in the ion-pair moiety. The extent of ion-pairing is found to depend on the applied potential. An indication of the onset of water chemisorption on the gold surface is also found with the present technique. On the basis of combined ATR and SNIFTIRS (subtractively normalized interfacial Fourier transform IR spectroscopy) experiments it is shown that the width of the deconvoluted nitrate band can be used to estimate the vicinity of the potential of zero charge (pzc). It was found that the pzc in 0.01 M HNO3 is close to that observed in 0.01 M HClO4, and that it shifts by ca. -100 mV per pH unit due to the specific adsorption of nitrate.