Abstract
Adsorption and desorption of cleaning products are among the most important contributions to the instability of mass standards. An optical method, the mirage effect, is proposed to investigate the adsorption/desorption of cleaning solvents on the surface of mass standards at conditions close to normal temperature and pressure (NTP). A theoretical model of the mirage effect in the presence of an adsorbable vapour is recalled, relating the amplitude and phase of the mirage deflection to the adsorption isotherm. Representing this isotherm with the BET (Brunauer, Emmett and Teller) equation and introducing an inverse procedure, the parameters characterizing the adsorption process, such as the amount of adsorbed matter in the first monolayer and the differential heat of adsorption, are obtained. Experimental results for the adsorption of acetone, ethanol and isopropanol on XSH alacrite are presented that agree qualitatively with results from more conventional methods.
Published Version
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