Abstract: The adsorption of 12-sillicotungstic acid(SiW₁₂)on the active carbon has been investigated in water, ethanol, acetic acid and butyl acetate medium. A diffusion model for SiW₁₂ adsorption in the micropore of active carbon has been proposed. The middle micropore of the active carbon plays an important role as a molecular sieve for adsorption of SiW₁₂. The water solvated SiW₁₂ molectiles can smoothly get into the micropore of diameter～1.7nm. However, for the SiW₁₂ molecules solvated by other solvents only the micropores ηgreater diameter wotild be fifled.

Key words: heteropoly acid, active carbon, adsorption, heterogenzation