A comparative study was carried out on the diffusion behavior of different diffusing species

including gases

non-electrolytes and electrolytes

in porous particles prepared in the laboratory and believed to have the same pore structure. The effective diffusivities of different gas pairs

hydrogen in nitrogen or in argon

and nitrogen or argon in hydrogen

were measured by the dynamic pulse response method. From the values of effective diffusivities

tortuosity factors were calculated and compared for different diffusion species in the pellets (with porosities from 0.234 to 0.632). The tortuosity factors for gas diffusion are only slightly dependent on the properties of diffusion species

while strongly dependent on the porosities of the pellets. The effective diffusivities of potassium chloride or lithium chloride in water and benzene in ethanol were also measured in a well-stirred reactor. The results clearly demonstrate that the tortuosity factors of the diffusion of a binary electrolyte are not so markedly influenced by the pellet porosity as compared with gas diffusion. The tortuosity factors for the diffusion of a non-electrolyte differ from those for diffusion of a binary electrolyte in water in the range of 20% to 60%.