Silica gel surface area

Further insight into molecular binding to the solid surface is possible from a determination of the surface area occupied by each molecule in a mono-layer. In a detailed study of the adsorption of a range of substances on silica gel (surface area 200 m2/g), Weis and coworkers9 found that a relatively small number of polynuclear aromatic substances occupied all available binding sites, indicating that the molecules are oriented parallel to the solid surface to... 

The polarization effects, isotopic effects (exchange of DjO for H2O), and non-ohmic behavior of adsorbed water on silica gel (surface area 660 mVg) are similar to those of an electrolyte solution [4]. The resistivity was found to decrease exponentially with water content and to increase roughly exponentially with OH content this was determined from a simultaneous measurement of resistivity and the near-infrared spectra of adsorbed water and surface hydroxyl groups. The adsorbed water on silica gel is immobile because the water molecule is hydrogen-bonded to two substrate hydroxyls, but the conductivity of silica gel increases as the amount of adsorbed water increases. 

Figure 6 Variation of silica gel surface area during drying as a function of treatment ( of ethanol washings before drying).

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