The contact angle, contact angle hysteresis, and interfacial tension w
ere measured using a model system consisting of mercury and halide aqu
eous solutions. The measured contact angle hysteresis was discussed in
terms of the surface roughness, chemical heterogeneity, and mechanica
l instability. The experimental results of contact angle measurements
were analyzed using the surface force theory of wetting films, which d
emonstrated the presence of hydrophobic forces. The origin of the hydr
ophobic force observed in the present system was discussed briefly. Th
e importance of hydrated halide anions in controlling the wettability
of mercury surfaces was demonstrated. Finally, a correlation between t
he interfacial tension and hydrophobic force was illustrated.