Knudsen diffusion in powders. Part II Effect of pore size distribution on surface areas obtained from diffusion measurements and correlation with mercury porosimetry

Surface areas obtained from diffusion of helium through powder beds at low pressure are compared with values derived from nitrogen adsorption (B.E.T.). A detailed study of the powder beds with mercury porosimetry shows that agreement between area evaluations depends on the fulfilment of randomness in the manner the various sizes of connected pores are distributed in space (the latter condition is described in Part I of this work). It is also shown that parameters for diffusion at low pressure can be estimated when the pore size distribution is known from mercury porosimetry measurements.