There has been a continuing interest in the structure of water and of aqueous solutions, and many studies have employed spectroscopic techniques. These have frequently involved absorption spectroscopy in the near-IR range, and Raman scattering. In general, however, the normal IR range has been but little used except for studies of HDO-containing solutions, and the region near 3500 cm−1of the intense H2O absorption has been almost completely avoided. Transmission techniques have been exclusively employed with absorption spectroscopy. Internal reflection spectroscopy (IRS) techniques have been employed to examine aqueous solutions, but the emphasis was placed on studying the solute rather than the solvent. Also, the solute concentrations which had been employed in transmission studies have been rather high. We now suggest the feasibility of carrying out structural studies of aqueous solutions by using IRS techniques to record spectra in the IR range, employing solutions of relatively low concentrations. For example, the lowest concentration of aqueous HCl solution examined by Ackermann1was 2.5 M by transmission techniques in the 4000-1100 cm−1range; in contrast, using IRS, the perturbations of the O-H stretching and deformation bands of H2O could be observed with 0.1 M HCl.