Experimental Observation of Critical Depletion: Nitrous Oxide Adsorption on Silica Gel

Abstract

The adsorption of nitrous oxide (N2O) on silica gel has been studied using a gravimetric apparatus under near critical conditions. In gravimetric measurements, the determination of the excess amount adsorbed depends on a buoyancy correction factor which accounts for the volumes of the adsorbent and the solid parts in the cell. The accurate measurement of the volume of the sorbent and the metal parts in the measuring cell plays an important role in the precise measurement of the excess adsorbed amount especially at high densities. To this aim, a new protocol has been proposed which accounts for non-negligible helium adsorption and thermal expansion of the sorbent and the solid parts of the balance. Helium isochores under moderate temperature and densities have been experimentally measured. The adsorption behavior of helium has been characterized using a nonlinear mobile adsorption model. The proposed protocol has then been applied for the measurement of the excess adsorbed amount of supercritical N2O on si...