We develop a crossover theory for critical adsorption of pure fluids in a s
emi-infinite system. In our previous publication [Phys. Lett. A 251, 212 (1
999)] we applied the theory to the analysis of experimental data for adsorp
tion of liquid SF6 on the critical isochore only. In this article we extend
the theory on the noncritical isochores and present a comparison of the th
eoretical predictions for the surface excess (Gibbs) adsorption with experi
mental data for CO2/silica and SF6/graphite systems. Good representation of
experimental data is achieved in the range of temperatures from the satura
ted temperature up to 1.15 T-c and densities 0.5 rho(c) less than or equal
to rho less than or equal to 1.5 rho(c). The optimization of the model to t
he excess isotherms in both systems indicates that they have surface critic
al behavior in the universality class of normal transition. However, in thi
s case model does not reproduce the excess adsorption data for SF6/graphite
system at temperatures tau = T/T-c -1 less than or equal to 0.02 at rho =
rho(c). Analysis of the excess adsorption data along the critical isochore
in SF6/graphite system indicates that the surface field h(1) vanishes linea
rly with tau as T --> T-c, which corresponds to the ordinary transition. (C
) 2000 American Institute of Physics. [S0021-9606(00)50406-1].