The adaptability of three parametric adsorption equations which were derived presuming the localized adsorption of a monolayer and a compressed gas-like non-localized adsorption model in the field of different potential energy from that of the gas phase for the upper adphase over a monolayer, was investigated. This was done by through Ar adsorption isotherms at 77K on microbeads SiO
2-gel and aerosil SiO
2-gels treated thermally at 250°-1000°C in comparison with a BET equation which was derived upon the basis of the stacked layer for the upper adphase region over a localized monolayer. The adaptability of experimental isotherms to each equation was confirmed by the fact that the BET equation agreeds with them in the range of relative pressure from 0.05 to 0.3 where the monolayer was completed and discrepancy from experimental ones was observed to rapidly increase in a range higher than 0.3, while three parameter adsorption equations agreed with in a range wider than that of the former, i. e., from 0.05 to 0.6 or 0.7 for Ar adsorption isotherms on aerosil SiO
2-gel and in nearly entire relative pressure range for those on microbeads SiO
2-gel.
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