Spectroscopic processes compared with electrochemical

In the present work in situ high-temperature electronic absorption spectroscopy was employed to identify the corrosion products of metals and alloys in fused salts. Corrosion of metals in molten salts under an inert atmosphere has an electrochemical origin and anodic dissolution was used here to facilitate the process studied. Spectroscopic investigation of stainless steel anodic dissolution in alkali chloride melts allows determining the sequence in which the steel components are dissolved. To interpret the observed phenomena, the spectra recorded after steel dissolution were compared with the absorption spectra of the melts containing the products of anodic dissolution of pure metals constituting the stainless steels studied. 

Instead, a wide variety of spectroscopic and electrochemical titration methods are often employed to determine the equilibrium constants for a molecular recognition process at several different temperatures, which are then analyzed by the van t Hoff equation to give the thermodynamic parameters for the process. However, there is a critical tradeoff between the accuracy of the value obtained and the convenience of the measurement since the thermodynamic parameters, evaluated through the van t Hoff treatment, do not take into account the possible temperature dependence of the enthalpy change, i.e. heat capacity, and are less accurate in principle. In fact, it has been demonstrated with some supramolecular systems that the van t Hoff treatment leads to a curved plot and therefore the thermodynamic parameters deviated considerably from those determined by calorimetry.3132 Hence one should be cautious in handling thermodynamic parameters determined by spectroscopic titration and particularly in comparing the values for distinct systems determined by different methods. 

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