Measurement of Gibbsian Surface Excess

The Gibbsian Surface Excesses (GSE) are the true experimental variables for measurement of equilibria and kinetics for pure and multicomponent gas-sol id adsorption. The gravimetric and volumetric methods, which are the most c ommonly used experimental procedures, are revisited. The common practice of ignoring helium adsorption during measurement of adsorbent density by heli um pycnometry and measurement of void volumes in adsorption apparatus by he lium expansion can lead to large errors in estimating GSE at high pressures and for less selectivity adsorbed components of a gas mixture. Methods to overcome these problems are described.