Gibbs Dividing Surface and Helium Adsorption

All adsorption data is based on the definition of Gibbs dividing surface , which is a purely mathematical transformation. Adsorption measurements in microporous solids necessitate experimental determination of the dividing surface . An international protocol does not exist on how to perform this important measurement. Commonly, helium is assumed not to adsorb and used as a probe molecule for this measurement. Each experimentalist chooses an arbitrary set of conditions, often without even disclosing them, which adds to the confusion in adsorption literature. Here, a self-consistent method for the analysis of helium data is proposed which does not assume non-adsorbing helium . The method is compared to others using the extensive set of helium /silicalite data. The Gibbs dividing surface and hence the helium isotherms at all temperatures are determined.