Electrochemists have not, in general, been slow to use instrumental techniques bor~rowed from other disciplines and adapt them to their own needs. Thus, for example, one can list electron spin resonance (e.s.r.), ellipsometry, specular reflectance, transmission studies and attenuated total reflection (a.t.r.) studies as examples of these. However, most of this work relates to measurements in the visible and u.v. regions. Turning to the use of infrared measurements in conjunction with electrochemistry, we find a much more limited field. There are studies, such as those of Poling 1, in which the electrode was removed from its environment and then studied spectroscopically, having first been dried. This approach is clearly the simplest and best point at which to begin, but the hazards are many. In the main, they arise from the uncertainty that the surface-adsorbed species remains unchanged during its transition from the electrochemical environment to that of the spectrometer. Secondly, there are a number of reported studies of surface-adsorbed species on electrodes, such as Ge, which are transparent to I.R. radiation. In this class come the a.t.r, studies of Mark and Pons, Trifonov and others 2-s. There are two significant disadvantages to this type of work. In the first place, the data so obtained relate to an electrode material which is not well studied from an electrochemical point of view, particularly in terms of electrosorption. Secondly, it is an electrode material, which is passive only over a limited range of potentials.
It will be clear from this that a study of electrosorbed species on a surface such as Pt is much to be desired, not only because the vast majority of electrochemical data relate to this metal, but also because one stands on much firmer ground in the making of potential measurements. Several authors have pointed this out, and one at least 6 refers obliquely to feasibility studies which suggest that such a goal is attainable. In the neighbouring discipline of surface chemistry, monolayers of organic adsorbates on thin films of Pt have been examined by Harrod et al. 7, Tomkins and Greenlet s, and Yates and King 9.
For these reasons it was decided to examine the feasibility of such a study here, and this paper reports the concepts, calculations and experimental results obtained by us. * The reflectance, R, here contains the attenuation factor, T~, due to radiation absorption during traverse of the electrolyte.