Adsorption of Water Vapor on E‐Glass

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Abstract
The thermodynamics of a water‐vapor‐E‐glass system were studied by adsorption‐isotherm analysis. The seven isotherms completed were Brunauer type IV with permanent hysteresis. The first adsorbed water layer could not be removed by pumping, indicating permanent hydrolysis. Application of heat removed the remaining water to close the hysteresis loop. Calculation of isosteric heat of adsorption indicates that the adsorbed state is between the solid and the liquid states, equivalent to the loss of one vibrational and one translational degree of freedom. A new plot of energy vs thickness is proposed which describes the adsorption independent of surface area, as contrasted to the usual energy‐vs‐volume plot which was found to depend on surface area. A modified Clausius‐Clapeyron equation is proposed for computing the isosteric heat of adsorption.

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