Measurement of Contact Angle of Water in Soils and Sand

The contact angle of water in soils and sand was measured using the infiltration and capillary rise method respectively. The contact angle of water to the soil is not zero and even in wettable soil the effective contact angle is much larger. The order of magnitude of the soil-water contact angle among five soils was as follows: Sandy loam soil > red soil > laterite soil > black soil > clay soil. In sand, the magnitude of contact angle was not influenced by the treatment of hydrophobic substance such as pyrogallol used in present study. The Poiseuille's equation worked well for soils but not for pure sand.