SUMMARYMeasurements were made of the contact angle for glycerol, di‐iodomethane and cis‐decalin drops settled on the surface of pellets prepared from sodium forms of clay fractions of soils before and after successive removal of organic matter, iron and aluminium. On the basis of contact angles thus measured and a modified Young equation, the dispersive and non‐dispersive components of the surface free energy of the clay fractions were calculated. It was found that the non‐dispersive component decreased linearly with an increase in organic matter content, and with Fe and Al in the clay fractions of the soils studied. However, the dispersive component was not dependent on organic matter content, but decreased with increasing content of Fe and Al in the clay fractions