Studies of the thermal stability of organic compounds adsorbed on clay minerals are of interest from several points of view, e.g. the type and strength of bonding forces between the organics and the clay surfaces (Chou & McAtee, 1969; Yariv et al., 1971; Lacher et al., 1981), and the effect of the clay surface on stability or degradation mechanism of the organic compounds adsorbed on clays (Bodenheimer et al., 1966; Yariv et al., 1971; Durand et al., 1972).