Determination of pore size distribution by gas adsorption

Gas adsorption is widely used for pore size distribution determination. This is accomplished by measuring the volume of gas adsorbed or desorbed, at constant temperature and over a wide range of pressures, to generate adsorption and desorption isotherms. Manual determination of adsorption and desorption isotherms is tedious and time consuming and, for routine use, automatic analyzers are preferred. 

In order to calculate a pore size distribution, a model must be selected, e.g. cylindrical pores, wedge shaped pores, ink bottle pores and so on. It is also necessary to decide which branch of the isotherm to employ, adsorption or desorption. During desorption the cores of the pores are emptied leaving a residual layer, the thickness of which has to be known, in order to calculate a pore size distribution. All of these variables affect the derived distribution. 

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